1 @c Copyright (C) 1988, 1989, 1992, 1993, 1994, 1996, 1998, 1999, 2000,
2 @c 2001, 2002, 2003, 2004, 2005, 2006 Free Software Foundation, Inc.
4 @c This is part of the GCC manual.
5 @c For copying conditions, see the file gcc.texi.
8 @chapter Extensions to the C Language Family
9 @cindex extensions, C language
10 @cindex C language extensions
13 GNU C provides several language features not found in ISO standard C@.
14 (The @option{-pedantic} option directs GCC to print a warning message if
15 any of these features is used.) To test for the availability of these
16 features in conditional compilation, check for a predefined macro
17 @code{__GNUC__}, which is always defined under GCC@.
19 These extensions are available in C and Objective-C@. Most of them are
20 also available in C++. @xref{C++ Extensions,,Extensions to the
21 C++ Language}, for extensions that apply @emph{only} to C++.
23 Some features that are in ISO C99 but not C89 or C++ are also, as
24 extensions, accepted by GCC in C89 mode and in C++.
27 * Statement Exprs:: Putting statements and declarations inside expressions.
28 * Local Labels:: Labels local to a block.
29 * Labels as Values:: Getting pointers to labels, and computed gotos.
30 * Nested Functions:: As in Algol and Pascal, lexical scoping of functions.
31 * Constructing Calls:: Dispatching a call to another function.
32 * Typeof:: @code{typeof}: referring to the type of an expression.
33 * Conditionals:: Omitting the middle operand of a @samp{?:} expression.
34 * Long Long:: Double-word integers---@code{long long int}.
35 * Complex:: Data types for complex numbers.
36 * Decimal Float:: Decimal Floating Point.
37 * Hex Floats:: Hexadecimal floating-point constants.
38 * Zero Length:: Zero-length arrays.
39 * Variable Length:: Arrays whose length is computed at run time.
40 * Empty Structures:: Structures with no members.
41 * Variadic Macros:: Macros with a variable number of arguments.
42 * Escaped Newlines:: Slightly looser rules for escaped newlines.
43 * Subscripting:: Any array can be subscripted, even if not an lvalue.
44 * Pointer Arith:: Arithmetic on @code{void}-pointers and function pointers.
45 * Initializers:: Non-constant initializers.
46 * Compound Literals:: Compound literals give structures, unions
48 * Designated Inits:: Labeling elements of initializers.
49 * Cast to Union:: Casting to union type from any member of the union.
50 * Case Ranges:: `case 1 ... 9' and such.
51 * Mixed Declarations:: Mixing declarations and code.
52 * Function Attributes:: Declaring that functions have no side effects,
53 or that they can never return.
54 * Attribute Syntax:: Formal syntax for attributes.
55 * Function Prototypes:: Prototype declarations and old-style definitions.
56 * C++ Comments:: C++ comments are recognized.
57 * Dollar Signs:: Dollar sign is allowed in identifiers.
58 * Character Escapes:: @samp{\e} stands for the character @key{ESC}.
59 * Variable Attributes:: Specifying attributes of variables.
60 * Type Attributes:: Specifying attributes of types.
61 * Alignment:: Inquiring about the alignment of a type or variable.
62 * Inline:: Defining inline functions (as fast as macros).
63 * Extended Asm:: Assembler instructions with C expressions as operands.
64 (With them you can define ``built-in'' functions.)
65 * Constraints:: Constraints for asm operands
66 * Asm Labels:: Specifying the assembler name to use for a C symbol.
67 * Explicit Reg Vars:: Defining variables residing in specified registers.
68 * Alternate Keywords:: @code{__const__}, @code{__asm__}, etc., for header files.
69 * Incomplete Enums:: @code{enum foo;}, with details to follow.
70 * Function Names:: Printable strings which are the name of the current
72 * Return Address:: Getting the return or frame address of a function.
73 * Vector Extensions:: Using vector instructions through built-in functions.
74 * Offsetof:: Special syntax for implementing @code{offsetof}.
75 * Atomic Builtins:: Built-in functions for atomic memory access.
76 * Object Size Checking:: Built-in functions for limited buffer overflow
78 * Other Builtins:: Other built-in functions.
79 * Target Builtins:: Built-in functions specific to particular targets.
80 * Target Format Checks:: Format checks specific to particular targets.
81 * Pragmas:: Pragmas accepted by GCC.
82 * Unnamed Fields:: Unnamed struct/union fields within structs/unions.
83 * Thread-Local:: Per-thread variables.
87 @section Statements and Declarations in Expressions
88 @cindex statements inside expressions
89 @cindex declarations inside expressions
90 @cindex expressions containing statements
91 @cindex macros, statements in expressions
93 @c the above section title wrapped and causes an underfull hbox.. i
94 @c changed it from "within" to "in". --mew 4feb93
95 A compound statement enclosed in parentheses may appear as an expression
96 in GNU C@. This allows you to use loops, switches, and local variables
99 Recall that a compound statement is a sequence of statements surrounded
100 by braces; in this construct, parentheses go around the braces. For
104 (@{ int y = foo (); int z;
111 is a valid (though slightly more complex than necessary) expression
112 for the absolute value of @code{foo ()}.
114 The last thing in the compound statement should be an expression
115 followed by a semicolon; the value of this subexpression serves as the
116 value of the entire construct. (If you use some other kind of statement
117 last within the braces, the construct has type @code{void}, and thus
118 effectively no value.)
120 This feature is especially useful in making macro definitions ``safe'' (so
121 that they evaluate each operand exactly once). For example, the
122 ``maximum'' function is commonly defined as a macro in standard C as
126 #define max(a,b) ((a) > (b) ? (a) : (b))
130 @cindex side effects, macro argument
131 But this definition computes either @var{a} or @var{b} twice, with bad
132 results if the operand has side effects. In GNU C, if you know the
133 type of the operands (here taken as @code{int}), you can define
134 the macro safely as follows:
137 #define maxint(a,b) \
138 (@{int _a = (a), _b = (b); _a > _b ? _a : _b; @})
141 Embedded statements are not allowed in constant expressions, such as
142 the value of an enumeration constant, the width of a bit-field, or
143 the initial value of a static variable.
145 If you don't know the type of the operand, you can still do this, but you
146 must use @code{typeof} (@pxref{Typeof}).
148 In G++, the result value of a statement expression undergoes array and
149 function pointer decay, and is returned by value to the enclosing
150 expression. For instance, if @code{A} is a class, then
159 will construct a temporary @code{A} object to hold the result of the
160 statement expression, and that will be used to invoke @code{Foo}.
161 Therefore the @code{this} pointer observed by @code{Foo} will not be the
164 Any temporaries created within a statement within a statement expression
165 will be destroyed at the statement's end. This makes statement
166 expressions inside macros slightly different from function calls. In
167 the latter case temporaries introduced during argument evaluation will
168 be destroyed at the end of the statement that includes the function
169 call. In the statement expression case they will be destroyed during
170 the statement expression. For instance,
173 #define macro(a) (@{__typeof__(a) b = (a); b + 3; @})
174 template<typename T> T function(T a) @{ T b = a; return b + 3; @}
184 will have different places where temporaries are destroyed. For the
185 @code{macro} case, the temporary @code{X} will be destroyed just after
186 the initialization of @code{b}. In the @code{function} case that
187 temporary will be destroyed when the function returns.
189 These considerations mean that it is probably a bad idea to use
190 statement-expressions of this form in header files that are designed to
191 work with C++. (Note that some versions of the GNU C Library contained
192 header files using statement-expression that lead to precisely this
195 Jumping into a statement expression with @code{goto} or using a
196 @code{switch} statement outside the statement expression with a
197 @code{case} or @code{default} label inside the statement expression is
198 not permitted. Jumping into a statement expression with a computed
199 @code{goto} (@pxref{Labels as Values}) yields undefined behavior.
200 Jumping out of a statement expression is permitted, but if the
201 statement expression is part of a larger expression then it is
202 unspecified which other subexpressions of that expression have been
203 evaluated except where the language definition requires certain
204 subexpressions to be evaluated before or after the statement
205 expression. In any case, as with a function call the evaluation of a
206 statement expression is not interleaved with the evaluation of other
207 parts of the containing expression. For example,
210 foo (), ((@{ bar1 (); goto a; 0; @}) + bar2 ()), baz();
214 will call @code{foo} and @code{bar1} and will not call @code{baz} but
215 may or may not call @code{bar2}. If @code{bar2} is called, it will be
216 called after @code{foo} and before @code{bar1}
219 @section Locally Declared Labels
221 @cindex macros, local labels
223 GCC allows you to declare @dfn{local labels} in any nested block
224 scope. A local label is just like an ordinary label, but you can
225 only reference it (with a @code{goto} statement, or by taking its
226 address) within the block in which it was declared.
228 A local label declaration looks like this:
231 __label__ @var{label};
238 __label__ @var{label1}, @var{label2}, /* @r{@dots{}} */;
241 Local label declarations must come at the beginning of the block,
242 before any ordinary declarations or statements.
244 The label declaration defines the label @emph{name}, but does not define
245 the label itself. You must do this in the usual way, with
246 @code{@var{label}:}, within the statements of the statement expression.
248 The local label feature is useful for complex macros. If a macro
249 contains nested loops, a @code{goto} can be useful for breaking out of
250 them. However, an ordinary label whose scope is the whole function
251 cannot be used: if the macro can be expanded several times in one
252 function, the label will be multiply defined in that function. A
253 local label avoids this problem. For example:
256 #define SEARCH(value, array, target) \
259 typeof (target) _SEARCH_target = (target); \
260 typeof (*(array)) *_SEARCH_array = (array); \
263 for (i = 0; i < max; i++) \
264 for (j = 0; j < max; j++) \
265 if (_SEARCH_array[i][j] == _SEARCH_target) \
266 @{ (value) = i; goto found; @} \
272 This could also be written using a statement-expression:
275 #define SEARCH(array, target) \
278 typeof (target) _SEARCH_target = (target); \
279 typeof (*(array)) *_SEARCH_array = (array); \
282 for (i = 0; i < max; i++) \
283 for (j = 0; j < max; j++) \
284 if (_SEARCH_array[i][j] == _SEARCH_target) \
285 @{ value = i; goto found; @} \
292 Local label declarations also make the labels they declare visible to
293 nested functions, if there are any. @xref{Nested Functions}, for details.
295 @node Labels as Values
296 @section Labels as Values
297 @cindex labels as values
298 @cindex computed gotos
299 @cindex goto with computed label
300 @cindex address of a label
302 You can get the address of a label defined in the current function
303 (or a containing function) with the unary operator @samp{&&}. The
304 value has type @code{void *}. This value is a constant and can be used
305 wherever a constant of that type is valid. For example:
313 To use these values, you need to be able to jump to one. This is done
314 with the computed goto statement@footnote{The analogous feature in
315 Fortran is called an assigned goto, but that name seems inappropriate in
316 C, where one can do more than simply store label addresses in label
317 variables.}, @code{goto *@var{exp};}. For example,
324 Any expression of type @code{void *} is allowed.
326 One way of using these constants is in initializing a static array that
327 will serve as a jump table:
330 static void *array[] = @{ &&foo, &&bar, &&hack @};
333 Then you can select a label with indexing, like this:
340 Note that this does not check whether the subscript is in bounds---array
341 indexing in C never does that.
343 Such an array of label values serves a purpose much like that of the
344 @code{switch} statement. The @code{switch} statement is cleaner, so
345 use that rather than an array unless the problem does not fit a
346 @code{switch} statement very well.
348 Another use of label values is in an interpreter for threaded code.
349 The labels within the interpreter function can be stored in the
350 threaded code for super-fast dispatching.
352 You may not use this mechanism to jump to code in a different function.
353 If you do that, totally unpredictable things will happen. The best way to
354 avoid this is to store the label address only in automatic variables and
355 never pass it as an argument.
357 An alternate way to write the above example is
360 static const int array[] = @{ &&foo - &&foo, &&bar - &&foo,
362 goto *(&&foo + array[i]);
366 This is more friendly to code living in shared libraries, as it reduces
367 the number of dynamic relocations that are needed, and by consequence,
368 allows the data to be read-only.
370 @node Nested Functions
371 @section Nested Functions
372 @cindex nested functions
373 @cindex downward funargs
376 A @dfn{nested function} is a function defined inside another function.
377 (Nested functions are not supported for GNU C++.) The nested function's
378 name is local to the block where it is defined. For example, here we
379 define a nested function named @code{square}, and call it twice:
383 foo (double a, double b)
385 double square (double z) @{ return z * z; @}
387 return square (a) + square (b);
392 The nested function can access all the variables of the containing
393 function that are visible at the point of its definition. This is
394 called @dfn{lexical scoping}. For example, here we show a nested
395 function which uses an inherited variable named @code{offset}:
399 bar (int *array, int offset, int size)
401 int access (int *array, int index)
402 @{ return array[index + offset]; @}
405 for (i = 0; i < size; i++)
406 /* @r{@dots{}} */ access (array, i) /* @r{@dots{}} */
411 Nested function definitions are permitted within functions in the places
412 where variable definitions are allowed; that is, in any block, mixed
413 with the other declarations and statements in the block.
415 It is possible to call the nested function from outside the scope of its
416 name by storing its address or passing the address to another function:
419 hack (int *array, int size)
421 void store (int index, int value)
422 @{ array[index] = value; @}
424 intermediate (store, size);
428 Here, the function @code{intermediate} receives the address of
429 @code{store} as an argument. If @code{intermediate} calls @code{store},
430 the arguments given to @code{store} are used to store into @code{array}.
431 But this technique works only so long as the containing function
432 (@code{hack}, in this example) does not exit.
434 If you try to call the nested function through its address after the
435 containing function has exited, all hell will break loose. If you try
436 to call it after a containing scope level has exited, and if it refers
437 to some of the variables that are no longer in scope, you may be lucky,
438 but it's not wise to take the risk. If, however, the nested function
439 does not refer to anything that has gone out of scope, you should be
442 GCC implements taking the address of a nested function using a technique
443 called @dfn{trampolines}. A paper describing them is available as
446 @uref{http://people.debian.org/~aaronl/Usenix88-lexic.pdf}.
448 A nested function can jump to a label inherited from a containing
449 function, provided the label was explicitly declared in the containing
450 function (@pxref{Local Labels}). Such a jump returns instantly to the
451 containing function, exiting the nested function which did the
452 @code{goto} and any intermediate functions as well. Here is an example:
456 bar (int *array, int offset, int size)
459 int access (int *array, int index)
463 return array[index + offset];
467 for (i = 0; i < size; i++)
468 /* @r{@dots{}} */ access (array, i) /* @r{@dots{}} */
472 /* @r{Control comes here from @code{access}
473 if it detects an error.} */
480 A nested function always has no linkage. Declaring one with
481 @code{extern} or @code{static} is erroneous. If you need to declare the nested function
482 before its definition, use @code{auto} (which is otherwise meaningless
483 for function declarations).
486 bar (int *array, int offset, int size)
489 auto int access (int *, int);
491 int access (int *array, int index)
495 return array[index + offset];
501 @node Constructing Calls
502 @section Constructing Function Calls
503 @cindex constructing calls
504 @cindex forwarding calls
506 Using the built-in functions described below, you can record
507 the arguments a function received, and call another function
508 with the same arguments, without knowing the number or types
511 You can also record the return value of that function call,
512 and later return that value, without knowing what data type
513 the function tried to return (as long as your caller expects
516 However, these built-in functions may interact badly with some
517 sophisticated features or other extensions of the language. It
518 is, therefore, not recommended to use them outside very simple
519 functions acting as mere forwarders for their arguments.
521 @deftypefn {Built-in Function} {void *} __builtin_apply_args ()
522 This built-in function returns a pointer to data
523 describing how to perform a call with the same arguments as were passed
524 to the current function.
526 The function saves the arg pointer register, structure value address,
527 and all registers that might be used to pass arguments to a function
528 into a block of memory allocated on the stack. Then it returns the
529 address of that block.
532 @deftypefn {Built-in Function} {void *} __builtin_apply (void (*@var{function})(), void *@var{arguments}, size_t @var{size})
533 This built-in function invokes @var{function}
534 with a copy of the parameters described by @var{arguments}
537 The value of @var{arguments} should be the value returned by
538 @code{__builtin_apply_args}. The argument @var{size} specifies the size
539 of the stack argument data, in bytes.
541 This function returns a pointer to data describing
542 how to return whatever value was returned by @var{function}. The data
543 is saved in a block of memory allocated on the stack.
545 It is not always simple to compute the proper value for @var{size}. The
546 value is used by @code{__builtin_apply} to compute the amount of data
547 that should be pushed on the stack and copied from the incoming argument
551 @deftypefn {Built-in Function} {void} __builtin_return (void *@var{result})
552 This built-in function returns the value described by @var{result} from
553 the containing function. You should specify, for @var{result}, a value
554 returned by @code{__builtin_apply}.
558 @section Referring to a Type with @code{typeof}
561 @cindex macros, types of arguments
563 Another way to refer to the type of an expression is with @code{typeof}.
564 The syntax of using of this keyword looks like @code{sizeof}, but the
565 construct acts semantically like a type name defined with @code{typedef}.
567 There are two ways of writing the argument to @code{typeof}: with an
568 expression or with a type. Here is an example with an expression:
575 This assumes that @code{x} is an array of pointers to functions;
576 the type described is that of the values of the functions.
578 Here is an example with a typename as the argument:
585 Here the type described is that of pointers to @code{int}.
587 If you are writing a header file that must work when included in ISO C
588 programs, write @code{__typeof__} instead of @code{typeof}.
589 @xref{Alternate Keywords}.
591 A @code{typeof}-construct can be used anywhere a typedef name could be
592 used. For example, you can use it in a declaration, in a cast, or inside
593 of @code{sizeof} or @code{typeof}.
595 @code{typeof} is often useful in conjunction with the
596 statements-within-expressions feature. Here is how the two together can
597 be used to define a safe ``maximum'' macro that operates on any
598 arithmetic type and evaluates each of its arguments exactly once:
602 (@{ typeof (a) _a = (a); \
603 typeof (b) _b = (b); \
604 _a > _b ? _a : _b; @})
607 @cindex underscores in variables in macros
608 @cindex @samp{_} in variables in macros
609 @cindex local variables in macros
610 @cindex variables, local, in macros
611 @cindex macros, local variables in
613 The reason for using names that start with underscores for the local
614 variables is to avoid conflicts with variable names that occur within the
615 expressions that are substituted for @code{a} and @code{b}. Eventually we
616 hope to design a new form of declaration syntax that allows you to declare
617 variables whose scopes start only after their initializers; this will be a
618 more reliable way to prevent such conflicts.
621 Some more examples of the use of @code{typeof}:
625 This declares @code{y} with the type of what @code{x} points to.
632 This declares @code{y} as an array of such values.
639 This declares @code{y} as an array of pointers to characters:
642 typeof (typeof (char *)[4]) y;
646 It is equivalent to the following traditional C declaration:
652 To see the meaning of the declaration using @code{typeof}, and why it
653 might be a useful way to write, rewrite it with these macros:
656 #define pointer(T) typeof(T *)
657 #define array(T, N) typeof(T [N])
661 Now the declaration can be rewritten this way:
664 array (pointer (char), 4) y;
668 Thus, @code{array (pointer (char), 4)} is the type of arrays of 4
669 pointers to @code{char}.
672 @emph{Compatibility Note:} In addition to @code{typeof}, GCC 2 supported
673 a more limited extension which permitted one to write
676 typedef @var{T} = @var{expr};
680 with the effect of declaring @var{T} to have the type of the expression
681 @var{expr}. This extension does not work with GCC 3 (versions between
682 3.0 and 3.2 will crash; 3.2.1 and later give an error). Code which
683 relies on it should be rewritten to use @code{typeof}:
686 typedef typeof(@var{expr}) @var{T};
690 This will work with all versions of GCC@.
693 @section Conditionals with Omitted Operands
694 @cindex conditional expressions, extensions
695 @cindex omitted middle-operands
696 @cindex middle-operands, omitted
697 @cindex extensions, @code{?:}
698 @cindex @code{?:} extensions
700 The middle operand in a conditional expression may be omitted. Then
701 if the first operand is nonzero, its value is the value of the conditional
704 Therefore, the expression
711 has the value of @code{x} if that is nonzero; otherwise, the value of
714 This example is perfectly equivalent to
720 @cindex side effect in ?:
721 @cindex ?: side effect
723 In this simple case, the ability to omit the middle operand is not
724 especially useful. When it becomes useful is when the first operand does,
725 or may (if it is a macro argument), contain a side effect. Then repeating
726 the operand in the middle would perform the side effect twice. Omitting
727 the middle operand uses the value already computed without the undesirable
728 effects of recomputing it.
731 @section Double-Word Integers
732 @cindex @code{long long} data types
733 @cindex double-word arithmetic
734 @cindex multiprecision arithmetic
735 @cindex @code{LL} integer suffix
736 @cindex @code{ULL} integer suffix
738 ISO C99 supports data types for integers that are at least 64 bits wide,
739 and as an extension GCC supports them in C89 mode and in C++.
740 Simply write @code{long long int} for a signed integer, or
741 @code{unsigned long long int} for an unsigned integer. To make an
742 integer constant of type @code{long long int}, add the suffix @samp{LL}
743 to the integer. To make an integer constant of type @code{unsigned long
744 long int}, add the suffix @samp{ULL} to the integer.
746 You can use these types in arithmetic like any other integer types.
747 Addition, subtraction, and bitwise boolean operations on these types
748 are open-coded on all types of machines. Multiplication is open-coded
749 if the machine supports fullword-to-doubleword a widening multiply
750 instruction. Division and shifts are open-coded only on machines that
751 provide special support. The operations that are not open-coded use
752 special library routines that come with GCC@.
754 There may be pitfalls when you use @code{long long} types for function
755 arguments, unless you declare function prototypes. If a function
756 expects type @code{int} for its argument, and you pass a value of type
757 @code{long long int}, confusion will result because the caller and the
758 subroutine will disagree about the number of bytes for the argument.
759 Likewise, if the function expects @code{long long int} and you pass
760 @code{int}. The best way to avoid such problems is to use prototypes.
763 @section Complex Numbers
764 @cindex complex numbers
765 @cindex @code{_Complex} keyword
766 @cindex @code{__complex__} keyword
768 ISO C99 supports complex floating data types, and as an extension GCC
769 supports them in C89 mode and in C++, and supports complex integer data
770 types which are not part of ISO C99. You can declare complex types
771 using the keyword @code{_Complex}. As an extension, the older GNU
772 keyword @code{__complex__} is also supported.
774 For example, @samp{_Complex double x;} declares @code{x} as a
775 variable whose real part and imaginary part are both of type
776 @code{double}. @samp{_Complex short int y;} declares @code{y} to
777 have real and imaginary parts of type @code{short int}; this is not
778 likely to be useful, but it shows that the set of complex types is
781 To write a constant with a complex data type, use the suffix @samp{i} or
782 @samp{j} (either one; they are equivalent). For example, @code{2.5fi}
783 has type @code{_Complex float} and @code{3i} has type
784 @code{_Complex int}. Such a constant always has a pure imaginary
785 value, but you can form any complex value you like by adding one to a
786 real constant. This is a GNU extension; if you have an ISO C99
787 conforming C library (such as GNU libc), and want to construct complex
788 constants of floating type, you should include @code{<complex.h>} and
789 use the macros @code{I} or @code{_Complex_I} instead.
791 @cindex @code{__real__} keyword
792 @cindex @code{__imag__} keyword
793 To extract the real part of a complex-valued expression @var{exp}, write
794 @code{__real__ @var{exp}}. Likewise, use @code{__imag__} to
795 extract the imaginary part. This is a GNU extension; for values of
796 floating type, you should use the ISO C99 functions @code{crealf},
797 @code{creal}, @code{creall}, @code{cimagf}, @code{cimag} and
798 @code{cimagl}, declared in @code{<complex.h>} and also provided as
799 built-in functions by GCC@.
801 @cindex complex conjugation
802 The operator @samp{~} performs complex conjugation when used on a value
803 with a complex type. This is a GNU extension; for values of
804 floating type, you should use the ISO C99 functions @code{conjf},
805 @code{conj} and @code{conjl}, declared in @code{<complex.h>} and also
806 provided as built-in functions by GCC@.
808 GCC can allocate complex automatic variables in a noncontiguous
809 fashion; it's even possible for the real part to be in a register while
810 the imaginary part is on the stack (or vice-versa). Only the DWARF2
811 debug info format can represent this, so use of DWARF2 is recommended.
812 If you are using the stabs debug info format, GCC describes a noncontiguous
813 complex variable as if it were two separate variables of noncomplex type.
814 If the variable's actual name is @code{foo}, the two fictitious
815 variables are named @code{foo$real} and @code{foo$imag}. You can
816 examine and set these two fictitious variables with your debugger.
819 @section Decimal Floating Point
820 @cindex decimal floating point
821 @cindex @code{_Decimal32} data type
822 @cindex @code{_Decimal64} data type
823 @cindex @code{_Decimal128} data type
824 @cindex @code{df} integer suffix
825 @cindex @code{dd} integer suffix
826 @cindex @code{dl} integer suffix
827 @cindex @code{DF} integer suffix
828 @cindex @code{DD} integer suffix
829 @cindex @code{DL} integer suffix
831 GNU C supports decimal floating point types in addition to the
832 standard floating-point types. This extension supports decimal
833 floating-point arithmetic as defined in IEEE-754R, the proposed
834 revision of IEEE-754. The C language extension is defined in ISO/IEC
835 DTR 24732, Draft 5. Support for this functionality will change when
836 it is accepted into the C standard and might change for new drafts
837 of the proposal. Calling conventions for any target might also change.
838 Not all targets support decimal floating point.
840 Support for decimal floating point includes the arithmetic operators
841 add, subtract, multiply, divide; unary arithmetic operators;
842 relational operators; equality operators; and conversions to and from
843 integer and other floating-point types. Use a suffix @samp{df} or
844 @samp{DF} in a literal constant of type @code{_Decimal32}, @samp{dd}
845 or @samp{DD} for @code{_Decimal64}, and @samp{dl} or @samp{DL} for
848 Passing a decimal floating-point value as an argument to a function
849 without a prototype is undefined.
851 Types @code{_Decimal32}, @code{_Decimal64}, and @code{_Decimal128}
852 are supported by the DWARF2 debug information format.
858 ISO C99 supports floating-point numbers written not only in the usual
859 decimal notation, such as @code{1.55e1}, but also numbers such as
860 @code{0x1.fp3} written in hexadecimal format. As a GNU extension, GCC
861 supports this in C89 mode (except in some cases when strictly
862 conforming) and in C++. In that format the
863 @samp{0x} hex introducer and the @samp{p} or @samp{P} exponent field are
864 mandatory. The exponent is a decimal number that indicates the power of
865 2 by which the significant part will be multiplied. Thus @samp{0x1.f} is
872 @samp{p3} multiplies it by 8, and the value of @code{0x1.fp3}
873 is the same as @code{1.55e1}.
875 Unlike for floating-point numbers in the decimal notation the exponent
876 is always required in the hexadecimal notation. Otherwise the compiler
877 would not be able to resolve the ambiguity of, e.g., @code{0x1.f}. This
878 could mean @code{1.0f} or @code{1.9375} since @samp{f} is also the
879 extension for floating-point constants of type @code{float}.
882 @section Arrays of Length Zero
883 @cindex arrays of length zero
884 @cindex zero-length arrays
885 @cindex length-zero arrays
886 @cindex flexible array members
888 Zero-length arrays are allowed in GNU C@. They are very useful as the
889 last element of a structure which is really a header for a variable-length
898 struct line *thisline = (struct line *)
899 malloc (sizeof (struct line) + this_length);
900 thisline->length = this_length;
903 In ISO C90, you would have to give @code{contents} a length of 1, which
904 means either you waste space or complicate the argument to @code{malloc}.
906 In ISO C99, you would use a @dfn{flexible array member}, which is
907 slightly different in syntax and semantics:
911 Flexible array members are written as @code{contents[]} without
915 Flexible array members have incomplete type, and so the @code{sizeof}
916 operator may not be applied. As a quirk of the original implementation
917 of zero-length arrays, @code{sizeof} evaluates to zero.
920 Flexible array members may only appear as the last member of a
921 @code{struct} that is otherwise non-empty.
924 A structure containing a flexible array member, or a union containing
925 such a structure (possibly recursively), may not be a member of a
926 structure or an element of an array. (However, these uses are
927 permitted by GCC as extensions.)
930 GCC versions before 3.0 allowed zero-length arrays to be statically
931 initialized, as if they were flexible arrays. In addition to those
932 cases that were useful, it also allowed initializations in situations
933 that would corrupt later data. Non-empty initialization of zero-length
934 arrays is now treated like any case where there are more initializer
935 elements than the array holds, in that a suitable warning about "excess
936 elements in array" is given, and the excess elements (all of them, in
937 this case) are ignored.
939 Instead GCC allows static initialization of flexible array members.
940 This is equivalent to defining a new structure containing the original
941 structure followed by an array of sufficient size to contain the data.
942 I.e.@: in the following, @code{f1} is constructed as if it were declared
948 @} f1 = @{ 1, @{ 2, 3, 4 @} @};
951 struct f1 f1; int data[3];
952 @} f2 = @{ @{ 1 @}, @{ 2, 3, 4 @} @};
956 The convenience of this extension is that @code{f1} has the desired
957 type, eliminating the need to consistently refer to @code{f2.f1}.
959 This has symmetry with normal static arrays, in that an array of
960 unknown size is also written with @code{[]}.
962 Of course, this extension only makes sense if the extra data comes at
963 the end of a top-level object, as otherwise we would be overwriting
964 data at subsequent offsets. To avoid undue complication and confusion
965 with initialization of deeply nested arrays, we simply disallow any
966 non-empty initialization except when the structure is the top-level
970 struct foo @{ int x; int y[]; @};
971 struct bar @{ struct foo z; @};
973 struct foo a = @{ 1, @{ 2, 3, 4 @} @}; // @r{Valid.}
974 struct bar b = @{ @{ 1, @{ 2, 3, 4 @} @} @}; // @r{Invalid.}
975 struct bar c = @{ @{ 1, @{ @} @} @}; // @r{Valid.}
976 struct foo d[1] = @{ @{ 1 @{ 2, 3, 4 @} @} @}; // @r{Invalid.}
979 @node Empty Structures
980 @section Structures With No Members
981 @cindex empty structures
982 @cindex zero-size structures
984 GCC permits a C structure to have no members:
991 The structure will have size zero. In C++, empty structures are part
992 of the language. G++ treats empty structures as if they had a single
993 member of type @code{char}.
995 @node Variable Length
996 @section Arrays of Variable Length
997 @cindex variable-length arrays
998 @cindex arrays of variable length
1001 Variable-length automatic arrays are allowed in ISO C99, and as an
1002 extension GCC accepts them in C89 mode and in C++. (However, GCC's
1003 implementation of variable-length arrays does not yet conform in detail
1004 to the ISO C99 standard.) These arrays are
1005 declared like any other automatic arrays, but with a length that is not
1006 a constant expression. The storage is allocated at the point of
1007 declaration and deallocated when the brace-level is exited. For
1012 concat_fopen (char *s1, char *s2, char *mode)
1014 char str[strlen (s1) + strlen (s2) + 1];
1017 return fopen (str, mode);
1021 @cindex scope of a variable length array
1022 @cindex variable-length array scope
1023 @cindex deallocating variable length arrays
1024 Jumping or breaking out of the scope of the array name deallocates the
1025 storage. Jumping into the scope is not allowed; you get an error
1028 @cindex @code{alloca} vs variable-length arrays
1029 You can use the function @code{alloca} to get an effect much like
1030 variable-length arrays. The function @code{alloca} is available in
1031 many other C implementations (but not in all). On the other hand,
1032 variable-length arrays are more elegant.
1034 There are other differences between these two methods. Space allocated
1035 with @code{alloca} exists until the containing @emph{function} returns.
1036 The space for a variable-length array is deallocated as soon as the array
1037 name's scope ends. (If you use both variable-length arrays and
1038 @code{alloca} in the same function, deallocation of a variable-length array
1039 will also deallocate anything more recently allocated with @code{alloca}.)
1041 You can also use variable-length arrays as arguments to functions:
1045 tester (int len, char data[len][len])
1051 The length of an array is computed once when the storage is allocated
1052 and is remembered for the scope of the array in case you access it with
1055 If you want to pass the array first and the length afterward, you can
1056 use a forward declaration in the parameter list---another GNU extension.
1060 tester (int len; char data[len][len], int len)
1066 @cindex parameter forward declaration
1067 The @samp{int len} before the semicolon is a @dfn{parameter forward
1068 declaration}, and it serves the purpose of making the name @code{len}
1069 known when the declaration of @code{data} is parsed.
1071 You can write any number of such parameter forward declarations in the
1072 parameter list. They can be separated by commas or semicolons, but the
1073 last one must end with a semicolon, which is followed by the ``real''
1074 parameter declarations. Each forward declaration must match a ``real''
1075 declaration in parameter name and data type. ISO C99 does not support
1076 parameter forward declarations.
1078 @node Variadic Macros
1079 @section Macros with a Variable Number of Arguments.
1080 @cindex variable number of arguments
1081 @cindex macro with variable arguments
1082 @cindex rest argument (in macro)
1083 @cindex variadic macros
1085 In the ISO C standard of 1999, a macro can be declared to accept a
1086 variable number of arguments much as a function can. The syntax for
1087 defining the macro is similar to that of a function. Here is an
1091 #define debug(format, ...) fprintf (stderr, format, __VA_ARGS__)
1094 Here @samp{@dots{}} is a @dfn{variable argument}. In the invocation of
1095 such a macro, it represents the zero or more tokens until the closing
1096 parenthesis that ends the invocation, including any commas. This set of
1097 tokens replaces the identifier @code{__VA_ARGS__} in the macro body
1098 wherever it appears. See the CPP manual for more information.
1100 GCC has long supported variadic macros, and used a different syntax that
1101 allowed you to give a name to the variable arguments just like any other
1102 argument. Here is an example:
1105 #define debug(format, args...) fprintf (stderr, format, args)
1108 This is in all ways equivalent to the ISO C example above, but arguably
1109 more readable and descriptive.
1111 GNU CPP has two further variadic macro extensions, and permits them to
1112 be used with either of the above forms of macro definition.
1114 In standard C, you are not allowed to leave the variable argument out
1115 entirely; but you are allowed to pass an empty argument. For example,
1116 this invocation is invalid in ISO C, because there is no comma after
1123 GNU CPP permits you to completely omit the variable arguments in this
1124 way. In the above examples, the compiler would complain, though since
1125 the expansion of the macro still has the extra comma after the format
1128 To help solve this problem, CPP behaves specially for variable arguments
1129 used with the token paste operator, @samp{##}. If instead you write
1132 #define debug(format, ...) fprintf (stderr, format, ## __VA_ARGS__)
1135 and if the variable arguments are omitted or empty, the @samp{##}
1136 operator causes the preprocessor to remove the comma before it. If you
1137 do provide some variable arguments in your macro invocation, GNU CPP
1138 does not complain about the paste operation and instead places the
1139 variable arguments after the comma. Just like any other pasted macro
1140 argument, these arguments are not macro expanded.
1142 @node Escaped Newlines
1143 @section Slightly Looser Rules for Escaped Newlines
1144 @cindex escaped newlines
1145 @cindex newlines (escaped)
1147 Recently, the preprocessor has relaxed its treatment of escaped
1148 newlines. Previously, the newline had to immediately follow a
1149 backslash. The current implementation allows whitespace in the form
1150 of spaces, horizontal and vertical tabs, and form feeds between the
1151 backslash and the subsequent newline. The preprocessor issues a
1152 warning, but treats it as a valid escaped newline and combines the two
1153 lines to form a single logical line. This works within comments and
1154 tokens, as well as between tokens. Comments are @emph{not} treated as
1155 whitespace for the purposes of this relaxation, since they have not
1156 yet been replaced with spaces.
1159 @section Non-Lvalue Arrays May Have Subscripts
1160 @cindex subscripting
1161 @cindex arrays, non-lvalue
1163 @cindex subscripting and function values
1164 In ISO C99, arrays that are not lvalues still decay to pointers, and
1165 may be subscripted, although they may not be modified or used after
1166 the next sequence point and the unary @samp{&} operator may not be
1167 applied to them. As an extension, GCC allows such arrays to be
1168 subscripted in C89 mode, though otherwise they do not decay to
1169 pointers outside C99 mode. For example,
1170 this is valid in GNU C though not valid in C89:
1174 struct foo @{int a[4];@};
1180 return f().a[index];
1186 @section Arithmetic on @code{void}- and Function-Pointers
1187 @cindex void pointers, arithmetic
1188 @cindex void, size of pointer to
1189 @cindex function pointers, arithmetic
1190 @cindex function, size of pointer to
1192 In GNU C, addition and subtraction operations are supported on pointers to
1193 @code{void} and on pointers to functions. This is done by treating the
1194 size of a @code{void} or of a function as 1.
1196 A consequence of this is that @code{sizeof} is also allowed on @code{void}
1197 and on function types, and returns 1.
1199 @opindex Wpointer-arith
1200 The option @option{-Wpointer-arith} requests a warning if these extensions
1204 @section Non-Constant Initializers
1205 @cindex initializers, non-constant
1206 @cindex non-constant initializers
1208 As in standard C++ and ISO C99, the elements of an aggregate initializer for an
1209 automatic variable are not required to be constant expressions in GNU C@.
1210 Here is an example of an initializer with run-time varying elements:
1213 foo (float f, float g)
1215 float beat_freqs[2] = @{ f-g, f+g @};
1220 @node Compound Literals
1221 @section Compound Literals
1222 @cindex constructor expressions
1223 @cindex initializations in expressions
1224 @cindex structures, constructor expression
1225 @cindex expressions, constructor
1226 @cindex compound literals
1227 @c The GNU C name for what C99 calls compound literals was "constructor expressions".
1229 ISO C99 supports compound literals. A compound literal looks like
1230 a cast containing an initializer. Its value is an object of the
1231 type specified in the cast, containing the elements specified in
1232 the initializer; it is an lvalue. As an extension, GCC supports
1233 compound literals in C89 mode and in C++.
1235 Usually, the specified type is a structure. Assume that
1236 @code{struct foo} and @code{structure} are declared as shown:
1239 struct foo @{int a; char b[2];@} structure;
1243 Here is an example of constructing a @code{struct foo} with a compound literal:
1246 structure = ((struct foo) @{x + y, 'a', 0@});
1250 This is equivalent to writing the following:
1254 struct foo temp = @{x + y, 'a', 0@};
1259 You can also construct an array. If all the elements of the compound literal
1260 are (made up of) simple constant expressions, suitable for use in
1261 initializers of objects of static storage duration, then the compound
1262 literal can be coerced to a pointer to its first element and used in
1263 such an initializer, as shown here:
1266 char **foo = (char *[]) @{ "x", "y", "z" @};
1269 Compound literals for scalar types and union types are is
1270 also allowed, but then the compound literal is equivalent
1273 As a GNU extension, GCC allows initialization of objects with static storage
1274 duration by compound literals (which is not possible in ISO C99, because
1275 the initializer is not a constant).
1276 It is handled as if the object was initialized only with the bracket
1277 enclosed list if compound literal's and object types match.
1278 The initializer list of the compound literal must be constant.
1279 If the object being initialized has array type of unknown size, the size is
1280 determined by compound literal size.
1283 static struct foo x = (struct foo) @{1, 'a', 'b'@};
1284 static int y[] = (int []) @{1, 2, 3@};
1285 static int z[] = (int [3]) @{1@};
1289 The above lines are equivalent to the following:
1291 static struct foo x = @{1, 'a', 'b'@};
1292 static int y[] = @{1, 2, 3@};
1293 static int z[] = @{1, 0, 0@};
1296 @node Designated Inits
1297 @section Designated Initializers
1298 @cindex initializers with labeled elements
1299 @cindex labeled elements in initializers
1300 @cindex case labels in initializers
1301 @cindex designated initializers
1303 Standard C89 requires the elements of an initializer to appear in a fixed
1304 order, the same as the order of the elements in the array or structure
1307 In ISO C99 you can give the elements in any order, specifying the array
1308 indices or structure field names they apply to, and GNU C allows this as
1309 an extension in C89 mode as well. This extension is not
1310 implemented in GNU C++.
1312 To specify an array index, write
1313 @samp{[@var{index}] =} before the element value. For example,
1316 int a[6] = @{ [4] = 29, [2] = 15 @};
1323 int a[6] = @{ 0, 0, 15, 0, 29, 0 @};
1327 The index values must be constant expressions, even if the array being
1328 initialized is automatic.
1330 An alternative syntax for this which has been obsolete since GCC 2.5 but
1331 GCC still accepts is to write @samp{[@var{index}]} before the element
1332 value, with no @samp{=}.
1334 To initialize a range of elements to the same value, write
1335 @samp{[@var{first} ... @var{last}] = @var{value}}. This is a GNU
1336 extension. For example,
1339 int widths[] = @{ [0 ... 9] = 1, [10 ... 99] = 2, [100] = 3 @};
1343 If the value in it has side-effects, the side-effects will happen only once,
1344 not for each initialized field by the range initializer.
1347 Note that the length of the array is the highest value specified
1350 In a structure initializer, specify the name of a field to initialize
1351 with @samp{.@var{fieldname} =} before the element value. For example,
1352 given the following structure,
1355 struct point @{ int x, y; @};
1359 the following initialization
1362 struct point p = @{ .y = yvalue, .x = xvalue @};
1369 struct point p = @{ xvalue, yvalue @};
1372 Another syntax which has the same meaning, obsolete since GCC 2.5, is
1373 @samp{@var{fieldname}:}, as shown here:
1376 struct point p = @{ y: yvalue, x: xvalue @};
1380 The @samp{[@var{index}]} or @samp{.@var{fieldname}} is known as a
1381 @dfn{designator}. You can also use a designator (or the obsolete colon
1382 syntax) when initializing a union, to specify which element of the union
1383 should be used. For example,
1386 union foo @{ int i; double d; @};
1388 union foo f = @{ .d = 4 @};
1392 will convert 4 to a @code{double} to store it in the union using
1393 the second element. By contrast, casting 4 to type @code{union foo}
1394 would store it into the union as the integer @code{i}, since it is
1395 an integer. (@xref{Cast to Union}.)
1397 You can combine this technique of naming elements with ordinary C
1398 initialization of successive elements. Each initializer element that
1399 does not have a designator applies to the next consecutive element of the
1400 array or structure. For example,
1403 int a[6] = @{ [1] = v1, v2, [4] = v4 @};
1410 int a[6] = @{ 0, v1, v2, 0, v4, 0 @};
1413 Labeling the elements of an array initializer is especially useful
1414 when the indices are characters or belong to an @code{enum} type.
1419 = @{ [' '] = 1, ['\t'] = 1, ['\h'] = 1,
1420 ['\f'] = 1, ['\n'] = 1, ['\r'] = 1 @};
1423 @cindex designator lists
1424 You can also write a series of @samp{.@var{fieldname}} and
1425 @samp{[@var{index}]} designators before an @samp{=} to specify a
1426 nested subobject to initialize; the list is taken relative to the
1427 subobject corresponding to the closest surrounding brace pair. For
1428 example, with the @samp{struct point} declaration above:
1431 struct point ptarray[10] = @{ [2].y = yv2, [2].x = xv2, [0].x = xv0 @};
1435 If the same field is initialized multiple times, it will have value from
1436 the last initialization. If any such overridden initialization has
1437 side-effect, it is unspecified whether the side-effect happens or not.
1438 Currently, GCC will discard them and issue a warning.
1441 @section Case Ranges
1443 @cindex ranges in case statements
1445 You can specify a range of consecutive values in a single @code{case} label,
1449 case @var{low} ... @var{high}:
1453 This has the same effect as the proper number of individual @code{case}
1454 labels, one for each integer value from @var{low} to @var{high}, inclusive.
1456 This feature is especially useful for ranges of ASCII character codes:
1462 @strong{Be careful:} Write spaces around the @code{...}, for otherwise
1463 it may be parsed wrong when you use it with integer values. For example,
1478 @section Cast to a Union Type
1479 @cindex cast to a union
1480 @cindex union, casting to a
1482 A cast to union type is similar to other casts, except that the type
1483 specified is a union type. You can specify the type either with
1484 @code{union @var{tag}} or with a typedef name. A cast to union is actually
1485 a constructor though, not a cast, and hence does not yield an lvalue like
1486 normal casts. (@xref{Compound Literals}.)
1488 The types that may be cast to the union type are those of the members
1489 of the union. Thus, given the following union and variables:
1492 union foo @{ int i; double d; @};
1498 both @code{x} and @code{y} can be cast to type @code{union foo}.
1500 Using the cast as the right-hand side of an assignment to a variable of
1501 union type is equivalent to storing in a member of the union:
1506 u = (union foo) x @equiv{} u.i = x
1507 u = (union foo) y @equiv{} u.d = y
1510 You can also use the union cast as a function argument:
1513 void hack (union foo);
1515 hack ((union foo) x);
1518 @node Mixed Declarations
1519 @section Mixed Declarations and Code
1520 @cindex mixed declarations and code
1521 @cindex declarations, mixed with code
1522 @cindex code, mixed with declarations
1524 ISO C99 and ISO C++ allow declarations and code to be freely mixed
1525 within compound statements. As an extension, GCC also allows this in
1526 C89 mode. For example, you could do:
1535 Each identifier is visible from where it is declared until the end of
1536 the enclosing block.
1538 @node Function Attributes
1539 @section Declaring Attributes of Functions
1540 @cindex function attributes
1541 @cindex declaring attributes of functions
1542 @cindex functions that never return
1543 @cindex functions that return more than once
1544 @cindex functions that have no side effects
1545 @cindex functions in arbitrary sections
1546 @cindex functions that behave like malloc
1547 @cindex @code{volatile} applied to function
1548 @cindex @code{const} applied to function
1549 @cindex functions with @code{printf}, @code{scanf}, @code{strftime} or @code{strfmon} style arguments
1550 @cindex functions with non-null pointer arguments
1551 @cindex functions that are passed arguments in registers on the 386
1552 @cindex functions that pop the argument stack on the 386
1553 @cindex functions that do not pop the argument stack on the 386
1555 In GNU C, you declare certain things about functions called in your program
1556 which help the compiler optimize function calls and check your code more
1559 The keyword @code{__attribute__} allows you to specify special
1560 attributes when making a declaration. This keyword is followed by an
1561 attribute specification inside double parentheses. The following
1562 attributes are currently defined for functions on all targets:
1563 @code{noreturn}, @code{returns_twice}, @code{noinline}, @code{always_inline},
1564 @code{flatten}, @code{pure}, @code{const}, @code{nothrow}, @code{sentinel},
1565 @code{format}, @code{format_arg}, @code{no_instrument_function},
1566 @code{section}, @code{constructor}, @code{destructor}, @code{used},
1567 @code{unused}, @code{deprecated}, @code{weak}, @code{malloc},
1568 @code{alias}, @code{warn_unused_result}, @code{nonnull}
1569 and @code{externally_visible}. Several other
1570 attributes are defined for functions on particular target systems. Other
1571 attributes, including @code{section} are supported for variables declarations
1572 (@pxref{Variable Attributes}) and for types (@pxref{Type Attributes}).
1574 You may also specify attributes with @samp{__} preceding and following
1575 each keyword. This allows you to use them in header files without
1576 being concerned about a possible macro of the same name. For example,
1577 you may use @code{__noreturn__} instead of @code{noreturn}.
1579 @xref{Attribute Syntax}, for details of the exact syntax for using
1583 @c Keep this table alphabetized by attribute name. Treat _ as space.
1585 @item alias ("@var{target}")
1586 @cindex @code{alias} attribute
1587 The @code{alias} attribute causes the declaration to be emitted as an
1588 alias for another symbol, which must be specified. For instance,
1591 void __f () @{ /* @r{Do something.} */; @}
1592 void f () __attribute__ ((weak, alias ("__f")));
1595 defines @samp{f} to be a weak alias for @samp{__f}. In C++, the
1596 mangled name for the target must be used. It is an error if @samp{__f}
1597 is not defined in the same translation unit.
1599 Not all target machines support this attribute.
1602 @cindex @code{always_inline} function attribute
1603 Generally, functions are not inlined unless optimization is specified.
1604 For functions declared inline, this attribute inlines the function even
1605 if no optimization level was specified.
1607 @cindex @code{flatten} function attribute
1609 Generally, inlining into a function is limited. For a function marked with
1610 this attribute, every call inside this function will be inlined, if possible.
1611 Whether the function itself is considered for inlining depends on its size and
1612 the current inlining parameters. The @code{flatten} attribute only works
1613 reliably in unit-at-a-time mode.
1616 @cindex functions that do pop the argument stack on the 386
1618 On the Intel 386, the @code{cdecl} attribute causes the compiler to
1619 assume that the calling function will pop off the stack space used to
1620 pass arguments. This is
1621 useful to override the effects of the @option{-mrtd} switch.
1624 @cindex @code{const} function attribute
1625 Many functions do not examine any values except their arguments, and
1626 have no effects except the return value. Basically this is just slightly
1627 more strict class than the @code{pure} attribute below, since function is not
1628 allowed to read global memory.
1630 @cindex pointer arguments
1631 Note that a function that has pointer arguments and examines the data
1632 pointed to must @emph{not} be declared @code{const}. Likewise, a
1633 function that calls a non-@code{const} function usually must not be
1634 @code{const}. It does not make sense for a @code{const} function to
1637 The attribute @code{const} is not implemented in GCC versions earlier
1638 than 2.5. An alternative way to declare that a function has no side
1639 effects, which works in the current version and in some older versions,
1643 typedef int intfn ();
1645 extern const intfn square;
1648 This approach does not work in GNU C++ from 2.6.0 on, since the language
1649 specifies that the @samp{const} must be attached to the return value.
1653 @cindex @code{constructor} function attribute
1654 @cindex @code{destructor} function attribute
1655 The @code{constructor} attribute causes the function to be called
1656 automatically before execution enters @code{main ()}. Similarly, the
1657 @code{destructor} attribute causes the function to be called
1658 automatically after @code{main ()} has completed or @code{exit ()} has
1659 been called. Functions with these attributes are useful for
1660 initializing data that will be used implicitly during the execution of
1663 These attributes are not currently implemented for Objective-C@.
1666 @cindex @code{deprecated} attribute.
1667 The @code{deprecated} attribute results in a warning if the function
1668 is used anywhere in the source file. This is useful when identifying
1669 functions that are expected to be removed in a future version of a
1670 program. The warning also includes the location of the declaration
1671 of the deprecated function, to enable users to easily find further
1672 information about why the function is deprecated, or what they should
1673 do instead. Note that the warnings only occurs for uses:
1676 int old_fn () __attribute__ ((deprecated));
1678 int (*fn_ptr)() = old_fn;
1681 results in a warning on line 3 but not line 2.
1683 The @code{deprecated} attribute can also be used for variables and
1684 types (@pxref{Variable Attributes}, @pxref{Type Attributes}.)
1687 @cindex @code{__declspec(dllexport)}
1688 On Microsoft Windows targets and Symbian OS targets the
1689 @code{dllexport} attribute causes the compiler to provide a global
1690 pointer to a pointer in a DLL, so that it can be referenced with the
1691 @code{dllimport} attribute. On Microsoft Windows targets, the pointer
1692 name is formed by combining @code{_imp__} and the function or variable
1695 You can use @code{__declspec(dllexport)} as a synonym for
1696 @code{__attribute__ ((dllexport))} for compatibility with other
1699 On systems that support the @code{visibility} attribute, this
1700 attribute also implies ``default'' visibility, unless a
1701 @code{visibility} attribute is explicitly specified. You should avoid
1702 the use of @code{dllexport} with ``hidden'' or ``internal''
1703 visibility; in the future GCC may issue an error for those cases.
1705 Currently, the @code{dllexport} attribute is ignored for inlined
1706 functions, unless the @option{-fkeep-inline-functions} flag has been
1707 used. The attribute is also ignored for undefined symbols.
1709 When applied to C++ classes, the attribute marks defined non-inlined
1710 member functions and static data members as exports. Static consts
1711 initialized in-class are not marked unless they are also defined
1714 For Microsoft Windows targets there are alternative methods for
1715 including the symbol in the DLL's export table such as using a
1716 @file{.def} file with an @code{EXPORTS} section or, with GNU ld, using
1717 the @option{--export-all} linker flag.
1720 @cindex @code{__declspec(dllimport)}
1721 On Microsoft Windows and Symbian OS targets, the @code{dllimport}
1722 attribute causes the compiler to reference a function or variable via
1723 a global pointer to a pointer that is set up by the DLL exporting the
1724 symbol. The attribute implies @code{extern} storage. On Microsoft
1725 Windows targets, the pointer name is formed by combining @code{_imp__}
1726 and the function or variable name.
1728 You can use @code{__declspec(dllimport)} as a synonym for
1729 @code{__attribute__ ((dllimport))} for compatibility with other
1732 Currently, the attribute is ignored for inlined functions. If the
1733 attribute is applied to a symbol @emph{definition}, an error is reported.
1734 If a symbol previously declared @code{dllimport} is later defined, the
1735 attribute is ignored in subsequent references, and a warning is emitted.
1736 The attribute is also overridden by a subsequent declaration as
1739 When applied to C++ classes, the attribute marks non-inlined
1740 member functions and static data members as imports. However, the
1741 attribute is ignored for virtual methods to allow creation of vtables
1744 On the SH Symbian OS target the @code{dllimport} attribute also has
1745 another affect---it can cause the vtable and run-time type information
1746 for a class to be exported. This happens when the class has a
1747 dllimport'ed constructor or a non-inline, non-pure virtual function
1748 and, for either of those two conditions, the class also has a inline
1749 constructor or destructor and has a key function that is defined in
1750 the current translation unit.
1752 For Microsoft Windows based targets the use of the @code{dllimport}
1753 attribute on functions is not necessary, but provides a small
1754 performance benefit by eliminating a thunk in the DLL@. The use of the
1755 @code{dllimport} attribute on imported variables was required on older
1756 versions of the GNU linker, but can now be avoided by passing the
1757 @option{--enable-auto-import} switch to the GNU linker. As with
1758 functions, using the attribute for a variable eliminates a thunk in
1761 One drawback to using this attribute is that a pointer to a function
1762 or variable marked as @code{dllimport} cannot be used as a constant
1763 address. On Microsoft Windows targets, the attribute can be disabled
1764 for functions by setting the @option{-mnop-fun-dllimport} flag.
1767 @cindex eight bit data on the H8/300, H8/300H, and H8S
1768 Use this attribute on the H8/300, H8/300H, and H8S to indicate that the specified
1769 variable should be placed into the eight bit data section.
1770 The compiler will generate more efficient code for certain operations
1771 on data in the eight bit data area. Note the eight bit data area is limited to
1774 You must use GAS and GLD from GNU binutils version 2.7 or later for
1775 this attribute to work correctly.
1777 @item exception_handler
1778 @cindex exception handler functions on the Blackfin processor
1779 Use this attribute on the Blackfin to indicate that the specified function
1780 is an exception handler. The compiler will generate function entry and
1781 exit sequences suitable for use in an exception handler when this
1782 attribute is present.
1785 @cindex functions which handle memory bank switching
1786 On 68HC11 and 68HC12 the @code{far} attribute causes the compiler to
1787 use a calling convention that takes care of switching memory banks when
1788 entering and leaving a function. This calling convention is also the
1789 default when using the @option{-mlong-calls} option.
1791 On 68HC12 the compiler will use the @code{call} and @code{rtc} instructions
1792 to call and return from a function.
1794 On 68HC11 the compiler will generate a sequence of instructions
1795 to invoke a board-specific routine to switch the memory bank and call the
1796 real function. The board-specific routine simulates a @code{call}.
1797 At the end of a function, it will jump to a board-specific routine
1798 instead of using @code{rts}. The board-specific return routine simulates
1802 @cindex functions that pop the argument stack on the 386
1803 On the Intel 386, the @code{fastcall} attribute causes the compiler to
1804 pass the first argument (if of integral type) in the register ECX and
1805 the second argument (if of integral type) in the register EDX@. Subsequent
1806 and other typed arguments are passed on the stack. The called function will
1807 pop the arguments off the stack. If the number of arguments is variable all
1808 arguments are pushed on the stack.
1810 @item format (@var{archetype}, @var{string-index}, @var{first-to-check})
1811 @cindex @code{format} function attribute
1813 The @code{format} attribute specifies that a function takes @code{printf},
1814 @code{scanf}, @code{strftime} or @code{strfmon} style arguments which
1815 should be type-checked against a format string. For example, the
1820 my_printf (void *my_object, const char *my_format, ...)
1821 __attribute__ ((format (printf, 2, 3)));
1825 causes the compiler to check the arguments in calls to @code{my_printf}
1826 for consistency with the @code{printf} style format string argument
1829 The parameter @var{archetype} determines how the format string is
1830 interpreted, and should be @code{printf}, @code{scanf}, @code{strftime}
1831 or @code{strfmon}. (You can also use @code{__printf__},
1832 @code{__scanf__}, @code{__strftime__} or @code{__strfmon__}.) The
1833 parameter @var{string-index} specifies which argument is the format
1834 string argument (starting from 1), while @var{first-to-check} is the
1835 number of the first argument to check against the format string. For
1836 functions where the arguments are not available to be checked (such as
1837 @code{vprintf}), specify the third parameter as zero. In this case the
1838 compiler only checks the format string for consistency. For
1839 @code{strftime} formats, the third parameter is required to be zero.
1840 Since non-static C++ methods have an implicit @code{this} argument, the
1841 arguments of such methods should be counted from two, not one, when
1842 giving values for @var{string-index} and @var{first-to-check}.
1844 In the example above, the format string (@code{my_format}) is the second
1845 argument of the function @code{my_print}, and the arguments to check
1846 start with the third argument, so the correct parameters for the format
1847 attribute are 2 and 3.
1849 @opindex ffreestanding
1850 @opindex fno-builtin
1851 The @code{format} attribute allows you to identify your own functions
1852 which take format strings as arguments, so that GCC can check the
1853 calls to these functions for errors. The compiler always (unless
1854 @option{-ffreestanding} or @option{-fno-builtin} is used) checks formats
1855 for the standard library functions @code{printf}, @code{fprintf},
1856 @code{sprintf}, @code{scanf}, @code{fscanf}, @code{sscanf}, @code{strftime},
1857 @code{vprintf}, @code{vfprintf} and @code{vsprintf} whenever such
1858 warnings are requested (using @option{-Wformat}), so there is no need to
1859 modify the header file @file{stdio.h}. In C99 mode, the functions
1860 @code{snprintf}, @code{vsnprintf}, @code{vscanf}, @code{vfscanf} and
1861 @code{vsscanf} are also checked. Except in strictly conforming C
1862 standard modes, the X/Open function @code{strfmon} is also checked as
1863 are @code{printf_unlocked} and @code{fprintf_unlocked}.
1864 @xref{C Dialect Options,,Options Controlling C Dialect}.
1866 The target may provide additional types of format checks.
1867 @xref{Target Format Checks,,Format Checks Specific to Particular
1870 @item format_arg (@var{string-index})
1871 @cindex @code{format_arg} function attribute
1872 @opindex Wformat-nonliteral
1873 The @code{format_arg} attribute specifies that a function takes a format
1874 string for a @code{printf}, @code{scanf}, @code{strftime} or
1875 @code{strfmon} style function and modifies it (for example, to translate
1876 it into another language), so the result can be passed to a
1877 @code{printf}, @code{scanf}, @code{strftime} or @code{strfmon} style
1878 function (with the remaining arguments to the format function the same
1879 as they would have been for the unmodified string). For example, the
1884 my_dgettext (char *my_domain, const char *my_format)
1885 __attribute__ ((format_arg (2)));
1889 causes the compiler to check the arguments in calls to a @code{printf},
1890 @code{scanf}, @code{strftime} or @code{strfmon} type function, whose
1891 format string argument is a call to the @code{my_dgettext} function, for
1892 consistency with the format string argument @code{my_format}. If the
1893 @code{format_arg} attribute had not been specified, all the compiler
1894 could tell in such calls to format functions would be that the format
1895 string argument is not constant; this would generate a warning when
1896 @option{-Wformat-nonliteral} is used, but the calls could not be checked
1897 without the attribute.
1899 The parameter @var{string-index} specifies which argument is the format
1900 string argument (starting from one). Since non-static C++ methods have
1901 an implicit @code{this} argument, the arguments of such methods should
1902 be counted from two.
1904 The @code{format-arg} attribute allows you to identify your own
1905 functions which modify format strings, so that GCC can check the
1906 calls to @code{printf}, @code{scanf}, @code{strftime} or @code{strfmon}
1907 type function whose operands are a call to one of your own function.
1908 The compiler always treats @code{gettext}, @code{dgettext}, and
1909 @code{dcgettext} in this manner except when strict ISO C support is
1910 requested by @option{-ansi} or an appropriate @option{-std} option, or
1911 @option{-ffreestanding} or @option{-fno-builtin}
1912 is used. @xref{C Dialect Options,,Options
1913 Controlling C Dialect}.
1915 @item function_vector
1916 @cindex calling functions through the function vector on the H8/300 processors
1917 Use this attribute on the H8/300, H8/300H, and H8S to indicate that the specified
1918 function should be called through the function vector. Calling a
1919 function through the function vector will reduce code size, however;
1920 the function vector has a limited size (maximum 128 entries on the H8/300
1921 and 64 entries on the H8/300H and H8S) and shares space with the interrupt vector.
1923 You must use GAS and GLD from GNU binutils version 2.7 or later for
1924 this attribute to work correctly.
1927 @cindex interrupt handler functions
1928 Use this attribute on the ARM, AVR, C4x, CRX, M32C, M32R/D, MS1, and Xstormy16
1929 ports to indicate that the specified function is an interrupt handler.
1930 The compiler will generate function entry and exit sequences suitable
1931 for use in an interrupt handler when this attribute is present.
1933 Note, interrupt handlers for the Blackfin, m68k, H8/300, H8/300H, H8S, and
1934 SH processors can be specified via the @code{interrupt_handler} attribute.
1936 Note, on the AVR, interrupts will be enabled inside the function.
1938 Note, for the ARM, you can specify the kind of interrupt to be handled by
1939 adding an optional parameter to the interrupt attribute like this:
1942 void f () __attribute__ ((interrupt ("IRQ")));
1945 Permissible values for this parameter are: IRQ, FIQ, SWI, ABORT and UNDEF@.
1947 @item interrupt_handler
1948 @cindex interrupt handler functions on the Blackfin, m68k, H8/300 and SH processors
1949 Use this attribute on the Blackfin, m68k, H8/300, H8/300H, H8S, and SH to
1950 indicate that the specified function is an interrupt handler. The compiler
1951 will generate function entry and exit sequences suitable for use in an
1952 interrupt handler when this attribute is present.
1955 @cindex User stack pointer in interrupts on the Blackfin
1956 When used together with @code{interrupt_handler}, @code{exception_handler}
1957 or @code{nmi_handler}, code will be generated to load the stack pointer
1958 from the USP register in the function prologue.
1960 @item long_call/short_call
1961 @cindex indirect calls on ARM
1962 This attribute specifies how a particular function is called on
1963 ARM@. Both attributes override the @option{-mlong-calls} (@pxref{ARM Options})
1964 command line switch and @code{#pragma long_calls} settings. The
1965 @code{long_call} attribute indicates that the function might be far
1966 away from the call site and require a different (more expensive)
1967 calling sequence. The @code{short_call} attribute always places
1968 the offset to the function from the call site into the @samp{BL}
1969 instruction directly.
1971 @item longcall/shortcall
1972 @cindex functions called via pointer on the RS/6000 and PowerPC
1973 On the Blackfin, RS/6000 and PowerPC, the @code{longcall} attribute
1974 indicates that the function might be far away from the call site and
1975 require a different (more expensive) calling sequence. The
1976 @code{shortcall} attribute indicates that the function is always close
1977 enough for the shorter calling sequence to be used. These attributes
1978 override both the @option{-mlongcall} switch and, on the RS/6000 and
1979 PowerPC, the @code{#pragma longcall} setting.
1981 @xref{RS/6000 and PowerPC Options}, for more information on whether long
1982 calls are necessary.
1985 @cindex indirect calls on MIPS
1986 This attribute specifies how a particular function is called on MIPS@.
1987 The attribute overrides the @option{-mlong-calls} (@pxref{MIPS Options})
1988 command line switch. This attribute causes the compiler to always call
1989 the function by first loading its address into a register, and then using
1990 the contents of that register.
1993 @cindex @code{malloc} attribute
1994 The @code{malloc} attribute is used to tell the compiler that a function
1995 may be treated as if any non-@code{NULL} pointer it returns cannot
1996 alias any other pointer valid when the function returns.
1997 This will often improve optimization.
1998 Standard functions with this property include @code{malloc} and
1999 @code{calloc}. @code{realloc}-like functions have this property as
2000 long as the old pointer is never referred to (including comparing it
2001 to the new pointer) after the function returns a non-@code{NULL}
2004 @item model (@var{model-name})
2005 @cindex function addressability on the M32R/D
2006 @cindex variable addressability on the IA-64
2008 On the M32R/D, use this attribute to set the addressability of an
2009 object, and of the code generated for a function. The identifier
2010 @var{model-name} is one of @code{small}, @code{medium}, or
2011 @code{large}, representing each of the code models.
2013 Small model objects live in the lower 16MB of memory (so that their
2014 addresses can be loaded with the @code{ld24} instruction), and are
2015 callable with the @code{bl} instruction.
2017 Medium model objects may live anywhere in the 32-bit address space (the
2018 compiler will generate @code{seth/add3} instructions to load their addresses),
2019 and are callable with the @code{bl} instruction.
2021 Large model objects may live anywhere in the 32-bit address space (the
2022 compiler will generate @code{seth/add3} instructions to load their addresses),
2023 and may not be reachable with the @code{bl} instruction (the compiler will
2024 generate the much slower @code{seth/add3/jl} instruction sequence).
2026 On IA-64, use this attribute to set the addressability of an object.
2027 At present, the only supported identifier for @var{model-name} is
2028 @code{small}, indicating addressability via ``small'' (22-bit)
2029 addresses (so that their addresses can be loaded with the @code{addl}
2030 instruction). Caveat: such addressing is by definition not position
2031 independent and hence this attribute must not be used for objects
2032 defined by shared libraries.
2035 @cindex function without a prologue/epilogue code
2036 Use this attribute on the ARM, AVR, C4x and IP2K ports to indicate that the
2037 specified function does not need prologue/epilogue sequences generated by
2038 the compiler. It is up to the programmer to provide these sequences.
2041 @cindex functions which do not handle memory bank switching on 68HC11/68HC12
2042 On 68HC11 and 68HC12 the @code{near} attribute causes the compiler to
2043 use the normal calling convention based on @code{jsr} and @code{rts}.
2044 This attribute can be used to cancel the effect of the @option{-mlong-calls}
2048 @cindex Allow nesting in an interrupt handler on the Blackfin processor.
2049 Use this attribute together with @code{interrupt_handler},
2050 @code{exception_handler} or @code{nmi_handler} to indicate that the function
2051 entry code should enable nested interrupts or exceptions.
2054 @cindex NMI handler functions on the Blackfin processor
2055 Use this attribute on the Blackfin to indicate that the specified function
2056 is an NMI handler. The compiler will generate function entry and
2057 exit sequences suitable for use in an NMI handler when this
2058 attribute is present.
2060 @item no_instrument_function
2061 @cindex @code{no_instrument_function} function attribute
2062 @opindex finstrument-functions
2063 If @option{-finstrument-functions} is given, profiling function calls will
2064 be generated at entry and exit of most user-compiled functions.
2065 Functions with this attribute will not be so instrumented.
2068 @cindex @code{noinline} function attribute
2069 This function attribute prevents a function from being considered for
2072 @item nonnull (@var{arg-index}, @dots{})
2073 @cindex @code{nonnull} function attribute
2074 The @code{nonnull} attribute specifies that some function parameters should
2075 be non-null pointers. For instance, the declaration:
2079 my_memcpy (void *dest, const void *src, size_t len)
2080 __attribute__((nonnull (1, 2)));
2084 causes the compiler to check that, in calls to @code{my_memcpy},
2085 arguments @var{dest} and @var{src} are non-null. If the compiler
2086 determines that a null pointer is passed in an argument slot marked
2087 as non-null, and the @option{-Wnonnull} option is enabled, a warning
2088 is issued. The compiler may also choose to make optimizations based
2089 on the knowledge that certain function arguments will not be null.
2091 If no argument index list is given to the @code{nonnull} attribute,
2092 all pointer arguments are marked as non-null. To illustrate, the
2093 following declaration is equivalent to the previous example:
2097 my_memcpy (void *dest, const void *src, size_t len)
2098 __attribute__((nonnull));
2102 @cindex @code{noreturn} function attribute
2103 A few standard library functions, such as @code{abort} and @code{exit},
2104 cannot return. GCC knows this automatically. Some programs define
2105 their own functions that never return. You can declare them
2106 @code{noreturn} to tell the compiler this fact. For example,
2110 void fatal () __attribute__ ((noreturn));
2113 fatal (/* @r{@dots{}} */)
2115 /* @r{@dots{}} */ /* @r{Print error message.} */ /* @r{@dots{}} */
2121 The @code{noreturn} keyword tells the compiler to assume that
2122 @code{fatal} cannot return. It can then optimize without regard to what
2123 would happen if @code{fatal} ever did return. This makes slightly
2124 better code. More importantly, it helps avoid spurious warnings of
2125 uninitialized variables.
2127 The @code{noreturn} keyword does not affect the exceptional path when that
2128 applies: a @code{noreturn}-marked function may still return to the caller
2129 by throwing an exception or calling @code{longjmp}.
2131 Do not assume that registers saved by the calling function are
2132 restored before calling the @code{noreturn} function.
2134 It does not make sense for a @code{noreturn} function to have a return
2135 type other than @code{void}.
2137 The attribute @code{noreturn} is not implemented in GCC versions
2138 earlier than 2.5. An alternative way to declare that a function does
2139 not return, which works in the current version and in some older
2140 versions, is as follows:
2143 typedef void voidfn ();
2145 volatile voidfn fatal;
2148 This approach does not work in GNU C++.
2151 @cindex @code{nothrow} function attribute
2152 The @code{nothrow} attribute is used to inform the compiler that a
2153 function cannot throw an exception. For example, most functions in
2154 the standard C library can be guaranteed not to throw an exception
2155 with the notable exceptions of @code{qsort} and @code{bsearch} that
2156 take function pointer arguments. The @code{nothrow} attribute is not
2157 implemented in GCC versions earlier than 3.3.
2160 @cindex @code{pure} function attribute
2161 Many functions have no effects except the return value and their
2162 return value depends only on the parameters and/or global variables.
2163 Such a function can be subject
2164 to common subexpression elimination and loop optimization just as an
2165 arithmetic operator would be. These functions should be declared
2166 with the attribute @code{pure}. For example,
2169 int square (int) __attribute__ ((pure));
2173 says that the hypothetical function @code{square} is safe to call
2174 fewer times than the program says.
2176 Some of common examples of pure functions are @code{strlen} or @code{memcmp}.
2177 Interesting non-pure functions are functions with infinite loops or those
2178 depending on volatile memory or other system resource, that may change between
2179 two consecutive calls (such as @code{feof} in a multithreading environment).
2181 The attribute @code{pure} is not implemented in GCC versions earlier
2184 @item regparm (@var{number})
2185 @cindex @code{regparm} attribute
2186 @cindex functions that are passed arguments in registers on the 386
2187 On the Intel 386, the @code{regparm} attribute causes the compiler to
2188 pass arguments number one to @var{number} if they are of integral type
2189 in registers EAX, EDX, and ECX instead of on the stack. Functions that
2190 take a variable number of arguments will continue to be passed all of their
2191 arguments on the stack.
2193 Beware that on some ELF systems this attribute is unsuitable for
2194 global functions in shared libraries with lazy binding (which is the
2195 default). Lazy binding will send the first call via resolving code in
2196 the loader, which might assume EAX, EDX and ECX can be clobbered, as
2197 per the standard calling conventions. Solaris 8 is affected by this.
2198 GNU systems with GLIBC 2.1 or higher, and FreeBSD, are believed to be
2199 safe since the loaders there save all registers. (Lazy binding can be
2200 disabled with the linker or the loader if desired, to avoid the
2204 @cindex @code{sseregparm} attribute
2205 On the Intel 386 with SSE support, the @code{sseregparm} attribute
2206 causes the compiler to pass up to 8 floating point arguments in
2207 SSE registers instead of on the stack. Functions that take a
2208 variable number of arguments will continue to pass all of their
2209 floating point arguments on the stack.
2211 @item force_align_arg_pointer
2212 @cindex @code{force_align_arg_pointer} attribute
2213 On the Intel x86, the @code{force_align_arg_pointer} attribute may be
2214 applied to individual function definitions, generating an alternate
2215 prologue and epilogue that realigns the runtime stack. This supports
2216 mixing legacy codes that run with a 4-byte aligned stack with modern
2217 codes that keep a 16-byte stack for SSE compatibility. The alternate
2218 prologue and epilogue are slower and bigger than the regular ones, and
2219 the alternate prologue requires a scratch register; this lowers the
2220 number of registers available if used in conjunction with the
2221 @code{regparm} attribute. The @code{force_align_arg_pointer}
2222 attribute is incompatible with nested functions; this is considered a
2226 @cindex @code{returns_twice} attribute
2227 The @code{returns_twice} attribute tells the compiler that a function may
2228 return more than one time. The compiler will ensure that all registers
2229 are dead before calling such a function and will emit a warning about
2230 the variables that may be clobbered after the second return from the
2231 function. Examples of such functions are @code{setjmp} and @code{vfork}.
2232 The @code{longjmp}-like counterpart of such function, if any, might need
2233 to be marked with the @code{noreturn} attribute.
2236 @cindex save all registers on the Blackfin, H8/300, H8/300H, and H8S
2237 Use this attribute on the Blackfin, H8/300, H8/300H, and H8S to indicate that
2238 all registers except the stack pointer should be saved in the prologue
2239 regardless of whether they are used or not.
2241 @item section ("@var{section-name}")
2242 @cindex @code{section} function attribute
2243 Normally, the compiler places the code it generates in the @code{text} section.
2244 Sometimes, however, you need additional sections, or you need certain
2245 particular functions to appear in special sections. The @code{section}
2246 attribute specifies that a function lives in a particular section.
2247 For example, the declaration:
2250 extern void foobar (void) __attribute__ ((section ("bar")));
2254 puts the function @code{foobar} in the @code{bar} section.
2256 Some file formats do not support arbitrary sections so the @code{section}
2257 attribute is not available on all platforms.
2258 If you need to map the entire contents of a module to a particular
2259 section, consider using the facilities of the linker instead.
2262 @cindex @code{sentinel} function attribute
2263 This function attribute ensures that a parameter in a function call is
2264 an explicit @code{NULL}. The attribute is only valid on variadic
2265 functions. By default, the sentinel is located at position zero, the
2266 last parameter of the function call. If an optional integer position
2267 argument P is supplied to the attribute, the sentinel must be located at
2268 position P counting backwards from the end of the argument list.
2271 __attribute__ ((sentinel))
2273 __attribute__ ((sentinel(0)))
2276 The attribute is automatically set with a position of 0 for the built-in
2277 functions @code{execl} and @code{execlp}. The built-in function
2278 @code{execle} has the attribute set with a position of 1.
2280 A valid @code{NULL} in this context is defined as zero with any pointer
2281 type. If your system defines the @code{NULL} macro with an integer type
2282 then you need to add an explicit cast. GCC replaces @code{stddef.h}
2283 with a copy that redefines NULL appropriately.
2285 The warnings for missing or incorrect sentinels are enabled with
2289 See long_call/short_call.
2292 See longcall/shortcall.
2295 @cindex signal handler functions on the AVR processors
2296 Use this attribute on the AVR to indicate that the specified
2297 function is a signal handler. The compiler will generate function
2298 entry and exit sequences suitable for use in a signal handler when this
2299 attribute is present. Interrupts will be disabled inside the function.
2302 Use this attribute on the SH to indicate an @code{interrupt_handler}
2303 function should switch to an alternate stack. It expects a string
2304 argument that names a global variable holding the address of the
2309 void f () __attribute__ ((interrupt_handler,
2310 sp_switch ("alt_stack")));
2314 @cindex functions that pop the argument stack on the 386
2315 On the Intel 386, the @code{stdcall} attribute causes the compiler to
2316 assume that the called function will pop off the stack space used to
2317 pass arguments, unless it takes a variable number of arguments.
2320 @cindex tiny data section on the H8/300H and H8S
2321 Use this attribute on the H8/300H and H8S to indicate that the specified
2322 variable should be placed into the tiny data section.
2323 The compiler will generate more efficient code for loads and stores
2324 on data in the tiny data section. Note the tiny data area is limited to
2325 slightly under 32kbytes of data.
2328 Use this attribute on the SH for an @code{interrupt_handler} to return using
2329 @code{trapa} instead of @code{rte}. This attribute expects an integer
2330 argument specifying the trap number to be used.
2333 @cindex @code{unused} attribute.
2334 This attribute, attached to a function, means that the function is meant
2335 to be possibly unused. GCC will not produce a warning for this
2339 @cindex @code{used} attribute.
2340 This attribute, attached to a function, means that code must be emitted
2341 for the function even if it appears that the function is not referenced.
2342 This is useful, for example, when the function is referenced only in
2345 @item visibility ("@var{visibility_type}")
2346 @cindex @code{visibility} attribute
2347 This attribute affects the linkage of the declaration to which it is attached.
2348 There are four supported @var{visibility_type} values: default,
2349 hidden, protected or internal visibility.
2352 void __attribute__ ((visibility ("protected")))
2353 f () @{ /* @r{Do something.} */; @}
2354 int i __attribute__ ((visibility ("hidden")));
2357 The possible values of @var{visibility_type} correspond to the
2358 visibility settings in the ELF gABI.
2361 @c keep this list of visibilities in alphabetical order.
2364 Default visibility is the normal case for the object file format.
2365 This value is available for the visibility attribute to override other
2366 options that may change the assumed visibility of entities.
2368 On ELF, default visibility means that the declaration is visible to other
2369 modules and, in shared libraries, means that the declared entity may be
2372 On Darwin, default visibility means that the declaration is visible to
2375 Default visibility corresponds to ``external linkage'' in the language.
2378 Hidden visibility indicates that the entity declared will have a new
2379 form of linkage, which we'll call ``hidden linkage''. Two
2380 declarations of an object with hidden linkage refer to the same object
2381 if they are in the same shared object.
2384 Internal visibility is like hidden visibility, but with additional
2385 processor specific semantics. Unless otherwise specified by the
2386 psABI, GCC defines internal visibility to mean that a function is
2387 @emph{never} called from another module. Compare this with hidden
2388 functions which, while they cannot be referenced directly by other
2389 modules, can be referenced indirectly via function pointers. By
2390 indicating that a function cannot be called from outside the module,
2391 GCC may for instance omit the load of a PIC register since it is known
2392 that the calling function loaded the correct value.
2395 Protected visibility is like default visibility except that it
2396 indicates that references within the defining module will bind to the
2397 definition in that module. That is, the declared entity cannot be
2398 overridden by another module.
2402 All visibilities are supported on many, but not all, ELF targets
2403 (supported when the assembler supports the @samp{.visibility}
2404 pseudo-op). Default visibility is supported everywhere. Hidden
2405 visibility is supported on Darwin targets.
2407 The visibility attribute should be applied only to declarations which
2408 would otherwise have external linkage. The attribute should be applied
2409 consistently, so that the same entity should not be declared with
2410 different settings of the attribute.
2412 In C++, the visibility attribute applies to types as well as functions
2413 and objects, because in C++ types have linkage. A class must not have
2414 greater visibility than its non-static data member types and bases,
2415 and class members default to the visibility of their class. Also, a
2416 declaration without explicit visibility is limited to the visibility
2419 In C++, you can mark member functions and static member variables of a
2420 class with the visibility attribute. This is useful if if you know a
2421 particular method or static member variable should only be used from
2422 one shared object; then you can mark it hidden while the rest of the
2423 class has default visibility. Care must be taken to avoid breaking
2424 the One Definition Rule; for example, it is usually not useful to mark
2425 an inline method as hidden without marking the whole class as hidden.
2427 A C++ namespace declaration can also have the visibility attribute.
2428 This attribute applies only to the particular namespace body, not to
2429 other definitions of the same namespace; it is equivalent to using
2430 @samp{#pragma GCC visibility} before and after the namespace
2431 definition (@pxref{Visibility Pragmas}).
2433 In C++, if a template argument has limited visibility, this
2434 restriction is implicitly propagated to the template instantiation.
2435 Otherwise, template instantiations and specializations default to the
2436 visibility of their template.
2438 If both the template and enclosing class have explicit visibility, the
2439 visibility from the template is used.
2441 @item warn_unused_result
2442 @cindex @code{warn_unused_result} attribute
2443 The @code{warn_unused_result} attribute causes a warning to be emitted
2444 if a caller of the function with this attribute does not use its
2445 return value. This is useful for functions where not checking
2446 the result is either a security problem or always a bug, such as
2450 int fn () __attribute__ ((warn_unused_result));
2453 if (fn () < 0) return -1;
2459 results in warning on line 5.
2462 @cindex @code{weak} attribute
2463 The @code{weak} attribute causes the declaration to be emitted as a weak
2464 symbol rather than a global. This is primarily useful in defining
2465 library functions which can be overridden in user code, though it can
2466 also be used with non-function declarations. Weak symbols are supported
2467 for ELF targets, and also for a.out targets when using the GNU assembler
2471 @itemx weakref ("@var{target}")
2472 @cindex @code{weakref} attribute
2473 The @code{weakref} attribute marks a declaration as a weak reference.
2474 Without arguments, it should be accompanied by an @code{alias} attribute
2475 naming the target symbol. Optionally, the @var{target} may be given as
2476 an argument to @code{weakref} itself. In either case, @code{weakref}
2477 implicitly marks the declaration as @code{weak}. Without a
2478 @var{target}, given as an argument to @code{weakref} or to @code{alias},
2479 @code{weakref} is equivalent to @code{weak}.
2482 static int x() __attribute__ ((weakref ("y")));
2483 /* is equivalent to... */
2484 static int x() __attribute__ ((weak, weakref, alias ("y")));
2486 static int x() __attribute__ ((weakref));
2487 static int x() __attribute__ ((alias ("y")));
2490 A weak reference is an alias that does not by itself require a
2491 definition to be given for the target symbol. If the target symbol is
2492 only referenced through weak references, then the becomes a @code{weak}
2493 undefined symbol. If it is directly referenced, however, then such
2494 strong references prevail, and a definition will be required for the
2495 symbol, not necessarily in the same translation unit.
2497 The effect is equivalent to moving all references to the alias to a
2498 separate translation unit, renaming the alias to the aliased symbol,
2499 declaring it as weak, compiling the two separate translation units and
2500 performing a reloadable link on them.
2502 At present, a declaration to which @code{weakref} is attached can
2503 only be @code{static}.
2505 @item externally_visible
2506 @cindex @code{externally_visible} attribute.
2507 This attribute, attached to a global variable or function nullify
2508 effect of @option{-fwhole-program} command line option, so the object
2509 remain visible outside the current compilation unit
2513 You can specify multiple attributes in a declaration by separating them
2514 by commas within the double parentheses or by immediately following an
2515 attribute declaration with another attribute declaration.
2517 @cindex @code{#pragma}, reason for not using
2518 @cindex pragma, reason for not using
2519 Some people object to the @code{__attribute__} feature, suggesting that
2520 ISO C's @code{#pragma} should be used instead. At the time
2521 @code{__attribute__} was designed, there were two reasons for not doing
2526 It is impossible to generate @code{#pragma} commands from a macro.
2529 There is no telling what the same @code{#pragma} might mean in another
2533 These two reasons applied to almost any application that might have been
2534 proposed for @code{#pragma}. It was basically a mistake to use
2535 @code{#pragma} for @emph{anything}.
2537 The ISO C99 standard includes @code{_Pragma}, which now allows pragmas
2538 to be generated from macros. In addition, a @code{#pragma GCC}
2539 namespace is now in use for GCC-specific pragmas. However, it has been
2540 found convenient to use @code{__attribute__} to achieve a natural
2541 attachment of attributes to their corresponding declarations, whereas
2542 @code{#pragma GCC} is of use for constructs that do not naturally form
2543 part of the grammar. @xref{Other Directives,,Miscellaneous
2544 Preprocessing Directives, cpp, The GNU C Preprocessor}.
2546 @node Attribute Syntax
2547 @section Attribute Syntax
2548 @cindex attribute syntax
2550 This section describes the syntax with which @code{__attribute__} may be
2551 used, and the constructs to which attribute specifiers bind, for the C
2552 language. Some details may vary for C++ and Objective-C@. Because of
2553 infelicities in the grammar for attributes, some forms described here
2554 may not be successfully parsed in all cases.
2556 There are some problems with the semantics of attributes in C++. For
2557 example, there are no manglings for attributes, although they may affect
2558 code generation, so problems may arise when attributed types are used in
2559 conjunction with templates or overloading. Similarly, @code{typeid}
2560 does not distinguish between types with different attributes. Support
2561 for attributes in C++ may be restricted in future to attributes on
2562 declarations only, but not on nested declarators.
2564 @xref{Function Attributes}, for details of the semantics of attributes
2565 applying to functions. @xref{Variable Attributes}, for details of the
2566 semantics of attributes applying to variables. @xref{Type Attributes},
2567 for details of the semantics of attributes applying to structure, union
2568 and enumerated types.
2570 An @dfn{attribute specifier} is of the form
2571 @code{__attribute__ ((@var{attribute-list}))}. An @dfn{attribute list}
2572 is a possibly empty comma-separated sequence of @dfn{attributes}, where
2573 each attribute is one of the following:
2577 Empty. Empty attributes are ignored.
2580 A word (which may be an identifier such as @code{unused}, or a reserved
2581 word such as @code{const}).
2584 A word, followed by, in parentheses, parameters for the attribute.
2585 These parameters take one of the following forms:
2589 An identifier. For example, @code{mode} attributes use this form.
2592 An identifier followed by a comma and a non-empty comma-separated list
2593 of expressions. For example, @code{format} attributes use this form.
2596 A possibly empty comma-separated list of expressions. For example,
2597 @code{format_arg} attributes use this form with the list being a single
2598 integer constant expression, and @code{alias} attributes use this form
2599 with the list being a single string constant.
2603 An @dfn{attribute specifier list} is a sequence of one or more attribute
2604 specifiers, not separated by any other tokens.
2606 In GNU C, an attribute specifier list may appear after the colon following a
2607 label, other than a @code{case} or @code{default} label. The only
2608 attribute it makes sense to use after a label is @code{unused}. This
2609 feature is intended for code generated by programs which contains labels
2610 that may be unused but which is compiled with @option{-Wall}. It would
2611 not normally be appropriate to use in it human-written code, though it
2612 could be useful in cases where the code that jumps to the label is
2613 contained within an @code{#ifdef} conditional. GNU C++ does not permit
2614 such placement of attribute lists, as it is permissible for a
2615 declaration, which could begin with an attribute list, to be labelled in
2616 C++. Declarations cannot be labelled in C90 or C99, so the ambiguity
2617 does not arise there.
2619 An attribute specifier list may appear as part of a @code{struct},
2620 @code{union} or @code{enum} specifier. It may go either immediately
2621 after the @code{struct}, @code{union} or @code{enum} keyword, or after
2622 the closing brace. The former syntax is preferred.
2623 Where attribute specifiers follow the closing brace, they are considered
2624 to relate to the structure, union or enumerated type defined, not to any
2625 enclosing declaration the type specifier appears in, and the type
2626 defined is not complete until after the attribute specifiers.
2627 @c Otherwise, there would be the following problems: a shift/reduce
2628 @c conflict between attributes binding the struct/union/enum and
2629 @c binding to the list of specifiers/qualifiers; and "aligned"
2630 @c attributes could use sizeof for the structure, but the size could be
2631 @c changed later by "packed" attributes.
2633 Otherwise, an attribute specifier appears as part of a declaration,
2634 counting declarations of unnamed parameters and type names, and relates
2635 to that declaration (which may be nested in another declaration, for
2636 example in the case of a parameter declaration), or to a particular declarator
2637 within a declaration. Where an
2638 attribute specifier is applied to a parameter declared as a function or
2639 an array, it should apply to the function or array rather than the
2640 pointer to which the parameter is implicitly converted, but this is not
2641 yet correctly implemented.
2643 Any list of specifiers and qualifiers at the start of a declaration may
2644 contain attribute specifiers, whether or not such a list may in that
2645 context contain storage class specifiers. (Some attributes, however,
2646 are essentially in the nature of storage class specifiers, and only make
2647 sense where storage class specifiers may be used; for example,
2648 @code{section}.) There is one necessary limitation to this syntax: the
2649 first old-style parameter declaration in a function definition cannot
2650 begin with an attribute specifier, because such an attribute applies to
2651 the function instead by syntax described below (which, however, is not
2652 yet implemented in this case). In some other cases, attribute
2653 specifiers are permitted by this grammar but not yet supported by the
2654 compiler. All attribute specifiers in this place relate to the
2655 declaration as a whole. In the obsolescent usage where a type of
2656 @code{int} is implied by the absence of type specifiers, such a list of
2657 specifiers and qualifiers may be an attribute specifier list with no
2658 other specifiers or qualifiers.
2660 At present, the first parameter in a function prototype must have some
2661 type specifier which is not an attribute specifier; this resolves an
2662 ambiguity in the interpretation of @code{void f(int
2663 (__attribute__((foo)) x))}, but is subject to change. At present, if
2664 the parentheses of a function declarator contain only attributes then
2665 those attributes are ignored, rather than yielding an error or warning
2666 or implying a single parameter of type int, but this is subject to
2669 An attribute specifier list may appear immediately before a declarator
2670 (other than the first) in a comma-separated list of declarators in a
2671 declaration of more than one identifier using a single list of
2672 specifiers and qualifiers. Such attribute specifiers apply
2673 only to the identifier before whose declarator they appear. For
2677 __attribute__((noreturn)) void d0 (void),
2678 __attribute__((format(printf, 1, 2))) d1 (const char *, ...),
2683 the @code{noreturn} attribute applies to all the functions
2684 declared; the @code{format} attribute only applies to @code{d1}.
2686 An attribute specifier list may appear immediately before the comma,
2687 @code{=} or semicolon terminating the declaration of an identifier other
2688 than a function definition. At present, such attribute specifiers apply
2689 to the declared object or function, but in future they may attach to the
2690 outermost adjacent declarator. In simple cases there is no difference,
2691 but, for example, in
2694 void (****f)(void) __attribute__((noreturn));
2698 at present the @code{noreturn} attribute applies to @code{f}, which
2699 causes a warning since @code{f} is not a function, but in future it may
2700 apply to the function @code{****f}. The precise semantics of what
2701 attributes in such cases will apply to are not yet specified. Where an
2702 assembler name for an object or function is specified (@pxref{Asm
2703 Labels}), at present the attribute must follow the @code{asm}
2704 specification; in future, attributes before the @code{asm} specification
2705 may apply to the adjacent declarator, and those after it to the declared
2708 An attribute specifier list may, in future, be permitted to appear after
2709 the declarator in a function definition (before any old-style parameter
2710 declarations or the function body).
2712 Attribute specifiers may be mixed with type qualifiers appearing inside
2713 the @code{[]} of a parameter array declarator, in the C99 construct by
2714 which such qualifiers are applied to the pointer to which the array is
2715 implicitly converted. Such attribute specifiers apply to the pointer,
2716 not to the array, but at present this is not implemented and they are
2719 An attribute specifier list may appear at the start of a nested
2720 declarator. At present, there are some limitations in this usage: the
2721 attributes correctly apply to the declarator, but for most individual
2722 attributes the semantics this implies are not implemented.
2723 When attribute specifiers follow the @code{*} of a pointer
2724 declarator, they may be mixed with any type qualifiers present.
2725 The following describes the formal semantics of this syntax. It will make the
2726 most sense if you are familiar with the formal specification of
2727 declarators in the ISO C standard.
2729 Consider (as in C99 subclause 6.7.5 paragraph 4) a declaration @code{T
2730 D1}, where @code{T} contains declaration specifiers that specify a type
2731 @var{Type} (such as @code{int}) and @code{D1} is a declarator that
2732 contains an identifier @var{ident}. The type specified for @var{ident}
2733 for derived declarators whose type does not include an attribute
2734 specifier is as in the ISO C standard.
2736 If @code{D1} has the form @code{( @var{attribute-specifier-list} D )},
2737 and the declaration @code{T D} specifies the type
2738 ``@var{derived-declarator-type-list} @var{Type}'' for @var{ident}, then
2739 @code{T D1} specifies the type ``@var{derived-declarator-type-list}
2740 @var{attribute-specifier-list} @var{Type}'' for @var{ident}.
2742 If @code{D1} has the form @code{*
2743 @var{type-qualifier-and-attribute-specifier-list} D}, and the
2744 declaration @code{T D} specifies the type
2745 ``@var{derived-declarator-type-list} @var{Type}'' for @var{ident}, then
2746 @code{T D1} specifies the type ``@var{derived-declarator-type-list}
2747 @var{type-qualifier-and-attribute-specifier-list} @var{Type}'' for
2753 void (__attribute__((noreturn)) ****f) (void);
2757 specifies the type ``pointer to pointer to pointer to pointer to
2758 non-returning function returning @code{void}''. As another example,
2761 char *__attribute__((aligned(8))) *f;
2765 specifies the type ``pointer to 8-byte-aligned pointer to @code{char}''.
2766 Note again that this does not work with most attributes; for example,
2767 the usage of @samp{aligned} and @samp{noreturn} attributes given above
2768 is not yet supported.
2770 For compatibility with existing code written for compiler versions that
2771 did not implement attributes on nested declarators, some laxity is
2772 allowed in the placing of attributes. If an attribute that only applies
2773 to types is applied to a declaration, it will be treated as applying to
2774 the type of that declaration. If an attribute that only applies to
2775 declarations is applied to the type of a declaration, it will be treated
2776 as applying to that declaration; and, for compatibility with code
2777 placing the attributes immediately before the identifier declared, such
2778 an attribute applied to a function return type will be treated as
2779 applying to the function type, and such an attribute applied to an array
2780 element type will be treated as applying to the array type. If an
2781 attribute that only applies to function types is applied to a
2782 pointer-to-function type, it will be treated as applying to the pointer
2783 target type; if such an attribute is applied to a function return type
2784 that is not a pointer-to-function type, it will be treated as applying
2785 to the function type.
2787 @node Function Prototypes
2788 @section Prototypes and Old-Style Function Definitions
2789 @cindex function prototype declarations
2790 @cindex old-style function definitions
2791 @cindex promotion of formal parameters
2793 GNU C extends ISO C to allow a function prototype to override a later
2794 old-style non-prototype definition. Consider the following example:
2797 /* @r{Use prototypes unless the compiler is old-fashioned.} */
2804 /* @r{Prototype function declaration.} */
2805 int isroot P((uid_t));
2807 /* @r{Old-style function definition.} */
2809 isroot (x) /* @r{??? lossage here ???} */
2816 Suppose the type @code{uid_t} happens to be @code{short}. ISO C does
2817 not allow this example, because subword arguments in old-style
2818 non-prototype definitions are promoted. Therefore in this example the
2819 function definition's argument is really an @code{int}, which does not
2820 match the prototype argument type of @code{short}.
2822 This restriction of ISO C makes it hard to write code that is portable
2823 to traditional C compilers, because the programmer does not know
2824 whether the @code{uid_t} type is @code{short}, @code{int}, or
2825 @code{long}. Therefore, in cases like these GNU C allows a prototype
2826 to override a later old-style definition. More precisely, in GNU C, a
2827 function prototype argument type overrides the argument type specified
2828 by a later old-style definition if the former type is the same as the
2829 latter type before promotion. Thus in GNU C the above example is
2830 equivalent to the following:
2843 GNU C++ does not support old-style function definitions, so this
2844 extension is irrelevant.
2847 @section C++ Style Comments
2849 @cindex C++ comments
2850 @cindex comments, C++ style
2852 In GNU C, you may use C++ style comments, which start with @samp{//} and
2853 continue until the end of the line. Many other C implementations allow
2854 such comments, and they are included in the 1999 C standard. However,
2855 C++ style comments are not recognized if you specify an @option{-std}
2856 option specifying a version of ISO C before C99, or @option{-ansi}
2857 (equivalent to @option{-std=c89}).
2860 @section Dollar Signs in Identifier Names
2862 @cindex dollar signs in identifier names
2863 @cindex identifier names, dollar signs in
2865 In GNU C, you may normally use dollar signs in identifier names.
2866 This is because many traditional C implementations allow such identifiers.
2867 However, dollar signs in identifiers are not supported on a few target
2868 machines, typically because the target assembler does not allow them.
2870 @node Character Escapes
2871 @section The Character @key{ESC} in Constants
2873 You can use the sequence @samp{\e} in a string or character constant to
2874 stand for the ASCII character @key{ESC}.
2877 @section Inquiring on Alignment of Types or Variables
2879 @cindex type alignment
2880 @cindex variable alignment
2882 The keyword @code{__alignof__} allows you to inquire about how an object
2883 is aligned, or the minimum alignment usually required by a type. Its
2884 syntax is just like @code{sizeof}.
2886 For example, if the target machine requires a @code{double} value to be
2887 aligned on an 8-byte boundary, then @code{__alignof__ (double)} is 8.
2888 This is true on many RISC machines. On more traditional machine
2889 designs, @code{__alignof__ (double)} is 4 or even 2.
2891 Some machines never actually require alignment; they allow reference to any
2892 data type even at an odd address. For these machines, @code{__alignof__}
2893 reports the @emph{recommended} alignment of a type.
2895 If the operand of @code{__alignof__} is an lvalue rather than a type,
2896 its value is the required alignment for its type, taking into account
2897 any minimum alignment specified with GCC's @code{__attribute__}
2898 extension (@pxref{Variable Attributes}). For example, after this
2902 struct foo @{ int x; char y; @} foo1;
2906 the value of @code{__alignof__ (foo1.y)} is 1, even though its actual
2907 alignment is probably 2 or 4, the same as @code{__alignof__ (int)}.
2909 It is an error to ask for the alignment of an incomplete type.
2911 @node Variable Attributes
2912 @section Specifying Attributes of Variables
2913 @cindex attribute of variables
2914 @cindex variable attributes
2916 The keyword @code{__attribute__} allows you to specify special
2917 attributes of variables or structure fields. This keyword is followed
2918 by an attribute specification inside double parentheses. Some
2919 attributes are currently defined generically for variables.
2920 Other attributes are defined for variables on particular target
2921 systems. Other attributes are available for functions
2922 (@pxref{Function Attributes}) and for types (@pxref{Type Attributes}).
2923 Other front ends might define more attributes
2924 (@pxref{C++ Extensions,,Extensions to the C++ Language}).
2926 You may also specify attributes with @samp{__} preceding and following
2927 each keyword. This allows you to use them in header files without
2928 being concerned about a possible macro of the same name. For example,
2929 you may use @code{__aligned__} instead of @code{aligned}.
2931 @xref{Attribute Syntax}, for details of the exact syntax for using
2935 @cindex @code{aligned} attribute
2936 @item aligned (@var{alignment})
2937 This attribute specifies a minimum alignment for the variable or
2938 structure field, measured in bytes. For example, the declaration:
2941 int x __attribute__ ((aligned (16))) = 0;
2945 causes the compiler to allocate the global variable @code{x} on a
2946 16-byte boundary. On a 68040, this could be used in conjunction with
2947 an @code{asm} expression to access the @code{move16} instruction which
2948 requires 16-byte aligned operands.
2950 You can also specify the alignment of structure fields. For example, to
2951 create a double-word aligned @code{int} pair, you could write:
2954 struct foo @{ int x[2] __attribute__ ((aligned (8))); @};
2958 This is an alternative to creating a union with a @code{double} member
2959 that forces the union to be double-word aligned.
2961 As in the preceding examples, you can explicitly specify the alignment
2962 (in bytes) that you wish the compiler to use for a given variable or
2963 structure field. Alternatively, you can leave out the alignment factor
2964 and just ask the compiler to align a variable or field to the maximum
2965 useful alignment for the target machine you are compiling for. For
2966 example, you could write:
2969 short array[3] __attribute__ ((aligned));
2972 Whenever you leave out the alignment factor in an @code{aligned} attribute
2973 specification, the compiler automatically sets the alignment for the declared
2974 variable or field to the largest alignment which is ever used for any data
2975 type on the target machine you are compiling for. Doing this can often make
2976 copy operations more efficient, because the compiler can use whatever
2977 instructions copy the biggest chunks of memory when performing copies to
2978 or from the variables or fields that you have aligned this way.
2980 The @code{aligned} attribute can only increase the alignment; but you
2981 can decrease it by specifying @code{packed} as well. See below.
2983 Note that the effectiveness of @code{aligned} attributes may be limited
2984 by inherent limitations in your linker. On many systems, the linker is
2985 only able to arrange for variables to be aligned up to a certain maximum
2986 alignment. (For some linkers, the maximum supported alignment may
2987 be very very small.) If your linker is only able to align variables
2988 up to a maximum of 8 byte alignment, then specifying @code{aligned(16)}
2989 in an @code{__attribute__} will still only provide you with 8 byte
2990 alignment. See your linker documentation for further information.
2992 @item cleanup (@var{cleanup_function})
2993 @cindex @code{cleanup} attribute
2994 The @code{cleanup} attribute runs a function when the variable goes
2995 out of scope. This attribute can only be applied to auto function
2996 scope variables; it may not be applied to parameters or variables
2997 with static storage duration. The function must take one parameter,
2998 a pointer to a type compatible with the variable. The return value
2999 of the function (if any) is ignored.
3001 If @option{-fexceptions} is enabled, then @var{cleanup_function}
3002 will be run during the stack unwinding that happens during the
3003 processing of the exception. Note that the @code{cleanup} attribute
3004 does not allow the exception to be caught, only to perform an action.
3005 It is undefined what happens if @var{cleanup_function} does not
3010 @cindex @code{common} attribute
3011 @cindex @code{nocommon} attribute
3014 The @code{common} attribute requests GCC to place a variable in
3015 ``common'' storage. The @code{nocommon} attribute requests the
3016 opposite---to allocate space for it directly.
3018 These attributes override the default chosen by the
3019 @option{-fno-common} and @option{-fcommon} flags respectively.
3022 @cindex @code{deprecated} attribute
3023 The @code{deprecated} attribute results in a warning if the variable
3024 is used anywhere in the source file. This is useful when identifying
3025 variables that are expected to be removed in a future version of a
3026 program. The warning also includes the location of the declaration
3027 of the deprecated variable, to enable users to easily find further
3028 information about why the variable is deprecated, or what they should
3029 do instead. Note that the warning only occurs for uses:
3032 extern int old_var __attribute__ ((deprecated));
3034 int new_fn () @{ return old_var; @}
3037 results in a warning on line 3 but not line 2.
3039 The @code{deprecated} attribute can also be used for functions and
3040 types (@pxref{Function Attributes}, @pxref{Type Attributes}.)
3042 @item mode (@var{mode})
3043 @cindex @code{mode} attribute
3044 This attribute specifies the data type for the declaration---whichever
3045 type corresponds to the mode @var{mode}. This in effect lets you
3046 request an integer or floating point type according to its width.
3048 You may also specify a mode of @samp{byte} or @samp{__byte__} to
3049 indicate the mode corresponding to a one-byte integer, @samp{word} or
3050 @samp{__word__} for the mode of a one-word integer, and @samp{pointer}
3051 or @samp{__pointer__} for the mode used to represent pointers.
3054 @cindex @code{packed} attribute
3055 The @code{packed} attribute specifies that a variable or structure field
3056 should have the smallest possible alignment---one byte for a variable,
3057 and one bit for a field, unless you specify a larger value with the
3058 @code{aligned} attribute.
3060 Here is a structure in which the field @code{x} is packed, so that it
3061 immediately follows @code{a}:
3067 int x[2] __attribute__ ((packed));
3071 @item section ("@var{section-name}")
3072 @cindex @code{section} variable attribute
3073 Normally, the compiler places the objects it generates in sections like
3074 @code{data} and @code{bss}. Sometimes, however, you need additional sections,
3075 or you need certain particular variables to appear in special sections,
3076 for example to map to special hardware. The @code{section}
3077 attribute specifies that a variable (or function) lives in a particular
3078 section. For example, this small program uses several specific section names:
3081 struct duart a __attribute__ ((section ("DUART_A"))) = @{ 0 @};
3082 struct duart b __attribute__ ((section ("DUART_B"))) = @{ 0 @};
3083 char stack[10000] __attribute__ ((section ("STACK"))) = @{ 0 @};
3084 int init_data __attribute__ ((section ("INITDATA"))) = 0;
3088 /* @r{Initialize stack pointer} */
3089 init_sp (stack + sizeof (stack));
3091 /* @r{Initialize initialized data} */
3092 memcpy (&init_data, &data, &edata - &data);
3094 /* @r{Turn on the serial ports} */
3101 Use the @code{section} attribute with an @emph{initialized} definition
3102 of a @emph{global} variable, as shown in the example. GCC issues
3103 a warning and otherwise ignores the @code{section} attribute in
3104 uninitialized variable declarations.
3106 You may only use the @code{section} attribute with a fully initialized
3107 global definition because of the way linkers work. The linker requires
3108 each object be defined once, with the exception that uninitialized
3109 variables tentatively go in the @code{common} (or @code{bss}) section
3110 and can be multiply ``defined''. You can force a variable to be
3111 initialized with the @option{-fno-common} flag or the @code{nocommon}
3114 Some file formats do not support arbitrary sections so the @code{section}
3115 attribute is not available on all platforms.
3116 If you need to map the entire contents of a module to a particular
3117 section, consider using the facilities of the linker instead.
3120 @cindex @code{shared} variable attribute
3121 On Microsoft Windows, in addition to putting variable definitions in a named
3122 section, the section can also be shared among all running copies of an
3123 executable or DLL@. For example, this small program defines shared data
3124 by putting it in a named section @code{shared} and marking the section
3128 int foo __attribute__((section ("shared"), shared)) = 0;
3133 /* @r{Read and write foo. All running
3134 copies see the same value.} */
3140 You may only use the @code{shared} attribute along with @code{section}
3141 attribute with a fully initialized global definition because of the way
3142 linkers work. See @code{section} attribute for more information.
3144 The @code{shared} attribute is only available on Microsoft Windows@.
3146 @item tls_model ("@var{tls_model}")
3147 @cindex @code{tls_model} attribute
3148 The @code{tls_model} attribute sets thread-local storage model
3149 (@pxref{Thread-Local}) of a particular @code{__thread} variable,
3150 overriding @option{-ftls-model=} command line switch on a per-variable
3152 The @var{tls_model} argument should be one of @code{global-dynamic},
3153 @code{local-dynamic}, @code{initial-exec} or @code{local-exec}.
3155 Not all targets support this attribute.
3158 This attribute, attached to a variable, means that the variable is meant
3159 to be possibly unused. GCC will not produce a warning for this
3162 @item vector_size (@var{bytes})
3163 This attribute specifies the vector size for the variable, measured in
3164 bytes. For example, the declaration:
3167 int foo __attribute__ ((vector_size (16)));
3171 causes the compiler to set the mode for @code{foo}, to be 16 bytes,
3172 divided into @code{int} sized units. Assuming a 32-bit int (a vector of
3173 4 units of 4 bytes), the corresponding mode of @code{foo} will be V4SI@.
3175 This attribute is only applicable to integral and float scalars,
3176 although arrays, pointers, and function return values are allowed in
3177 conjunction with this construct.
3179 Aggregates with this attribute are invalid, even if they are of the same
3180 size as a corresponding scalar. For example, the declaration:
3183 struct S @{ int a; @};
3184 struct S __attribute__ ((vector_size (16))) foo;
3188 is invalid even if the size of the structure is the same as the size of
3192 The @code{selectany} attribute causes an initialized global variable to
3193 have link-once semantics. When multiple definitions of the variable are
3194 encountered by the linker, the first is selected and the remainder are
3195 discarded. Following usage by the Microsoft compiler, the linker is told
3196 @emph{not} to warn about size or content differences of the multiple
3199 Although the primary usage of this attribute is for POD types, the
3200 attribute can also be applied to global C++ objects that are initialized
3201 by a constructor. In this case, the static initialization and destruction
3202 code for the object is emitted in each translation defining the object,
3203 but the calls to the constructor and destructor are protected by a
3204 link-once guard variable.
3206 The @code{selectany} attribute is only available on Microsoft Windows
3207 targets. You can use @code{__declspec (selectany)} as a synonym for
3208 @code{__attribute__ ((selectany))} for compatibility with other
3212 The @code{weak} attribute is described in @xref{Function Attributes}.
3215 The @code{dllimport} attribute is described in @xref{Function Attributes}.
3218 The @code{dllexport} attribute is described in @xref{Function Attributes}.
3222 @subsection M32R/D Variable Attributes
3224 One attribute is currently defined for the M32R/D@.
3227 @item model (@var{model-name})
3228 @cindex variable addressability on the M32R/D
3229 Use this attribute on the M32R/D to set the addressability of an object.
3230 The identifier @var{model-name} is one of @code{small}, @code{medium},
3231 or @code{large}, representing each of the code models.
3233 Small model objects live in the lower 16MB of memory (so that their
3234 addresses can be loaded with the @code{ld24} instruction).
3236 Medium and large model objects may live anywhere in the 32-bit address space
3237 (the compiler will generate @code{seth/add3} instructions to load their
3241 @subsection i386 Variable Attributes
3243 Two attributes are currently defined for i386 configurations:
3244 @code{ms_struct} and @code{gcc_struct}
3249 @cindex @code{ms_struct} attribute
3250 @cindex @code{gcc_struct} attribute
3252 If @code{packed} is used on a structure, or if bit-fields are used
3253 it may be that the Microsoft ABI packs them differently
3254 than GCC would normally pack them. Particularly when moving packed
3255 data between functions compiled with GCC and the native Microsoft compiler
3256 (either via function call or as data in a file), it may be necessary to access
3259 Currently @option{-m[no-]ms-bitfields} is provided for the Microsoft Windows X86
3260 compilers to match the native Microsoft compiler.
3262 The Microsoft structure layout algorithm is fairly simple with the exception
3263 of the bitfield packing:
3265 The padding and alignment of members of structures and whether a bit field
3266 can straddle a storage-unit boundary
3269 @item Structure members are stored sequentially in the order in which they are
3270 declared: the first member has the lowest memory address and the last member
3273 @item Every data object has an alignment-requirement. The alignment-requirement
3274 for all data except structures, unions, and arrays is either the size of the
3275 object or the current packing size (specified with either the aligned attribute
3276 or the pack pragma), whichever is less. For structures, unions, and arrays,
3277 the alignment-requirement is the largest alignment-requirement of its members.
3278 Every object is allocated an offset so that:
3280 offset % alignment-requirement == 0
3282 @item Adjacent bit fields are packed into the same 1-, 2-, or 4-byte allocation
3283 unit if the integral types are the same size and if the next bit field fits
3284 into the current allocation unit without crossing the boundary imposed by the
3285 common alignment requirements of the bit fields.
3288 Handling of zero-length bitfields:
3290 MSVC interprets zero-length bitfields in the following ways:
3293 @item If a zero-length bitfield is inserted between two bitfields that would
3294 normally be coalesced, the bitfields will not be coalesced.
3301 unsigned long bf_1 : 12;
3303 unsigned long bf_2 : 12;
3307 The size of @code{t1} would be 8 bytes with the zero-length bitfield. If the
3308 zero-length bitfield were removed, @code{t1}'s size would be 4 bytes.
3310 @item If a zero-length bitfield is inserted after a bitfield, @code{foo}, and the
3311 alignment of the zero-length bitfield is greater than the member that follows it,
3312 @code{bar}, @code{bar} will be aligned as the type of the zero-length bitfield.
3332 For @code{t2}, @code{bar} will be placed at offset 2, rather than offset 1.
3333 Accordingly, the size of @code{t2} will be 4. For @code{t3}, the zero-length
3334 bitfield will not affect the alignment of @code{bar} or, as a result, the size
3337 Taking this into account, it is important to note the following:
3340 @item If a zero-length bitfield follows a normal bitfield, the type of the
3341 zero-length bitfield may affect the alignment of the structure as whole. For
3342 example, @code{t2} has a size of 4 bytes, since the zero-length bitfield follows a
3343 normal bitfield, and is of type short.
3345 @item Even if a zero-length bitfield is not followed by a normal bitfield, it may
3346 still affect the alignment of the structure:
3356 Here, @code{t4} will take up 4 bytes.
3359 @item Zero-length bitfields following non-bitfield members are ignored:
3370 Here, @code{t5} will take up 2 bytes.
3374 @subsection Xstormy16 Variable Attributes
3376 One attribute is currently defined for xstormy16 configurations:
3381 @cindex @code{below100} attribute
3383 If a variable has the @code{below100} attribute (@code{BELOW100} is
3384 allowed also), GCC will place the variable in the first 0x100 bytes of
3385 memory and use special opcodes to access it. Such variables will be
3386 placed in either the @code{.bss_below100} section or the
3387 @code{.data_below100} section.
3391 @node Type Attributes
3392 @section Specifying Attributes of Types
3393 @cindex attribute of types
3394 @cindex type attributes
3396 The keyword @code{__attribute__} allows you to specify special
3397 attributes of @code{struct} and @code{union} types when you define
3398 such types. This keyword is followed by an attribute specification
3399 inside double parentheses. Seven attributes are currently defined for
3400 types: @code{aligned}, @code{packed}, @code{transparent_union},
3401 @code{unused}, @code{deprecated}, @code{visibility}, and
3402 @code{may_alias}. Other attributes are defined for functions
3403 (@pxref{Function Attributes}) and for variables (@pxref{Variable
3406 You may also specify any one of these attributes with @samp{__}
3407 preceding and following its keyword. This allows you to use these
3408 attributes in header files without being concerned about a possible
3409 macro of the same name. For example, you may use @code{__aligned__}
3410 instead of @code{aligned}.
3412 You may specify type attributes either in a @code{typedef} declaration
3413 or in an enum, struct or union type declaration or definition.
3415 For an enum, struct or union type, you may specify attributes either
3416 between the enum, struct or union tag and the name of the type, or
3417 just past the closing curly brace of the @emph{definition}. The
3418 former syntax is preferred.
3420 @xref{Attribute Syntax}, for details of the exact syntax for using
3424 @cindex @code{aligned} attribute
3425 @item aligned (@var{alignment})
3426 This attribute specifies a minimum alignment (in bytes) for variables
3427 of the specified type. For example, the declarations:
3430 struct S @{ short f[3]; @} __attribute__ ((aligned (8)));
3431 typedef int more_aligned_int __attribute__ ((aligned (8)));
3435 force the compiler to insure (as far as it can) that each variable whose
3436 type is @code{struct S} or @code{more_aligned_int} will be allocated and
3437 aligned @emph{at least} on a 8-byte boundary. On a SPARC, having all
3438 variables of type @code{struct S} aligned to 8-byte boundaries allows
3439 the compiler to use the @code{ldd} and @code{std} (doubleword load and
3440 store) instructions when copying one variable of type @code{struct S} to
3441 another, thus improving run-time efficiency.
3443 Note that the alignment of any given @code{struct} or @code{union} type
3444 is required by the ISO C standard to be at least a perfect multiple of
3445 the lowest common multiple of the alignments of all of the members of
3446 the @code{struct} or @code{union} in question. This means that you @emph{can}
3447 effectively adjust the alignment of a @code{struct} or @code{union}
3448 type by attaching an @code{aligned} attribute to any one of the members
3449 of such a type, but the notation illustrated in the example above is a
3450 more obvious, intuitive, and readable way to request the compiler to
3451 adjust the alignment of an entire @code{struct} or @code{union} type.
3453 As in the preceding example, you can explicitly specify the alignment
3454 (in bytes) that you wish the compiler to use for a given @code{struct}
3455 or @code{union} type. Alternatively, you can leave out the alignment factor
3456 and just ask the compiler to align a type to the maximum
3457 useful alignment for the target machine you are compiling for. For
3458 example, you could write:
3461 struct S @{ short f[3]; @} __attribute__ ((aligned));
3464 Whenever you leave out the alignment factor in an @code{aligned}
3465 attribute specification, the compiler automatically sets the alignment
3466 for the type to the largest alignment which is ever used for any data
3467 type on the target machine you are compiling for. Doing this can often
3468 make copy operations more efficient, because the compiler can use
3469 whatever instructions copy the biggest chunks of memory when performing
3470 copies to or from the variables which have types that you have aligned
3473 In the example above, if the size of each @code{short} is 2 bytes, then
3474 the size of the entire @code{struct S} type is 6 bytes. The smallest
3475 power of two which is greater than or equal to that is 8, so the
3476 compiler sets the alignment for the entire @code{struct S} type to 8
3479 Note that although you can ask the compiler to select a time-efficient
3480 alignment for a given type and then declare only individual stand-alone
3481 objects of that type, the compiler's ability to select a time-efficient
3482 alignment is primarily useful only when you plan to create arrays of
3483 variables having the relevant (efficiently aligned) type. If you
3484 declare or use arrays of variables of an efficiently-aligned type, then
3485 it is likely that your program will also be doing pointer arithmetic (or
3486 subscripting, which amounts to the same thing) on pointers to the
3487 relevant type, and the code that the compiler generates for these
3488 pointer arithmetic operations will often be more efficient for
3489 efficiently-aligned types than for other types.
3491 The @code{aligned} attribute can only increase the alignment; but you
3492 can decrease it by specifying @code{packed} as well. See below.
3494 Note that the effectiveness of @code{aligned} attributes may be limited
3495 by inherent limitations in your linker. On many systems, the linker is
3496 only able to arrange for variables to be aligned up to a certain maximum
3497 alignment. (For some linkers, the maximum supported alignment may
3498 be very very small.) If your linker is only able to align variables
3499 up to a maximum of 8 byte alignment, then specifying @code{aligned(16)}
3500 in an @code{__attribute__} will still only provide you with 8 byte
3501 alignment. See your linker documentation for further information.
3504 This attribute, attached to @code{struct} or @code{union} type
3505 definition, specifies that each member (other than zero-width bitfields)
3506 of the structure or union is placed to minimize the memory required. When
3507 attached to an @code{enum} definition, it indicates that the smallest
3508 integral type should be used.
3510 @opindex fshort-enums
3511 Specifying this attribute for @code{struct} and @code{union} types is
3512 equivalent to specifying the @code{packed} attribute on each of the
3513 structure or union members. Specifying the @option{-fshort-enums}
3514 flag on the line is equivalent to specifying the @code{packed}
3515 attribute on all @code{enum} definitions.
3517 In the following example @code{struct my_packed_struct}'s members are
3518 packed closely together, but the internal layout of its @code{s} member
3519 is not packed---to do that, @code{struct my_unpacked_struct} would need to
3523 struct my_unpacked_struct
3529 struct __attribute__ ((__packed__)) my_packed_struct
3533 struct my_unpacked_struct s;
3537 You may only specify this attribute on the definition of a @code{enum},
3538 @code{struct} or @code{union}, not on a @code{typedef} which does not
3539 also define the enumerated type, structure or union.
3541 @item transparent_union
3542 This attribute, attached to a @code{union} type definition, indicates
3543 that any function parameter having that union type causes calls to that
3544 function to be treated in a special way.
3546 First, the argument corresponding to a transparent union type can be of
3547 any type in the union; no cast is required. Also, if the union contains
3548 a pointer type, the corresponding argument can be a null pointer
3549 constant or a void pointer expression; and if the union contains a void
3550 pointer type, the corresponding argument can be any pointer expression.
3551 If the union member type is a pointer, qualifiers like @code{const} on
3552 the referenced type must be respected, just as with normal pointer
3555 Second, the argument is passed to the function using the calling
3556 conventions of the first member of the transparent union, not the calling
3557 conventions of the union itself. All members of the union must have the
3558 same machine representation; this is necessary for this argument passing
3561 Transparent unions are designed for library functions that have multiple
3562 interfaces for compatibility reasons. For example, suppose the
3563 @code{wait} function must accept either a value of type @code{int *} to
3564 comply with Posix, or a value of type @code{union wait *} to comply with
3565 the 4.1BSD interface. If @code{wait}'s parameter were @code{void *},
3566 @code{wait} would accept both kinds of arguments, but it would also
3567 accept any other pointer type and this would make argument type checking
3568 less useful. Instead, @code{<sys/wait.h>} might define the interface
3576 @} wait_status_ptr_t __attribute__ ((__transparent_union__));
3578 pid_t wait (wait_status_ptr_t);
3581 This interface allows either @code{int *} or @code{union wait *}
3582 arguments to be passed, using the @code{int *} calling convention.
3583 The program can call @code{wait} with arguments of either type:
3586 int w1 () @{ int w; return wait (&w); @}
3587 int w2 () @{ union wait w; return wait (&w); @}
3590 With this interface, @code{wait}'s implementation might look like this:
3593 pid_t wait (wait_status_ptr_t p)
3595 return waitpid (-1, p.__ip, 0);
3600 When attached to a type (including a @code{union} or a @code{struct}),
3601 this attribute means that variables of that type are meant to appear
3602 possibly unused. GCC will not produce a warning for any variables of
3603 that type, even if the variable appears to do nothing. This is often
3604 the case with lock or thread classes, which are usually defined and then
3605 not referenced, but contain constructors and destructors that have
3606 nontrivial bookkeeping functions.
3609 The @code{deprecated} attribute results in a warning if the type
3610 is used anywhere in the source file. This is useful when identifying
3611 types that are expected to be removed in a future version of a program.
3612 If possible, the warning also includes the location of the declaration
3613 of the deprecated type, to enable users to easily find further
3614 information about why the type is deprecated, or what they should do
3615 instead. Note that the warnings only occur for uses and then only
3616 if the type is being applied to an identifier that itself is not being
3617 declared as deprecated.
3620 typedef int T1 __attribute__ ((deprecated));
3624 typedef T1 T3 __attribute__ ((deprecated));
3625 T3 z __attribute__ ((deprecated));
3628 results in a warning on line 2 and 3 but not lines 4, 5, or 6. No
3629 warning is issued for line 4 because T2 is not explicitly
3630 deprecated. Line 5 has no warning because T3 is explicitly
3631 deprecated. Similarly for line 6.
3633 The @code{deprecated} attribute can also be used for functions and
3634 variables (@pxref{Function Attributes}, @pxref{Variable Attributes}.)
3637 Accesses to objects with types with this attribute are not subjected to
3638 type-based alias analysis, but are instead assumed to be able to alias
3639 any other type of objects, just like the @code{char} type. See
3640 @option{-fstrict-aliasing} for more information on aliasing issues.
3645 typedef short __attribute__((__may_alias__)) short_a;
3651 short_a *b = (short_a *) &a;
3655 if (a == 0x12345678)
3662 If you replaced @code{short_a} with @code{short} in the variable
3663 declaration, the above program would abort when compiled with
3664 @option{-fstrict-aliasing}, which is on by default at @option{-O2} or
3665 above in recent GCC versions.
3669 In C++, attribute visibility (@pxref{Function Attributes}) can also be
3670 applied to class, struct, union and enum types. Unlike other type
3671 attributes, the attribute must appear between the initial keyword and
3672 the name of the type; it cannot appear after the body of the type.
3674 Note that the type visibility is applied to vague linkage entities
3675 associated with the class (vtable, typeinfo node, etc.). In
3676 particular, if a class is thrown as an exception in one shared object
3677 and caught in another, the class must have default visibility.
3678 Otherwise the two shared objects will be unable to use the same
3679 typeinfo node and exception handling will break.
3681 @subsection ARM Type Attributes
3683 On those ARM targets that support @code{dllimport} (such as Symbian
3684 OS), you can use the @code{notshared} attribute to indicate that the
3685 virtual table and other similar data for a class should not be
3686 exported from a DLL@. For example:
3689 class __declspec(notshared) C @{
3691 __declspec(dllimport) C();
3695 __declspec(dllexport)
3699 In this code, @code{C::C} is exported from the current DLL, but the
3700 virtual table for @code{C} is not exported. (You can use
3701 @code{__attribute__} instead of @code{__declspec} if you prefer, but
3702 most Symbian OS code uses @code{__declspec}.)
3704 @subsection i386 Type Attributes
3706 Two attributes are currently defined for i386 configurations:
3707 @code{ms_struct} and @code{gcc_struct}
3711 @cindex @code{ms_struct}
3712 @cindex @code{gcc_struct}
3714 If @code{packed} is used on a structure, or if bit-fields are used
3715 it may be that the Microsoft ABI packs them differently
3716 than GCC would normally pack them. Particularly when moving packed
3717 data between functions compiled with GCC and the native Microsoft compiler
3718 (either via function call or as data in a file), it may be necessary to access
3721 Currently @option{-m[no-]ms-bitfields} is provided for the Microsoft Windows X86
3722 compilers to match the native Microsoft compiler.
3725 To specify multiple attributes, separate them by commas within the
3726 double parentheses: for example, @samp{__attribute__ ((aligned (16),
3730 @section An Inline Function is As Fast As a Macro
3731 @cindex inline functions
3732 @cindex integrating function code
3734 @cindex macros, inline alternative
3736 By declaring a function @code{inline}, you can direct GCC to
3737 integrate that function's code into the code for its callers. This
3738 makes execution faster by eliminating the function-call overhead; in
3739 addition, if any of the actual argument values are constant, their known
3740 values may permit simplifications at compile time so that not all of the
3741 inline function's code needs to be included. The effect on code size is
3742 less predictable; object code may be larger or smaller with function
3743 inlining, depending on the particular case. Inlining of functions is an
3744 optimization and it really ``works'' only in optimizing compilation. If
3745 you don't use @option{-O}, no function is really inline.
3747 Inline functions are included in the ISO C99 standard, but there are
3748 currently substantial differences between what GCC implements and what
3749 the ISO C99 standard requires.
3751 To declare a function inline, use the @code{inline} keyword in its
3752 declaration, like this:
3762 (If you are writing a header file to be included in ISO C programs, write
3763 @code{__inline__} instead of @code{inline}. @xref{Alternate Keywords}.)
3764 You can also make all ``simple enough'' functions inline with the option
3765 @option{-finline-functions}.
3768 Note that certain usages in a function definition can make it unsuitable
3769 for inline substitution. Among these usages are: use of varargs, use of
3770 alloca, use of variable sized data types (@pxref{Variable Length}),
3771 use of computed goto (@pxref{Labels as Values}), use of nonlocal goto,
3772 and nested functions (@pxref{Nested Functions}). Using @option{-Winline}
3773 will warn when a function marked @code{inline} could not be substituted,
3774 and will give the reason for the failure.
3776 Note that in C and Objective-C, unlike C++, the @code{inline} keyword
3777 does not affect the linkage of the function.
3779 @cindex automatic @code{inline} for C++ member fns
3780 @cindex @code{inline} automatic for C++ member fns
3781 @cindex member fns, automatically @code{inline}
3782 @cindex C++ member fns, automatically @code{inline}
3783 @opindex fno-default-inline
3784 GCC automatically inlines member functions defined within the class
3785 body of C++ programs even if they are not explicitly declared
3786 @code{inline}. (You can override this with @option{-fno-default-inline};
3787 @pxref{C++ Dialect Options,,Options Controlling C++ Dialect}.)
3789 @cindex inline functions, omission of
3790 @opindex fkeep-inline-functions
3791 When a function is both inline and @code{static}, if all calls to the
3792 function are integrated into the caller, and the function's address is
3793 never used, then the function's own assembler code is never referenced.
3794 In this case, GCC does not actually output assembler code for the
3795 function, unless you specify the option @option{-fkeep-inline-functions}.
3796 Some calls cannot be integrated for various reasons (in particular,
3797 calls that precede the function's definition cannot be integrated, and
3798 neither can recursive calls within the definition). If there is a
3799 nonintegrated call, then the function is compiled to assembler code as
3800 usual. The function must also be compiled as usual if the program
3801 refers to its address, because that can't be inlined.
3803 @cindex non-static inline function
3804 When an inline function is not @code{static}, then the compiler must assume
3805 that there may be calls from other source files; since a global symbol can
3806 be defined only once in any program, the function must not be defined in
3807 the other source files, so the calls therein cannot be integrated.
3808 Therefore, a non-@code{static} inline function is always compiled on its
3809 own in the usual fashion.
3811 If you specify both @code{inline} and @code{extern} in the function
3812 definition, then the definition is used only for inlining. In no case
3813 is the function compiled on its own, not even if you refer to its
3814 address explicitly. Such an address becomes an external reference, as
3815 if you had only declared the function, and had not defined it.
3817 This combination of @code{inline} and @code{extern} has almost the
3818 effect of a macro. The way to use it is to put a function definition in
3819 a header file with these keywords, and put another copy of the
3820 definition (lacking @code{inline} and @code{extern}) in a library file.
3821 The definition in the header file will cause most calls to the function
3822 to be inlined. If any uses of the function remain, they will refer to
3823 the single copy in the library.
3825 Since GCC eventually will implement ISO C99 semantics for
3826 inline functions, it is best to use @code{static inline} only
3827 to guarantee compatibility. (The
3828 existing semantics will remain available when @option{-std=gnu89} is
3829 specified, but eventually the default will be @option{-std=gnu99} and
3830 that will implement the C99 semantics, though it does not do so yet.)
3832 GCC does not inline any functions when not optimizing unless you specify
3833 the @samp{always_inline} attribute for the function, like this:
3836 /* @r{Prototype.} */
3837 inline void foo (const char) __attribute__((always_inline));
3841 @section Assembler Instructions with C Expression Operands
3842 @cindex extended @code{asm}
3843 @cindex @code{asm} expressions
3844 @cindex assembler instructions
3847 In an assembler instruction using @code{asm}, you can specify the
3848 operands of the instruction using C expressions. This means you need not
3849 guess which registers or memory locations will contain the data you want
3852 You must specify an assembler instruction template much like what
3853 appears in a machine description, plus an operand constraint string for
3856 For example, here is how to use the 68881's @code{fsinx} instruction:
3859 asm ("fsinx %1,%0" : "=f" (result) : "f" (angle));
3863 Here @code{angle} is the C expression for the input operand while
3864 @code{result} is that of the output operand. Each has @samp{"f"} as its
3865 operand constraint, saying that a floating point register is required.
3866 The @samp{=} in @samp{=f} indicates that the operand is an output; all
3867 output operands' constraints must use @samp{=}. The constraints use the
3868 same language used in the machine description (@pxref{Constraints}).
3870 Each operand is described by an operand-constraint string followed by
3871 the C expression in parentheses. A colon separates the assembler
3872 template from the first output operand and another separates the last
3873 output operand from the first input, if any. Commas separate the
3874 operands within each group. The total number of operands is currently
3875 limited to 30; this limitation may be lifted in some future version of
3878 If there are no output operands but there are input operands, you must
3879 place two consecutive colons surrounding the place where the output
3882 As of GCC version 3.1, it is also possible to specify input and output
3883 operands using symbolic names which can be referenced within the
3884 assembler code. These names are specified inside square brackets
3885 preceding the constraint string, and can be referenced inside the
3886 assembler code using @code{%[@var{name}]} instead of a percentage sign
3887 followed by the operand number. Using named operands the above example
3891 asm ("fsinx %[angle],%[output]"
3892 : [output] "=f" (result)
3893 : [angle] "f" (angle));
3897 Note that the symbolic operand names have no relation whatsoever to
3898 other C identifiers. You may use any name you like, even those of
3899 existing C symbols, but you must ensure that no two operands within the same
3900 assembler construct use the same symbolic name.
3902 Output operand expressions must be lvalues; the compiler can check this.
3903 The input operands need not be lvalues. The compiler cannot check
3904 whether the operands have data types that are reasonable for the
3905 instruction being executed. It does not parse the assembler instruction
3906 template and does not know what it means or even whether it is valid
3907 assembler input. The extended @code{asm} feature is most often used for
3908 machine instructions the compiler itself does not know exist. If
3909 the output expression cannot be directly addressed (for example, it is a
3910 bit-field), your constraint must allow a register. In that case, GCC
3911 will use the register as the output of the @code{asm}, and then store
3912 that register into the output.
3914 The ordinary output operands must be write-only; GCC will assume that
3915 the values in these operands before the instruction are dead and need
3916 not be generated. Extended asm supports input-output or read-write
3917 operands. Use the constraint character @samp{+} to indicate such an
3918 operand and list it with the output operands. You should only use
3919 read-write operands when the constraints for the operand (or the
3920 operand in which only some of the bits are to be changed) allow a
3923 You may, as an alternative, logically split its function into two
3924 separate operands, one input operand and one write-only output
3925 operand. The connection between them is expressed by constraints
3926 which say they need to be in the same location when the instruction
3927 executes. You can use the same C expression for both operands, or
3928 different expressions. For example, here we write the (fictitious)
3929 @samp{combine} instruction with @code{bar} as its read-only source
3930 operand and @code{foo} as its read-write destination:
3933 asm ("combine %2,%0" : "=r" (foo) : "0" (foo), "g" (bar));
3937 The constraint @samp{"0"} for operand 1 says that it must occupy the
3938 same location as operand 0. A number in constraint is allowed only in
3939 an input operand and it must refer to an output operand.
3941 Only a number in the constraint can guarantee that one operand will be in
3942 the same place as another. The mere fact that @code{foo} is the value
3943 of both operands is not enough to guarantee that they will be in the
3944 same place in the generated assembler code. The following would not
3948 asm ("combine %2,%0" : "=r" (foo) : "r" (foo), "g" (bar));
3951 Various optimizations or reloading could cause operands 0 and 1 to be in
3952 different registers; GCC knows no reason not to do so. For example, the
3953 compiler might find a copy of the value of @code{foo} in one register and
3954 use it for operand 1, but generate the output operand 0 in a different
3955 register (copying it afterward to @code{foo}'s own address). Of course,
3956 since the register for operand 1 is not even mentioned in the assembler
3957 code, the result will not work, but GCC can't tell that.
3959 As of GCC version 3.1, one may write @code{[@var{name}]} instead of
3960 the operand number for a matching constraint. For example:
3963 asm ("cmoveq %1,%2,%[result]"
3964 : [result] "=r"(result)
3965 : "r" (test), "r"(new), "[result]"(old));
3968 Sometimes you need to make an @code{asm} operand be a specific register,
3969 but there's no matching constraint letter for that register @emph{by
3970 itself}. To force the operand into that register, use a local variable
3971 for the operand and specify the register in the variable declaration.
3972 @xref{Explicit Reg Vars}. Then for the @code{asm} operand, use any
3973 register constraint letter that matches the register:
3976 register int *p1 asm ("r0") = @dots{};
3977 register int *p2 asm ("r1") = @dots{};
3978 register int *result asm ("r0");
3979 asm ("sysint" : "=r" (result) : "0" (p1), "r" (p2));
3982 @anchor{Example of asm with clobbered asm reg}
3983 In the above example, beware that a register that is call-clobbered by
3984 the target ABI will be overwritten by any function call in the
3985 assignment, including library calls for arithmetic operators.
3986 Assuming it is a call-clobbered register, this may happen to @code{r0}
3987 above by the assignment to @code{p2}. If you have to use such a
3988 register, use temporary variables for expressions between the register
3993 register int *p1 asm ("r0") = @dots{};
3994 register int *p2 asm ("r1") = t1;
3995 register int *result asm ("r0");
3996 asm ("sysint" : "=r" (result) : "0" (p1), "r" (p2));
3999 Some instructions clobber specific hard registers. To describe this,
4000 write a third colon after the input operands, followed by the names of
4001 the clobbered hard registers (given as strings). Here is a realistic
4002 example for the VAX:
4005 asm volatile ("movc3 %0,%1,%2"
4006 : /* @r{no outputs} */
4007 : "g" (from), "g" (to), "g" (count)
4008 : "r0", "r1", "r2", "r3", "r4", "r5");
4011 You may not write a clobber description in a way that overlaps with an
4012 input or output operand. For example, you may not have an operand
4013 describing a register class with one member if you mention that register
4014 in the clobber list. Variables declared to live in specific registers
4015 (@pxref{Explicit Reg Vars}), and used as asm input or output operands must
4016 have no part mentioned in the clobber description.
4017 There is no way for you to specify that an input
4018 operand is modified without also specifying it as an output
4019 operand. Note that if all the output operands you specify are for this
4020 purpose (and hence unused), you will then also need to specify
4021 @code{volatile} for the @code{asm} construct, as described below, to
4022 prevent GCC from deleting the @code{asm} statement as unused.
4024 If you refer to a particular hardware register from the assembler code,
4025 you will probably have to list the register after the third colon to
4026 tell the compiler the register's value is modified. In some assemblers,
4027 the register names begin with @samp{%}; to produce one @samp{%} in the
4028 assembler code, you must write @samp{%%} in the input.
4030 If your assembler instruction can alter the condition code register, add
4031 @samp{cc} to the list of clobbered registers. GCC on some machines
4032 represents the condition codes as a specific hardware register;
4033 @samp{cc} serves to name this register. On other machines, the
4034 condition code is handled differently, and specifying @samp{cc} has no
4035 effect. But it is valid no matter what the machine.
4037 If your assembler instructions access memory in an unpredictable
4038 fashion, add @samp{memory} to the list of clobbered registers. This
4039 will cause GCC to not keep memory values cached in registers across the
4040 assembler instruction and not optimize stores or loads to that memory.
4041 You will also want to add the @code{volatile} keyword if the memory
4042 affected is not listed in the inputs or outputs of the @code{asm}, as
4043 the @samp{memory} clobber does not count as a side-effect of the
4044 @code{asm}. If you know how large the accessed memory is, you can add
4045 it as input or output but if this is not known, you should add
4046 @samp{memory}. As an example, if you access ten bytes of a string, you
4047 can use a memory input like:
4050 @{"m"( (@{ struct @{ char x[10]; @} *p = (void *)ptr ; *p; @}) )@}.
4053 Note that in the following example the memory input is necessary,
4054 otherwise GCC might optimize the store to @code{x} away:
4061 asm ("magic stuff accessing an 'int' pointed to by '%1'"
4062 "=&d" (r) : "a" (y), "m" (*y));
4067 You can put multiple assembler instructions together in a single
4068 @code{asm} template, separated by the characters normally used in assembly
4069 code for the system. A combination that works in most places is a newline
4070 to break the line, plus a tab character to move to the instruction field
4071 (written as @samp{\n\t}). Sometimes semicolons can be used, if the
4072 assembler allows semicolons as a line-breaking character. Note that some
4073 assembler dialects use semicolons to start a comment.
4074 The input operands are guaranteed not to use any of the clobbered
4075 registers, and neither will the output operands' addresses, so you can
4076 read and write the clobbered registers as many times as you like. Here
4077 is an example of multiple instructions in a template; it assumes the
4078 subroutine @code{_foo} accepts arguments in registers 9 and 10:
4081 asm ("movl %0,r9\n\tmovl %1,r10\n\tcall _foo"
4083 : "g" (from), "g" (to)
4087 Unless an output operand has the @samp{&} constraint modifier, GCC
4088 may allocate it in the same register as an unrelated input operand, on
4089 the assumption the inputs are consumed before the outputs are produced.
4090 This assumption may be false if the assembler code actually consists of
4091 more than one instruction. In such a case, use @samp{&} for each output
4092 operand that may not overlap an input. @xref{Modifiers}.
4094 If you want to test the condition code produced by an assembler
4095 instruction, you must include a branch and a label in the @code{asm}
4096 construct, as follows:
4099 asm ("clr %0\n\tfrob %1\n\tbeq 0f\n\tmov #1,%0\n0:"
4105 This assumes your assembler supports local labels, as the GNU assembler
4106 and most Unix assemblers do.
4108 Speaking of labels, jumps from one @code{asm} to another are not
4109 supported. The compiler's optimizers do not know about these jumps, and
4110 therefore they cannot take account of them when deciding how to
4113 @cindex macros containing @code{asm}
4114 Usually the most convenient way to use these @code{asm} instructions is to
4115 encapsulate them in macros that look like functions. For example,
4119 (@{ double __value, __arg = (x); \
4120 asm ("fsinx %1,%0": "=f" (__value): "f" (__arg)); \
4125 Here the variable @code{__arg} is used to make sure that the instruction
4126 operates on a proper @code{double} value, and to accept only those
4127 arguments @code{x} which can convert automatically to a @code{double}.
4129 Another way to make sure the instruction operates on the correct data
4130 type is to use a cast in the @code{asm}. This is different from using a
4131 variable @code{__arg} in that it converts more different types. For
4132 example, if the desired type were @code{int}, casting the argument to
4133 @code{int} would accept a pointer with no complaint, while assigning the
4134 argument to an @code{int} variable named @code{__arg} would warn about
4135 using a pointer unless the caller explicitly casts it.
4137 If an @code{asm} has output operands, GCC assumes for optimization
4138 purposes the instruction has no side effects except to change the output
4139 operands. This does not mean instructions with a side effect cannot be
4140 used, but you must be careful, because the compiler may eliminate them
4141 if the output operands aren't used, or move them out of loops, or
4142 replace two with one if they constitute a common subexpression. Also,
4143 if your instruction does have a side effect on a variable that otherwise
4144 appears not to change, the old value of the variable may be reused later
4145 if it happens to be found in a register.
4147 You can prevent an @code{asm} instruction from being deleted
4148 by writing the keyword @code{volatile} after
4149 the @code{asm}. For example:
4152 #define get_and_set_priority(new) \
4154 asm volatile ("get_and_set_priority %0, %1" \
4155 : "=g" (__old) : "g" (new)); \
4160 The @code{volatile} keyword indicates that the instruction has
4161 important side-effects. GCC will not delete a volatile @code{asm} if
4162 it is reachable. (The instruction can still be deleted if GCC can
4163 prove that control-flow will never reach the location of the
4164 instruction.) Note that even a volatile @code{asm} instruction
4165 can be moved relative to other code, including across jump
4166 instructions. For example, on many targets there is a system
4167 register which can be set to control the rounding mode of
4168 floating point operations. You might try
4169 setting it with a volatile @code{asm}, like this PowerPC example:
4172 asm volatile("mtfsf 255,%0" : : "f" (fpenv));
4177 This will not work reliably, as the compiler may move the addition back
4178 before the volatile @code{asm}. To make it work you need to add an
4179 artificial dependency to the @code{asm} referencing a variable in the code
4180 you don't want moved, for example:
4183 asm volatile ("mtfsf 255,%1" : "=X"(sum): "f"(fpenv));
4187 Similarly, you can't expect a
4188 sequence of volatile @code{asm} instructions to remain perfectly
4189 consecutive. If you want consecutive output, use a single @code{asm}.
4190 Also, GCC will perform some optimizations across a volatile @code{asm}
4191 instruction; GCC does not ``forget everything'' when it encounters
4192 a volatile @code{asm} instruction the way some other compilers do.
4194 An @code{asm} instruction without any output operands will be treated
4195 identically to a volatile @code{asm} instruction.
4197 It is a natural idea to look for a way to give access to the condition
4198 code left by the assembler instruction. However, when we attempted to
4199 implement this, we found no way to make it work reliably. The problem
4200 is that output operands might need reloading, which would result in
4201 additional following ``store'' instructions. On most machines, these
4202 instructions would alter the condition code before there was time to
4203 test it. This problem doesn't arise for ordinary ``test'' and
4204 ``compare'' instructions because they don't have any output operands.
4206 For reasons similar to those described above, it is not possible to give
4207 an assembler instruction access to the condition code left by previous
4210 If you are writing a header file that should be includable in ISO C
4211 programs, write @code{__asm__} instead of @code{asm}. @xref{Alternate
4214 @subsection Size of an @code{asm}
4216 Some targets require that GCC track the size of each instruction used in
4217 order to generate correct code. Because the final length of an
4218 @code{asm} is only known by the assembler, GCC must make an estimate as
4219 to how big it will be. The estimate is formed by counting the number of
4220 statements in the pattern of the @code{asm} and multiplying that by the
4221 length of the longest instruction on that processor. Statements in the
4222 @code{asm} are identified by newline characters and whatever statement
4223 separator characters are supported by the assembler; on most processors
4224 this is the `@code{;}' character.
4226 Normally, GCC's estimate is perfectly adequate to ensure that correct
4227 code is generated, but it is possible to confuse the compiler if you use
4228 pseudo instructions or assembler macros that expand into multiple real
4229 instructions or if you use assembler directives that expand to more
4230 space in the object file than would be needed for a single instruction.
4231 If this happens then the assembler will produce a diagnostic saying that
4232 a label is unreachable.
4234 @subsection i386 floating point asm operands
4236 There are several rules on the usage of stack-like regs in
4237 asm_operands insns. These rules apply only to the operands that are
4242 Given a set of input regs that die in an asm_operands, it is
4243 necessary to know which are implicitly popped by the asm, and
4244 which must be explicitly popped by gcc.
4246 An input reg that is implicitly popped by the asm must be
4247 explicitly clobbered, unless it is constrained to match an
4251 For any input reg that is implicitly popped by an asm, it is
4252 necessary to know how to adjust the stack to compensate for the pop.
4253 If any non-popped input is closer to the top of the reg-stack than
4254 the implicitly popped reg, it would not be possible to know what the
4255 stack looked like---it's not clear how the rest of the stack ``slides
4258 All implicitly popped input regs must be closer to the top of
4259 the reg-stack than any input that is not implicitly popped.
4261 It is possible that if an input dies in an insn, reload might
4262 use the input reg for an output reload. Consider this example:
4265 asm ("foo" : "=t" (a) : "f" (b));
4268 This asm says that input B is not popped by the asm, and that
4269 the asm pushes a result onto the reg-stack, i.e., the stack is one
4270 deeper after the asm than it was before. But, it is possible that
4271 reload will think that it can use the same reg for both the input and
4272 the output, if input B dies in this insn.
4274 If any input operand uses the @code{f} constraint, all output reg
4275 constraints must use the @code{&} earlyclobber.
4277 The asm above would be written as
4280 asm ("foo" : "=&t" (a) : "f" (b));
4284 Some operands need to be in particular places on the stack. All
4285 output operands fall in this category---there is no other way to
4286 know which regs the outputs appear in unless the user indicates
4287 this in the constraints.
4289 Output operands must specifically indicate which reg an output
4290 appears in after an asm. @code{=f} is not allowed: the operand
4291 constraints must select a class with a single reg.
4294 Output operands may not be ``inserted'' between existing stack regs.
4295 Since no 387 opcode uses a read/write operand, all output operands
4296 are dead before the asm_operands, and are pushed by the asm_operands.
4297 It makes no sense to push anywhere but the top of the reg-stack.
4299 Output operands must start at the top of the reg-stack: output
4300 operands may not ``skip'' a reg.
4303 Some asm statements may need extra stack space for internal
4304 calculations. This can be guaranteed by clobbering stack registers
4305 unrelated to the inputs and outputs.
4309 Here are a couple of reasonable asms to want to write. This asm
4310 takes one input, which is internally popped, and produces two outputs.
4313 asm ("fsincos" : "=t" (cos), "=u" (sin) : "0" (inp));
4316 This asm takes two inputs, which are popped by the @code{fyl2xp1} opcode,
4317 and replaces them with one output. The user must code the @code{st(1)}
4318 clobber for reg-stack.c to know that @code{fyl2xp1} pops both inputs.
4321 asm ("fyl2xp1" : "=t" (result) : "0" (x), "u" (y) : "st(1)");
4327 @section Controlling Names Used in Assembler Code
4328 @cindex assembler names for identifiers
4329 @cindex names used in assembler code
4330 @cindex identifiers, names in assembler code
4332 You can specify the name to be used in the assembler code for a C
4333 function or variable by writing the @code{asm} (or @code{__asm__})
4334 keyword after the declarator as follows:
4337 int foo asm ("myfoo") = 2;
4341 This specifies that the name to be used for the variable @code{foo} in
4342 the assembler code should be @samp{myfoo} rather than the usual
4345 On systems where an underscore is normally prepended to the name of a C
4346 function or variable, this feature allows you to define names for the
4347 linker that do not start with an underscore.
4349 It does not make sense to use this feature with a non-static local
4350 variable since such variables do not have assembler names. If you are
4351 trying to put the variable in a particular register, see @ref{Explicit
4352 Reg Vars}. GCC presently accepts such code with a warning, but will
4353 probably be changed to issue an error, rather than a warning, in the
4356 You cannot use @code{asm} in this way in a function @emph{definition}; but
4357 you can get the same effect by writing a declaration for the function
4358 before its definition and putting @code{asm} there, like this:
4361 extern func () asm ("FUNC");
4368 It is up to you to make sure that the assembler names you choose do not
4369 conflict with any other assembler symbols. Also, you must not use a
4370 register name; that would produce completely invalid assembler code. GCC
4371 does not as yet have the ability to store static variables in registers.
4372 Perhaps that will be added.
4374 @node Explicit Reg Vars
4375 @section Variables in Specified Registers
4376 @cindex explicit register variables
4377 @cindex variables in specified registers
4378 @cindex specified registers
4379 @cindex registers, global allocation
4381 GNU C allows you to put a few global variables into specified hardware
4382 registers. You can also specify the register in which an ordinary
4383 register variable should be allocated.
4387 Global register variables reserve registers throughout the program.
4388 This may be useful in programs such as programming language
4389 interpreters which have a couple of global variables that are accessed
4393 Local register variables in specific registers do not reserve the
4394 registers, except at the point where they are used as input or output
4395 operands in an @code{asm} statement and the @code{asm} statement itself is
4396 not deleted. The compiler's data flow analysis is capable of determining
4397 where the specified registers contain live values, and where they are
4398 available for other uses. Stores into local register variables may be deleted
4399 when they appear to be dead according to dataflow analysis. References
4400 to local register variables may be deleted or moved or simplified.
4402 These local variables are sometimes convenient for use with the extended
4403 @code{asm} feature (@pxref{Extended Asm}), if you want to write one
4404 output of the assembler instruction directly into a particular register.
4405 (This will work provided the register you specify fits the constraints
4406 specified for that operand in the @code{asm}.)
4414 @node Global Reg Vars
4415 @subsection Defining Global Register Variables
4416 @cindex global register variables
4417 @cindex registers, global variables in
4419 You can define a global register variable in GNU C like this:
4422 register int *foo asm ("a5");
4426 Here @code{a5} is the name of the register which should be used. Choose a
4427 register which is normally saved and restored by function calls on your
4428 machine, so that library routines will not clobber it.
4430 Naturally the register name is cpu-dependent, so you would need to
4431 conditionalize your program according to cpu type. The register
4432 @code{a5} would be a good choice on a 68000 for a variable of pointer
4433 type. On machines with register windows, be sure to choose a ``global''
4434 register that is not affected magically by the function call mechanism.
4436 In addition, operating systems on one type of cpu may differ in how they
4437 name the registers; then you would need additional conditionals. For
4438 example, some 68000 operating systems call this register @code{%a5}.
4440 Eventually there may be a way of asking the compiler to choose a register
4441 automatically, but first we need to figure out how it should choose and
4442 how to enable you to guide the choice. No solution is evident.
4444 Defining a global register variable in a certain register reserves that
4445 register entirely for this use, at least within the current compilation.
4446 The register will not be allocated for any other purpose in the functions
4447 in the current compilation. The register will not be saved and restored by
4448 these functions. Stores into this register are never deleted even if they
4449 would appear to be dead, but references may be deleted or moved or
4452 It is not safe to access the global register variables from signal
4453 handlers, or from more than one thread of control, because the system
4454 library routines may temporarily use the register for other things (unless
4455 you recompile them specially for the task at hand).
4457 @cindex @code{qsort}, and global register variables
4458 It is not safe for one function that uses a global register variable to
4459 call another such function @code{foo} by way of a third function
4460 @code{lose} that was compiled without knowledge of this variable (i.e.@: in a
4461 different source file in which the variable wasn't declared). This is
4462 because @code{lose} might save the register and put some other value there.
4463 For example, you can't expect a global register variable to be available in
4464 the comparison-function that you pass to @code{qsort}, since @code{qsort}
4465 might have put something else in that register. (If you are prepared to
4466 recompile @code{qsort} with the same global register variable, you can
4467 solve this problem.)
4469 If you want to recompile @code{qsort} or other source files which do not
4470 actually use your global register variable, so that they will not use that
4471 register for any other purpose, then it suffices to specify the compiler
4472 option @option{-ffixed-@var{reg}}. You need not actually add a global
4473 register declaration to their source code.
4475 A function which can alter the value of a global register variable cannot
4476 safely be called from a function compiled without this variable, because it
4477 could clobber the value the caller expects to find there on return.
4478 Therefore, the function which is the entry point into the part of the
4479 program that uses the global register variable must explicitly save and
4480 restore the value which belongs to its caller.
4482 @cindex register variable after @code{longjmp}
4483 @cindex global register after @code{longjmp}
4484 @cindex value after @code{longjmp}
4487 On most machines, @code{longjmp} will restore to each global register
4488 variable the value it had at the time of the @code{setjmp}. On some
4489 machines, however, @code{longjmp} will not change the value of global
4490 register variables. To be portable, the function that called @code{setjmp}
4491 should make other arrangements to save the values of the global register
4492 variables, and to restore them in a @code{longjmp}. This way, the same
4493 thing will happen regardless of what @code{longjmp} does.
4495 All global register variable declarations must precede all function
4496 definitions. If such a declaration could appear after function
4497 definitions, the declaration would be too late to prevent the register from
4498 being used for other purposes in the preceding functions.
4500 Global register variables may not have initial values, because an
4501 executable file has no means to supply initial contents for a register.
4503 On the SPARC, there are reports that g3 @dots{} g7 are suitable
4504 registers, but certain library functions, such as @code{getwd}, as well
4505 as the subroutines for division and remainder, modify g3 and g4. g1 and
4506 g2 are local temporaries.
4508 On the 68000, a2 @dots{} a5 should be suitable, as should d2 @dots{} d7.
4509 Of course, it will not do to use more than a few of those.
4511 @node Local Reg Vars
4512 @subsection Specifying Registers for Local Variables
4513 @cindex local variables, specifying registers
4514 @cindex specifying registers for local variables
4515 @cindex registers for local variables
4517 You can define a local register variable with a specified register
4521 register int *foo asm ("a5");
4525 Here @code{a5} is the name of the register which should be used. Note
4526 that this is the same syntax used for defining global register
4527 variables, but for a local variable it would appear within a function.
4529 Naturally the register name is cpu-dependent, but this is not a
4530 problem, since specific registers are most often useful with explicit
4531 assembler instructions (@pxref{Extended Asm}). Both of these things
4532 generally require that you conditionalize your program according to
4535 In addition, operating systems on one type of cpu may differ in how they
4536 name the registers; then you would need additional conditionals. For
4537 example, some 68000 operating systems call this register @code{%a5}.
4539 Defining such a register variable does not reserve the register; it
4540 remains available for other uses in places where flow control determines
4541 the variable's value is not live.
4543 This option does not guarantee that GCC will generate code that has
4544 this variable in the register you specify at all times. You may not
4545 code an explicit reference to this register in the @emph{assembler
4546 instruction template} part of an @code{asm} statement and assume it will
4547 always refer to this variable. However, using the variable as an
4548 @code{asm} @emph{operand} guarantees that the specified register is used
4551 Stores into local register variables may be deleted when they appear to be dead
4552 according to dataflow analysis. References to local register variables may
4553 be deleted or moved or simplified.
4555 As for global register variables, it's recommended that you choose a
4556 register which is normally saved and restored by function calls on
4557 your machine, so that library routines will not clobber it. A common
4558 pitfall is to initialize multiple call-clobbered registers with
4559 arbitrary expressions, where a function call or library call for an
4560 arithmetic operator will overwrite a register value from a previous
4561 assignment, for example @code{r0} below:
4563 register int *p1 asm ("r0") = @dots{};
4564 register int *p2 asm ("r1") = @dots{};
4566 In those cases, a solution is to use a temporary variable for
4567 each arbitrary expression. @xref{Example of asm with clobbered asm reg}.
4569 @node Alternate Keywords
4570 @section Alternate Keywords
4571 @cindex alternate keywords
4572 @cindex keywords, alternate
4574 @option{-ansi} and the various @option{-std} options disable certain
4575 keywords. This causes trouble when you want to use GNU C extensions, or
4576 a general-purpose header file that should be usable by all programs,
4577 including ISO C programs. The keywords @code{asm}, @code{typeof} and
4578 @code{inline} are not available in programs compiled with
4579 @option{-ansi} or @option{-std} (although @code{inline} can be used in a
4580 program compiled with @option{-std=c99}). The ISO C99 keyword
4581 @code{restrict} is only available when @option{-std=gnu99} (which will
4582 eventually be the default) or @option{-std=c99} (or the equivalent
4583 @option{-std=iso9899:1999}) is used.
4585 The way to solve these problems is to put @samp{__} at the beginning and
4586 end of each problematical keyword. For example, use @code{__asm__}
4587 instead of @code{asm}, and @code{__inline__} instead of @code{inline}.
4589 Other C compilers won't accept these alternative keywords; if you want to
4590 compile with another compiler, you can define the alternate keywords as
4591 macros to replace them with the customary keywords. It looks like this:
4599 @findex __extension__
4601 @option{-pedantic} and other options cause warnings for many GNU C extensions.
4603 prevent such warnings within one expression by writing
4604 @code{__extension__} before the expression. @code{__extension__} has no
4605 effect aside from this.
4607 @node Incomplete Enums
4608 @section Incomplete @code{enum} Types
4610 You can define an @code{enum} tag without specifying its possible values.
4611 This results in an incomplete type, much like what you get if you write
4612 @code{struct foo} without describing the elements. A later declaration
4613 which does specify the possible values completes the type.
4615 You can't allocate variables or storage using the type while it is
4616 incomplete. However, you can work with pointers to that type.
4618 This extension may not be very useful, but it makes the handling of
4619 @code{enum} more consistent with the way @code{struct} and @code{union}
4622 This extension is not supported by GNU C++.
4624 @node Function Names
4625 @section Function Names as Strings
4626 @cindex @code{__func__} identifier
4627 @cindex @code{__FUNCTION__} identifier
4628 @cindex @code{__PRETTY_FUNCTION__} identifier
4630 GCC provides three magic variables which hold the name of the current
4631 function, as a string. The first of these is @code{__func__}, which
4632 is part of the C99 standard:
4635 The identifier @code{__func__} is implicitly declared by the translator
4636 as if, immediately following the opening brace of each function
4637 definition, the declaration
4640 static const char __func__[] = "function-name";
4643 appeared, where function-name is the name of the lexically-enclosing
4644 function. This name is the unadorned name of the function.
4647 @code{__FUNCTION__} is another name for @code{__func__}. Older
4648 versions of GCC recognize only this name. However, it is not
4649 standardized. For maximum portability, we recommend you use
4650 @code{__func__}, but provide a fallback definition with the
4654 #if __STDC_VERSION__ < 199901L
4656 # define __func__ __FUNCTION__
4658 # define __func__ "<unknown>"
4663 In C, @code{__PRETTY_FUNCTION__} is yet another name for
4664 @code{__func__}. However, in C++, @code{__PRETTY_FUNCTION__} contains
4665 the type signature of the function as well as its bare name. For
4666 example, this program:
4670 extern int printf (char *, ...);
4677 printf ("__FUNCTION__ = %s\n", __FUNCTION__);
4678 printf ("__PRETTY_FUNCTION__ = %s\n", __PRETTY_FUNCTION__);
4696 __PRETTY_FUNCTION__ = void a::sub(int)
4699 These identifiers are not preprocessor macros. In GCC 3.3 and
4700 earlier, in C only, @code{__FUNCTION__} and @code{__PRETTY_FUNCTION__}
4701 were treated as string literals; they could be used to initialize
4702 @code{char} arrays, and they could be concatenated with other string
4703 literals. GCC 3.4 and later treat them as variables, like
4704 @code{__func__}. In C++, @code{__FUNCTION__} and
4705 @code{__PRETTY_FUNCTION__} have always been variables.
4707 @node Return Address
4708 @section Getting the Return or Frame Address of a Function
4710 These functions may be used to get information about the callers of a
4713 @deftypefn {Built-in Function} {void *} __builtin_return_address (unsigned int @var{level})
4714 This function returns the return address of the current function, or of
4715 one of its callers. The @var{level} argument is number of frames to
4716 scan up the call stack. A value of @code{0} yields the return address
4717 of the current function, a value of @code{1} yields the return address
4718 of the caller of the current function, and so forth. When inlining
4719 the expected behavior is that the function will return the address of
4720 the function that will be returned to. To work around this behavior use
4721 the @code{noinline} function attribute.
4723 The @var{level} argument must be a constant integer.
4725 On some machines it may be impossible to determine the return address of
4726 any function other than the current one; in such cases, or when the top
4727 of the stack has been reached, this function will return @code{0} or a
4728 random value. In addition, @code{__builtin_frame_address} may be used
4729 to determine if the top of the stack has been reached.
4731 This function should only be used with a nonzero argument for debugging
4735 @deftypefn {Built-in Function} {void *} __builtin_frame_address (unsigned int @var{level})
4736 This function is similar to @code{__builtin_return_address}, but it
4737 returns the address of the function frame rather than the return address
4738 of the function. Calling @code{__builtin_frame_address} with a value of
4739 @code{0} yields the frame address of the current function, a value of
4740 @code{1} yields the frame address of the caller of the current function,
4743 The frame is the area on the stack which holds local variables and saved
4744 registers. The frame address is normally the address of the first word
4745 pushed on to the stack by the function. However, the exact definition
4746 depends upon the processor and the calling convention. If the processor
4747 has a dedicated frame pointer register, and the function has a frame,
4748 then @code{__builtin_frame_address} will return the value of the frame
4751 On some machines it may be impossible to determine the frame address of
4752 any function other than the current one; in such cases, or when the top
4753 of the stack has been reached, this function will return @code{0} if
4754 the first frame pointer is properly initialized by the startup code.
4756 This function should only be used with a nonzero argument for debugging
4760 @node Vector Extensions
4761 @section Using vector instructions through built-in functions
4763 On some targets, the instruction set contains SIMD vector instructions that
4764 operate on multiple values contained in one large register at the same time.
4765 For example, on the i386 the MMX, 3Dnow! and SSE extensions can be used
4768 The first step in using these extensions is to provide the necessary data
4769 types. This should be done using an appropriate @code{typedef}:
4772 typedef int v4si __attribute__ ((vector_size (16)));
4775 The @code{int} type specifies the base type, while the attribute specifies
4776 the vector size for the variable, measured in bytes. For example, the
4777 declaration above causes the compiler to set the mode for the @code{v4si}
4778 type to be 16 bytes wide and divided into @code{int} sized units. For
4779 a 32-bit @code{int} this means a vector of 4 units of 4 bytes, and the
4780 corresponding mode of @code{foo} will be @acronym{V4SI}.
4782 The @code{vector_size} attribute is only applicable to integral and
4783 float scalars, although arrays, pointers, and function return values
4784 are allowed in conjunction with this construct.
4786 All the basic integer types can be used as base types, both as signed
4787 and as unsigned: @code{char}, @code{short}, @code{int}, @code{long},
4788 @code{long long}. In addition, @code{float} and @code{double} can be
4789 used to build floating-point vector types.
4791 Specifying a combination that is not valid for the current architecture
4792 will cause GCC to synthesize the instructions using a narrower mode.
4793 For example, if you specify a variable of type @code{V4SI} and your
4794 architecture does not allow for this specific SIMD type, GCC will
4795 produce code that uses 4 @code{SIs}.
4797 The types defined in this manner can be used with a subset of normal C
4798 operations. Currently, GCC will allow using the following operators
4799 on these types: @code{+, -, *, /, unary minus, ^, |, &, ~}@.
4801 The operations behave like C++ @code{valarrays}. Addition is defined as
4802 the addition of the corresponding elements of the operands. For
4803 example, in the code below, each of the 4 elements in @var{a} will be
4804 added to the corresponding 4 elements in @var{b} and the resulting
4805 vector will be stored in @var{c}.
4808 typedef int v4si __attribute__ ((vector_size (16)));
4815 Subtraction, multiplication, division, and the logical operations
4816 operate in a similar manner. Likewise, the result of using the unary
4817 minus or complement operators on a vector type is a vector whose
4818 elements are the negative or complemented values of the corresponding
4819 elements in the operand.
4821 You can declare variables and use them in function calls and returns, as
4822 well as in assignments and some casts. You can specify a vector type as
4823 a return type for a function. Vector types can also be used as function
4824 arguments. It is possible to cast from one vector type to another,
4825 provided they are of the same size (in fact, you can also cast vectors
4826 to and from other datatypes of the same size).
4828 You cannot operate between vectors of different lengths or different
4829 signedness without a cast.
4831 A port that supports hardware vector operations, usually provides a set
4832 of built-in functions that can be used to operate on vectors. For
4833 example, a function to add two vectors and multiply the result by a
4834 third could look like this:
4837 v4si f (v4si a, v4si b, v4si c)
4839 v4si tmp = __builtin_addv4si (a, b);
4840 return __builtin_mulv4si (tmp, c);
4847 @findex __builtin_offsetof
4849 GCC implements for both C and C++ a syntactic extension to implement
4850 the @code{offsetof} macro.
4854 "__builtin_offsetof" "(" @code{typename} "," offsetof_member_designator ")"
4856 offsetof_member_designator:
4858 | offsetof_member_designator "." @code{identifier}
4859 | offsetof_member_designator "[" @code{expr} "]"
4862 This extension is sufficient such that
4865 #define offsetof(@var{type}, @var{member}) __builtin_offsetof (@var{type}, @var{member})
4868 is a suitable definition of the @code{offsetof} macro. In C++, @var{type}
4869 may be dependent. In either case, @var{member} may consist of a single
4870 identifier, or a sequence of member accesses and array references.
4872 @node Atomic Builtins
4873 @section Built-in functions for atomic memory access
4875 The following builtins are intended to be compatible with those described
4876 in the @cite{Intel Itanium Processor-specific Application Binary Interface},
4877 section 7.4. As such, they depart from the normal GCC practice of using
4878 the ``__builtin_'' prefix, and further that they are overloaded such that
4879 they work on multiple types.
4881 The definition given in the Intel documentation allows only for the use of
4882 the types @code{int}, @code{long}, @code{long long} as well as their unsigned
4883 counterparts. GCC will allow any integral scalar or pointer type that is
4884 1, 2, 4 or 8 bytes in length.
4886 Not all operations are supported by all target processors. If a particular
4887 operation cannot be implemented on the target processor, a warning will be
4888 generated and a call an external function will be generated. The external
4889 function will carry the same name as the builtin, with an additional suffix
4890 @samp{_@var{n}} where @var{n} is the size of the data type.
4892 @c ??? Should we have a mechanism to suppress this warning? This is almost
4893 @c useful for implementing the operation under the control of an external
4896 In most cases, these builtins are considered a @dfn{full barrier}. That is,
4897 no memory operand will be moved across the operation, either forward or
4898 backward. Further, instructions will be issued as necessary to prevent the
4899 processor from speculating loads across the operation and from queuing stores
4900 after the operation.
4902 All of the routines are are described in the Intel documentation to take
4903 ``an optional list of variables protected by the memory barrier''. It's
4904 not clear what is meant by that; it could mean that @emph{only} the
4905 following variables are protected, or it could mean that these variables
4906 should in addition be protected. At present GCC ignores this list and
4907 protects all variables which are globally accessible. If in the future
4908 we make some use of this list, an empty list will continue to mean all
4909 globally accessible variables.
4912 @item @var{type} __sync_fetch_and_add (@var{type} *ptr, @var{type} value, ...)
4913 @itemx @var{type} __sync_fetch_and_sub (@var{type} *ptr, @var{type} value, ...)
4914 @itemx @var{type} __sync_fetch_and_or (@var{type} *ptr, @var{type} value, ...)
4915 @itemx @var{type} __sync_fetch_and_and (@var{type} *ptr, @var{type} value, ...)
4916 @itemx @var{type} __sync_fetch_and_xor (@var{type} *ptr, @var{type} value, ...)
4917 @itemx @var{type} __sync_fetch_and_nand (@var{type} *ptr, @var{type} value, ...)
4918 @findex __sync_fetch_and_add
4919 @findex __sync_fetch_and_sub
4920 @findex __sync_fetch_and_or
4921 @findex __sync_fetch_and_and
4922 @findex __sync_fetch_and_xor
4923 @findex __sync_fetch_and_nand
4924 These builtins perform the operation suggested by the name, and
4925 returns the value that had previously been in memory. That is,
4928 @{ tmp = *ptr; *ptr @var{op}= value; return tmp; @}
4929 @{ tmp = *ptr; *ptr = ~tmp & value; return tmp; @} // nand
4932 @item @var{type} __sync_add_and_fetch (@var{type} *ptr, @var{type} value, ...)
4933 @itemx @var{type} __sync_sub_and_fetch (@var{type} *ptr, @var{type} value, ...)
4934 @itemx @var{type} __sync_or_and_fetch (@var{type} *ptr, @var{type} value, ...)
4935 @itemx @var{type} __sync_and_and_fetch (@var{type} *ptr, @var{type} value, ...)
4936 @itemx @var{type} __sync_xor_and_fetch (@var{type} *ptr, @var{type} value, ...)
4937 @itemx @var{type} __sync_nand_and_fetch (@var{type} *ptr, @var{type} value, ...)
4938 @findex __sync_add_and_fetch
4939 @findex __sync_sub_and_fetch
4940 @findex __sync_or_and_fetch
4941 @findex __sync_and_and_fetch
4942 @findex __sync_xor_and_fetch
4943 @findex __sync_nand_and_fetch
4944 These builtins perform the operation suggested by the name, and
4945 return the new value. That is,
4948 @{ *ptr @var{op}= value; return *ptr; @}
4949 @{ *ptr = ~*ptr & value; return *ptr; @} // nand
4952 @item bool __sync_bool_compare_and_swap (@var{type} *ptr, @var{type} oldval @var{type} newval, ...)
4953 @itemx @var{type} __sync_val_compare_and_swap (@var{type} *ptr, @var{type} oldval @var{type} newval, ...)
4954 @findex __sync_bool_compare_and_swap
4955 @findex __sync_val_compare_and_swap
4956 These builtins perform an atomic compare and swap. That is, if the current
4957 value of @code{*@var{ptr}} is @var{oldval}, then write @var{newval} into
4960 The ``bool'' version returns true if the comparison is successful and
4961 @var{newval} was written. The ``val'' version returns the contents
4962 of @code{*@var{ptr}} before the operation.
4964 @item __sync_synchronize (...)
4965 @findex __sync_synchronize
4966 This builtin issues a full memory barrier.
4968 @item @var{type} __sync_lock_test_and_set (@var{type} *ptr, @var{type} value, ...)
4969 @findex __sync_lock_test_and_set
4970 This builtin, as described by Intel, is not a traditional test-and-set
4971 operation, but rather an atomic exchange operation. It writes @var{value}
4972 into @code{*@var{ptr}}, and returns the previous contents of
4975 Many targets have only minimal support for such locks, and do not support
4976 a full exchange operation. In this case, a target may support reduced
4977 functionality here by which the @emph{only} valid value to store is the
4978 immediate constant 1. The exact value actually stored in @code{*@var{ptr}}
4979 is implementation defined.
4981 This builtin is not a full barrier, but rather an @dfn{acquire barrier}.
4982 This means that references after the builtin cannot move to (or be
4983 speculated to) before the builtin, but previous memory stores may not
4984 be globally visible yet, and previous memory loads may not yet be
4987 @item void __sync_lock_release (@var{type} *ptr, ...)
4988 @findex __sync_lock_release
4989 This builtin releases the lock acquired by @code{__sync_lock_test_and_set}.
4990 Normally this means writing the constant 0 to @code{*@var{ptr}}.
4992 This builtin is not a full barrier, but rather a @dfn{release barrier}.
4993 This means that all previous memory stores are globally visible, and all
4994 previous memory loads have been satisfied, but following memory reads
4995 are not prevented from being speculated to before the barrier.
4998 @node Object Size Checking
4999 @section Object Size Checking Builtins
5000 @findex __builtin_object_size
5001 @findex __builtin___memcpy_chk
5002 @findex __builtin___mempcpy_chk
5003 @findex __builtin___memmove_chk
5004 @findex __builtin___memset_chk
5005 @findex __builtin___strcpy_chk
5006 @findex __builtin___stpcpy_chk
5007 @findex __builtin___strncpy_chk
5008 @findex __builtin___strcat_chk
5009 @findex __builtin___strncat_chk
5010 @findex __builtin___sprintf_chk
5011 @findex __builtin___snprintf_chk
5012 @findex __builtin___vsprintf_chk
5013 @findex __builtin___vsnprintf_chk
5014 @findex __builtin___printf_chk
5015 @findex __builtin___vprintf_chk
5016 @findex __builtin___fprintf_chk
5017 @findex __builtin___vfprintf_chk
5019 GCC implements a limited buffer overflow protection mechanism
5020 that can prevent some buffer overflow attacks.
5022 @deftypefn {Built-in Function} {size_t} __builtin_object_size (void * @var{ptr}, int @var{type})
5023 is a built-in construct that returns a constant number of bytes from
5024 @var{ptr} to the end of the object @var{ptr} pointer points to
5025 (if known at compile time). @code{__builtin_object_size} never evaluates
5026 its arguments for side-effects. If there are any side-effects in them, it
5027 returns @code{(size_t) -1} for @var{type} 0 or 1 and @code{(size_t) 0}
5028 for @var{type} 2 or 3. If there are multiple objects @var{ptr} can
5029 point to and all of them are known at compile time, the returned number
5030 is the maximum of remaining byte counts in those objects if @var{type} & 2 is
5031 0 and minimum if nonzero. If it is not possible to determine which objects
5032 @var{ptr} points to at compile time, @code{__builtin_object_size} should
5033 return @code{(size_t) -1} for @var{type} 0 or 1 and @code{(size_t) 0}
5034 for @var{type} 2 or 3.
5036 @var{type} is an integer constant from 0 to 3. If the least significant
5037 bit is clear, objects are whole variables, if it is set, a closest
5038 surrounding subobject is considered the object a pointer points to.
5039 The second bit determines if maximum or minimum of remaining bytes
5043 struct V @{ char buf1[10]; int b; char buf2[10]; @} var;
5044 char *p = &var.buf1[1], *q = &var.b;
5046 /* Here the object p points to is var. */
5047 assert (__builtin_object_size (p, 0) == sizeof (var) - 1);
5048 /* The subobject p points to is var.buf1. */
5049 assert (__builtin_object_size (p, 1) == sizeof (var.buf1) - 1);
5050 /* The object q points to is var. */
5051 assert (__builtin_object_size (q, 0)
5052 == (char *) (&var + 1) - (char *) &var.b);
5053 /* The subobject q points to is var.b. */
5054 assert (__builtin_object_size (q, 1) == sizeof (var.b));
5058 There are built-in functions added for many common string operation
5059 functions, e.g. for @code{memcpy} @code{__builtin___memcpy_chk}
5060 built-in is provided. This built-in has an additional last argument,
5061 which is the number of bytes remaining in object the @var{dest}
5062 argument points to or @code{(size_t) -1} if the size is not known.
5064 The built-in functions are optimized into the normal string functions
5065 like @code{memcpy} if the last argument is @code{(size_t) -1} or if
5066 it is known at compile time that the destination object will not
5067 be overflown. If the compiler can determine at compile time the
5068 object will be always overflown, it issues a warning.
5070 The intended use can be e.g.
5074 #define bos0(dest) __builtin_object_size (dest, 0)
5075 #define memcpy(dest, src, n) \
5076 __builtin___memcpy_chk (dest, src, n, bos0 (dest))
5080 /* It is unknown what object p points to, so this is optimized
5081 into plain memcpy - no checking is possible. */
5082 memcpy (p, "abcde", n);
5083 /* Destination is known and length too. It is known at compile
5084 time there will be no overflow. */
5085 memcpy (&buf[5], "abcde", 5);
5086 /* Destination is known, but the length is not known at compile time.
5087 This will result in __memcpy_chk call that can check for overflow
5089 memcpy (&buf[5], "abcde", n);
5090 /* Destination is known and it is known at compile time there will
5091 be overflow. There will be a warning and __memcpy_chk call that
5092 will abort the program at runtime. */
5093 memcpy (&buf[6], "abcde", 5);
5096 Such built-in functions are provided for @code{memcpy}, @code{mempcpy},
5097 @code{memmove}, @code{memset}, @code{strcpy}, @code{stpcpy}, @code{strncpy},
5098 @code{strcat} and @code{strncat}.
5100 There are also checking built-in functions for formatted output functions.
5102 int __builtin___sprintf_chk (char *s, int flag, size_t os, const char *fmt, ...);
5103 int __builtin___snprintf_chk (char *s, size_t maxlen, int flag, size_t os,
5104 const char *fmt, ...);
5105 int __builtin___vsprintf_chk (char *s, int flag, size_t os, const char *fmt,
5107 int __builtin___vsnprintf_chk (char *s, size_t maxlen, int flag, size_t os,
5108 const char *fmt, va_list ap);
5111 The added @var{flag} argument is passed unchanged to @code{__sprintf_chk}
5112 etc. functions and can contain implementation specific flags on what
5113 additional security measures the checking function might take, such as
5114 handling @code{%n} differently.
5116 The @var{os} argument is the object size @var{s} points to, like in the
5117 other built-in functions. There is a small difference in the behavior
5118 though, if @var{os} is @code{(size_t) -1}, the built-in functions are
5119 optimized into the non-checking functions only if @var{flag} is 0, otherwise
5120 the checking function is called with @var{os} argument set to
5123 In addition to this, there are checking built-in functions
5124 @code{__builtin___printf_chk}, @code{__builtin___vprintf_chk},
5125 @code{__builtin___fprintf_chk} and @code{__builtin___vfprintf_chk}.
5126 These have just one additional argument, @var{flag}, right before
5127 format string @var{fmt}. If the compiler is able to optimize them to
5128 @code{fputc} etc. functions, it will, otherwise the checking function
5129 should be called and the @var{flag} argument passed to it.
5131 @node Other Builtins
5132 @section Other built-in functions provided by GCC
5133 @cindex built-in functions
5134 @findex __builtin_isgreater
5135 @findex __builtin_isgreaterequal
5136 @findex __builtin_isless
5137 @findex __builtin_islessequal
5138 @findex __builtin_islessgreater
5139 @findex __builtin_isunordered
5140 @findex __builtin_powi
5141 @findex __builtin_powif
5142 @findex __builtin_powil
5300 @findex fprintf_unlocked
5302 @findex fputs_unlocked
5412 @findex printf_unlocked
5441 @findex significandf
5442 @findex significandl
5513 GCC provides a large number of built-in functions other than the ones
5514 mentioned above. Some of these are for internal use in the processing
5515 of exceptions or variable-length argument lists and will not be
5516 documented here because they may change from time to time; we do not
5517 recommend general use of these functions.
5519 The remaining functions are provided for optimization purposes.
5521 @opindex fno-builtin
5522 GCC includes built-in versions of many of the functions in the standard
5523 C library. The versions prefixed with @code{__builtin_} will always be
5524 treated as having the same meaning as the C library function even if you
5525 specify the @option{-fno-builtin} option. (@pxref{C Dialect Options})
5526 Many of these functions are only optimized in certain cases; if they are
5527 not optimized in a particular case, a call to the library function will
5532 Outside strict ISO C mode (@option{-ansi}, @option{-std=c89} or
5533 @option{-std=c99}), the functions
5534 @code{_exit}, @code{alloca}, @code{bcmp}, @code{bzero},
5535 @code{dcgettext}, @code{dgettext}, @code{dremf}, @code{dreml},
5536 @code{drem}, @code{exp10f}, @code{exp10l}, @code{exp10}, @code{ffsll},
5537 @code{ffsl}, @code{ffs}, @code{fprintf_unlocked}, @code{fputs_unlocked},
5538 @code{gammaf}, @code{gammal}, @code{gamma}, @code{gettext},
5539 @code{index}, @code{isascii}, @code{j0f}, @code{j0l}, @code{j0},
5540 @code{j1f}, @code{j1l}, @code{j1}, @code{jnf}, @code{jnl}, @code{jn},
5541 @code{mempcpy}, @code{pow10f}, @code{pow10l}, @code{pow10},
5542 @code{printf_unlocked}, @code{rindex}, @code{scalbf}, @code{scalbl},
5543 @code{scalb}, @code{signbit}, @code{signbitf}, @code{signbitl},
5544 @code{significandf}, @code{significandl}, @code{significand},
5545 @code{sincosf}, @code{sincosl}, @code{sincos}, @code{stpcpy},
5546 @code{stpncpy}, @code{strcasecmp}, @code{strdup}, @code{strfmon},
5547 @code{strncasecmp}, @code{strndup}, @code{toascii}, @code{y0f},
5548 @code{y0l}, @code{y0}, @code{y1f}, @code{y1l}, @code{y1}, @code{ynf},
5549 @code{ynl} and @code{yn}
5550 may be handled as built-in functions.
5551 All these functions have corresponding versions
5552 prefixed with @code{__builtin_}, which may be used even in strict C89
5555 The ISO C99 functions
5556 @code{_Exit}, @code{acoshf}, @code{acoshl}, @code{acosh}, @code{asinhf},
5557 @code{asinhl}, @code{asinh}, @code{atanhf}, @code{atanhl}, @code{atanh},
5558 @code{cabsf}, @code{cabsl}, @code{cabs}, @code{cacosf}, @code{cacoshf},
5559 @code{cacoshl}, @code{cacosh}, @code{cacosl}, @code{cacos},
5560 @code{cargf}, @code{cargl}, @code{carg}, @code{casinf}, @code{casinhf},
5561 @code{casinhl}, @code{casinh}, @code{casinl}, @code{casin},
5562 @code{catanf}, @code{catanhf}, @code{catanhl}, @code{catanh},
5563 @code{catanl}, @code{catan}, @code{cbrtf}, @code{cbrtl}, @code{cbrt},
5564 @code{ccosf}, @code{ccoshf}, @code{ccoshl}, @code{ccosh}, @code{ccosl},
5565 @code{ccos}, @code{cexpf}, @code{cexpl}, @code{cexp}, @code{cimagf},
5566 @code{cimagl}, @code{cimag}, @code{clogf}, @code{clogl}, @code{clog},
5567 @code{conjf}, @code{conjl}, @code{conj}, @code{copysignf}, @code{copysignl},
5568 @code{copysign}, @code{cpowf}, @code{cpowl}, @code{cpow}, @code{cprojf},
5569 @code{cprojl}, @code{cproj}, @code{crealf}, @code{creall}, @code{creal},
5570 @code{csinf}, @code{csinhf}, @code{csinhl}, @code{csinh}, @code{csinl},
5571 @code{csin}, @code{csqrtf}, @code{csqrtl}, @code{csqrt}, @code{ctanf},
5572 @code{ctanhf}, @code{ctanhl}, @code{ctanh}, @code{ctanl}, @code{ctan},
5573 @code{erfcf}, @code{erfcl}, @code{erfc}, @code{erff}, @code{erfl},
5574 @code{erf}, @code{exp2f}, @code{exp2l}, @code{exp2}, @code{expm1f},
5575 @code{expm1l}, @code{expm1}, @code{fdimf}, @code{fdiml}, @code{fdim},
5576 @code{fmaf}, @code{fmal}, @code{fmaxf}, @code{fmaxl}, @code{fmax},
5577 @code{fma}, @code{fminf}, @code{fminl}, @code{fmin}, @code{hypotf},
5578 @code{hypotl}, @code{hypot}, @code{ilogbf}, @code{ilogbl}, @code{ilogb},
5579 @code{imaxabs}, @code{isblank}, @code{iswblank}, @code{lgammaf},
5580 @code{lgammal}, @code{lgamma}, @code{llabs}, @code{llrintf}, @code{llrintl},
5581 @code{llrint}, @code{llroundf}, @code{llroundl}, @code{llround},
5582 @code{log1pf}, @code{log1pl}, @code{log1p}, @code{log2f}, @code{log2l},
5583 @code{log2}, @code{logbf}, @code{logbl}, @code{logb}, @code{lrintf},
5584 @code{lrintl}, @code{lrint}, @code{lroundf}, @code{lroundl},
5585 @code{lround}, @code{nearbyintf}, @code{nearbyintl}, @code{nearbyint},
5586 @code{nextafterf}, @code{nextafterl}, @code{nextafter},
5587 @code{nexttowardf}, @code{nexttowardl}, @code{nexttoward},
5588 @code{remainderf}, @code{remainderl}, @code{remainder}, @code{remquof},
5589 @code{remquol}, @code{remquo}, @code{rintf}, @code{rintl}, @code{rint},
5590 @code{roundf}, @code{roundl}, @code{round}, @code{scalblnf},
5591 @code{scalblnl}, @code{scalbln}, @code{scalbnf}, @code{scalbnl},
5592 @code{scalbn}, @code{snprintf}, @code{tgammaf}, @code{tgammal},
5593 @code{tgamma}, @code{truncf}, @code{truncl}, @code{trunc},
5594 @code{vfscanf}, @code{vscanf}, @code{vsnprintf} and @code{vsscanf}
5595 are handled as built-in functions
5596 except in strict ISO C90 mode (@option{-ansi} or @option{-std=c89}).
5598 There are also built-in versions of the ISO C99 functions
5599 @code{acosf}, @code{acosl}, @code{asinf}, @code{asinl}, @code{atan2f},
5600 @code{atan2l}, @code{atanf}, @code{atanl}, @code{ceilf}, @code{ceill},
5601 @code{cosf}, @code{coshf}, @code{coshl}, @code{cosl}, @code{expf},
5602 @code{expl}, @code{fabsf}, @code{fabsl}, @code{floorf}, @code{floorl},
5603 @code{fmodf}, @code{fmodl}, @code{frexpf}, @code{frexpl}, @code{ldexpf},
5604 @code{ldexpl}, @code{log10f}, @code{log10l}, @code{logf}, @code{logl},
5605 @code{modfl}, @code{modf}, @code{powf}, @code{powl}, @code{sinf},
5606 @code{sinhf}, @code{sinhl}, @code{sinl}, @code{sqrtf}, @code{sqrtl},
5607 @code{tanf}, @code{tanhf}, @code{tanhl} and @code{tanl}
5608 that are recognized in any mode since ISO C90 reserves these names for
5609 the purpose to which ISO C99 puts them. All these functions have
5610 corresponding versions prefixed with @code{__builtin_}.
5612 The ISO C94 functions
5613 @code{iswalnum}, @code{iswalpha}, @code{iswcntrl}, @code{iswdigit},
5614 @code{iswgraph}, @code{iswlower}, @code{iswprint}, @code{iswpunct},
5615 @code{iswspace}, @code{iswupper}, @code{iswxdigit}, @code{towlower} and
5617 are handled as built-in functions
5618 except in strict ISO C90 mode (@option{-ansi} or @option{-std=c89}).
5620 The ISO C90 functions
5621 @code{abort}, @code{abs}, @code{acos}, @code{asin}, @code{atan2},
5622 @code{atan}, @code{calloc}, @code{ceil}, @code{cosh}, @code{cos},
5623 @code{exit}, @code{exp}, @code{fabs}, @code{floor}, @code{fmod},
5624 @code{fprintf}, @code{fputs}, @code{frexp}, @code{fscanf},
5625 @code{isalnum}, @code{isalpha}, @code{iscntrl}, @code{isdigit},
5626 @code{isgraph}, @code{islower}, @code{isprint}, @code{ispunct},
5627 @code{isspace}, @code{isupper}, @code{isxdigit}, @code{tolower},
5628 @code{toupper}, @code{labs}, @code{ldexp}, @code{log10}, @code{log},
5629 @code{malloc}, @code{memcmp}, @code{memcpy}, @code{memset}, @code{modf},
5630 @code{pow}, @code{printf}, @code{putchar}, @code{puts}, @code{scanf},
5631 @code{sinh}, @code{sin}, @code{snprintf}, @code{sprintf}, @code{sqrt},
5632 @code{sscanf}, @code{strcat}, @code{strchr}, @code{strcmp},
5633 @code{strcpy}, @code{strcspn}, @code{strlen}, @code{strncat},
5634 @code{strncmp}, @code{strncpy}, @code{strpbrk}, @code{strrchr},
5635 @code{strspn}, @code{strstr}, @code{tanh}, @code{tan}, @code{vfprintf},
5636 @code{vprintf} and @code{vsprintf}
5637 are all recognized as built-in functions unless
5638 @option{-fno-builtin} is specified (or @option{-fno-builtin-@var{function}}
5639 is specified for an individual function). All of these functions have
5640 corresponding versions prefixed with @code{__builtin_}.
5642 GCC provides built-in versions of the ISO C99 floating point comparison
5643 macros that avoid raising exceptions for unordered operands. They have
5644 the same names as the standard macros ( @code{isgreater},
5645 @code{isgreaterequal}, @code{isless}, @code{islessequal},
5646 @code{islessgreater}, and @code{isunordered}) , with @code{__builtin_}
5647 prefixed. We intend for a library implementor to be able to simply
5648 @code{#define} each standard macro to its built-in equivalent.
5650 @deftypefn {Built-in Function} int __builtin_types_compatible_p (@var{type1}, @var{type2})
5652 You can use the built-in function @code{__builtin_types_compatible_p} to
5653 determine whether two types are the same.
5655 This built-in function returns 1 if the unqualified versions of the
5656 types @var{type1} and @var{type2} (which are types, not expressions) are
5657 compatible, 0 otherwise. The result of this built-in function can be
5658 used in integer constant expressions.
5660 This built-in function ignores top level qualifiers (e.g., @code{const},
5661 @code{volatile}). For example, @code{int} is equivalent to @code{const
5664 The type @code{int[]} and @code{int[5]} are compatible. On the other
5665 hand, @code{int} and @code{char *} are not compatible, even if the size
5666 of their types, on the particular architecture are the same. Also, the
5667 amount of pointer indirection is taken into account when determining
5668 similarity. Consequently, @code{short *} is not similar to
5669 @code{short **}. Furthermore, two types that are typedefed are
5670 considered compatible if their underlying types are compatible.
5672 An @code{enum} type is not considered to be compatible with another
5673 @code{enum} type even if both are compatible with the same integer
5674 type; this is what the C standard specifies.
5675 For example, @code{enum @{foo, bar@}} is not similar to
5676 @code{enum @{hot, dog@}}.
5678 You would typically use this function in code whose execution varies
5679 depending on the arguments' types. For example:
5685 if (__builtin_types_compatible_p (typeof (x), long double)) \
5686 tmp = foo_long_double (tmp); \
5687 else if (__builtin_types_compatible_p (typeof (x), double)) \
5688 tmp = foo_double (tmp); \
5689 else if (__builtin_types_compatible_p (typeof (x), float)) \
5690 tmp = foo_float (tmp); \
5697 @emph{Note:} This construct is only available for C@.
5701 @deftypefn {Built-in Function} @var{type} __builtin_choose_expr (@var{const_exp}, @var{exp1}, @var{exp2})
5703 You can use the built-in function @code{__builtin_choose_expr} to
5704 evaluate code depending on the value of a constant expression. This
5705 built-in function returns @var{exp1} if @var{const_exp}, which is a
5706 constant expression that must be able to be determined at compile time,
5707 is nonzero. Otherwise it returns 0.
5709 This built-in function is analogous to the @samp{? :} operator in C,
5710 except that the expression returned has its type unaltered by promotion
5711 rules. Also, the built-in function does not evaluate the expression
5712 that was not chosen. For example, if @var{const_exp} evaluates to true,
5713 @var{exp2} is not evaluated even if it has side-effects.
5715 This built-in function can return an lvalue if the chosen argument is an
5718 If @var{exp1} is returned, the return type is the same as @var{exp1}'s
5719 type. Similarly, if @var{exp2} is returned, its return type is the same
5726 __builtin_choose_expr ( \
5727 __builtin_types_compatible_p (typeof (x), double), \
5729 __builtin_choose_expr ( \
5730 __builtin_types_compatible_p (typeof (x), float), \
5732 /* @r{The void expression results in a compile-time error} \
5733 @r{when assigning the result to something.} */ \
5737 @emph{Note:} This construct is only available for C@. Furthermore, the
5738 unused expression (@var{exp1} or @var{exp2} depending on the value of
5739 @var{const_exp}) may still generate syntax errors. This may change in
5744 @deftypefn {Built-in Function} int __builtin_constant_p (@var{exp})
5745 You can use the built-in function @code{__builtin_constant_p} to
5746 determine if a value is known to be constant at compile-time and hence
5747 that GCC can perform constant-folding on expressions involving that
5748 value. The argument of the function is the value to test. The function
5749 returns the integer 1 if the argument is known to be a compile-time
5750 constant and 0 if it is not known to be a compile-time constant. A
5751 return of 0 does not indicate that the value is @emph{not} a constant,
5752 but merely that GCC cannot prove it is a constant with the specified
5753 value of the @option{-O} option.
5755 You would typically use this function in an embedded application where
5756 memory was a critical resource. If you have some complex calculation,
5757 you may want it to be folded if it involves constants, but need to call
5758 a function if it does not. For example:
5761 #define Scale_Value(X) \
5762 (__builtin_constant_p (X) \
5763 ? ((X) * SCALE + OFFSET) : Scale (X))
5766 You may use this built-in function in either a macro or an inline
5767 function. However, if you use it in an inlined function and pass an
5768 argument of the function as the argument to the built-in, GCC will
5769 never return 1 when you call the inline function with a string constant
5770 or compound literal (@pxref{Compound Literals}) and will not return 1
5771 when you pass a constant numeric value to the inline function unless you
5772 specify the @option{-O} option.
5774 You may also use @code{__builtin_constant_p} in initializers for static
5775 data. For instance, you can write
5778 static const int table[] = @{
5779 __builtin_constant_p (EXPRESSION) ? (EXPRESSION) : -1,
5785 This is an acceptable initializer even if @var{EXPRESSION} is not a
5786 constant expression. GCC must be more conservative about evaluating the
5787 built-in in this case, because it has no opportunity to perform
5790 Previous versions of GCC did not accept this built-in in data
5791 initializers. The earliest version where it is completely safe is
5795 @deftypefn {Built-in Function} long __builtin_expect (long @var{exp}, long @var{c})
5796 @opindex fprofile-arcs
5797 You may use @code{__builtin_expect} to provide the compiler with
5798 branch prediction information. In general, you should prefer to
5799 use actual profile feedback for this (@option{-fprofile-arcs}), as
5800 programmers are notoriously bad at predicting how their programs
5801 actually perform. However, there are applications in which this
5802 data is hard to collect.
5804 The return value is the value of @var{exp}, which should be an
5805 integral expression. The value of @var{c} must be a compile-time
5806 constant. The semantics of the built-in are that it is expected
5807 that @var{exp} == @var{c}. For example:
5810 if (__builtin_expect (x, 0))
5815 would indicate that we do not expect to call @code{foo}, since
5816 we expect @code{x} to be zero. Since you are limited to integral
5817 expressions for @var{exp}, you should use constructions such as
5820 if (__builtin_expect (ptr != NULL, 1))
5825 when testing pointer or floating-point values.
5828 @deftypefn {Built-in Function} void __builtin_prefetch (const void *@var{addr}, ...)
5829 This function is used to minimize cache-miss latency by moving data into
5830 a cache before it is accessed.
5831 You can insert calls to @code{__builtin_prefetch} into code for which
5832 you know addresses of data in memory that is likely to be accessed soon.
5833 If the target supports them, data prefetch instructions will be generated.
5834 If the prefetch is done early enough before the access then the data will
5835 be in the cache by the time it is accessed.
5837 The value of @var{addr} is the address of the memory to prefetch.
5838 There are two optional arguments, @var{rw} and @var{locality}.
5839 The value of @var{rw} is a compile-time constant one or zero; one
5840 means that the prefetch is preparing for a write to the memory address
5841 and zero, the default, means that the prefetch is preparing for a read.
5842 The value @var{locality} must be a compile-time constant integer between
5843 zero and three. A value of zero means that the data has no temporal
5844 locality, so it need not be left in the cache after the access. A value
5845 of three means that the data has a high degree of temporal locality and
5846 should be left in all levels of cache possible. Values of one and two
5847 mean, respectively, a low or moderate degree of temporal locality. The
5851 for (i = 0; i < n; i++)
5854 __builtin_prefetch (&a[i+j], 1, 1);
5855 __builtin_prefetch (&b[i+j], 0, 1);
5860 Data prefetch does not generate faults if @var{addr} is invalid, but
5861 the address expression itself must be valid. For example, a prefetch
5862 of @code{p->next} will not fault if @code{p->next} is not a valid
5863 address, but evaluation will fault if @code{p} is not a valid address.
5865 If the target does not support data prefetch, the address expression
5866 is evaluated if it includes side effects but no other code is generated
5867 and GCC does not issue a warning.
5870 @deftypefn {Built-in Function} double __builtin_huge_val (void)
5871 Returns a positive infinity, if supported by the floating-point format,
5872 else @code{DBL_MAX}. This function is suitable for implementing the
5873 ISO C macro @code{HUGE_VAL}.
5876 @deftypefn {Built-in Function} float __builtin_huge_valf (void)
5877 Similar to @code{__builtin_huge_val}, except the return type is @code{float}.
5880 @deftypefn {Built-in Function} {long double} __builtin_huge_vall (void)
5881 Similar to @code{__builtin_huge_val}, except the return
5882 type is @code{long double}.
5885 @deftypefn {Built-in Function} double __builtin_inf (void)
5886 Similar to @code{__builtin_huge_val}, except a warning is generated
5887 if the target floating-point format does not support infinities.
5890 @deftypefn {Built-in Function} _Decimal32 __builtin_infd32 (void)
5891 Similar to @code{__builtin_inf}, except the return type is @code{_Decimal32}.
5894 @deftypefn {Built-in Function} _Decimal64 __builtin_infd64 (void)
5895 Similar to @code{__builtin_inf}, except the return type is @code{_Decimal64}.
5898 @deftypefn {Built-in Function} _Decimal128 __builtin_infd128 (void)
5899 Similar to @code{__builtin_inf}, except the return type is @code{_Decimal128}.
5902 @deftypefn {Built-in Function} float __builtin_inff (void)
5903 Similar to @code{__builtin_inf}, except the return type is @code{float}.
5904 This function is suitable for implementing the ISO C99 macro @code{INFINITY}.
5907 @deftypefn {Built-in Function} {long double} __builtin_infl (void)
5908 Similar to @code{__builtin_inf}, except the return
5909 type is @code{long double}.
5912 @deftypefn {Built-in Function} double __builtin_nan (const char *str)
5913 This is an implementation of the ISO C99 function @code{nan}.
5915 Since ISO C99 defines this function in terms of @code{strtod}, which we
5916 do not implement, a description of the parsing is in order. The string
5917 is parsed as by @code{strtol}; that is, the base is recognized by
5918 leading @samp{0} or @samp{0x} prefixes. The number parsed is placed
5919 in the significand such that the least significant bit of the number
5920 is at the least significant bit of the significand. The number is
5921 truncated to fit the significand field provided. The significand is
5922 forced to be a quiet NaN@.
5924 This function, if given a string literal all of which would have been
5925 consumed by strtol, is evaluated early enough that it is considered a
5926 compile-time constant.
5929 @deftypefn {Built-in Function} _Decimal32 __builtin_nand32 (const char *str)
5930 Similar to @code{__builtin_nan}, except the return type is @code{_Decimal32}.
5933 @deftypefn {Built-in Function} _Decimal64 __builtin_nand64 (const char *str)
5934 Similar to @code{__builtin_nan}, except the return type is @code{_Decimal64}.
5937 @deftypefn {Built-in Function} _Decimal128 __builtin_nand128 (const char *str)
5938 Similar to @code{__builtin_nan}, except the return type is @code{_Decimal128}.
5941 @deftypefn {Built-in Function} float __builtin_nanf (const char *str)
5942 Similar to @code{__builtin_nan}, except the return type is @code{float}.
5945 @deftypefn {Built-in Function} {long double} __builtin_nanl (const char *str)
5946 Similar to @code{__builtin_nan}, except the return type is @code{long double}.
5949 @deftypefn {Built-in Function} double __builtin_nans (const char *str)
5950 Similar to @code{__builtin_nan}, except the significand is forced
5951 to be a signaling NaN@. The @code{nans} function is proposed by
5952 @uref{http://www.open-std.org/jtc1/sc22/wg14/www/docs/n965.htm,,WG14 N965}.
5955 @deftypefn {Built-in Function} float __builtin_nansf (const char *str)
5956 Similar to @code{__builtin_nans}, except the return type is @code{float}.
5959 @deftypefn {Built-in Function} {long double} __builtin_nansl (const char *str)
5960 Similar to @code{__builtin_nans}, except the return type is @code{long double}.
5963 @deftypefn {Built-in Function} int __builtin_ffs (unsigned int x)
5964 Returns one plus the index of the least significant 1-bit of @var{x}, or
5965 if @var{x} is zero, returns zero.
5968 @deftypefn {Built-in Function} int __builtin_clz (unsigned int x)
5969 Returns the number of leading 0-bits in @var{x}, starting at the most
5970 significant bit position. If @var{x} is 0, the result is undefined.
5973 @deftypefn {Built-in Function} int __builtin_ctz (unsigned int x)
5974 Returns the number of trailing 0-bits in @var{x}, starting at the least
5975 significant bit position. If @var{x} is 0, the result is undefined.
5978 @deftypefn {Built-in Function} int __builtin_popcount (unsigned int x)
5979 Returns the number of 1-bits in @var{x}.
5982 @deftypefn {Built-in Function} int __builtin_parity (unsigned int x)
5983 Returns the parity of @var{x}, i.e.@: the number of 1-bits in @var{x}
5987 @deftypefn {Built-in Function} int __builtin_ffsl (unsigned long)
5988 Similar to @code{__builtin_ffs}, except the argument type is
5989 @code{unsigned long}.
5992 @deftypefn {Built-in Function} int __builtin_clzl (unsigned long)
5993 Similar to @code{__builtin_clz}, except the argument type is
5994 @code{unsigned long}.
5997 @deftypefn {Built-in Function} int __builtin_ctzl (unsigned long)
5998 Similar to @code{__builtin_ctz}, except the argument type is
5999 @code{unsigned long}.
6002 @deftypefn {Built-in Function} int __builtin_popcountl (unsigned long)
6003 Similar to @code{__builtin_popcount}, except the argument type is
6004 @code{unsigned long}.
6007 @deftypefn {Built-in Function} int __builtin_parityl (unsigned long)
6008 Similar to @code{__builtin_parity}, except the argument type is
6009 @code{unsigned long}.
6012 @deftypefn {Built-in Function} int __builtin_ffsll (unsigned long long)
6013 Similar to @code{__builtin_ffs}, except the argument type is
6014 @code{unsigned long long}.
6017 @deftypefn {Built-in Function} int __builtin_clzll (unsigned long long)
6018 Similar to @code{__builtin_clz}, except the argument type is
6019 @code{unsigned long long}.
6022 @deftypefn {Built-in Function} int __builtin_ctzll (unsigned long long)
6023 Similar to @code{__builtin_ctz}, except the argument type is
6024 @code{unsigned long long}.
6027 @deftypefn {Built-in Function} int __builtin_popcountll (unsigned long long)
6028 Similar to @code{__builtin_popcount}, except the argument type is
6029 @code{unsigned long long}.
6032 @deftypefn {Built-in Function} int __builtin_parityll (unsigned long long)
6033 Similar to @code{__builtin_parity}, except the argument type is
6034 @code{unsigned long long}.
6037 @deftypefn {Built-in Function} double __builtin_powi (double, int)
6038 Returns the first argument raised to the power of the second. Unlike the
6039 @code{pow} function no guarantees about precision and rounding are made.
6042 @deftypefn {Built-in Function} float __builtin_powif (float, int)
6043 Similar to @code{__builtin_powi}, except the argument and return types
6047 @deftypefn {Built-in Function} {long double} __builtin_powil (long double, int)
6048 Similar to @code{__builtin_powi}, except the argument and return types
6049 are @code{long double}.
6053 @node Target Builtins
6054 @section Built-in Functions Specific to Particular Target Machines
6056 On some target machines, GCC supports many built-in functions specific
6057 to those machines. Generally these generate calls to specific machine
6058 instructions, but allow the compiler to schedule those calls.
6061 * Alpha Built-in Functions::
6062 * ARM Built-in Functions::
6063 * Blackfin Built-in Functions::
6064 * FR-V Built-in Functions::
6065 * X86 Built-in Functions::
6066 * MIPS DSP Built-in Functions::
6067 * MIPS Paired-Single Support::
6068 * PowerPC AltiVec Built-in Functions::
6069 * SPARC VIS Built-in Functions::
6072 @node Alpha Built-in Functions
6073 @subsection Alpha Built-in Functions
6075 These built-in functions are available for the Alpha family of
6076 processors, depending on the command-line switches used.
6078 The following built-in functions are always available. They
6079 all generate the machine instruction that is part of the name.
6082 long __builtin_alpha_implver (void)
6083 long __builtin_alpha_rpcc (void)
6084 long __builtin_alpha_amask (long)
6085 long __builtin_alpha_cmpbge (long, long)
6086 long __builtin_alpha_extbl (long, long)
6087 long __builtin_alpha_extwl (long, long)
6088 long __builtin_alpha_extll (long, long)
6089 long __builtin_alpha_extql (long, long)
6090 long __builtin_alpha_extwh (long, long)
6091 long __builtin_alpha_extlh (long, long)
6092 long __builtin_alpha_extqh (long, long)
6093 long __builtin_alpha_insbl (long, long)
6094 long __builtin_alpha_inswl (long, long)
6095 long __builtin_alpha_insll (long, long)
6096 long __builtin_alpha_insql (long, long)
6097 long __builtin_alpha_inswh (long, long)
6098 long __builtin_alpha_inslh (long, long)
6099 long __builtin_alpha_insqh (long, long)
6100 long __builtin_alpha_mskbl (long, long)
6101 long __builtin_alpha_mskwl (long, long)
6102 long __builtin_alpha_mskll (long, long)
6103 long __builtin_alpha_mskql (long, long)
6104 long __builtin_alpha_mskwh (long, long)
6105 long __builtin_alpha_msklh (long, long)
6106 long __builtin_alpha_mskqh (long, long)
6107 long __builtin_alpha_umulh (long, long)
6108 long __builtin_alpha_zap (long, long)
6109 long __builtin_alpha_zapnot (long, long)
6112 The following built-in functions are always with @option{-mmax}
6113 or @option{-mcpu=@var{cpu}} where @var{cpu} is @code{pca56} or
6114 later. They all generate the machine instruction that is part
6118 long __builtin_alpha_pklb (long)
6119 long __builtin_alpha_pkwb (long)
6120 long __builtin_alpha_unpkbl (long)
6121 long __builtin_alpha_unpkbw (long)
6122 long __builtin_alpha_minub8 (long, long)
6123 long __builtin_alpha_minsb8 (long, long)
6124 long __builtin_alpha_minuw4 (long, long)
6125 long __builtin_alpha_minsw4 (long, long)
6126 long __builtin_alpha_maxub8 (long, long)
6127 long __builtin_alpha_maxsb8 (long, long)
6128 long __builtin_alpha_maxuw4 (long, long)
6129 long __builtin_alpha_maxsw4 (long, long)
6130 long __builtin_alpha_perr (long, long)
6133 The following built-in functions are always with @option{-mcix}
6134 or @option{-mcpu=@var{cpu}} where @var{cpu} is @code{ev67} or
6135 later. They all generate the machine instruction that is part
6139 long __builtin_alpha_cttz (long)
6140 long __builtin_alpha_ctlz (long)
6141 long __builtin_alpha_ctpop (long)
6144 The following builtins are available on systems that use the OSF/1
6145 PALcode. Normally they invoke the @code{rduniq} and @code{wruniq}
6146 PAL calls, but when invoked with @option{-mtls-kernel}, they invoke
6147 @code{rdval} and @code{wrval}.
6150 void *__builtin_thread_pointer (void)
6151 void __builtin_set_thread_pointer (void *)
6154 @node ARM Built-in Functions
6155 @subsection ARM Built-in Functions
6157 These built-in functions are available for the ARM family of
6158 processors, when the @option{-mcpu=iwmmxt} switch is used:
6161 typedef int v2si __attribute__ ((vector_size (8)));
6162 typedef short v4hi __attribute__ ((vector_size (8)));
6163 typedef char v8qi __attribute__ ((vector_size (8)));
6165 int __builtin_arm_getwcx (int)
6166 void __builtin_arm_setwcx (int, int)
6167 int __builtin_arm_textrmsb (v8qi, int)
6168 int __builtin_arm_textrmsh (v4hi, int)
6169 int __builtin_arm_textrmsw (v2si, int)
6170 int __builtin_arm_textrmub (v8qi, int)
6171 int __builtin_arm_textrmuh (v4hi, int)
6172 int __builtin_arm_textrmuw (v2si, int)
6173 v8qi __builtin_arm_tinsrb (v8qi, int)
6174 v4hi __builtin_arm_tinsrh (v4hi, int)
6175 v2si __builtin_arm_tinsrw (v2si, int)
6176 long long __builtin_arm_tmia (long long, int, int)
6177 long long __builtin_arm_tmiabb (long long, int, int)
6178 long long __builtin_arm_tmiabt (long long, int, int)
6179 long long __builtin_arm_tmiaph (long long, int, int)
6180 long long __builtin_arm_tmiatb (long long, int, int)
6181 long long __builtin_arm_tmiatt (long long, int, int)
6182 int __builtin_arm_tmovmskb (v8qi)
6183 int __builtin_arm_tmovmskh (v4hi)
6184 int __builtin_arm_tmovmskw (v2si)
6185 long long __builtin_arm_waccb (v8qi)
6186 long long __builtin_arm_wacch (v4hi)
6187 long long __builtin_arm_waccw (v2si)
6188 v8qi __builtin_arm_waddb (v8qi, v8qi)
6189 v8qi __builtin_arm_waddbss (v8qi, v8qi)
6190 v8qi __builtin_arm_waddbus (v8qi, v8qi)
6191 v4hi __builtin_arm_waddh (v4hi, v4hi)
6192 v4hi __builtin_arm_waddhss (v4hi, v4hi)
6193 v4hi __builtin_arm_waddhus (v4hi, v4hi)
6194 v2si __builtin_arm_waddw (v2si, v2si)
6195 v2si __builtin_arm_waddwss (v2si, v2si)
6196 v2si __builtin_arm_waddwus (v2si, v2si)
6197 v8qi __builtin_arm_walign (v8qi, v8qi, int)
6198 long long __builtin_arm_wand(long long, long long)
6199 long long __builtin_arm_wandn (long long, long long)
6200 v8qi __builtin_arm_wavg2b (v8qi, v8qi)
6201 v8qi __builtin_arm_wavg2br (v8qi, v8qi)
6202 v4hi __builtin_arm_wavg2h (v4hi, v4hi)
6203 v4hi __builtin_arm_wavg2hr (v4hi, v4hi)
6204 v8qi __builtin_arm_wcmpeqb (v8qi, v8qi)
6205 v4hi __builtin_arm_wcmpeqh (v4hi, v4hi)
6206 v2si __builtin_arm_wcmpeqw (v2si, v2si)
6207 v8qi __builtin_arm_wcmpgtsb (v8qi, v8qi)
6208 v4hi __builtin_arm_wcmpgtsh (v4hi, v4hi)
6209 v2si __builtin_arm_wcmpgtsw (v2si, v2si)
6210 v8qi __builtin_arm_wcmpgtub (v8qi, v8qi)
6211 v4hi __builtin_arm_wcmpgtuh (v4hi, v4hi)
6212 v2si __builtin_arm_wcmpgtuw (v2si, v2si)
6213 long long __builtin_arm_wmacs (long long, v4hi, v4hi)
6214 long long __builtin_arm_wmacsz (v4hi, v4hi)
6215 long long __builtin_arm_wmacu (long long, v4hi, v4hi)
6216 long long __builtin_arm_wmacuz (v4hi, v4hi)
6217 v4hi __builtin_arm_wmadds (v4hi, v4hi)
6218 v4hi __builtin_arm_wmaddu (v4hi, v4hi)
6219 v8qi __builtin_arm_wmaxsb (v8qi, v8qi)
6220 v4hi __builtin_arm_wmaxsh (v4hi, v4hi)
6221 v2si __builtin_arm_wmaxsw (v2si, v2si)
6222 v8qi __builtin_arm_wmaxub (v8qi, v8qi)
6223 v4hi __builtin_arm_wmaxuh (v4hi, v4hi)
6224 v2si __builtin_arm_wmaxuw (v2si, v2si)
6225 v8qi __builtin_arm_wminsb (v8qi, v8qi)
6226 v4hi __builtin_arm_wminsh (v4hi, v4hi)
6227 v2si __builtin_arm_wminsw (v2si, v2si)
6228 v8qi __builtin_arm_wminub (v8qi, v8qi)
6229 v4hi __builtin_arm_wminuh (v4hi, v4hi)
6230 v2si __builtin_arm_wminuw (v2si, v2si)
6231 v4hi __builtin_arm_wmulsm (v4hi, v4hi)
6232 v4hi __builtin_arm_wmulul (v4hi, v4hi)
6233 v4hi __builtin_arm_wmulum (v4hi, v4hi)
6234 long long __builtin_arm_wor (long long, long long)
6235 v2si __builtin_arm_wpackdss (long long, long long)
6236 v2si __builtin_arm_wpackdus (long long, long long)
6237 v8qi __builtin_arm_wpackhss (v4hi, v4hi)
6238 v8qi __builtin_arm_wpackhus (v4hi, v4hi)
6239 v4hi __builtin_arm_wpackwss (v2si, v2si)
6240 v4hi __builtin_arm_wpackwus (v2si, v2si)
6241 long long __builtin_arm_wrord (long long, long long)
6242 long long __builtin_arm_wrordi (long long, int)
6243 v4hi __builtin_arm_wrorh (v4hi, long long)
6244 v4hi __builtin_arm_wrorhi (v4hi, int)
6245 v2si __builtin_arm_wrorw (v2si, long long)
6246 v2si __builtin_arm_wrorwi (v2si, int)
6247 v2si __builtin_arm_wsadb (v8qi, v8qi)
6248 v2si __builtin_arm_wsadbz (v8qi, v8qi)
6249 v2si __builtin_arm_wsadh (v4hi, v4hi)
6250 v2si __builtin_arm_wsadhz (v4hi, v4hi)
6251 v4hi __builtin_arm_wshufh (v4hi, int)
6252 long long __builtin_arm_wslld (long long, long long)
6253 long long __builtin_arm_wslldi (long long, int)
6254 v4hi __builtin_arm_wsllh (v4hi, long long)
6255 v4hi __builtin_arm_wsllhi (v4hi, int)
6256 v2si __builtin_arm_wsllw (v2si, long long)
6257 v2si __builtin_arm_wsllwi (v2si, int)
6258 long long __builtin_arm_wsrad (long long, long long)
6259 long long __builtin_arm_wsradi (long long, int)
6260 v4hi __builtin_arm_wsrah (v4hi, long long)
6261 v4hi __builtin_arm_wsrahi (v4hi, int)
6262 v2si __builtin_arm_wsraw (v2si, long long)
6263 v2si __builtin_arm_wsrawi (v2si, int)
6264 long long __builtin_arm_wsrld (long long, long long)
6265 long long __builtin_arm_wsrldi (long long, int)
6266 v4hi __builtin_arm_wsrlh (v4hi, long long)
6267 v4hi __builtin_arm_wsrlhi (v4hi, int)
6268 v2si __builtin_arm_wsrlw (v2si, long long)
6269 v2si __builtin_arm_wsrlwi (v2si, int)
6270 v8qi __builtin_arm_wsubb (v8qi, v8qi)
6271 v8qi __builtin_arm_wsubbss (v8qi, v8qi)
6272 v8qi __builtin_arm_wsubbus (v8qi, v8qi)
6273 v4hi __builtin_arm_wsubh (v4hi, v4hi)
6274 v4hi __builtin_arm_wsubhss (v4hi, v4hi)
6275 v4hi __builtin_arm_wsubhus (v4hi, v4hi)
6276 v2si __builtin_arm_wsubw (v2si, v2si)
6277 v2si __builtin_arm_wsubwss (v2si, v2si)
6278 v2si __builtin_arm_wsubwus (v2si, v2si)
6279 v4hi __builtin_arm_wunpckehsb (v8qi)
6280 v2si __builtin_arm_wunpckehsh (v4hi)
6281 long long __builtin_arm_wunpckehsw (v2si)
6282 v4hi __builtin_arm_wunpckehub (v8qi)
6283 v2si __builtin_arm_wunpckehuh (v4hi)
6284 long long __builtin_arm_wunpckehuw (v2si)
6285 v4hi __builtin_arm_wunpckelsb (v8qi)
6286 v2si __builtin_arm_wunpckelsh (v4hi)
6287 long long __builtin_arm_wunpckelsw (v2si)
6288 v4hi __builtin_arm_wunpckelub (v8qi)
6289 v2si __builtin_arm_wunpckeluh (v4hi)
6290 long long __builtin_arm_wunpckeluw (v2si)
6291 v8qi __builtin_arm_wunpckihb (v8qi, v8qi)
6292 v4hi __builtin_arm_wunpckihh (v4hi, v4hi)
6293 v2si __builtin_arm_wunpckihw (v2si, v2si)
6294 v8qi __builtin_arm_wunpckilb (v8qi, v8qi)
6295 v4hi __builtin_arm_wunpckilh (v4hi, v4hi)
6296 v2si __builtin_arm_wunpckilw (v2si, v2si)
6297 long long __builtin_arm_wxor (long long, long long)
6298 long long __builtin_arm_wzero ()
6301 @node Blackfin Built-in Functions
6302 @subsection Blackfin Built-in Functions
6304 Currently, there are two Blackfin-specific built-in functions. These are
6305 used for generating @code{CSYNC} and @code{SSYNC} machine insns without
6306 using inline assembly; by using these built-in functions the compiler can
6307 automatically add workarounds for hardware errata involving these
6308 instructions. These functions are named as follows:
6311 void __builtin_bfin_csync (void)
6312 void __builtin_bfin_ssync (void)
6315 @node FR-V Built-in Functions
6316 @subsection FR-V Built-in Functions
6318 GCC provides many FR-V-specific built-in functions. In general,
6319 these functions are intended to be compatible with those described
6320 by @cite{FR-V Family, Softune C/C++ Compiler Manual (V6), Fujitsu
6321 Semiconductor}. The two exceptions are @code{__MDUNPACKH} and
6322 @code{__MBTOHE}, the gcc forms of which pass 128-bit values by
6323 pointer rather than by value.
6325 Most of the functions are named after specific FR-V instructions.
6326 Such functions are said to be ``directly mapped'' and are summarized
6327 here in tabular form.
6331 * Directly-mapped Integer Functions::
6332 * Directly-mapped Media Functions::
6333 * Raw read/write Functions::
6334 * Other Built-in Functions::
6337 @node Argument Types
6338 @subsubsection Argument Types
6340 The arguments to the built-in functions can be divided into three groups:
6341 register numbers, compile-time constants and run-time values. In order
6342 to make this classification clear at a glance, the arguments and return
6343 values are given the following pseudo types:
6345 @multitable @columnfractions .20 .30 .15 .35
6346 @item Pseudo type @tab Real C type @tab Constant? @tab Description
6347 @item @code{uh} @tab @code{unsigned short} @tab No @tab an unsigned halfword
6348 @item @code{uw1} @tab @code{unsigned int} @tab No @tab an unsigned word
6349 @item @code{sw1} @tab @code{int} @tab No @tab a signed word
6350 @item @code{uw2} @tab @code{unsigned long long} @tab No
6351 @tab an unsigned doubleword
6352 @item @code{sw2} @tab @code{long long} @tab No @tab a signed doubleword
6353 @item @code{const} @tab @code{int} @tab Yes @tab an integer constant
6354 @item @code{acc} @tab @code{int} @tab Yes @tab an ACC register number
6355 @item @code{iacc} @tab @code{int} @tab Yes @tab an IACC register number
6358 These pseudo types are not defined by GCC, they are simply a notational
6359 convenience used in this manual.
6361 Arguments of type @code{uh}, @code{uw1}, @code{sw1}, @code{uw2}
6362 and @code{sw2} are evaluated at run time. They correspond to
6363 register operands in the underlying FR-V instructions.
6365 @code{const} arguments represent immediate operands in the underlying
6366 FR-V instructions. They must be compile-time constants.
6368 @code{acc} arguments are evaluated at compile time and specify the number
6369 of an accumulator register. For example, an @code{acc} argument of 2
6370 will select the ACC2 register.
6372 @code{iacc} arguments are similar to @code{acc} arguments but specify the
6373 number of an IACC register. See @pxref{Other Built-in Functions}
6376 @node Directly-mapped Integer Functions
6377 @subsubsection Directly-mapped Integer Functions
6379 The functions listed below map directly to FR-V I-type instructions.
6381 @multitable @columnfractions .45 .32 .23
6382 @item Function prototype @tab Example usage @tab Assembly output
6383 @item @code{sw1 __ADDSS (sw1, sw1)}
6384 @tab @code{@var{c} = __ADDSS (@var{a}, @var{b})}
6385 @tab @code{ADDSS @var{a},@var{b},@var{c}}
6386 @item @code{sw1 __SCAN (sw1, sw1)}
6387 @tab @code{@var{c} = __SCAN (@var{a}, @var{b})}
6388 @tab @code{SCAN @var{a},@var{b},@var{c}}
6389 @item @code{sw1 __SCUTSS (sw1)}
6390 @tab @code{@var{b} = __SCUTSS (@var{a})}
6391 @tab @code{SCUTSS @var{a},@var{b}}
6392 @item @code{sw1 __SLASS (sw1, sw1)}
6393 @tab @code{@var{c} = __SLASS (@var{a}, @var{b})}
6394 @tab @code{SLASS @var{a},@var{b},@var{c}}
6395 @item @code{void __SMASS (sw1, sw1)}
6396 @tab @code{__SMASS (@var{a}, @var{b})}
6397 @tab @code{SMASS @var{a},@var{b}}
6398 @item @code{void __SMSSS (sw1, sw1)}
6399 @tab @code{__SMSSS (@var{a}, @var{b})}
6400 @tab @code{SMSSS @var{a},@var{b}}
6401 @item @code{void __SMU (sw1, sw1)}
6402 @tab @code{__SMU (@var{a}, @var{b})}
6403 @tab @code{SMU @var{a},@var{b}}
6404 @item @code{sw2 __SMUL (sw1, sw1)}
6405 @tab @code{@var{c} = __SMUL (@var{a}, @var{b})}
6406 @tab @code{SMUL @var{a},@var{b},@var{c}}
6407 @item @code{sw1 __SUBSS (sw1, sw1)}
6408 @tab @code{@var{c} = __SUBSS (@var{a}, @var{b})}
6409 @tab @code{SUBSS @var{a},@var{b},@var{c}}
6410 @item @code{uw2 __UMUL (uw1, uw1)}
6411 @tab @code{@var{c} = __UMUL (@var{a}, @var{b})}
6412 @tab @code{UMUL @var{a},@var{b},@var{c}}
6415 @node Directly-mapped Media Functions
6416 @subsubsection Directly-mapped Media Functions
6418 The functions listed below map directly to FR-V M-type instructions.
6420 @multitable @columnfractions .45 .32 .23
6421 @item Function prototype @tab Example usage @tab Assembly output
6422 @item @code{uw1 __MABSHS (sw1)}
6423 @tab @code{@var{b} = __MABSHS (@var{a})}
6424 @tab @code{MABSHS @var{a},@var{b}}
6425 @item @code{void __MADDACCS (acc, acc)}
6426 @tab @code{__MADDACCS (@var{b}, @var{a})}
6427 @tab @code{MADDACCS @var{a},@var{b}}
6428 @item @code{sw1 __MADDHSS (sw1, sw1)}
6429 @tab @code{@var{c} = __MADDHSS (@var{a}, @var{b})}
6430 @tab @code{MADDHSS @var{a},@var{b},@var{c}}
6431 @item @code{uw1 __MADDHUS (uw1, uw1)}
6432 @tab @code{@var{c} = __MADDHUS (@var{a}, @var{b})}
6433 @tab @code{MADDHUS @var{a},@var{b},@var{c}}
6434 @item @code{uw1 __MAND (uw1, uw1)}
6435 @tab @code{@var{c} = __MAND (@var{a}, @var{b})}
6436 @tab @code{MAND @var{a},@var{b},@var{c}}
6437 @item @code{void __MASACCS (acc, acc)}
6438 @tab @code{__MASACCS (@var{b}, @var{a})}
6439 @tab @code{MASACCS @var{a},@var{b}}
6440 @item @code{uw1 __MAVEH (uw1, uw1)}
6441 @tab @code{@var{c} = __MAVEH (@var{a}, @var{b})}
6442 @tab @code{MAVEH @var{a},@var{b},@var{c}}
6443 @item @code{uw2 __MBTOH (uw1)}
6444 @tab @code{@var{b} = __MBTOH (@var{a})}
6445 @tab @code{MBTOH @var{a},@var{b}}
6446 @item @code{void __MBTOHE (uw1 *, uw1)}
6447 @tab @code{__MBTOHE (&@var{b}, @var{a})}
6448 @tab @code{MBTOHE @var{a},@var{b}}
6449 @item @code{void __MCLRACC (acc)}
6450 @tab @code{__MCLRACC (@var{a})}
6451 @tab @code{MCLRACC @var{a}}
6452 @item @code{void __MCLRACCA (void)}
6453 @tab @code{__MCLRACCA ()}
6454 @tab @code{MCLRACCA}
6455 @item @code{uw1 __Mcop1 (uw1, uw1)}
6456 @tab @code{@var{c} = __Mcop1 (@var{a}, @var{b})}
6457 @tab @code{Mcop1 @var{a},@var{b},@var{c}}
6458 @item @code{uw1 __Mcop2 (uw1, uw1)}
6459 @tab @code{@var{c} = __Mcop2 (@var{a}, @var{b})}
6460 @tab @code{Mcop2 @var{a},@var{b},@var{c}}
6461 @item @code{uw1 __MCPLHI (uw2, const)}
6462 @tab @code{@var{c} = __MCPLHI (@var{a}, @var{b})}
6463 @tab @code{MCPLHI @var{a},#@var{b},@var{c}}
6464 @item @code{uw1 __MCPLI (uw2, const)}
6465 @tab @code{@var{c} = __MCPLI (@var{a}, @var{b})}
6466 @tab @code{MCPLI @var{a},#@var{b},@var{c}}
6467 @item @code{void __MCPXIS (acc, sw1, sw1)}
6468 @tab @code{__MCPXIS (@var{c}, @var{a}, @var{b})}
6469 @tab @code{MCPXIS @var{a},@var{b},@var{c}}
6470 @item @code{void __MCPXIU (acc, uw1, uw1)}
6471 @tab @code{__MCPXIU (@var{c}, @var{a}, @var{b})}
6472 @tab @code{MCPXIU @var{a},@var{b},@var{c}}
6473 @item @code{void __MCPXRS (acc, sw1, sw1)}
6474 @tab @code{__MCPXRS (@var{c}, @var{a}, @var{b})}
6475 @tab @code{MCPXRS @var{a},@var{b},@var{c}}
6476 @item @code{void __MCPXRU (acc, uw1, uw1)}
6477 @tab @code{__MCPXRU (@var{c}, @var{a}, @var{b})}
6478 @tab @code{MCPXRU @var{a},@var{b},@var{c}}
6479 @item @code{uw1 __MCUT (acc, uw1)}
6480 @tab @code{@var{c} = __MCUT (@var{a}, @var{b})}
6481 @tab @code{MCUT @var{a},@var{b},@var{c}}
6482 @item @code{uw1 __MCUTSS (acc, sw1)}
6483 @tab @code{@var{c} = __MCUTSS (@var{a}, @var{b})}
6484 @tab @code{MCUTSS @var{a},@var{b},@var{c}}
6485 @item @code{void __MDADDACCS (acc, acc)}
6486 @tab @code{__MDADDACCS (@var{b}, @var{a})}
6487 @tab @code{MDADDACCS @var{a},@var{b}}
6488 @item @code{void __MDASACCS (acc, acc)}
6489 @tab @code{__MDASACCS (@var{b}, @var{a})}
6490 @tab @code{MDASACCS @var{a},@var{b}}
6491 @item @code{uw2 __MDCUTSSI (acc, const)}
6492 @tab @code{@var{c} = __MDCUTSSI (@var{a}, @var{b})}
6493 @tab @code{MDCUTSSI @var{a},#@var{b},@var{c}}
6494 @item @code{uw2 __MDPACKH (uw2, uw2)}
6495 @tab @code{@var{c} = __MDPACKH (@var{a}, @var{b})}
6496 @tab @code{MDPACKH @var{a},@var{b},@var{c}}
6497 @item @code{uw2 __MDROTLI (uw2, const)}
6498 @tab @code{@var{c} = __MDROTLI (@var{a}, @var{b})}
6499 @tab @code{MDROTLI @var{a},#@var{b},@var{c}}
6500 @item @code{void __MDSUBACCS (acc, acc)}
6501 @tab @code{__MDSUBACCS (@var{b}, @var{a})}
6502 @tab @code{MDSUBACCS @var{a},@var{b}}
6503 @item @code{void __MDUNPACKH (uw1 *, uw2)}
6504 @tab @code{__MDUNPACKH (&@var{b}, @var{a})}
6505 @tab @code{MDUNPACKH @var{a},@var{b}}
6506 @item @code{uw2 __MEXPDHD (uw1, const)}
6507 @tab @code{@var{c} = __MEXPDHD (@var{a}, @var{b})}
6508 @tab @code{MEXPDHD @var{a},#@var{b},@var{c}}
6509 @item @code{uw1 __MEXPDHW (uw1, const)}
6510 @tab @code{@var{c} = __MEXPDHW (@var{a}, @var{b})}
6511 @tab @code{MEXPDHW @var{a},#@var{b},@var{c}}
6512 @item @code{uw1 __MHDSETH (uw1, const)}
6513 @tab @code{@var{c} = __MHDSETH (@var{a}, @var{b})}
6514 @tab @code{MHDSETH @var{a},#@var{b},@var{c}}
6515 @item @code{sw1 __MHDSETS (const)}
6516 @tab @code{@var{b} = __MHDSETS (@var{a})}
6517 @tab @code{MHDSETS #@var{a},@var{b}}
6518 @item @code{uw1 __MHSETHIH (uw1, const)}
6519 @tab @code{@var{b} = __MHSETHIH (@var{b}, @var{a})}
6520 @tab @code{MHSETHIH #@var{a},@var{b}}
6521 @item @code{sw1 __MHSETHIS (sw1, const)}
6522 @tab @code{@var{b} = __MHSETHIS (@var{b}, @var{a})}
6523 @tab @code{MHSETHIS #@var{a},@var{b}}
6524 @item @code{uw1 __MHSETLOH (uw1, const)}
6525 @tab @code{@var{b} = __MHSETLOH (@var{b}, @var{a})}
6526 @tab @code{MHSETLOH #@var{a},@var{b}}
6527 @item @code{sw1 __MHSETLOS (sw1, const)}
6528 @tab @code{@var{b} = __MHSETLOS (@var{b}, @var{a})}
6529 @tab @code{MHSETLOS #@var{a},@var{b}}
6530 @item @code{uw1 __MHTOB (uw2)}
6531 @tab @code{@var{b} = __MHTOB (@var{a})}
6532 @tab @code{MHTOB @var{a},@var{b}}
6533 @item @code{void __MMACHS (acc, sw1, sw1)}
6534 @tab @code{__MMACHS (@var{c}, @var{a}, @var{b})}
6535 @tab @code{MMACHS @var{a},@var{b},@var{c}}
6536 @item @code{void __MMACHU (acc, uw1, uw1)}
6537 @tab @code{__MMACHU (@var{c}, @var{a}, @var{b})}
6538 @tab @code{MMACHU @var{a},@var{b},@var{c}}
6539 @item @code{void __MMRDHS (acc, sw1, sw1)}
6540 @tab @code{__MMRDHS (@var{c}, @var{a}, @var{b})}
6541 @tab @code{MMRDHS @var{a},@var{b},@var{c}}
6542 @item @code{void __MMRDHU (acc, uw1, uw1)}
6543 @tab @code{__MMRDHU (@var{c}, @var{a}, @var{b})}
6544 @tab @code{MMRDHU @var{a},@var{b},@var{c}}
6545 @item @code{void __MMULHS (acc, sw1, sw1)}
6546 @tab @code{__MMULHS (@var{c}, @var{a}, @var{b})}
6547 @tab @code{MMULHS @var{a},@var{b},@var{c}}
6548 @item @code{void __MMULHU (acc, uw1, uw1)}
6549 @tab @code{__MMULHU (@var{c}, @var{a}, @var{b})}
6550 @tab @code{MMULHU @var{a},@var{b},@var{c}}
6551 @item @code{void __MMULXHS (acc, sw1, sw1)}
6552 @tab @code{__MMULXHS (@var{c}, @var{a}, @var{b})}
6553 @tab @code{MMULXHS @var{a},@var{b},@var{c}}
6554 @item @code{void __MMULXHU (acc, uw1, uw1)}
6555 @tab @code{__MMULXHU (@var{c}, @var{a}, @var{b})}
6556 @tab @code{MMULXHU @var{a},@var{b},@var{c}}
6557 @item @code{uw1 __MNOT (uw1)}
6558 @tab @code{@var{b} = __MNOT (@var{a})}
6559 @tab @code{MNOT @var{a},@var{b}}
6560 @item @code{uw1 __MOR (uw1, uw1)}
6561 @tab @code{@var{c} = __MOR (@var{a}, @var{b})}
6562 @tab @code{MOR @var{a},@var{b},@var{c}}
6563 @item @code{uw1 __MPACKH (uh, uh)}
6564 @tab @code{@var{c} = __MPACKH (@var{a}, @var{b})}
6565 @tab @code{MPACKH @var{a},@var{b},@var{c}}
6566 @item @code{sw2 __MQADDHSS (sw2, sw2)}
6567 @tab @code{@var{c} = __MQADDHSS (@var{a}, @var{b})}
6568 @tab @code{MQADDHSS @var{a},@var{b},@var{c}}
6569 @item @code{uw2 __MQADDHUS (uw2, uw2)}
6570 @tab @code{@var{c} = __MQADDHUS (@var{a}, @var{b})}
6571 @tab @code{MQADDHUS @var{a},@var{b},@var{c}}
6572 @item @code{void __MQCPXIS (acc, sw2, sw2)}
6573 @tab @code{__MQCPXIS (@var{c}, @var{a}, @var{b})}
6574 @tab @code{MQCPXIS @var{a},@var{b},@var{c}}
6575 @item @code{void __MQCPXIU (acc, uw2, uw2)}
6576 @tab @code{__MQCPXIU (@var{c}, @var{a}, @var{b})}
6577 @tab @code{MQCPXIU @var{a},@var{b},@var{c}}
6578 @item @code{void __MQCPXRS (acc, sw2, sw2)}
6579 @tab @code{__MQCPXRS (@var{c}, @var{a}, @var{b})}
6580 @tab @code{MQCPXRS @var{a},@var{b},@var{c}}
6581 @item @code{void __MQCPXRU (acc, uw2, uw2)}
6582 @tab @code{__MQCPXRU (@var{c}, @var{a}, @var{b})}
6583 @tab @code{MQCPXRU @var{a},@var{b},@var{c}}
6584 @item @code{sw2 __MQLCLRHS (sw2, sw2)}
6585 @tab @code{@var{c} = __MQLCLRHS (@var{a}, @var{b})}
6586 @tab @code{MQLCLRHS @var{a},@var{b},@var{c}}
6587 @item @code{sw2 __MQLMTHS (sw2, sw2)}
6588 @tab @code{@var{c} = __MQLMTHS (@var{a}, @var{b})}
6589 @tab @code{MQLMTHS @var{a},@var{b},@var{c}}
6590 @item @code{void __MQMACHS (acc, sw2, sw2)}
6591 @tab @code{__MQMACHS (@var{c}, @var{a}, @var{b})}
6592 @tab @code{MQMACHS @var{a},@var{b},@var{c}}
6593 @item @code{void __MQMACHU (acc, uw2, uw2)}
6594 @tab @code{__MQMACHU (@var{c}, @var{a}, @var{b})}
6595 @tab @code{MQMACHU @var{a},@var{b},@var{c}}
6596 @item @code{void __MQMACXHS (acc, sw2, sw2)}
6597 @tab @code{__MQMACXHS (@var{c}, @var{a}, @var{b})}
6598 @tab @code{MQMACXHS @var{a},@var{b},@var{c}}
6599 @item @code{void __MQMULHS (acc, sw2, sw2)}
6600 @tab @code{__MQMULHS (@var{c}, @var{a}, @var{b})}
6601 @tab @code{MQMULHS @var{a},@var{b},@var{c}}
6602 @item @code{void __MQMULHU (acc, uw2, uw2)}
6603 @tab @code{__MQMULHU (@var{c}, @var{a}, @var{b})}
6604 @tab @code{MQMULHU @var{a},@var{b},@var{c}}
6605 @item @code{void __MQMULXHS (acc, sw2, sw2)}
6606 @tab @code{__MQMULXHS (@var{c}, @var{a}, @var{b})}
6607 @tab @code{MQMULXHS @var{a},@var{b},@var{c}}
6608 @item @code{void __MQMULXHU (acc, uw2, uw2)}
6609 @tab @code{__MQMULXHU (@var{c}, @var{a}, @var{b})}
6610 @tab @code{MQMULXHU @var{a},@var{b},@var{c}}
6611 @item @code{sw2 __MQSATHS (sw2, sw2)}
6612 @tab @code{@var{c} = __MQSATHS (@var{a}, @var{b})}
6613 @tab @code{MQSATHS @var{a},@var{b},@var{c}}
6614 @item @code{uw2 __MQSLLHI (uw2, int)}
6615 @tab @code{@var{c} = __MQSLLHI (@var{a}, @var{b})}
6616 @tab @code{MQSLLHI @var{a},@var{b},@var{c}}
6617 @item @code{sw2 __MQSRAHI (sw2, int)}
6618 @tab @code{@var{c} = __MQSRAHI (@var{a}, @var{b})}
6619 @tab @code{MQSRAHI @var{a},@var{b},@var{c}}
6620 @item @code{sw2 __MQSUBHSS (sw2, sw2)}
6621 @tab @code{@var{c} = __MQSUBHSS (@var{a}, @var{b})}
6622 @tab @code{MQSUBHSS @var{a},@var{b},@var{c}}
6623 @item @code{uw2 __MQSUBHUS (uw2, uw2)}
6624 @tab @code{@var{c} = __MQSUBHUS (@var{a}, @var{b})}
6625 @tab @code{MQSUBHUS @var{a},@var{b},@var{c}}
6626 @item @code{void __MQXMACHS (acc, sw2, sw2)}
6627 @tab @code{__MQXMACHS (@var{c}, @var{a}, @var{b})}
6628 @tab @code{MQXMACHS @var{a},@var{b},@var{c}}
6629 @item @code{void __MQXMACXHS (acc, sw2, sw2)}
6630 @tab @code{__MQXMACXHS (@var{c}, @var{a}, @var{b})}
6631 @tab @code{MQXMACXHS @var{a},@var{b},@var{c}}
6632 @item @code{uw1 __MRDACC (acc)}
6633 @tab @code{@var{b} = __MRDACC (@var{a})}
6634 @tab @code{MRDACC @var{a},@var{b}}
6635 @item @code{uw1 __MRDACCG (acc)}
6636 @tab @code{@var{b} = __MRDACCG (@var{a})}
6637 @tab @code{MRDACCG @var{a},@var{b}}
6638 @item @code{uw1 __MROTLI (uw1, const)}
6639 @tab @code{@var{c} = __MROTLI (@var{a}, @var{b})}
6640 @tab @code{MROTLI @var{a},#@var{b},@var{c}}
6641 @item @code{uw1 __MROTRI (uw1, const)}
6642 @tab @code{@var{c} = __MROTRI (@var{a}, @var{b})}
6643 @tab @code{MROTRI @var{a},#@var{b},@var{c}}
6644 @item @code{sw1 __MSATHS (sw1, sw1)}
6645 @tab @code{@var{c} = __MSATHS (@var{a}, @var{b})}
6646 @tab @code{MSATHS @var{a},@var{b},@var{c}}
6647 @item @code{uw1 __MSATHU (uw1, uw1)}
6648 @tab @code{@var{c} = __MSATHU (@var{a}, @var{b})}
6649 @tab @code{MSATHU @var{a},@var{b},@var{c}}
6650 @item @code{uw1 __MSLLHI (uw1, const)}
6651 @tab @code{@var{c} = __MSLLHI (@var{a}, @var{b})}
6652 @tab @code{MSLLHI @var{a},#@var{b},@var{c}}
6653 @item @code{sw1 __MSRAHI (sw1, const)}
6654 @tab @code{@var{c} = __MSRAHI (@var{a}, @var{b})}
6655 @tab @code{MSRAHI @var{a},#@var{b},@var{c}}
6656 @item @code{uw1 __MSRLHI (uw1, const)}
6657 @tab @code{@var{c} = __MSRLHI (@var{a}, @var{b})}
6658 @tab @code{MSRLHI @var{a},#@var{b},@var{c}}
6659 @item @code{void __MSUBACCS (acc, acc)}
6660 @tab @code{__MSUBACCS (@var{b}, @var{a})}
6661 @tab @code{MSUBACCS @var{a},@var{b}}
6662 @item @code{sw1 __MSUBHSS (sw1, sw1)}
6663 @tab @code{@var{c} = __MSUBHSS (@var{a}, @var{b})}
6664 @tab @code{MSUBHSS @var{a},@var{b},@var{c}}
6665 @item @code{uw1 __MSUBHUS (uw1, uw1)}
6666 @tab @code{@var{c} = __MSUBHUS (@var{a}, @var{b})}
6667 @tab @code{MSUBHUS @var{a},@var{b},@var{c}}
6668 @item @code{void __MTRAP (void)}
6669 @tab @code{__MTRAP ()}
6671 @item @code{uw2 __MUNPACKH (uw1)}
6672 @tab @code{@var{b} = __MUNPACKH (@var{a})}
6673 @tab @code{MUNPACKH @var{a},@var{b}}
6674 @item @code{uw1 __MWCUT (uw2, uw1)}
6675 @tab @code{@var{c} = __MWCUT (@var{a}, @var{b})}
6676 @tab @code{MWCUT @var{a},@var{b},@var{c}}
6677 @item @code{void __MWTACC (acc, uw1)}
6678 @tab @code{__MWTACC (@var{b}, @var{a})}
6679 @tab @code{MWTACC @var{a},@var{b}}
6680 @item @code{void __MWTACCG (acc, uw1)}
6681 @tab @code{__MWTACCG (@var{b}, @var{a})}
6682 @tab @code{MWTACCG @var{a},@var{b}}
6683 @item @code{uw1 __MXOR (uw1, uw1)}
6684 @tab @code{@var{c} = __MXOR (@var{a}, @var{b})}
6685 @tab @code{MXOR @var{a},@var{b},@var{c}}
6688 @node Raw read/write Functions
6689 @subsubsection Raw read/write Functions
6691 This sections describes built-in functions related to read and write
6692 instructions to access memory. These functions generate
6693 @code{membar} instructions to flush the I/O load and stores where
6694 appropriate, as described in Fujitsu's manual described above.
6698 @item unsigned char __builtin_read8 (void *@var{data})
6699 @item unsigned short __builtin_read16 (void *@var{data})
6700 @item unsigned long __builtin_read32 (void *@var{data})
6701 @item unsigned long long __builtin_read64 (void *@var{data})
6703 @item void __builtin_write8 (void *@var{data}, unsigned char @var{datum})
6704 @item void __builtin_write16 (void *@var{data}, unsigned short @var{datum})
6705 @item void __builtin_write32 (void *@var{data}, unsigned long @var{datum})
6706 @item void __builtin_write64 (void *@var{data}, unsigned long long @var{datum})
6709 @node Other Built-in Functions
6710 @subsubsection Other Built-in Functions
6712 This section describes built-in functions that are not named after
6713 a specific FR-V instruction.
6716 @item sw2 __IACCreadll (iacc @var{reg})
6717 Return the full 64-bit value of IACC0@. The @var{reg} argument is reserved
6718 for future expansion and must be 0.
6720 @item sw1 __IACCreadl (iacc @var{reg})
6721 Return the value of IACC0H if @var{reg} is 0 and IACC0L if @var{reg} is 1.
6722 Other values of @var{reg} are rejected as invalid.
6724 @item void __IACCsetll (iacc @var{reg}, sw2 @var{x})
6725 Set the full 64-bit value of IACC0 to @var{x}. The @var{reg} argument
6726 is reserved for future expansion and must be 0.
6728 @item void __IACCsetl (iacc @var{reg}, sw1 @var{x})
6729 Set IACC0H to @var{x} if @var{reg} is 0 and IACC0L to @var{x} if @var{reg}
6730 is 1. Other values of @var{reg} are rejected as invalid.
6732 @item void __data_prefetch0 (const void *@var{x})
6733 Use the @code{dcpl} instruction to load the contents of address @var{x}
6734 into the data cache.
6736 @item void __data_prefetch (const void *@var{x})
6737 Use the @code{nldub} instruction to load the contents of address @var{x}
6738 into the data cache. The instruction will be issued in slot I1@.
6741 @node X86 Built-in Functions
6742 @subsection X86 Built-in Functions
6744 These built-in functions are available for the i386 and x86-64 family
6745 of computers, depending on the command-line switches used.
6747 Note that, if you specify command-line switches such as @option{-msse},
6748 the compiler could use the extended instruction sets even if the built-ins
6749 are not used explicitly in the program. For this reason, applications
6750 which perform runtime CPU detection must compile separate files for each
6751 supported architecture, using the appropriate flags. In particular,
6752 the file containing the CPU detection code should be compiled without
6755 The following machine modes are available for use with MMX built-in functions
6756 (@pxref{Vector Extensions}): @code{V2SI} for a vector of two 32-bit integers,
6757 @code{V4HI} for a vector of four 16-bit integers, and @code{V8QI} for a
6758 vector of eight 8-bit integers. Some of the built-in functions operate on
6759 MMX registers as a whole 64-bit entity, these use @code{DI} as their mode.
6761 If 3Dnow extensions are enabled, @code{V2SF} is used as a mode for a vector
6762 of two 32-bit floating point values.
6764 If SSE extensions are enabled, @code{V4SF} is used for a vector of four 32-bit
6765 floating point values. Some instructions use a vector of four 32-bit
6766 integers, these use @code{V4SI}. Finally, some instructions operate on an
6767 entire vector register, interpreting it as a 128-bit integer, these use mode
6770 The following built-in functions are made available by @option{-mmmx}.
6771 All of them generate the machine instruction that is part of the name.
6774 v8qi __builtin_ia32_paddb (v8qi, v8qi)
6775 v4hi __builtin_ia32_paddw (v4hi, v4hi)
6776 v2si __builtin_ia32_paddd (v2si, v2si)
6777 v8qi __builtin_ia32_psubb (v8qi, v8qi)
6778 v4hi __builtin_ia32_psubw (v4hi, v4hi)
6779 v2si __builtin_ia32_psubd (v2si, v2si)
6780 v8qi __builtin_ia32_paddsb (v8qi, v8qi)
6781 v4hi __builtin_ia32_paddsw (v4hi, v4hi)
6782 v8qi __builtin_ia32_psubsb (v8qi, v8qi)
6783 v4hi __builtin_ia32_psubsw (v4hi, v4hi)
6784 v8qi __builtin_ia32_paddusb (v8qi, v8qi)
6785 v4hi __builtin_ia32_paddusw (v4hi, v4hi)
6786 v8qi __builtin_ia32_psubusb (v8qi, v8qi)
6787 v4hi __builtin_ia32_psubusw (v4hi, v4hi)
6788 v4hi __builtin_ia32_pmullw (v4hi, v4hi)
6789 v4hi __builtin_ia32_pmulhw (v4hi, v4hi)
6790 di __builtin_ia32_pand (di, di)
6791 di __builtin_ia32_pandn (di,di)
6792 di __builtin_ia32_por (di, di)
6793 di __builtin_ia32_pxor (di, di)
6794 v8qi __builtin_ia32_pcmpeqb (v8qi, v8qi)
6795 v4hi __builtin_ia32_pcmpeqw (v4hi, v4hi)
6796 v2si __builtin_ia32_pcmpeqd (v2si, v2si)
6797 v8qi __builtin_ia32_pcmpgtb (v8qi, v8qi)
6798 v4hi __builtin_ia32_pcmpgtw (v4hi, v4hi)
6799 v2si __builtin_ia32_pcmpgtd (v2si, v2si)
6800 v8qi __builtin_ia32_punpckhbw (v8qi, v8qi)
6801 v4hi __builtin_ia32_punpckhwd (v4hi, v4hi)
6802 v2si __builtin_ia32_punpckhdq (v2si, v2si)
6803 v8qi __builtin_ia32_punpcklbw (v8qi, v8qi)
6804 v4hi __builtin_ia32_punpcklwd (v4hi, v4hi)
6805 v2si __builtin_ia32_punpckldq (v2si, v2si)
6806 v8qi __builtin_ia32_packsswb (v4hi, v4hi)
6807 v4hi __builtin_ia32_packssdw (v2si, v2si)
6808 v8qi __builtin_ia32_packuswb (v4hi, v4hi)
6811 The following built-in functions are made available either with
6812 @option{-msse}, or with a combination of @option{-m3dnow} and
6813 @option{-march=athlon}. All of them generate the machine
6814 instruction that is part of the name.
6817 v4hi __builtin_ia32_pmulhuw (v4hi, v4hi)
6818 v8qi __builtin_ia32_pavgb (v8qi, v8qi)
6819 v4hi __builtin_ia32_pavgw (v4hi, v4hi)
6820 v4hi __builtin_ia32_psadbw (v8qi, v8qi)
6821 v8qi __builtin_ia32_pmaxub (v8qi, v8qi)
6822 v4hi __builtin_ia32_pmaxsw (v4hi, v4hi)
6823 v8qi __builtin_ia32_pminub (v8qi, v8qi)
6824 v4hi __builtin_ia32_pminsw (v4hi, v4hi)
6825 int __builtin_ia32_pextrw (v4hi, int)
6826 v4hi __builtin_ia32_pinsrw (v4hi, int, int)
6827 int __builtin_ia32_pmovmskb (v8qi)
6828 void __builtin_ia32_maskmovq (v8qi, v8qi, char *)
6829 void __builtin_ia32_movntq (di *, di)
6830 void __builtin_ia32_sfence (void)
6833 The following built-in functions are available when @option{-msse} is used.
6834 All of them generate the machine instruction that is part of the name.
6837 int __builtin_ia32_comieq (v4sf, v4sf)
6838 int __builtin_ia32_comineq (v4sf, v4sf)
6839 int __builtin_ia32_comilt (v4sf, v4sf)
6840 int __builtin_ia32_comile (v4sf, v4sf)
6841 int __builtin_ia32_comigt (v4sf, v4sf)
6842 int __builtin_ia32_comige (v4sf, v4sf)
6843 int __builtin_ia32_ucomieq (v4sf, v4sf)
6844 int __builtin_ia32_ucomineq (v4sf, v4sf)
6845 int __builtin_ia32_ucomilt (v4sf, v4sf)
6846 int __builtin_ia32_ucomile (v4sf, v4sf)
6847 int __builtin_ia32_ucomigt (v4sf, v4sf)
6848 int __builtin_ia32_ucomige (v4sf, v4sf)
6849 v4sf __builtin_ia32_addps (v4sf, v4sf)
6850 v4sf __builtin_ia32_subps (v4sf, v4sf)
6851 v4sf __builtin_ia32_mulps (v4sf, v4sf)
6852 v4sf __builtin_ia32_divps (v4sf, v4sf)
6853 v4sf __builtin_ia32_addss (v4sf, v4sf)
6854 v4sf __builtin_ia32_subss (v4sf, v4sf)
6855 v4sf __builtin_ia32_mulss (v4sf, v4sf)
6856 v4sf __builtin_ia32_divss (v4sf, v4sf)
6857 v4si __builtin_ia32_cmpeqps (v4sf, v4sf)
6858 v4si __builtin_ia32_cmpltps (v4sf, v4sf)
6859 v4si __builtin_ia32_cmpleps (v4sf, v4sf)
6860 v4si __builtin_ia32_cmpgtps (v4sf, v4sf)
6861 v4si __builtin_ia32_cmpgeps (v4sf, v4sf)
6862 v4si __builtin_ia32_cmpunordps (v4sf, v4sf)
6863 v4si __builtin_ia32_cmpneqps (v4sf, v4sf)
6864 v4si __builtin_ia32_cmpnltps (v4sf, v4sf)
6865 v4si __builtin_ia32_cmpnleps (v4sf, v4sf)
6866 v4si __builtin_ia32_cmpngtps (v4sf, v4sf)
6867 v4si __builtin_ia32_cmpngeps (v4sf, v4sf)
6868 v4si __builtin_ia32_cmpordps (v4sf, v4sf)
6869 v4si __builtin_ia32_cmpeqss (v4sf, v4sf)
6870 v4si __builtin_ia32_cmpltss (v4sf, v4sf)
6871 v4si __builtin_ia32_cmpless (v4sf, v4sf)
6872 v4si __builtin_ia32_cmpunordss (v4sf, v4sf)
6873 v4si __builtin_ia32_cmpneqss (v4sf, v4sf)
6874 v4si __builtin_ia32_cmpnlts (v4sf, v4sf)
6875 v4si __builtin_ia32_cmpnless (v4sf, v4sf)
6876 v4si __builtin_ia32_cmpordss (v4sf, v4sf)
6877 v4sf __builtin_ia32_maxps (v4sf, v4sf)
6878 v4sf __builtin_ia32_maxss (v4sf, v4sf)
6879 v4sf __builtin_ia32_minps (v4sf, v4sf)
6880 v4sf __builtin_ia32_minss (v4sf, v4sf)
6881 v4sf __builtin_ia32_andps (v4sf, v4sf)
6882 v4sf __builtin_ia32_andnps (v4sf, v4sf)
6883 v4sf __builtin_ia32_orps (v4sf, v4sf)
6884 v4sf __builtin_ia32_xorps (v4sf, v4sf)
6885 v4sf __builtin_ia32_movss (v4sf, v4sf)
6886 v4sf __builtin_ia32_movhlps (v4sf, v4sf)
6887 v4sf __builtin_ia32_movlhps (v4sf, v4sf)
6888 v4sf __builtin_ia32_unpckhps (v4sf, v4sf)
6889 v4sf __builtin_ia32_unpcklps (v4sf, v4sf)
6890 v4sf __builtin_ia32_cvtpi2ps (v4sf, v2si)
6891 v4sf __builtin_ia32_cvtsi2ss (v4sf, int)
6892 v2si __builtin_ia32_cvtps2pi (v4sf)
6893 int __builtin_ia32_cvtss2si (v4sf)
6894 v2si __builtin_ia32_cvttps2pi (v4sf)
6895 int __builtin_ia32_cvttss2si (v4sf)
6896 v4sf __builtin_ia32_rcpps (v4sf)
6897 v4sf __builtin_ia32_rsqrtps (v4sf)
6898 v4sf __builtin_ia32_sqrtps (v4sf)
6899 v4sf __builtin_ia32_rcpss (v4sf)
6900 v4sf __builtin_ia32_rsqrtss (v4sf)
6901 v4sf __builtin_ia32_sqrtss (v4sf)
6902 v4sf __builtin_ia32_shufps (v4sf, v4sf, int)
6903 void __builtin_ia32_movntps (float *, v4sf)
6904 int __builtin_ia32_movmskps (v4sf)
6907 The following built-in functions are available when @option{-msse} is used.
6910 @item v4sf __builtin_ia32_loadaps (float *)
6911 Generates the @code{movaps} machine instruction as a load from memory.
6912 @item void __builtin_ia32_storeaps (float *, v4sf)
6913 Generates the @code{movaps} machine instruction as a store to memory.
6914 @item v4sf __builtin_ia32_loadups (float *)
6915 Generates the @code{movups} machine instruction as a load from memory.
6916 @item void __builtin_ia32_storeups (float *, v4sf)
6917 Generates the @code{movups} machine instruction as a store to memory.
6918 @item v4sf __builtin_ia32_loadsss (float *)
6919 Generates the @code{movss} machine instruction as a load from memory.
6920 @item void __builtin_ia32_storess (float *, v4sf)
6921 Generates the @code{movss} machine instruction as a store to memory.
6922 @item v4sf __builtin_ia32_loadhps (v4sf, v2si *)
6923 Generates the @code{movhps} machine instruction as a load from memory.
6924 @item v4sf __builtin_ia32_loadlps (v4sf, v2si *)
6925 Generates the @code{movlps} machine instruction as a load from memory
6926 @item void __builtin_ia32_storehps (v4sf, v2si *)
6927 Generates the @code{movhps} machine instruction as a store to memory.
6928 @item void __builtin_ia32_storelps (v4sf, v2si *)
6929 Generates the @code{movlps} machine instruction as a store to memory.
6932 The following built-in functions are available when @option{-msse3} is used.
6933 All of them generate the machine instruction that is part of the name.
6936 v2df __builtin_ia32_addsubpd (v2df, v2df)
6937 v2df __builtin_ia32_addsubps (v2df, v2df)
6938 v2df __builtin_ia32_haddpd (v2df, v2df)
6939 v2df __builtin_ia32_haddps (v2df, v2df)
6940 v2df __builtin_ia32_hsubpd (v2df, v2df)
6941 v2df __builtin_ia32_hsubps (v2df, v2df)
6942 v16qi __builtin_ia32_lddqu (char const *)
6943 void __builtin_ia32_monitor (void *, unsigned int, unsigned int)
6944 v2df __builtin_ia32_movddup (v2df)
6945 v4sf __builtin_ia32_movshdup (v4sf)
6946 v4sf __builtin_ia32_movsldup (v4sf)
6947 void __builtin_ia32_mwait (unsigned int, unsigned int)
6950 The following built-in functions are available when @option{-msse3} is used.
6953 @item v2df __builtin_ia32_loadddup (double const *)
6954 Generates the @code{movddup} machine instruction as a load from memory.
6957 The following built-in functions are available when @option{-m3dnow} is used.
6958 All of them generate the machine instruction that is part of the name.
6961 void __builtin_ia32_femms (void)
6962 v8qi __builtin_ia32_pavgusb (v8qi, v8qi)
6963 v2si __builtin_ia32_pf2id (v2sf)
6964 v2sf __builtin_ia32_pfacc (v2sf, v2sf)
6965 v2sf __builtin_ia32_pfadd (v2sf, v2sf)
6966 v2si __builtin_ia32_pfcmpeq (v2sf, v2sf)
6967 v2si __builtin_ia32_pfcmpge (v2sf, v2sf)
6968 v2si __builtin_ia32_pfcmpgt (v2sf, v2sf)
6969 v2sf __builtin_ia32_pfmax (v2sf, v2sf)
6970 v2sf __builtin_ia32_pfmin (v2sf, v2sf)
6971 v2sf __builtin_ia32_pfmul (v2sf, v2sf)
6972 v2sf __builtin_ia32_pfrcp (v2sf)
6973 v2sf __builtin_ia32_pfrcpit1 (v2sf, v2sf)
6974 v2sf __builtin_ia32_pfrcpit2 (v2sf, v2sf)
6975 v2sf __builtin_ia32_pfrsqrt (v2sf)
6976 v2sf __builtin_ia32_pfrsqrtit1 (v2sf, v2sf)
6977 v2sf __builtin_ia32_pfsub (v2sf, v2sf)
6978 v2sf __builtin_ia32_pfsubr (v2sf, v2sf)
6979 v2sf __builtin_ia32_pi2fd (v2si)
6980 v4hi __builtin_ia32_pmulhrw (v4hi, v4hi)
6983 The following built-in functions are available when both @option{-m3dnow}
6984 and @option{-march=athlon} are used. All of them generate the machine
6985 instruction that is part of the name.
6988 v2si __builtin_ia32_pf2iw (v2sf)
6989 v2sf __builtin_ia32_pfnacc (v2sf, v2sf)
6990 v2sf __builtin_ia32_pfpnacc (v2sf, v2sf)
6991 v2sf __builtin_ia32_pi2fw (v2si)
6992 v2sf __builtin_ia32_pswapdsf (v2sf)
6993 v2si __builtin_ia32_pswapdsi (v2si)
6996 @node MIPS DSP Built-in Functions
6997 @subsection MIPS DSP Built-in Functions
6999 The MIPS DSP Application-Specific Extension (ASE) includes new
7000 instructions that are designed to improve the performance of DSP and
7001 media applications. It provides instructions that operate on packed
7002 8-bit integer data, Q15 fractional data and Q31 fractional data.
7004 GCC supports MIPS DSP operations using both the generic
7005 vector extensions (@pxref{Vector Extensions}) and a collection of
7006 MIPS-specific built-in functions. Both kinds of support are
7007 enabled by the @option{-mdsp} command-line option.
7009 At present, GCC only provides support for operations on 32-bit
7010 vectors. The vector type associated with 8-bit integer data is
7011 usually called @code{v4i8} and the vector type associated with Q15 is
7012 usually called @code{v2q15}. They can be defined in C as follows:
7015 typedef char v4i8 __attribute__ ((vector_size(4)));
7016 typedef short v2q15 __attribute__ ((vector_size(4)));
7019 @code{v4i8} and @code{v2q15} values are initialized in the same way as
7020 aggregates. For example:
7023 v4i8 a = @{1, 2, 3, 4@};
7025 b = (v4i8) @{5, 6, 7, 8@};
7027 v2q15 c = @{0x0fcb, 0x3a75@};
7029 d = (v2q15) @{0.1234 * 0x1.0p15, 0.4567 * 0x1.0p15@};
7032 @emph{Note:} The CPU's endianness determines the order in which values
7033 are packed. On little-endian targets, the first value is the least
7034 significant and the last value is the most significant. The opposite
7035 order applies to big-endian targets. For example, the code above will
7036 set the lowest byte of @code{a} to @code{1} on little-endian targets
7037 and @code{4} on big-endian targets.
7039 @emph{Note:} Q15 and Q31 values must be initialized with their integer
7040 representation. As shown in this example, the integer representation
7041 of a Q15 value can be obtained by multiplying the fractional value by
7042 @code{0x1.0p15}. The equivalent for Q31 values is to multiply by
7045 The table below lists the @code{v4i8} and @code{v2q15} operations for which
7046 hardware support exists. @code{a} and @code{b} are @code{v4i8} values,
7047 and @code{c} and @code{d} are @code{v2q15} values.
7049 @multitable @columnfractions .50 .50
7050 @item C code @tab MIPS instruction
7051 @item @code{a + b} @tab @code{addu.qb}
7052 @item @code{c + d} @tab @code{addq.ph}
7053 @item @code{a - b} @tab @code{subu.qb}
7054 @item @code{c - d} @tab @code{subq.ph}
7057 It is easier to describe the DSP built-in functions if we first define
7058 the following types:
7063 typedef long long a64;
7066 @code{q31} and @code{i32} are actually the same as @code{int}, but we
7067 use @code{q31} to indicate a Q31 fractional value and @code{i32} to
7068 indicate a 32-bit integer value. Similarly, @code{a64} is the same as
7069 @code{long long}, but we use @code{a64} to indicate values that will
7070 be placed in one of the four DSP accumulators (@code{$ac0},
7071 @code{$ac1}, @code{$ac2} or @code{$ac3}).
7073 Also, some built-in functions prefer or require immediate numbers as
7074 parameters, because the corresponding DSP instructions accept both immediate
7075 numbers and register operands, or accept immediate numbers only. The
7076 immediate parameters are listed as follows.
7084 imm_n32_31: -32 to 31.
7085 imm_n512_511: -512 to 511.
7088 The following built-in functions map directly to a particular MIPS DSP
7089 instruction. Please refer to the architecture specification
7090 for details on what each instruction does.
7093 v2q15 __builtin_mips_addq_ph (v2q15, v2q15)
7094 v2q15 __builtin_mips_addq_s_ph (v2q15, v2q15)
7095 q31 __builtin_mips_addq_s_w (q31, q31)
7096 v4i8 __builtin_mips_addu_qb (v4i8, v4i8)
7097 v4i8 __builtin_mips_addu_s_qb (v4i8, v4i8)
7098 v2q15 __builtin_mips_subq_ph (v2q15, v2q15)
7099 v2q15 __builtin_mips_subq_s_ph (v2q15, v2q15)
7100 q31 __builtin_mips_subq_s_w (q31, q31)
7101 v4i8 __builtin_mips_subu_qb (v4i8, v4i8)
7102 v4i8 __builtin_mips_subu_s_qb (v4i8, v4i8)
7103 i32 __builtin_mips_addsc (i32, i32)
7104 i32 __builtin_mips_addwc (i32, i32)
7105 i32 __builtin_mips_modsub (i32, i32)
7106 i32 __builtin_mips_raddu_w_qb (v4i8)
7107 v2q15 __builtin_mips_absq_s_ph (v2q15)
7108 q31 __builtin_mips_absq_s_w (q31)
7109 v4i8 __builtin_mips_precrq_qb_ph (v2q15, v2q15)
7110 v2q15 __builtin_mips_precrq_ph_w (q31, q31)
7111 v2q15 __builtin_mips_precrq_rs_ph_w (q31, q31)
7112 v4i8 __builtin_mips_precrqu_s_qb_ph (v2q15, v2q15)
7113 q31 __builtin_mips_preceq_w_phl (v2q15)
7114 q31 __builtin_mips_preceq_w_phr (v2q15)
7115 v2q15 __builtin_mips_precequ_ph_qbl (v4i8)
7116 v2q15 __builtin_mips_precequ_ph_qbr (v4i8)
7117 v2q15 __builtin_mips_precequ_ph_qbla (v4i8)
7118 v2q15 __builtin_mips_precequ_ph_qbra (v4i8)
7119 v2q15 __builtin_mips_preceu_ph_qbl (v4i8)
7120 v2q15 __builtin_mips_preceu_ph_qbr (v4i8)
7121 v2q15 __builtin_mips_preceu_ph_qbla (v4i8)
7122 v2q15 __builtin_mips_preceu_ph_qbra (v4i8)
7123 v4i8 __builtin_mips_shll_qb (v4i8, imm0_7)
7124 v4i8 __builtin_mips_shll_qb (v4i8, i32)
7125 v2q15 __builtin_mips_shll_ph (v2q15, imm0_15)
7126 v2q15 __builtin_mips_shll_ph (v2q15, i32)
7127 v2q15 __builtin_mips_shll_s_ph (v2q15, imm0_15)
7128 v2q15 __builtin_mips_shll_s_ph (v2q15, i32)
7129 q31 __builtin_mips_shll_s_w (q31, imm0_31)
7130 q31 __builtin_mips_shll_s_w (q31, i32)
7131 v4i8 __builtin_mips_shrl_qb (v4i8, imm0_7)
7132 v4i8 __builtin_mips_shrl_qb (v4i8, i32)
7133 v2q15 __builtin_mips_shra_ph (v2q15, imm0_15)
7134 v2q15 __builtin_mips_shra_ph (v2q15, i32)
7135 v2q15 __builtin_mips_shra_r_ph (v2q15, imm0_15)
7136 v2q15 __builtin_mips_shra_r_ph (v2q15, i32)
7137 q31 __builtin_mips_shra_r_w (q31, imm0_31)
7138 q31 __builtin_mips_shra_r_w (q31, i32)
7139 v2q15 __builtin_mips_muleu_s_ph_qbl (v4i8, v2q15)
7140 v2q15 __builtin_mips_muleu_s_ph_qbr (v4i8, v2q15)
7141 v2q15 __builtin_mips_mulq_rs_ph (v2q15, v2q15)
7142 q31 __builtin_mips_muleq_s_w_phl (v2q15, v2q15)
7143 q31 __builtin_mips_muleq_s_w_phr (v2q15, v2q15)
7144 a64 __builtin_mips_dpau_h_qbl (a64, v4i8, v4i8)
7145 a64 __builtin_mips_dpau_h_qbr (a64, v4i8, v4i8)
7146 a64 __builtin_mips_dpsu_h_qbl (a64, v4i8, v4i8)
7147 a64 __builtin_mips_dpsu_h_qbr (a64, v4i8, v4i8)
7148 a64 __builtin_mips_dpaq_s_w_ph (a64, v2q15, v2q15)
7149 a64 __builtin_mips_dpaq_sa_l_w (a64, q31, q31)
7150 a64 __builtin_mips_dpsq_s_w_ph (a64, v2q15, v2q15)
7151 a64 __builtin_mips_dpsq_sa_l_w (a64, q31, q31)
7152 a64 __builtin_mips_mulsaq_s_w_ph (a64, v2q15, v2q15)
7153 a64 __builtin_mips_maq_s_w_phl (a64, v2q15, v2q15)
7154 a64 __builtin_mips_maq_s_w_phr (a64, v2q15, v2q15)
7155 a64 __builtin_mips_maq_sa_w_phl (a64, v2q15, v2q15)
7156 a64 __builtin_mips_maq_sa_w_phr (a64, v2q15, v2q15)
7157 i32 __builtin_mips_bitrev (i32)
7158 i32 __builtin_mips_insv (i32, i32)
7159 v4i8 __builtin_mips_repl_qb (imm0_255)
7160 v4i8 __builtin_mips_repl_qb (i32)
7161 v2q15 __builtin_mips_repl_ph (imm_n512_511)
7162 v2q15 __builtin_mips_repl_ph (i32)
7163 void __builtin_mips_cmpu_eq_qb (v4i8, v4i8)
7164 void __builtin_mips_cmpu_lt_qb (v4i8, v4i8)
7165 void __builtin_mips_cmpu_le_qb (v4i8, v4i8)
7166 i32 __builtin_mips_cmpgu_eq_qb (v4i8, v4i8)
7167 i32 __builtin_mips_cmpgu_lt_qb (v4i8, v4i8)
7168 i32 __builtin_mips_cmpgu_le_qb (v4i8, v4i8)
7169 void __builtin_mips_cmp_eq_ph (v2q15, v2q15)
7170 void __builtin_mips_cmp_lt_ph (v2q15, v2q15)
7171 void __builtin_mips_cmp_le_ph (v2q15, v2q15)
7172 v4i8 __builtin_mips_pick_qb (v4i8, v4i8)
7173 v2q15 __builtin_mips_pick_ph (v2q15, v2q15)
7174 v2q15 __builtin_mips_packrl_ph (v2q15, v2q15)
7175 i32 __builtin_mips_extr_w (a64, imm0_31)
7176 i32 __builtin_mips_extr_w (a64, i32)
7177 i32 __builtin_mips_extr_r_w (a64, imm0_31)
7178 i32 __builtin_mips_extr_s_h (a64, i32)
7179 i32 __builtin_mips_extr_rs_w (a64, imm0_31)
7180 i32 __builtin_mips_extr_rs_w (a64, i32)
7181 i32 __builtin_mips_extr_s_h (a64, imm0_31)
7182 i32 __builtin_mips_extr_r_w (a64, i32)
7183 i32 __builtin_mips_extp (a64, imm0_31)
7184 i32 __builtin_mips_extp (a64, i32)
7185 i32 __builtin_mips_extpdp (a64, imm0_31)
7186 i32 __builtin_mips_extpdp (a64, i32)
7187 a64 __builtin_mips_shilo (a64, imm_n32_31)
7188 a64 __builtin_mips_shilo (a64, i32)
7189 a64 __builtin_mips_mthlip (a64, i32)
7190 void __builtin_mips_wrdsp (i32, imm0_63)
7191 i32 __builtin_mips_rddsp (imm0_63)
7192 i32 __builtin_mips_lbux (void *, i32)
7193 i32 __builtin_mips_lhx (void *, i32)
7194 i32 __builtin_mips_lwx (void *, i32)
7195 i32 __builtin_mips_bposge32 (void)
7198 @node MIPS Paired-Single Support
7199 @subsection MIPS Paired-Single Support
7201 The MIPS64 architecture includes a number of instructions that
7202 operate on pairs of single-precision floating-point values.
7203 Each pair is packed into a 64-bit floating-point register,
7204 with one element being designated the ``upper half'' and
7205 the other being designated the ``lower half''.
7207 GCC supports paired-single operations using both the generic
7208 vector extensions (@pxref{Vector Extensions}) and a collection of
7209 MIPS-specific built-in functions. Both kinds of support are
7210 enabled by the @option{-mpaired-single} command-line option.
7212 The vector type associated with paired-single values is usually
7213 called @code{v2sf}. It can be defined in C as follows:
7216 typedef float v2sf __attribute__ ((vector_size (8)));
7219 @code{v2sf} values are initialized in the same way as aggregates.
7223 v2sf a = @{1.5, 9.1@};
7226 b = (v2sf) @{e, f@};
7229 @emph{Note:} The CPU's endianness determines which value is stored in
7230 the upper half of a register and which value is stored in the lower half.
7231 On little-endian targets, the first value is the lower one and the second
7232 value is the upper one. The opposite order applies to big-endian targets.
7233 For example, the code above will set the lower half of @code{a} to
7234 @code{1.5} on little-endian targets and @code{9.1} on big-endian targets.
7237 * Paired-Single Arithmetic::
7238 * Paired-Single Built-in Functions::
7239 * MIPS-3D Built-in Functions::
7242 @node Paired-Single Arithmetic
7243 @subsubsection Paired-Single Arithmetic
7245 The table below lists the @code{v2sf} operations for which hardware
7246 support exists. @code{a}, @code{b} and @code{c} are @code{v2sf}
7247 values and @code{x} is an integral value.
7249 @multitable @columnfractions .50 .50
7250 @item C code @tab MIPS instruction
7251 @item @code{a + b} @tab @code{add.ps}
7252 @item @code{a - b} @tab @code{sub.ps}
7253 @item @code{-a} @tab @code{neg.ps}
7254 @item @code{a * b} @tab @code{mul.ps}
7255 @item @code{a * b + c} @tab @code{madd.ps}
7256 @item @code{a * b - c} @tab @code{msub.ps}
7257 @item @code{-(a * b + c)} @tab @code{nmadd.ps}
7258 @item @code{-(a * b - c)} @tab @code{nmsub.ps}
7259 @item @code{x ? a : b} @tab @code{movn.ps}/@code{movz.ps}
7262 Note that the multiply-accumulate instructions can be disabled
7263 using the command-line option @code{-mno-fused-madd}.
7265 @node Paired-Single Built-in Functions
7266 @subsubsection Paired-Single Built-in Functions
7268 The following paired-single functions map directly to a particular
7269 MIPS instruction. Please refer to the architecture specification
7270 for details on what each instruction does.
7273 @item v2sf __builtin_mips_pll_ps (v2sf, v2sf)
7274 Pair lower lower (@code{pll.ps}).
7276 @item v2sf __builtin_mips_pul_ps (v2sf, v2sf)
7277 Pair upper lower (@code{pul.ps}).
7279 @item v2sf __builtin_mips_plu_ps (v2sf, v2sf)
7280 Pair lower upper (@code{plu.ps}).
7282 @item v2sf __builtin_mips_puu_ps (v2sf, v2sf)
7283 Pair upper upper (@code{puu.ps}).
7285 @item v2sf __builtin_mips_cvt_ps_s (float, float)
7286 Convert pair to paired single (@code{cvt.ps.s}).
7288 @item float __builtin_mips_cvt_s_pl (v2sf)
7289 Convert pair lower to single (@code{cvt.s.pl}).
7291 @item float __builtin_mips_cvt_s_pu (v2sf)
7292 Convert pair upper to single (@code{cvt.s.pu}).
7294 @item v2sf __builtin_mips_abs_ps (v2sf)
7295 Absolute value (@code{abs.ps}).
7297 @item v2sf __builtin_mips_alnv_ps (v2sf, v2sf, int)
7298 Align variable (@code{alnv.ps}).
7300 @emph{Note:} The value of the third parameter must be 0 or 4
7301 modulo 8, otherwise the result will be unpredictable. Please read the
7302 instruction description for details.
7305 The following multi-instruction functions are also available.
7306 In each case, @var{cond} can be any of the 16 floating-point conditions:
7307 @code{f}, @code{un}, @code{eq}, @code{ueq}, @code{olt}, @code{ult},
7308 @code{ole}, @code{ule}, @code{sf}, @code{ngle}, @code{seq}, @code{ngl},
7309 @code{lt}, @code{nge}, @code{le} or @code{ngt}.
7312 @item v2sf __builtin_mips_movt_c_@var{cond}_ps (v2sf @var{a}, v2sf @var{b}, v2sf @var{c}, v2sf @var{d})
7313 @itemx v2sf __builtin_mips_movf_c_@var{cond}_ps (v2sf @var{a}, v2sf @var{b}, v2sf @var{c}, v2sf @var{d})
7314 Conditional move based on floating point comparison (@code{c.@var{cond}.ps},
7315 @code{movt.ps}/@code{movf.ps}).
7317 The @code{movt} functions return the value @var{x} computed by:
7320 c.@var{cond}.ps @var{cc},@var{a},@var{b}
7321 mov.ps @var{x},@var{c}
7322 movt.ps @var{x},@var{d},@var{cc}
7325 The @code{movf} functions are similar but use @code{movf.ps} instead
7328 @item int __builtin_mips_upper_c_@var{cond}_ps (v2sf @var{a}, v2sf @var{b})
7329 @itemx int __builtin_mips_lower_c_@var{cond}_ps (v2sf @var{a}, v2sf @var{b})
7330 Comparison of two paired-single values (@code{c.@var{cond}.ps},
7331 @code{bc1t}/@code{bc1f}).
7333 These functions compare @var{a} and @var{b} using @code{c.@var{cond}.ps}
7334 and return either the upper or lower half of the result. For example:
7338 if (__builtin_mips_upper_c_eq_ps (a, b))
7339 upper_halves_are_equal ();
7341 upper_halves_are_unequal ();
7343 if (__builtin_mips_lower_c_eq_ps (a, b))
7344 lower_halves_are_equal ();
7346 lower_halves_are_unequal ();
7350 @node MIPS-3D Built-in Functions
7351 @subsubsection MIPS-3D Built-in Functions
7353 The MIPS-3D Application-Specific Extension (ASE) includes additional
7354 paired-single instructions that are designed to improve the performance
7355 of 3D graphics operations. Support for these instructions is controlled
7356 by the @option{-mips3d} command-line option.
7358 The functions listed below map directly to a particular MIPS-3D
7359 instruction. Please refer to the architecture specification for
7360 more details on what each instruction does.
7363 @item v2sf __builtin_mips_addr_ps (v2sf, v2sf)
7364 Reduction add (@code{addr.ps}).
7366 @item v2sf __builtin_mips_mulr_ps (v2sf, v2sf)
7367 Reduction multiply (@code{mulr.ps}).
7369 @item v2sf __builtin_mips_cvt_pw_ps (v2sf)
7370 Convert paired single to paired word (@code{cvt.pw.ps}).
7372 @item v2sf __builtin_mips_cvt_ps_pw (v2sf)
7373 Convert paired word to paired single (@code{cvt.ps.pw}).
7375 @item float __builtin_mips_recip1_s (float)
7376 @itemx double __builtin_mips_recip1_d (double)
7377 @itemx v2sf __builtin_mips_recip1_ps (v2sf)
7378 Reduced precision reciprocal (sequence step 1) (@code{recip1.@var{fmt}}).
7380 @item float __builtin_mips_recip2_s (float, float)
7381 @itemx double __builtin_mips_recip2_d (double, double)
7382 @itemx v2sf __builtin_mips_recip2_ps (v2sf, v2sf)
7383 Reduced precision reciprocal (sequence step 2) (@code{recip2.@var{fmt}}).
7385 @item float __builtin_mips_rsqrt1_s (float)
7386 @itemx double __builtin_mips_rsqrt1_d (double)
7387 @itemx v2sf __builtin_mips_rsqrt1_ps (v2sf)
7388 Reduced precision reciprocal square root (sequence step 1)
7389 (@code{rsqrt1.@var{fmt}}).
7391 @item float __builtin_mips_rsqrt2_s (float, float)
7392 @itemx double __builtin_mips_rsqrt2_d (double, double)
7393 @itemx v2sf __builtin_mips_rsqrt2_ps (v2sf, v2sf)
7394 Reduced precision reciprocal square root (sequence step 2)
7395 (@code{rsqrt2.@var{fmt}}).
7398 The following multi-instruction functions are also available.
7399 In each case, @var{cond} can be any of the 16 floating-point conditions:
7400 @code{f}, @code{un}, @code{eq}, @code{ueq}, @code{olt}, @code{ult},
7401 @code{ole}, @code{ule}, @code{sf}, @code{ngle}, @code{seq},
7402 @code{ngl}, @code{lt}, @code{nge}, @code{le} or @code{ngt}.
7405 @item int __builtin_mips_cabs_@var{cond}_s (float @var{a}, float @var{b})
7406 @itemx int __builtin_mips_cabs_@var{cond}_d (double @var{a}, double @var{b})
7407 Absolute comparison of two scalar values (@code{cabs.@var{cond}.@var{fmt}},
7408 @code{bc1t}/@code{bc1f}).
7410 These functions compare @var{a} and @var{b} using @code{cabs.@var{cond}.s}
7411 or @code{cabs.@var{cond}.d} and return the result as a boolean value.
7416 if (__builtin_mips_cabs_eq_s (a, b))
7422 @item int __builtin_mips_upper_cabs_@var{cond}_ps (v2sf @var{a}, v2sf @var{b})
7423 @itemx int __builtin_mips_lower_cabs_@var{cond}_ps (v2sf @var{a}, v2sf @var{b})
7424 Absolute comparison of two paired-single values (@code{cabs.@var{cond}.ps},
7425 @code{bc1t}/@code{bc1f}).
7427 These functions compare @var{a} and @var{b} using @code{cabs.@var{cond}.ps}
7428 and return either the upper or lower half of the result. For example:
7432 if (__builtin_mips_upper_cabs_eq_ps (a, b))
7433 upper_halves_are_equal ();
7435 upper_halves_are_unequal ();
7437 if (__builtin_mips_lower_cabs_eq_ps (a, b))
7438 lower_halves_are_equal ();
7440 lower_halves_are_unequal ();
7443 @item v2sf __builtin_mips_movt_cabs_@var{cond}_ps (v2sf @var{a}, v2sf @var{b}, v2sf @var{c}, v2sf @var{d})
7444 @itemx v2sf __builtin_mips_movf_cabs_@var{cond}_ps (v2sf @var{a}, v2sf @var{b}, v2sf @var{c}, v2sf @var{d})
7445 Conditional move based on absolute comparison (@code{cabs.@var{cond}.ps},
7446 @code{movt.ps}/@code{movf.ps}).
7448 The @code{movt} functions return the value @var{x} computed by:
7451 cabs.@var{cond}.ps @var{cc},@var{a},@var{b}
7452 mov.ps @var{x},@var{c}
7453 movt.ps @var{x},@var{d},@var{cc}
7456 The @code{movf} functions are similar but use @code{movf.ps} instead
7459 @item int __builtin_mips_any_c_@var{cond}_ps (v2sf @var{a}, v2sf @var{b})
7460 @itemx int __builtin_mips_all_c_@var{cond}_ps (v2sf @var{a}, v2sf @var{b})
7461 @itemx int __builtin_mips_any_cabs_@var{cond}_ps (v2sf @var{a}, v2sf @var{b})
7462 @itemx int __builtin_mips_all_cabs_@var{cond}_ps (v2sf @var{a}, v2sf @var{b})
7463 Comparison of two paired-single values
7464 (@code{c.@var{cond}.ps}/@code{cabs.@var{cond}.ps},
7465 @code{bc1any2t}/@code{bc1any2f}).
7467 These functions compare @var{a} and @var{b} using @code{c.@var{cond}.ps}
7468 or @code{cabs.@var{cond}.ps}. The @code{any} forms return true if either
7469 result is true and the @code{all} forms return true if both results are true.
7474 if (__builtin_mips_any_c_eq_ps (a, b))
7479 if (__builtin_mips_all_c_eq_ps (a, b))
7485 @item int __builtin_mips_any_c_@var{cond}_4s (v2sf @var{a}, v2sf @var{b}, v2sf @var{c}, v2sf @var{d})
7486 @itemx int __builtin_mips_all_c_@var{cond}_4s (v2sf @var{a}, v2sf @var{b}, v2sf @var{c}, v2sf @var{d})
7487 @itemx int __builtin_mips_any_cabs_@var{cond}_4s (v2sf @var{a}, v2sf @var{b}, v2sf @var{c}, v2sf @var{d})
7488 @itemx int __builtin_mips_all_cabs_@var{cond}_4s (v2sf @var{a}, v2sf @var{b}, v2sf @var{c}, v2sf @var{d})
7489 Comparison of four paired-single values
7490 (@code{c.@var{cond}.ps}/@code{cabs.@var{cond}.ps},
7491 @code{bc1any4t}/@code{bc1any4f}).
7493 These functions use @code{c.@var{cond}.ps} or @code{cabs.@var{cond}.ps}
7494 to compare @var{a} with @var{b} and to compare @var{c} with @var{d}.
7495 The @code{any} forms return true if any of the four results are true
7496 and the @code{all} forms return true if all four results are true.
7501 if (__builtin_mips_any_c_eq_4s (a, b, c, d))
7506 if (__builtin_mips_all_c_eq_4s (a, b, c, d))
7513 @node PowerPC AltiVec Built-in Functions
7514 @subsection PowerPC AltiVec Built-in Functions
7516 GCC provides an interface for the PowerPC family of processors to access
7517 the AltiVec operations described in Motorola's AltiVec Programming
7518 Interface Manual. The interface is made available by including
7519 @code{<altivec.h>} and using @option{-maltivec} and
7520 @option{-mabi=altivec}. The interface supports the following vector
7524 vector unsigned char
7528 vector unsigned short
7539 GCC's implementation of the high-level language interface available from
7540 C and C++ code differs from Motorola's documentation in several ways.
7545 A vector constant is a list of constant expressions within curly braces.
7548 A vector initializer requires no cast if the vector constant is of the
7549 same type as the variable it is initializing.
7552 If @code{signed} or @code{unsigned} is omitted, the signedness of the
7553 vector type is the default signedness of the base type. The default
7554 varies depending on the operating system, so a portable program should
7555 always specify the signedness.
7558 Compiling with @option{-maltivec} adds keywords @code{__vector},
7559 @code{__pixel}, and @code{__bool}. Macros @option{vector},
7560 @code{pixel}, and @code{bool} are defined in @code{<altivec.h>} and can
7564 GCC allows using a @code{typedef} name as the type specifier for a
7568 For C, overloaded functions are implemented with macros so the following
7572 vec_add ((vector signed int)@{1, 2, 3, 4@}, foo);
7575 Since @code{vec_add} is a macro, the vector constant in the example
7576 is treated as four separate arguments. Wrap the entire argument in
7577 parentheses for this to work.
7580 @emph{Note:} Only the @code{<altivec.h>} interface is supported.
7581 Internally, GCC uses built-in functions to achieve the functionality in
7582 the aforementioned header file, but they are not supported and are
7583 subject to change without notice.
7585 The following interfaces are supported for the generic and specific
7586 AltiVec operations and the AltiVec predicates. In cases where there
7587 is a direct mapping between generic and specific operations, only the
7588 generic names are shown here, although the specific operations can also
7591 Arguments that are documented as @code{const int} require literal
7592 integral values within the range required for that operation.
7595 vector signed char vec_abs (vector signed char);
7596 vector signed short vec_abs (vector signed short);
7597 vector signed int vec_abs (vector signed int);
7598 vector float vec_abs (vector float);
7600 vector signed char vec_abss (vector signed char);
7601 vector signed short vec_abss (vector signed short);
7602 vector signed int vec_abss (vector signed int);
7604 vector signed char vec_add (vector bool char, vector signed char);
7605 vector signed char vec_add (vector signed char, vector bool char);
7606 vector signed char vec_add (vector signed char, vector signed char);
7607 vector unsigned char vec_add (vector bool char, vector unsigned char);
7608 vector unsigned char vec_add (vector unsigned char, vector bool char);
7609 vector unsigned char vec_add (vector unsigned char,
7610 vector unsigned char);
7611 vector signed short vec_add (vector bool short, vector signed short);
7612 vector signed short vec_add (vector signed short, vector bool short);
7613 vector signed short vec_add (vector signed short, vector signed short);
7614 vector unsigned short vec_add (vector bool short,
7615 vector unsigned short);
7616 vector unsigned short vec_add (vector unsigned short,
7618 vector unsigned short vec_add (vector unsigned short,
7619 vector unsigned short);
7620 vector signed int vec_add (vector bool int, vector signed int);
7621 vector signed int vec_add (vector signed int, vector bool int);
7622 vector signed int vec_add (vector signed int, vector signed int);
7623 vector unsigned int vec_add (vector bool int, vector unsigned int);
7624 vector unsigned int vec_add (vector unsigned int, vector bool int);
7625 vector unsigned int vec_add (vector unsigned int, vector unsigned int);
7626 vector float vec_add (vector float, vector float);
7628 vector float vec_vaddfp (vector float, vector float);
7630 vector signed int vec_vadduwm (vector bool int, vector signed int);
7631 vector signed int vec_vadduwm (vector signed int, vector bool int);
7632 vector signed int vec_vadduwm (vector signed int, vector signed int);
7633 vector unsigned int vec_vadduwm (vector bool int, vector unsigned int);
7634 vector unsigned int vec_vadduwm (vector unsigned int, vector bool int);
7635 vector unsigned int vec_vadduwm (vector unsigned int,
7636 vector unsigned int);
7638 vector signed short vec_vadduhm (vector bool short,
7639 vector signed short);
7640 vector signed short vec_vadduhm (vector signed short,
7642 vector signed short vec_vadduhm (vector signed short,
7643 vector signed short);
7644 vector unsigned short vec_vadduhm (vector bool short,
7645 vector unsigned short);
7646 vector unsigned short vec_vadduhm (vector unsigned short,
7648 vector unsigned short vec_vadduhm (vector unsigned short,
7649 vector unsigned short);
7651 vector signed char vec_vaddubm (vector bool char, vector signed char);
7652 vector signed char vec_vaddubm (vector signed char, vector bool char);
7653 vector signed char vec_vaddubm (vector signed char, vector signed char);
7654 vector unsigned char vec_vaddubm (vector bool char,
7655 vector unsigned char);
7656 vector unsigned char vec_vaddubm (vector unsigned char,
7658 vector unsigned char vec_vaddubm (vector unsigned char,
7659 vector unsigned char);
7661 vector unsigned int vec_addc (vector unsigned int, vector unsigned int);
7663 vector unsigned char vec_adds (vector bool char, vector unsigned char);
7664 vector unsigned char vec_adds (vector unsigned char, vector bool char);
7665 vector unsigned char vec_adds (vector unsigned char,
7666 vector unsigned char);
7667 vector signed char vec_adds (vector bool char, vector signed char);
7668 vector signed char vec_adds (vector signed char, vector bool char);
7669 vector signed char vec_adds (vector signed char, vector signed char);
7670 vector unsigned short vec_adds (vector bool short,
7671 vector unsigned short);
7672 vector unsigned short vec_adds (vector unsigned short,
7674 vector unsigned short vec_adds (vector unsigned short,
7675 vector unsigned short);
7676 vector signed short vec_adds (vector bool short, vector signed short);
7677 vector signed short vec_adds (vector signed short, vector bool short);
7678 vector signed short vec_adds (vector signed short, vector signed short);
7679 vector unsigned int vec_adds (vector bool int, vector unsigned int);
7680 vector unsigned int vec_adds (vector unsigned int, vector bool int);
7681 vector unsigned int vec_adds (vector unsigned int, vector unsigned int);
7682 vector signed int vec_adds (vector bool int, vector signed int);
7683 vector signed int vec_adds (vector signed int, vector bool int);
7684 vector signed int vec_adds (vector signed int, vector signed int);
7686 vector signed int vec_vaddsws (vector bool int, vector signed int);
7687 vector signed int vec_vaddsws (vector signed int, vector bool int);
7688 vector signed int vec_vaddsws (vector signed int, vector signed int);
7690 vector unsigned int vec_vadduws (vector bool int, vector unsigned int);
7691 vector unsigned int vec_vadduws (vector unsigned int, vector bool int);
7692 vector unsigned int vec_vadduws (vector unsigned int,
7693 vector unsigned int);
7695 vector signed short vec_vaddshs (vector bool short,
7696 vector signed short);
7697 vector signed short vec_vaddshs (vector signed short,
7699 vector signed short vec_vaddshs (vector signed short,
7700 vector signed short);
7702 vector unsigned short vec_vadduhs (vector bool short,
7703 vector unsigned short);
7704 vector unsigned short vec_vadduhs (vector unsigned short,
7706 vector unsigned short vec_vadduhs (vector unsigned short,
7707 vector unsigned short);
7709 vector signed char vec_vaddsbs (vector bool char, vector signed char);
7710 vector signed char vec_vaddsbs (vector signed char, vector bool char);
7711 vector signed char vec_vaddsbs (vector signed char, vector signed char);
7713 vector unsigned char vec_vaddubs (vector bool char,
7714 vector unsigned char);
7715 vector unsigned char vec_vaddubs (vector unsigned char,
7717 vector unsigned char vec_vaddubs (vector unsigned char,
7718 vector unsigned char);
7720 vector float vec_and (vector float, vector float);
7721 vector float vec_and (vector float, vector bool int);
7722 vector float vec_and (vector bool int, vector float);
7723 vector bool int vec_and (vector bool int, vector bool int);
7724 vector signed int vec_and (vector bool int, vector signed int);
7725 vector signed int vec_and (vector signed int, vector bool int);
7726 vector signed int vec_and (vector signed int, vector signed int);
7727 vector unsigned int vec_and (vector bool int, vector unsigned int);
7728 vector unsigned int vec_and (vector unsigned int, vector bool int);
7729 vector unsigned int vec_and (vector unsigned int, vector unsigned int);
7730 vector bool short vec_and (vector bool short, vector bool short);
7731 vector signed short vec_and (vector bool short, vector signed short);
7732 vector signed short vec_and (vector signed short, vector bool short);
7733 vector signed short vec_and (vector signed short, vector signed short);
7734 vector unsigned short vec_and (vector bool short,
7735 vector unsigned short);
7736 vector unsigned short vec_and (vector unsigned short,
7738 vector unsigned short vec_and (vector unsigned short,
7739 vector unsigned short);
7740 vector signed char vec_and (vector bool char, vector signed char);
7741 vector bool char vec_and (vector bool char, vector bool char);
7742 vector signed char vec_and (vector signed char, vector bool char);
7743 vector signed char vec_and (vector signed char, vector signed char);
7744 vector unsigned char vec_and (vector bool char, vector unsigned char);
7745 vector unsigned char vec_and (vector unsigned char, vector bool char);
7746 vector unsigned char vec_and (vector unsigned char,
7747 vector unsigned char);
7749 vector float vec_andc (vector float, vector float);
7750 vector float vec_andc (vector float, vector bool int);
7751 vector float vec_andc (vector bool int, vector float);
7752 vector bool int vec_andc (vector bool int, vector bool int);
7753 vector signed int vec_andc (vector bool int, vector signed int);
7754 vector signed int vec_andc (vector signed int, vector bool int);
7755 vector signed int vec_andc (vector signed int, vector signed int);
7756 vector unsigned int vec_andc (vector bool int, vector unsigned int);
7757 vector unsigned int vec_andc (vector unsigned int, vector bool int);
7758 vector unsigned int vec_andc (vector unsigned int, vector unsigned int);
7759 vector bool short vec_andc (vector bool short, vector bool short);
7760 vector signed short vec_andc (vector bool short, vector signed short);
7761 vector signed short vec_andc (vector signed short, vector bool short);
7762 vector signed short vec_andc (vector signed short, vector signed short);
7763 vector unsigned short vec_andc (vector bool short,
7764 vector unsigned short);
7765 vector unsigned short vec_andc (vector unsigned short,
7767 vector unsigned short vec_andc (vector unsigned short,
7768 vector unsigned short);
7769 vector signed char vec_andc (vector bool char, vector signed char);
7770 vector bool char vec_andc (vector bool char, vector bool char);
7771 vector signed char vec_andc (vector signed char, vector bool char);
7772 vector signed char vec_andc (vector signed char, vector signed char);
7773 vector unsigned char vec_andc (vector bool char, vector unsigned char);
7774 vector unsigned char vec_andc (vector unsigned char, vector bool char);
7775 vector unsigned char vec_andc (vector unsigned char,
7776 vector unsigned char);
7778 vector unsigned char vec_avg (vector unsigned char,
7779 vector unsigned char);
7780 vector signed char vec_avg (vector signed char, vector signed char);
7781 vector unsigned short vec_avg (vector unsigned short,
7782 vector unsigned short);
7783 vector signed short vec_avg (vector signed short, vector signed short);
7784 vector unsigned int vec_avg (vector unsigned int, vector unsigned int);
7785 vector signed int vec_avg (vector signed int, vector signed int);
7787 vector signed int vec_vavgsw (vector signed int, vector signed int);
7789 vector unsigned int vec_vavguw (vector unsigned int,
7790 vector unsigned int);
7792 vector signed short vec_vavgsh (vector signed short,
7793 vector signed short);
7795 vector unsigned short vec_vavguh (vector unsigned short,
7796 vector unsigned short);
7798 vector signed char vec_vavgsb (vector signed char, vector signed char);
7800 vector unsigned char vec_vavgub (vector unsigned char,
7801 vector unsigned char);
7803 vector float vec_ceil (vector float);
7805 vector signed int vec_cmpb (vector float, vector float);
7807 vector bool char vec_cmpeq (vector signed char, vector signed char);
7808 vector bool char vec_cmpeq (vector unsigned char, vector unsigned char);
7809 vector bool short vec_cmpeq (vector signed short, vector signed short);
7810 vector bool short vec_cmpeq (vector unsigned short,
7811 vector unsigned short);
7812 vector bool int vec_cmpeq (vector signed int, vector signed int);
7813 vector bool int vec_cmpeq (vector unsigned int, vector unsigned int);
7814 vector bool int vec_cmpeq (vector float, vector float);
7816 vector bool int vec_vcmpeqfp (vector float, vector float);
7818 vector bool int vec_vcmpequw (vector signed int, vector signed int);
7819 vector bool int vec_vcmpequw (vector unsigned int, vector unsigned int);
7821 vector bool short vec_vcmpequh (vector signed short,
7822 vector signed short);
7823 vector bool short vec_vcmpequh (vector unsigned short,
7824 vector unsigned short);
7826 vector bool char vec_vcmpequb (vector signed char, vector signed char);
7827 vector bool char vec_vcmpequb (vector unsigned char,
7828 vector unsigned char);
7830 vector bool int vec_cmpge (vector float, vector float);
7832 vector bool char vec_cmpgt (vector unsigned char, vector unsigned char);
7833 vector bool char vec_cmpgt (vector signed char, vector signed char);
7834 vector bool short vec_cmpgt (vector unsigned short,
7835 vector unsigned short);
7836 vector bool short vec_cmpgt (vector signed short, vector signed short);
7837 vector bool int vec_cmpgt (vector unsigned int, vector unsigned int);
7838 vector bool int vec_cmpgt (vector signed int, vector signed int);
7839 vector bool int vec_cmpgt (vector float, vector float);
7841 vector bool int vec_vcmpgtfp (vector float, vector float);
7843 vector bool int vec_vcmpgtsw (vector signed int, vector signed int);
7845 vector bool int vec_vcmpgtuw (vector unsigned int, vector unsigned int);
7847 vector bool short vec_vcmpgtsh (vector signed short,
7848 vector signed short);
7850 vector bool short vec_vcmpgtuh (vector unsigned short,
7851 vector unsigned short);
7853 vector bool char vec_vcmpgtsb (vector signed char, vector signed char);
7855 vector bool char vec_vcmpgtub (vector unsigned char,
7856 vector unsigned char);
7858 vector bool int vec_cmple (vector float, vector float);
7860 vector bool char vec_cmplt (vector unsigned char, vector unsigned char);
7861 vector bool char vec_cmplt (vector signed char, vector signed char);
7862 vector bool short vec_cmplt (vector unsigned short,
7863 vector unsigned short);
7864 vector bool short vec_cmplt (vector signed short, vector signed short);
7865 vector bool int vec_cmplt (vector unsigned int, vector unsigned int);
7866 vector bool int vec_cmplt (vector signed int, vector signed int);
7867 vector bool int vec_cmplt (vector float, vector float);
7869 vector float vec_ctf (vector unsigned int, const int);
7870 vector float vec_ctf (vector signed int, const int);
7872 vector float vec_vcfsx (vector signed int, const int);
7874 vector float vec_vcfux (vector unsigned int, const int);
7876 vector signed int vec_cts (vector float, const int);
7878 vector unsigned int vec_ctu (vector float, const int);
7880 void vec_dss (const int);
7882 void vec_dssall (void);
7884 void vec_dst (const vector unsigned char *, int, const int);
7885 void vec_dst (const vector signed char *, int, const int);
7886 void vec_dst (const vector bool char *, int, const int);
7887 void vec_dst (const vector unsigned short *, int, const int);
7888 void vec_dst (const vector signed short *, int, const int);
7889 void vec_dst (const vector bool short *, int, const int);
7890 void vec_dst (const vector pixel *, int, const int);
7891 void vec_dst (const vector unsigned int *, int, const int);
7892 void vec_dst (const vector signed int *, int, const int);
7893 void vec_dst (const vector bool int *, int, const int);
7894 void vec_dst (const vector float *, int, const int);
7895 void vec_dst (const unsigned char *, int, const int);
7896 void vec_dst (const signed char *, int, const int);
7897 void vec_dst (const unsigned short *, int, const int);
7898 void vec_dst (const short *, int, const int);
7899 void vec_dst (const unsigned int *, int, const int);
7900 void vec_dst (const int *, int, const int);
7901 void vec_dst (const unsigned long *, int, const int);
7902 void vec_dst (const long *, int, const int);
7903 void vec_dst (const float *, int, const int);
7905 void vec_dstst (const vector unsigned char *, int, const int);
7906 void vec_dstst (const vector signed char *, int, const int);
7907 void vec_dstst (const vector bool char *, int, const int);
7908 void vec_dstst (const vector unsigned short *, int, const int);
7909 void vec_dstst (const vector signed short *, int, const int);
7910 void vec_dstst (const vector bool short *, int, const int);
7911 void vec_dstst (const vector pixel *, int, const int);
7912 void vec_dstst (const vector unsigned int *, int, const int);
7913 void vec_dstst (const vector signed int *, int, const int);
7914 void vec_dstst (const vector bool int *, int, const int);
7915 void vec_dstst (const vector float *, int, const int);
7916 void vec_dstst (const unsigned char *, int, const int);
7917 void vec_dstst (const signed char *, int, const int);
7918 void vec_dstst (const unsigned short *, int, const int);
7919 void vec_dstst (const short *, int, const int);
7920 void vec_dstst (const unsigned int *, int, const int);
7921 void vec_dstst (const int *, int, const int);
7922 void vec_dstst (const unsigned long *, int, const int);
7923 void vec_dstst (const long *, int, const int);
7924 void vec_dstst (const float *, int, const int);
7926 void vec_dststt (const vector unsigned char *, int, const int);
7927 void vec_dststt (const vector signed char *, int, const int);
7928 void vec_dststt (const vector bool char *, int, const int);
7929 void vec_dststt (const vector unsigned short *, int, const int);
7930 void vec_dststt (const vector signed short *, int, const int);
7931 void vec_dststt (const vector bool short *, int, const int);
7932 void vec_dststt (const vector pixel *, int, const int);
7933 void vec_dststt (const vector unsigned int *, int, const int);
7934 void vec_dststt (const vector signed int *, int, const int);
7935 void vec_dststt (const vector bool int *, int, const int);
7936 void vec_dststt (const vector float *, int, const int);
7937 void vec_dststt (const unsigned char *, int, const int);
7938 void vec_dststt (const signed char *, int, const int);
7939 void vec_dststt (const unsigned short *, int, const int);
7940 void vec_dststt (const short *, int, const int);
7941 void vec_dststt (const unsigned int *, int, const int);
7942 void vec_dststt (const int *, int, const int);
7943 void vec_dststt (const unsigned long *, int, const int);
7944 void vec_dststt (const long *, int, const int);
7945 void vec_dststt (const float *, int, const int);
7947 void vec_dstt (const vector unsigned char *, int, const int);
7948 void vec_dstt (const vector signed char *, int, const int);
7949 void vec_dstt (const vector bool char *, int, const int);
7950 void vec_dstt (const vector unsigned short *, int, const int);
7951 void vec_dstt (const vector signed short *, int, const int);
7952 void vec_dstt (const vector bool short *, int, const int);
7953 void vec_dstt (const vector pixel *, int, const int);
7954 void vec_dstt (const vector unsigned int *, int, const int);
7955 void vec_dstt (const vector signed int *, int, const int);
7956 void vec_dstt (const vector bool int *, int, const int);
7957 void vec_dstt (const vector float *, int, const int);
7958 void vec_dstt (const unsigned char *, int, const int);
7959 void vec_dstt (const signed char *, int, const int);
7960 void vec_dstt (const unsigned short *, int, const int);
7961 void vec_dstt (const short *, int, const int);
7962 void vec_dstt (const unsigned int *, int, const int);
7963 void vec_dstt (const int *, int, const int);
7964 void vec_dstt (const unsigned long *, int, const int);
7965 void vec_dstt (const long *, int, const int);
7966 void vec_dstt (const float *, int, const int);
7968 vector float vec_expte (vector float);
7970 vector float vec_floor (vector float);
7972 vector float vec_ld (int, const vector float *);
7973 vector float vec_ld (int, const float *);
7974 vector bool int vec_ld (int, const vector bool int *);
7975 vector signed int vec_ld (int, const vector signed int *);
7976 vector signed int vec_ld (int, const int *);
7977 vector signed int vec_ld (int, const long *);
7978 vector unsigned int vec_ld (int, const vector unsigned int *);
7979 vector unsigned int vec_ld (int, const unsigned int *);
7980 vector unsigned int vec_ld (int, const unsigned long *);
7981 vector bool short vec_ld (int, const vector bool short *);
7982 vector pixel vec_ld (int, const vector pixel *);
7983 vector signed short vec_ld (int, const vector signed short *);
7984 vector signed short vec_ld (int, const short *);
7985 vector unsigned short vec_ld (int, const vector unsigned short *);
7986 vector unsigned short vec_ld (int, const unsigned short *);
7987 vector bool char vec_ld (int, const vector bool char *);
7988 vector signed char vec_ld (int, const vector signed char *);
7989 vector signed char vec_ld (int, const signed char *);
7990 vector unsigned char vec_ld (int, const vector unsigned char *);
7991 vector unsigned char vec_ld (int, const unsigned char *);
7993 vector signed char vec_lde (int, const signed char *);
7994 vector unsigned char vec_lde (int, const unsigned char *);
7995 vector signed short vec_lde (int, const short *);
7996 vector unsigned short vec_lde (int, const unsigned short *);
7997 vector float vec_lde (int, const float *);
7998 vector signed int vec_lde (int, const int *);
7999 vector unsigned int vec_lde (int, const unsigned int *);
8000 vector signed int vec_lde (int, const long *);
8001 vector unsigned int vec_lde (int, const unsigned long *);
8003 vector float vec_lvewx (int, float *);
8004 vector signed int vec_lvewx (int, int *);
8005 vector unsigned int vec_lvewx (int, unsigned int *);
8006 vector signed int vec_lvewx (int, long *);
8007 vector unsigned int vec_lvewx (int, unsigned long *);
8009 vector signed short vec_lvehx (int, short *);
8010 vector unsigned short vec_lvehx (int, unsigned short *);
8012 vector signed char vec_lvebx (int, char *);
8013 vector unsigned char vec_lvebx (int, unsigned char *);
8015 vector float vec_ldl (int, const vector float *);
8016 vector float vec_ldl (int, const float *);
8017 vector bool int vec_ldl (int, const vector bool int *);
8018 vector signed int vec_ldl (int, const vector signed int *);
8019 vector signed int vec_ldl (int, const int *);
8020 vector signed int vec_ldl (int, const long *);
8021 vector unsigned int vec_ldl (int, const vector unsigned int *);
8022 vector unsigned int vec_ldl (int, const unsigned int *);
8023 vector unsigned int vec_ldl (int, const unsigned long *);
8024 vector bool short vec_ldl (int, const vector bool short *);
8025 vector pixel vec_ldl (int, const vector pixel *);
8026 vector signed short vec_ldl (int, const vector signed short *);
8027 vector signed short vec_ldl (int, const short *);
8028 vector unsigned short vec_ldl (int, const vector unsigned short *);
8029 vector unsigned short vec_ldl (int, const unsigned short *);
8030 vector bool char vec_ldl (int, const vector bool char *);
8031 vector signed char vec_ldl (int, const vector signed char *);
8032 vector signed char vec_ldl (int, const signed char *);
8033 vector unsigned char vec_ldl (int, const vector unsigned char *);
8034 vector unsigned char vec_ldl (int, const unsigned char *);
8036 vector float vec_loge (vector float);
8038 vector unsigned char vec_lvsl (int, const volatile unsigned char *);
8039 vector unsigned char vec_lvsl (int, const volatile signed char *);
8040 vector unsigned char vec_lvsl (int, const volatile unsigned short *);
8041 vector unsigned char vec_lvsl (int, const volatile short *);
8042 vector unsigned char vec_lvsl (int, const volatile unsigned int *);
8043 vector unsigned char vec_lvsl (int, const volatile int *);
8044 vector unsigned char vec_lvsl (int, const volatile unsigned long *);
8045 vector unsigned char vec_lvsl (int, const volatile long *);
8046 vector unsigned char vec_lvsl (int, const volatile float *);
8048 vector unsigned char vec_lvsr (int, const volatile unsigned char *);
8049 vector unsigned char vec_lvsr (int, const volatile signed char *);
8050 vector unsigned char vec_lvsr (int, const volatile unsigned short *);
8051 vector unsigned char vec_lvsr (int, const volatile short *);
8052 vector unsigned char vec_lvsr (int, const volatile unsigned int *);
8053 vector unsigned char vec_lvsr (int, const volatile int *);
8054 vector unsigned char vec_lvsr (int, const volatile unsigned long *);
8055 vector unsigned char vec_lvsr (int, const volatile long *);
8056 vector unsigned char vec_lvsr (int, const volatile float *);
8058 vector float vec_madd (vector float, vector float, vector float);
8060 vector signed short vec_madds (vector signed short,
8061 vector signed short,
8062 vector signed short);
8064 vector unsigned char vec_max (vector bool char, vector unsigned char);
8065 vector unsigned char vec_max (vector unsigned char, vector bool char);
8066 vector unsigned char vec_max (vector unsigned char,
8067 vector unsigned char);
8068 vector signed char vec_max (vector bool char, vector signed char);
8069 vector signed char vec_max (vector signed char, vector bool char);
8070 vector signed char vec_max (vector signed char, vector signed char);
8071 vector unsigned short vec_max (vector bool short,
8072 vector unsigned short);
8073 vector unsigned short vec_max (vector unsigned short,
8075 vector unsigned short vec_max (vector unsigned short,
8076 vector unsigned short);
8077 vector signed short vec_max (vector bool short, vector signed short);
8078 vector signed short vec_max (vector signed short, vector bool short);
8079 vector signed short vec_max (vector signed short, vector signed short);
8080 vector unsigned int vec_max (vector bool int, vector unsigned int);
8081 vector unsigned int vec_max (vector unsigned int, vector bool int);
8082 vector unsigned int vec_max (vector unsigned int, vector unsigned int);
8083 vector signed int vec_max (vector bool int, vector signed int);
8084 vector signed int vec_max (vector signed int, vector bool int);
8085 vector signed int vec_max (vector signed int, vector signed int);
8086 vector float vec_max (vector float, vector float);
8088 vector float vec_vmaxfp (vector float, vector float);
8090 vector signed int vec_vmaxsw (vector bool int, vector signed int);
8091 vector signed int vec_vmaxsw (vector signed int, vector bool int);
8092 vector signed int vec_vmaxsw (vector signed int, vector signed int);
8094 vector unsigned int vec_vmaxuw (vector bool int, vector unsigned int);
8095 vector unsigned int vec_vmaxuw (vector unsigned int, vector bool int);
8096 vector unsigned int vec_vmaxuw (vector unsigned int,
8097 vector unsigned int);
8099 vector signed short vec_vmaxsh (vector bool short, vector signed short);
8100 vector signed short vec_vmaxsh (vector signed short, vector bool short);
8101 vector signed short vec_vmaxsh (vector signed short,
8102 vector signed short);
8104 vector unsigned short vec_vmaxuh (vector bool short,
8105 vector unsigned short);
8106 vector unsigned short vec_vmaxuh (vector unsigned short,
8108 vector unsigned short vec_vmaxuh (vector unsigned short,
8109 vector unsigned short);
8111 vector signed char vec_vmaxsb (vector bool char, vector signed char);
8112 vector signed char vec_vmaxsb (vector signed char, vector bool char);
8113 vector signed char vec_vmaxsb (vector signed char, vector signed char);
8115 vector unsigned char vec_vmaxub (vector bool char,
8116 vector unsigned char);
8117 vector unsigned char vec_vmaxub (vector unsigned char,
8119 vector unsigned char vec_vmaxub (vector unsigned char,
8120 vector unsigned char);
8122 vector bool char vec_mergeh (vector bool char, vector bool char);
8123 vector signed char vec_mergeh (vector signed char, vector signed char);
8124 vector unsigned char vec_mergeh (vector unsigned char,
8125 vector unsigned char);
8126 vector bool short vec_mergeh (vector bool short, vector bool short);
8127 vector pixel vec_mergeh (vector pixel, vector pixel);
8128 vector signed short vec_mergeh (vector signed short,
8129 vector signed short);
8130 vector unsigned short vec_mergeh (vector unsigned short,
8131 vector unsigned short);
8132 vector float vec_mergeh (vector float, vector float);
8133 vector bool int vec_mergeh (vector bool int, vector bool int);
8134 vector signed int vec_mergeh (vector signed int, vector signed int);
8135 vector unsigned int vec_mergeh (vector unsigned int,
8136 vector unsigned int);
8138 vector float vec_vmrghw (vector float, vector float);
8139 vector bool int vec_vmrghw (vector bool int, vector bool int);
8140 vector signed int vec_vmrghw (vector signed int, vector signed int);
8141 vector unsigned int vec_vmrghw (vector unsigned int,
8142 vector unsigned int);
8144 vector bool short vec_vmrghh (vector bool short, vector bool short);
8145 vector signed short vec_vmrghh (vector signed short,
8146 vector signed short);
8147 vector unsigned short vec_vmrghh (vector unsigned short,
8148 vector unsigned short);
8149 vector pixel vec_vmrghh (vector pixel, vector pixel);
8151 vector bool char vec_vmrghb (vector bool char, vector bool char);
8152 vector signed char vec_vmrghb (vector signed char, vector signed char);
8153 vector unsigned char vec_vmrghb (vector unsigned char,
8154 vector unsigned char);
8156 vector bool char vec_mergel (vector bool char, vector bool char);
8157 vector signed char vec_mergel (vector signed char, vector signed char);
8158 vector unsigned char vec_mergel (vector unsigned char,
8159 vector unsigned char);
8160 vector bool short vec_mergel (vector bool short, vector bool short);
8161 vector pixel vec_mergel (vector pixel, vector pixel);
8162 vector signed short vec_mergel (vector signed short,
8163 vector signed short);
8164 vector unsigned short vec_mergel (vector unsigned short,
8165 vector unsigned short);
8166 vector float vec_mergel (vector float, vector float);
8167 vector bool int vec_mergel (vector bool int, vector bool int);
8168 vector signed int vec_mergel (vector signed int, vector signed int);
8169 vector unsigned int vec_mergel (vector unsigned int,
8170 vector unsigned int);
8172 vector float vec_vmrglw (vector float, vector float);
8173 vector signed int vec_vmrglw (vector signed int, vector signed int);
8174 vector unsigned int vec_vmrglw (vector unsigned int,
8175 vector unsigned int);
8176 vector bool int vec_vmrglw (vector bool int, vector bool int);
8178 vector bool short vec_vmrglh (vector bool short, vector bool short);
8179 vector signed short vec_vmrglh (vector signed short,
8180 vector signed short);
8181 vector unsigned short vec_vmrglh (vector unsigned short,
8182 vector unsigned short);
8183 vector pixel vec_vmrglh (vector pixel, vector pixel);
8185 vector bool char vec_vmrglb (vector bool char, vector bool char);
8186 vector signed char vec_vmrglb (vector signed char, vector signed char);
8187 vector unsigned char vec_vmrglb (vector unsigned char,
8188 vector unsigned char);
8190 vector unsigned short vec_mfvscr (void);
8192 vector unsigned char vec_min (vector bool char, vector unsigned char);
8193 vector unsigned char vec_min (vector unsigned char, vector bool char);
8194 vector unsigned char vec_min (vector unsigned char,
8195 vector unsigned char);
8196 vector signed char vec_min (vector bool char, vector signed char);
8197 vector signed char vec_min (vector signed char, vector bool char);
8198 vector signed char vec_min (vector signed char, vector signed char);
8199 vector unsigned short vec_min (vector bool short,
8200 vector unsigned short);
8201 vector unsigned short vec_min (vector unsigned short,
8203 vector unsigned short vec_min (vector unsigned short,
8204 vector unsigned short);
8205 vector signed short vec_min (vector bool short, vector signed short);
8206 vector signed short vec_min (vector signed short, vector bool short);
8207 vector signed short vec_min (vector signed short, vector signed short);
8208 vector unsigned int vec_min (vector bool int, vector unsigned int);
8209 vector unsigned int vec_min (vector unsigned int, vector bool int);
8210 vector unsigned int vec_min (vector unsigned int, vector unsigned int);
8211 vector signed int vec_min (vector bool int, vector signed int);
8212 vector signed int vec_min (vector signed int, vector bool int);
8213 vector signed int vec_min (vector signed int, vector signed int);
8214 vector float vec_min (vector float, vector float);
8216 vector float vec_vminfp (vector float, vector float);
8218 vector signed int vec_vminsw (vector bool int, vector signed int);
8219 vector signed int vec_vminsw (vector signed int, vector bool int);
8220 vector signed int vec_vminsw (vector signed int, vector signed int);
8222 vector unsigned int vec_vminuw (vector bool int, vector unsigned int);
8223 vector unsigned int vec_vminuw (vector unsigned int, vector bool int);
8224 vector unsigned int vec_vminuw (vector unsigned int,
8225 vector unsigned int);
8227 vector signed short vec_vminsh (vector bool short, vector signed short);
8228 vector signed short vec_vminsh (vector signed short, vector bool short);
8229 vector signed short vec_vminsh (vector signed short,
8230 vector signed short);
8232 vector unsigned short vec_vminuh (vector bool short,
8233 vector unsigned short);
8234 vector unsigned short vec_vminuh (vector unsigned short,
8236 vector unsigned short vec_vminuh (vector unsigned short,
8237 vector unsigned short);
8239 vector signed char vec_vminsb (vector bool char, vector signed char);
8240 vector signed char vec_vminsb (vector signed char, vector bool char);
8241 vector signed char vec_vminsb (vector signed char, vector signed char);
8243 vector unsigned char vec_vminub (vector bool char,
8244 vector unsigned char);
8245 vector unsigned char vec_vminub (vector unsigned char,
8247 vector unsigned char vec_vminub (vector unsigned char,
8248 vector unsigned char);
8250 vector signed short vec_mladd (vector signed short,
8251 vector signed short,
8252 vector signed short);
8253 vector signed short vec_mladd (vector signed short,
8254 vector unsigned short,
8255 vector unsigned short);
8256 vector signed short vec_mladd (vector unsigned short,
8257 vector signed short,
8258 vector signed short);
8259 vector unsigned short vec_mladd (vector unsigned short,
8260 vector unsigned short,
8261 vector unsigned short);
8263 vector signed short vec_mradds (vector signed short,
8264 vector signed short,
8265 vector signed short);
8267 vector unsigned int vec_msum (vector unsigned char,
8268 vector unsigned char,
8269 vector unsigned int);
8270 vector signed int vec_msum (vector signed char,
8271 vector unsigned char,
8273 vector unsigned int vec_msum (vector unsigned short,
8274 vector unsigned short,
8275 vector unsigned int);
8276 vector signed int vec_msum (vector signed short,
8277 vector signed short,
8280 vector signed int vec_vmsumshm (vector signed short,
8281 vector signed short,
8284 vector unsigned int vec_vmsumuhm (vector unsigned short,
8285 vector unsigned short,
8286 vector unsigned int);
8288 vector signed int vec_vmsummbm (vector signed char,
8289 vector unsigned char,
8292 vector unsigned int vec_vmsumubm (vector unsigned char,
8293 vector unsigned char,
8294 vector unsigned int);
8296 vector unsigned int vec_msums (vector unsigned short,
8297 vector unsigned short,
8298 vector unsigned int);
8299 vector signed int vec_msums (vector signed short,
8300 vector signed short,
8303 vector signed int vec_vmsumshs (vector signed short,
8304 vector signed short,
8307 vector unsigned int vec_vmsumuhs (vector unsigned short,
8308 vector unsigned short,
8309 vector unsigned int);
8311 void vec_mtvscr (vector signed int);
8312 void vec_mtvscr (vector unsigned int);
8313 void vec_mtvscr (vector bool int);
8314 void vec_mtvscr (vector signed short);
8315 void vec_mtvscr (vector unsigned short);
8316 void vec_mtvscr (vector bool short);
8317 void vec_mtvscr (vector pixel);
8318 void vec_mtvscr (vector signed char);
8319 void vec_mtvscr (vector unsigned char);
8320 void vec_mtvscr (vector bool char);
8322 vector unsigned short vec_mule (vector unsigned char,
8323 vector unsigned char);
8324 vector signed short vec_mule (vector signed char,
8325 vector signed char);
8326 vector unsigned int vec_mule (vector unsigned short,
8327 vector unsigned short);
8328 vector signed int vec_mule (vector signed short, vector signed short);
8330 vector signed int vec_vmulesh (vector signed short,
8331 vector signed short);
8333 vector unsigned int vec_vmuleuh (vector unsigned short,
8334 vector unsigned short);
8336 vector signed short vec_vmulesb (vector signed char,
8337 vector signed char);
8339 vector unsigned short vec_vmuleub (vector unsigned char,
8340 vector unsigned char);
8342 vector unsigned short vec_mulo (vector unsigned char,
8343 vector unsigned char);
8344 vector signed short vec_mulo (vector signed char, vector signed char);
8345 vector unsigned int vec_mulo (vector unsigned short,
8346 vector unsigned short);
8347 vector signed int vec_mulo (vector signed short, vector signed short);
8349 vector signed int vec_vmulosh (vector signed short,
8350 vector signed short);
8352 vector unsigned int vec_vmulouh (vector unsigned short,
8353 vector unsigned short);
8355 vector signed short vec_vmulosb (vector signed char,
8356 vector signed char);
8358 vector unsigned short vec_vmuloub (vector unsigned char,
8359 vector unsigned char);
8361 vector float vec_nmsub (vector float, vector float, vector float);
8363 vector float vec_nor (vector float, vector float);
8364 vector signed int vec_nor (vector signed int, vector signed int);
8365 vector unsigned int vec_nor (vector unsigned int, vector unsigned int);
8366 vector bool int vec_nor (vector bool int, vector bool int);
8367 vector signed short vec_nor (vector signed short, vector signed short);
8368 vector unsigned short vec_nor (vector unsigned short,
8369 vector unsigned short);
8370 vector bool short vec_nor (vector bool short, vector bool short);
8371 vector signed char vec_nor (vector signed char, vector signed char);
8372 vector unsigned char vec_nor (vector unsigned char,
8373 vector unsigned char);
8374 vector bool char vec_nor (vector bool char, vector bool char);
8376 vector float vec_or (vector float, vector float);
8377 vector float vec_or (vector float, vector bool int);
8378 vector float vec_or (vector bool int, vector float);
8379 vector bool int vec_or (vector bool int, vector bool int);
8380 vector signed int vec_or (vector bool int, vector signed int);
8381 vector signed int vec_or (vector signed int, vector bool int);
8382 vector signed int vec_or (vector signed int, vector signed int);
8383 vector unsigned int vec_or (vector bool int, vector unsigned int);
8384 vector unsigned int vec_or (vector unsigned int, vector bool int);
8385 vector unsigned int vec_or (vector unsigned int, vector unsigned int);
8386 vector bool short vec_or (vector bool short, vector bool short);
8387 vector signed short vec_or (vector bool short, vector signed short);
8388 vector signed short vec_or (vector signed short, vector bool short);
8389 vector signed short vec_or (vector signed short, vector signed short);
8390 vector unsigned short vec_or (vector bool short, vector unsigned short);
8391 vector unsigned short vec_or (vector unsigned short, vector bool short);
8392 vector unsigned short vec_or (vector unsigned short,
8393 vector unsigned short);
8394 vector signed char vec_or (vector bool char, vector signed char);
8395 vector bool char vec_or (vector bool char, vector bool char);
8396 vector signed char vec_or (vector signed char, vector bool char);
8397 vector signed char vec_or (vector signed char, vector signed char);
8398 vector unsigned char vec_or (vector bool char, vector unsigned char);
8399 vector unsigned char vec_or (vector unsigned char, vector bool char);
8400 vector unsigned char vec_or (vector unsigned char,
8401 vector unsigned char);
8403 vector signed char vec_pack (vector signed short, vector signed short);
8404 vector unsigned char vec_pack (vector unsigned short,
8405 vector unsigned short);
8406 vector bool char vec_pack (vector bool short, vector bool short);
8407 vector signed short vec_pack (vector signed int, vector signed int);
8408 vector unsigned short vec_pack (vector unsigned int,
8409 vector unsigned int);
8410 vector bool short vec_pack (vector bool int, vector bool int);
8412 vector bool short vec_vpkuwum (vector bool int, vector bool int);
8413 vector signed short vec_vpkuwum (vector signed int, vector signed int);
8414 vector unsigned short vec_vpkuwum (vector unsigned int,
8415 vector unsigned int);
8417 vector bool char vec_vpkuhum (vector bool short, vector bool short);
8418 vector signed char vec_vpkuhum (vector signed short,
8419 vector signed short);
8420 vector unsigned char vec_vpkuhum (vector unsigned short,
8421 vector unsigned short);
8423 vector pixel vec_packpx (vector unsigned int, vector unsigned int);
8425 vector unsigned char vec_packs (vector unsigned short,
8426 vector unsigned short);
8427 vector signed char vec_packs (vector signed short, vector signed short);
8428 vector unsigned short vec_packs (vector unsigned int,
8429 vector unsigned int);
8430 vector signed short vec_packs (vector signed int, vector signed int);
8432 vector signed short vec_vpkswss (vector signed int, vector signed int);
8434 vector unsigned short vec_vpkuwus (vector unsigned int,
8435 vector unsigned int);
8437 vector signed char vec_vpkshss (vector signed short,
8438 vector signed short);
8440 vector unsigned char vec_vpkuhus (vector unsigned short,
8441 vector unsigned short);
8443 vector unsigned char vec_packsu (vector unsigned short,
8444 vector unsigned short);
8445 vector unsigned char vec_packsu (vector signed short,
8446 vector signed short);
8447 vector unsigned short vec_packsu (vector unsigned int,
8448 vector unsigned int);
8449 vector unsigned short vec_packsu (vector signed int, vector signed int);
8451 vector unsigned short vec_vpkswus (vector signed int,
8454 vector unsigned char vec_vpkshus (vector signed short,
8455 vector signed short);
8457 vector float vec_perm (vector float,
8459 vector unsigned char);
8460 vector signed int vec_perm (vector signed int,
8462 vector unsigned char);
8463 vector unsigned int vec_perm (vector unsigned int,
8464 vector unsigned int,
8465 vector unsigned char);
8466 vector bool int vec_perm (vector bool int,
8468 vector unsigned char);
8469 vector signed short vec_perm (vector signed short,
8470 vector signed short,
8471 vector unsigned char);
8472 vector unsigned short vec_perm (vector unsigned short,
8473 vector unsigned short,
8474 vector unsigned char);
8475 vector bool short vec_perm (vector bool short,
8477 vector unsigned char);
8478 vector pixel vec_perm (vector pixel,
8480 vector unsigned char);
8481 vector signed char vec_perm (vector signed char,
8483 vector unsigned char);
8484 vector unsigned char vec_perm (vector unsigned char,
8485 vector unsigned char,
8486 vector unsigned char);
8487 vector bool char vec_perm (vector bool char,
8489 vector unsigned char);
8491 vector float vec_re (vector float);
8493 vector signed char vec_rl (vector signed char,
8494 vector unsigned char);
8495 vector unsigned char vec_rl (vector unsigned char,
8496 vector unsigned char);
8497 vector signed short vec_rl (vector signed short, vector unsigned short);
8498 vector unsigned short vec_rl (vector unsigned short,
8499 vector unsigned short);
8500 vector signed int vec_rl (vector signed int, vector unsigned int);
8501 vector unsigned int vec_rl (vector unsigned int, vector unsigned int);
8503 vector signed int vec_vrlw (vector signed int, vector unsigned int);
8504 vector unsigned int vec_vrlw (vector unsigned int, vector unsigned int);
8506 vector signed short vec_vrlh (vector signed short,
8507 vector unsigned short);
8508 vector unsigned short vec_vrlh (vector unsigned short,
8509 vector unsigned short);
8511 vector signed char vec_vrlb (vector signed char, vector unsigned char);
8512 vector unsigned char vec_vrlb (vector unsigned char,
8513 vector unsigned char);
8515 vector float vec_round (vector float);
8517 vector float vec_rsqrte (vector float);
8519 vector float vec_sel (vector float, vector float, vector bool int);
8520 vector float vec_sel (vector float, vector float, vector unsigned int);
8521 vector signed int vec_sel (vector signed int,
8524 vector signed int vec_sel (vector signed int,
8526 vector unsigned int);
8527 vector unsigned int vec_sel (vector unsigned int,
8528 vector unsigned int,
8530 vector unsigned int vec_sel (vector unsigned int,
8531 vector unsigned int,
8532 vector unsigned int);
8533 vector bool int vec_sel (vector bool int,
8536 vector bool int vec_sel (vector bool int,
8538 vector unsigned int);
8539 vector signed short vec_sel (vector signed short,
8540 vector signed short,
8542 vector signed short vec_sel (vector signed short,
8543 vector signed short,
8544 vector unsigned short);
8545 vector unsigned short vec_sel (vector unsigned short,
8546 vector unsigned short,
8548 vector unsigned short vec_sel (vector unsigned short,
8549 vector unsigned short,
8550 vector unsigned short);
8551 vector bool short vec_sel (vector bool short,
8554 vector bool short vec_sel (vector bool short,
8556 vector unsigned short);
8557 vector signed char vec_sel (vector signed char,
8560 vector signed char vec_sel (vector signed char,
8562 vector unsigned char);
8563 vector unsigned char vec_sel (vector unsigned char,
8564 vector unsigned char,
8566 vector unsigned char vec_sel (vector unsigned char,
8567 vector unsigned char,
8568 vector unsigned char);
8569 vector bool char vec_sel (vector bool char,
8572 vector bool char vec_sel (vector bool char,
8574 vector unsigned char);
8576 vector signed char vec_sl (vector signed char,
8577 vector unsigned char);
8578 vector unsigned char vec_sl (vector unsigned char,
8579 vector unsigned char);
8580 vector signed short vec_sl (vector signed short, vector unsigned short);
8581 vector unsigned short vec_sl (vector unsigned short,
8582 vector unsigned short);
8583 vector signed int vec_sl (vector signed int, vector unsigned int);
8584 vector unsigned int vec_sl (vector unsigned int, vector unsigned int);
8586 vector signed int vec_vslw (vector signed int, vector unsigned int);
8587 vector unsigned int vec_vslw (vector unsigned int, vector unsigned int);
8589 vector signed short vec_vslh (vector signed short,
8590 vector unsigned short);
8591 vector unsigned short vec_vslh (vector unsigned short,
8592 vector unsigned short);
8594 vector signed char vec_vslb (vector signed char, vector unsigned char);
8595 vector unsigned char vec_vslb (vector unsigned char,
8596 vector unsigned char);
8598 vector float vec_sld (vector float, vector float, const int);
8599 vector signed int vec_sld (vector signed int,
8602 vector unsigned int vec_sld (vector unsigned int,
8603 vector unsigned int,
8605 vector bool int vec_sld (vector bool int,
8608 vector signed short vec_sld (vector signed short,
8609 vector signed short,
8611 vector unsigned short vec_sld (vector unsigned short,
8612 vector unsigned short,
8614 vector bool short vec_sld (vector bool short,
8617 vector pixel vec_sld (vector pixel,
8620 vector signed char vec_sld (vector signed char,
8623 vector unsigned char vec_sld (vector unsigned char,
8624 vector unsigned char,
8626 vector bool char vec_sld (vector bool char,
8630 vector signed int vec_sll (vector signed int,
8631 vector unsigned int);
8632 vector signed int vec_sll (vector signed int,
8633 vector unsigned short);
8634 vector signed int vec_sll (vector signed int,
8635 vector unsigned char);
8636 vector unsigned int vec_sll (vector unsigned int,
8637 vector unsigned int);
8638 vector unsigned int vec_sll (vector unsigned int,
8639 vector unsigned short);
8640 vector unsigned int vec_sll (vector unsigned int,
8641 vector unsigned char);
8642 vector bool int vec_sll (vector bool int,
8643 vector unsigned int);
8644 vector bool int vec_sll (vector bool int,
8645 vector unsigned short);
8646 vector bool int vec_sll (vector bool int,
8647 vector unsigned char);
8648 vector signed short vec_sll (vector signed short,
8649 vector unsigned int);
8650 vector signed short vec_sll (vector signed short,
8651 vector unsigned short);
8652 vector signed short vec_sll (vector signed short,
8653 vector unsigned char);
8654 vector unsigned short vec_sll (vector unsigned short,
8655 vector unsigned int);
8656 vector unsigned short vec_sll (vector unsigned short,
8657 vector unsigned short);
8658 vector unsigned short vec_sll (vector unsigned short,
8659 vector unsigned char);
8660 vector bool short vec_sll (vector bool short, vector unsigned int);
8661 vector bool short vec_sll (vector bool short, vector unsigned short);
8662 vector bool short vec_sll (vector bool short, vector unsigned char);
8663 vector pixel vec_sll (vector pixel, vector unsigned int);
8664 vector pixel vec_sll (vector pixel, vector unsigned short);
8665 vector pixel vec_sll (vector pixel, vector unsigned char);
8666 vector signed char vec_sll (vector signed char, vector unsigned int);
8667 vector signed char vec_sll (vector signed char, vector unsigned short);
8668 vector signed char vec_sll (vector signed char, vector unsigned char);
8669 vector unsigned char vec_sll (vector unsigned char,
8670 vector unsigned int);
8671 vector unsigned char vec_sll (vector unsigned char,
8672 vector unsigned short);
8673 vector unsigned char vec_sll (vector unsigned char,
8674 vector unsigned char);
8675 vector bool char vec_sll (vector bool char, vector unsigned int);
8676 vector bool char vec_sll (vector bool char, vector unsigned short);
8677 vector bool char vec_sll (vector bool char, vector unsigned char);
8679 vector float vec_slo (vector float, vector signed char);
8680 vector float vec_slo (vector float, vector unsigned char);
8681 vector signed int vec_slo (vector signed int, vector signed char);
8682 vector signed int vec_slo (vector signed int, vector unsigned char);
8683 vector unsigned int vec_slo (vector unsigned int, vector signed char);
8684 vector unsigned int vec_slo (vector unsigned int, vector unsigned char);
8685 vector signed short vec_slo (vector signed short, vector signed char);
8686 vector signed short vec_slo (vector signed short, vector unsigned char);
8687 vector unsigned short vec_slo (vector unsigned short,
8688 vector signed char);
8689 vector unsigned short vec_slo (vector unsigned short,
8690 vector unsigned char);
8691 vector pixel vec_slo (vector pixel, vector signed char);
8692 vector pixel vec_slo (vector pixel, vector unsigned char);
8693 vector signed char vec_slo (vector signed char, vector signed char);
8694 vector signed char vec_slo (vector signed char, vector unsigned char);
8695 vector unsigned char vec_slo (vector unsigned char, vector signed char);
8696 vector unsigned char vec_slo (vector unsigned char,
8697 vector unsigned char);
8699 vector signed char vec_splat (vector signed char, const int);
8700 vector unsigned char vec_splat (vector unsigned char, const int);
8701 vector bool char vec_splat (vector bool char, const int);
8702 vector signed short vec_splat (vector signed short, const int);
8703 vector unsigned short vec_splat (vector unsigned short, const int);
8704 vector bool short vec_splat (vector bool short, const int);
8705 vector pixel vec_splat (vector pixel, const int);
8706 vector float vec_splat (vector float, const int);
8707 vector signed int vec_splat (vector signed int, const int);
8708 vector unsigned int vec_splat (vector unsigned int, const int);
8709 vector bool int vec_splat (vector bool int, const int);
8711 vector float vec_vspltw (vector float, const int);
8712 vector signed int vec_vspltw (vector signed int, const int);
8713 vector unsigned int vec_vspltw (vector unsigned int, const int);
8714 vector bool int vec_vspltw (vector bool int, const int);
8716 vector bool short vec_vsplth (vector bool short, const int);
8717 vector signed short vec_vsplth (vector signed short, const int);
8718 vector unsigned short vec_vsplth (vector unsigned short, const int);
8719 vector pixel vec_vsplth (vector pixel, const int);
8721 vector signed char vec_vspltb (vector signed char, const int);
8722 vector unsigned char vec_vspltb (vector unsigned char, const int);
8723 vector bool char vec_vspltb (vector bool char, const int);
8725 vector signed char vec_splat_s8 (const int);
8727 vector signed short vec_splat_s16 (const int);
8729 vector signed int vec_splat_s32 (const int);
8731 vector unsigned char vec_splat_u8 (const int);
8733 vector unsigned short vec_splat_u16 (const int);
8735 vector unsigned int vec_splat_u32 (const int);
8737 vector signed char vec_sr (vector signed char, vector unsigned char);
8738 vector unsigned char vec_sr (vector unsigned char,
8739 vector unsigned char);
8740 vector signed short vec_sr (vector signed short,
8741 vector unsigned short);
8742 vector unsigned short vec_sr (vector unsigned short,
8743 vector unsigned short);
8744 vector signed int vec_sr (vector signed int, vector unsigned int);
8745 vector unsigned int vec_sr (vector unsigned int, vector unsigned int);
8747 vector signed int vec_vsrw (vector signed int, vector unsigned int);
8748 vector unsigned int vec_vsrw (vector unsigned int, vector unsigned int);
8750 vector signed short vec_vsrh (vector signed short,
8751 vector unsigned short);
8752 vector unsigned short vec_vsrh (vector unsigned short,
8753 vector unsigned short);
8755 vector signed char vec_vsrb (vector signed char, vector unsigned char);
8756 vector unsigned char vec_vsrb (vector unsigned char,
8757 vector unsigned char);
8759 vector signed char vec_sra (vector signed char, vector unsigned char);
8760 vector unsigned char vec_sra (vector unsigned char,
8761 vector unsigned char);
8762 vector signed short vec_sra (vector signed short,
8763 vector unsigned short);
8764 vector unsigned short vec_sra (vector unsigned short,
8765 vector unsigned short);
8766 vector signed int vec_sra (vector signed int, vector unsigned int);
8767 vector unsigned int vec_sra (vector unsigned int, vector unsigned int);
8769 vector signed int vec_vsraw (vector signed int, vector unsigned int);
8770 vector unsigned int vec_vsraw (vector unsigned int,
8771 vector unsigned int);
8773 vector signed short vec_vsrah (vector signed short,
8774 vector unsigned short);
8775 vector unsigned short vec_vsrah (vector unsigned short,
8776 vector unsigned short);
8778 vector signed char vec_vsrab (vector signed char, vector unsigned char);
8779 vector unsigned char vec_vsrab (vector unsigned char,
8780 vector unsigned char);
8782 vector signed int vec_srl (vector signed int, vector unsigned int);
8783 vector signed int vec_srl (vector signed int, vector unsigned short);
8784 vector signed int vec_srl (vector signed int, vector unsigned char);
8785 vector unsigned int vec_srl (vector unsigned int, vector unsigned int);
8786 vector unsigned int vec_srl (vector unsigned int,
8787 vector unsigned short);
8788 vector unsigned int vec_srl (vector unsigned int, vector unsigned char);
8789 vector bool int vec_srl (vector bool int, vector unsigned int);
8790 vector bool int vec_srl (vector bool int, vector unsigned short);
8791 vector bool int vec_srl (vector bool int, vector unsigned char);
8792 vector signed short vec_srl (vector signed short, vector unsigned int);
8793 vector signed short vec_srl (vector signed short,
8794 vector unsigned short);
8795 vector signed short vec_srl (vector signed short, vector unsigned char);
8796 vector unsigned short vec_srl (vector unsigned short,
8797 vector unsigned int);
8798 vector unsigned short vec_srl (vector unsigned short,
8799 vector unsigned short);
8800 vector unsigned short vec_srl (vector unsigned short,
8801 vector unsigned char);
8802 vector bool short vec_srl (vector bool short, vector unsigned int);
8803 vector bool short vec_srl (vector bool short, vector unsigned short);
8804 vector bool short vec_srl (vector bool short, vector unsigned char);
8805 vector pixel vec_srl (vector pixel, vector unsigned int);
8806 vector pixel vec_srl (vector pixel, vector unsigned short);
8807 vector pixel vec_srl (vector pixel, vector unsigned char);
8808 vector signed char vec_srl (vector signed char, vector unsigned int);
8809 vector signed char vec_srl (vector signed char, vector unsigned short);
8810 vector signed char vec_srl (vector signed char, vector unsigned char);
8811 vector unsigned char vec_srl (vector unsigned char,
8812 vector unsigned int);
8813 vector unsigned char vec_srl (vector unsigned char,
8814 vector unsigned short);
8815 vector unsigned char vec_srl (vector unsigned char,
8816 vector unsigned char);
8817 vector bool char vec_srl (vector bool char, vector unsigned int);
8818 vector bool char vec_srl (vector bool char, vector unsigned short);
8819 vector bool char vec_srl (vector bool char, vector unsigned char);
8821 vector float vec_sro (vector float, vector signed char);
8822 vector float vec_sro (vector float, vector unsigned char);
8823 vector signed int vec_sro (vector signed int, vector signed char);
8824 vector signed int vec_sro (vector signed int, vector unsigned char);
8825 vector unsigned int vec_sro (vector unsigned int, vector signed char);
8826 vector unsigned int vec_sro (vector unsigned int, vector unsigned char);
8827 vector signed short vec_sro (vector signed short, vector signed char);
8828 vector signed short vec_sro (vector signed short, vector unsigned char);
8829 vector unsigned short vec_sro (vector unsigned short,
8830 vector signed char);
8831 vector unsigned short vec_sro (vector unsigned short,
8832 vector unsigned char);
8833 vector pixel vec_sro (vector pixel, vector signed char);
8834 vector pixel vec_sro (vector pixel, vector unsigned char);
8835 vector signed char vec_sro (vector signed char, vector signed char);
8836 vector signed char vec_sro (vector signed char, vector unsigned char);
8837 vector unsigned char vec_sro (vector unsigned char, vector signed char);
8838 vector unsigned char vec_sro (vector unsigned char,
8839 vector unsigned char);
8841 void vec_st (vector float, int, vector float *);
8842 void vec_st (vector float, int, float *);
8843 void vec_st (vector signed int, int, vector signed int *);
8844 void vec_st (vector signed int, int, int *);
8845 void vec_st (vector unsigned int, int, vector unsigned int *);
8846 void vec_st (vector unsigned int, int, unsigned int *);
8847 void vec_st (vector bool int, int, vector bool int *);
8848 void vec_st (vector bool int, int, unsigned int *);
8849 void vec_st (vector bool int, int, int *);
8850 void vec_st (vector signed short, int, vector signed short *);
8851 void vec_st (vector signed short, int, short *);
8852 void vec_st (vector unsigned short, int, vector unsigned short *);
8853 void vec_st (vector unsigned short, int, unsigned short *);
8854 void vec_st (vector bool short, int, vector bool short *);
8855 void vec_st (vector bool short, int, unsigned short *);
8856 void vec_st (vector pixel, int, vector pixel *);
8857 void vec_st (vector pixel, int, unsigned short *);
8858 void vec_st (vector pixel, int, short *);
8859 void vec_st (vector bool short, int, short *);
8860 void vec_st (vector signed char, int, vector signed char *);
8861 void vec_st (vector signed char, int, signed char *);
8862 void vec_st (vector unsigned char, int, vector unsigned char *);
8863 void vec_st (vector unsigned char, int, unsigned char *);
8864 void vec_st (vector bool char, int, vector bool char *);
8865 void vec_st (vector bool char, int, unsigned char *);
8866 void vec_st (vector bool char, int, signed char *);
8868 void vec_ste (vector signed char, int, signed char *);
8869 void vec_ste (vector unsigned char, int, unsigned char *);
8870 void vec_ste (vector bool char, int, signed char *);
8871 void vec_ste (vector bool char, int, unsigned char *);
8872 void vec_ste (vector signed short, int, short *);
8873 void vec_ste (vector unsigned short, int, unsigned short *);
8874 void vec_ste (vector bool short, int, short *);
8875 void vec_ste (vector bool short, int, unsigned short *);
8876 void vec_ste (vector pixel, int, short *);
8877 void vec_ste (vector pixel, int, unsigned short *);
8878 void vec_ste (vector float, int, float *);
8879 void vec_ste (vector signed int, int, int *);
8880 void vec_ste (vector unsigned int, int, unsigned int *);
8881 void vec_ste (vector bool int, int, int *);
8882 void vec_ste (vector bool int, int, unsigned int *);
8884 void vec_stvewx (vector float, int, float *);
8885 void vec_stvewx (vector signed int, int, int *);
8886 void vec_stvewx (vector unsigned int, int, unsigned int *);
8887 void vec_stvewx (vector bool int, int, int *);
8888 void vec_stvewx (vector bool int, int, unsigned int *);
8890 void vec_stvehx (vector signed short, int, short *);
8891 void vec_stvehx (vector unsigned short, int, unsigned short *);
8892 void vec_stvehx (vector bool short, int, short *);
8893 void vec_stvehx (vector bool short, int, unsigned short *);
8894 void vec_stvehx (vector pixel, int, short *);
8895 void vec_stvehx (vector pixel, int, unsigned short *);
8897 void vec_stvebx (vector signed char, int, signed char *);
8898 void vec_stvebx (vector unsigned char, int, unsigned char *);
8899 void vec_stvebx (vector bool char, int, signed char *);
8900 void vec_stvebx (vector bool char, int, unsigned char *);
8902 void vec_stl (vector float, int, vector float *);
8903 void vec_stl (vector float, int, float *);
8904 void vec_stl (vector signed int, int, vector signed int *);
8905 void vec_stl (vector signed int, int, int *);
8906 void vec_stl (vector unsigned int, int, vector unsigned int *);
8907 void vec_stl (vector unsigned int, int, unsigned int *);
8908 void vec_stl (vector bool int, int, vector bool int *);
8909 void vec_stl (vector bool int, int, unsigned int *);
8910 void vec_stl (vector bool int, int, int *);
8911 void vec_stl (vector signed short, int, vector signed short *);
8912 void vec_stl (vector signed short, int, short *);
8913 void vec_stl (vector unsigned short, int, vector unsigned short *);
8914 void vec_stl (vector unsigned short, int, unsigned short *);
8915 void vec_stl (vector bool short, int, vector bool short *);
8916 void vec_stl (vector bool short, int, unsigned short *);
8917 void vec_stl (vector bool short, int, short *);
8918 void vec_stl (vector pixel, int, vector pixel *);
8919 void vec_stl (vector pixel, int, unsigned short *);
8920 void vec_stl (vector pixel, int, short *);
8921 void vec_stl (vector signed char, int, vector signed char *);
8922 void vec_stl (vector signed char, int, signed char *);
8923 void vec_stl (vector unsigned char, int, vector unsigned char *);
8924 void vec_stl (vector unsigned char, int, unsigned char *);
8925 void vec_stl (vector bool char, int, vector bool char *);
8926 void vec_stl (vector bool char, int, unsigned char *);
8927 void vec_stl (vector bool char, int, signed char *);
8929 vector signed char vec_sub (vector bool char, vector signed char);
8930 vector signed char vec_sub (vector signed char, vector bool char);
8931 vector signed char vec_sub (vector signed char, vector signed char);
8932 vector unsigned char vec_sub (vector bool char, vector unsigned char);
8933 vector unsigned char vec_sub (vector unsigned char, vector bool char);
8934 vector unsigned char vec_sub (vector unsigned char,
8935 vector unsigned char);
8936 vector signed short vec_sub (vector bool short, vector signed short);
8937 vector signed short vec_sub (vector signed short, vector bool short);
8938 vector signed short vec_sub (vector signed short, vector signed short);
8939 vector unsigned short vec_sub (vector bool short,
8940 vector unsigned short);
8941 vector unsigned short vec_sub (vector unsigned short,
8943 vector unsigned short vec_sub (vector unsigned short,
8944 vector unsigned short);
8945 vector signed int vec_sub (vector bool int, vector signed int);
8946 vector signed int vec_sub (vector signed int, vector bool int);
8947 vector signed int vec_sub (vector signed int, vector signed int);
8948 vector unsigned int vec_sub (vector bool int, vector unsigned int);
8949 vector unsigned int vec_sub (vector unsigned int, vector bool int);
8950 vector unsigned int vec_sub (vector unsigned int, vector unsigned int);
8951 vector float vec_sub (vector float, vector float);
8953 vector float vec_vsubfp (vector float, vector float);
8955 vector signed int vec_vsubuwm (vector bool int, vector signed int);
8956 vector signed int vec_vsubuwm (vector signed int, vector bool int);
8957 vector signed int vec_vsubuwm (vector signed int, vector signed int);
8958 vector unsigned int vec_vsubuwm (vector bool int, vector unsigned int);
8959 vector unsigned int vec_vsubuwm (vector unsigned int, vector bool int);
8960 vector unsigned int vec_vsubuwm (vector unsigned int,
8961 vector unsigned int);
8963 vector signed short vec_vsubuhm (vector bool short,
8964 vector signed short);
8965 vector signed short vec_vsubuhm (vector signed short,
8967 vector signed short vec_vsubuhm (vector signed short,
8968 vector signed short);
8969 vector unsigned short vec_vsubuhm (vector bool short,
8970 vector unsigned short);
8971 vector unsigned short vec_vsubuhm (vector unsigned short,
8973 vector unsigned short vec_vsubuhm (vector unsigned short,
8974 vector unsigned short);
8976 vector signed char vec_vsububm (vector bool char, vector signed char);
8977 vector signed char vec_vsububm (vector signed char, vector bool char);
8978 vector signed char vec_vsububm (vector signed char, vector signed char);
8979 vector unsigned char vec_vsububm (vector bool char,
8980 vector unsigned char);
8981 vector unsigned char vec_vsububm (vector unsigned char,
8983 vector unsigned char vec_vsububm (vector unsigned char,
8984 vector unsigned char);
8986 vector unsigned int vec_subc (vector unsigned int, vector unsigned int);
8988 vector unsigned char vec_subs (vector bool char, vector unsigned char);
8989 vector unsigned char vec_subs (vector unsigned char, vector bool char);
8990 vector unsigned char vec_subs (vector unsigned char,
8991 vector unsigned char);
8992 vector signed char vec_subs (vector bool char, vector signed char);
8993 vector signed char vec_subs (vector signed char, vector bool char);
8994 vector signed char vec_subs (vector signed char, vector signed char);
8995 vector unsigned short vec_subs (vector bool short,
8996 vector unsigned short);
8997 vector unsigned short vec_subs (vector unsigned short,
8999 vector unsigned short vec_subs (vector unsigned short,
9000 vector unsigned short);
9001 vector signed short vec_subs (vector bool short, vector signed short);
9002 vector signed short vec_subs (vector signed short, vector bool short);
9003 vector signed short vec_subs (vector signed short, vector signed short);
9004 vector unsigned int vec_subs (vector bool int, vector unsigned int);
9005 vector unsigned int vec_subs (vector unsigned int, vector bool int);
9006 vector unsigned int vec_subs (vector unsigned int, vector unsigned int);
9007 vector signed int vec_subs (vector bool int, vector signed int);
9008 vector signed int vec_subs (vector signed int, vector bool int);
9009 vector signed int vec_subs (vector signed int, vector signed int);
9011 vector signed int vec_vsubsws (vector bool int, vector signed int);
9012 vector signed int vec_vsubsws (vector signed int, vector bool int);
9013 vector signed int vec_vsubsws (vector signed int, vector signed int);
9015 vector unsigned int vec_vsubuws (vector bool int, vector unsigned int);
9016 vector unsigned int vec_vsubuws (vector unsigned int, vector bool int);
9017 vector unsigned int vec_vsubuws (vector unsigned int,
9018 vector unsigned int);
9020 vector signed short vec_vsubshs (vector bool short,
9021 vector signed short);
9022 vector signed short vec_vsubshs (vector signed short,
9024 vector signed short vec_vsubshs (vector signed short,
9025 vector signed short);
9027 vector unsigned short vec_vsubuhs (vector bool short,
9028 vector unsigned short);
9029 vector unsigned short vec_vsubuhs (vector unsigned short,
9031 vector unsigned short vec_vsubuhs (vector unsigned short,
9032 vector unsigned short);
9034 vector signed char vec_vsubsbs (vector bool char, vector signed char);
9035 vector signed char vec_vsubsbs (vector signed char, vector bool char);
9036 vector signed char vec_vsubsbs (vector signed char, vector signed char);
9038 vector unsigned char vec_vsububs (vector bool char,
9039 vector unsigned char);
9040 vector unsigned char vec_vsububs (vector unsigned char,
9042 vector unsigned char vec_vsububs (vector unsigned char,
9043 vector unsigned char);
9045 vector unsigned int vec_sum4s (vector unsigned char,
9046 vector unsigned int);
9047 vector signed int vec_sum4s (vector signed char, vector signed int);
9048 vector signed int vec_sum4s (vector signed short, vector signed int);
9050 vector signed int vec_vsum4shs (vector signed short, vector signed int);
9052 vector signed int vec_vsum4sbs (vector signed char, vector signed int);
9054 vector unsigned int vec_vsum4ubs (vector unsigned char,
9055 vector unsigned int);
9057 vector signed int vec_sum2s (vector signed int, vector signed int);
9059 vector signed int vec_sums (vector signed int, vector signed int);
9061 vector float vec_trunc (vector float);
9063 vector signed short vec_unpackh (vector signed char);
9064 vector bool short vec_unpackh (vector bool char);
9065 vector signed int vec_unpackh (vector signed short);
9066 vector bool int vec_unpackh (vector bool short);
9067 vector unsigned int vec_unpackh (vector pixel);
9069 vector bool int vec_vupkhsh (vector bool short);
9070 vector signed int vec_vupkhsh (vector signed short);
9072 vector unsigned int vec_vupkhpx (vector pixel);
9074 vector bool short vec_vupkhsb (vector bool char);
9075 vector signed short vec_vupkhsb (vector signed char);
9077 vector signed short vec_unpackl (vector signed char);
9078 vector bool short vec_unpackl (vector bool char);
9079 vector unsigned int vec_unpackl (vector pixel);
9080 vector signed int vec_unpackl (vector signed short);
9081 vector bool int vec_unpackl (vector bool short);
9083 vector unsigned int vec_vupklpx (vector pixel);
9085 vector bool int vec_vupklsh (vector bool short);
9086 vector signed int vec_vupklsh (vector signed short);
9088 vector bool short vec_vupklsb (vector bool char);
9089 vector signed short vec_vupklsb (vector signed char);
9091 vector float vec_xor (vector float, vector float);
9092 vector float vec_xor (vector float, vector bool int);
9093 vector float vec_xor (vector bool int, vector float);
9094 vector bool int vec_xor (vector bool int, vector bool int);
9095 vector signed int vec_xor (vector bool int, vector signed int);
9096 vector signed int vec_xor (vector signed int, vector bool int);
9097 vector signed int vec_xor (vector signed int, vector signed int);
9098 vector unsigned int vec_xor (vector bool int, vector unsigned int);
9099 vector unsigned int vec_xor (vector unsigned int, vector bool int);
9100 vector unsigned int vec_xor (vector unsigned int, vector unsigned int);
9101 vector bool short vec_xor (vector bool short, vector bool short);
9102 vector signed short vec_xor (vector bool short, vector signed short);
9103 vector signed short vec_xor (vector signed short, vector bool short);
9104 vector signed short vec_xor (vector signed short, vector signed short);
9105 vector unsigned short vec_xor (vector bool short,
9106 vector unsigned short);
9107 vector unsigned short vec_xor (vector unsigned short,
9109 vector unsigned short vec_xor (vector unsigned short,
9110 vector unsigned short);
9111 vector signed char vec_xor (vector bool char, vector signed char);
9112 vector bool char vec_xor (vector bool char, vector bool char);
9113 vector signed char vec_xor (vector signed char, vector bool char);
9114 vector signed char vec_xor (vector signed char, vector signed char);
9115 vector unsigned char vec_xor (vector bool char, vector unsigned char);
9116 vector unsigned char vec_xor (vector unsigned char, vector bool char);
9117 vector unsigned char vec_xor (vector unsigned char,
9118 vector unsigned char);
9120 int vec_all_eq (vector signed char, vector bool char);
9121 int vec_all_eq (vector signed char, vector signed char);
9122 int vec_all_eq (vector unsigned char, vector bool char);
9123 int vec_all_eq (vector unsigned char, vector unsigned char);
9124 int vec_all_eq (vector bool char, vector bool char);
9125 int vec_all_eq (vector bool char, vector unsigned char);
9126 int vec_all_eq (vector bool char, vector signed char);
9127 int vec_all_eq (vector signed short, vector bool short);
9128 int vec_all_eq (vector signed short, vector signed short);
9129 int vec_all_eq (vector unsigned short, vector bool short);
9130 int vec_all_eq (vector unsigned short, vector unsigned short);
9131 int vec_all_eq (vector bool short, vector bool short);
9132 int vec_all_eq (vector bool short, vector unsigned short);
9133 int vec_all_eq (vector bool short, vector signed short);
9134 int vec_all_eq (vector pixel, vector pixel);
9135 int vec_all_eq (vector signed int, vector bool int);
9136 int vec_all_eq (vector signed int, vector signed int);
9137 int vec_all_eq (vector unsigned int, vector bool int);
9138 int vec_all_eq (vector unsigned int, vector unsigned int);
9139 int vec_all_eq (vector bool int, vector bool int);
9140 int vec_all_eq (vector bool int, vector unsigned int);
9141 int vec_all_eq (vector bool int, vector signed int);
9142 int vec_all_eq (vector float, vector float);
9144 int vec_all_ge (vector bool char, vector unsigned char);
9145 int vec_all_ge (vector unsigned char, vector bool char);
9146 int vec_all_ge (vector unsigned char, vector unsigned char);
9147 int vec_all_ge (vector bool char, vector signed char);
9148 int vec_all_ge (vector signed char, vector bool char);
9149 int vec_all_ge (vector signed char, vector signed char);
9150 int vec_all_ge (vector bool short, vector unsigned short);
9151 int vec_all_ge (vector unsigned short, vector bool short);
9152 int vec_all_ge (vector unsigned short, vector unsigned short);
9153 int vec_all_ge (vector signed short, vector signed short);
9154 int vec_all_ge (vector bool short, vector signed short);
9155 int vec_all_ge (vector signed short, vector bool short);
9156 int vec_all_ge (vector bool int, vector unsigned int);
9157 int vec_all_ge (vector unsigned int, vector bool int);
9158 int vec_all_ge (vector unsigned int, vector unsigned int);
9159 int vec_all_ge (vector bool int, vector signed int);
9160 int vec_all_ge (vector signed int, vector bool int);
9161 int vec_all_ge (vector signed int, vector signed int);
9162 int vec_all_ge (vector float, vector float);
9164 int vec_all_gt (vector bool char, vector unsigned char);
9165 int vec_all_gt (vector unsigned char, vector bool char);
9166 int vec_all_gt (vector unsigned char, vector unsigned char);
9167 int vec_all_gt (vector bool char, vector signed char);
9168 int vec_all_gt (vector signed char, vector bool char);
9169 int vec_all_gt (vector signed char, vector signed char);
9170 int vec_all_gt (vector bool short, vector unsigned short);
9171 int vec_all_gt (vector unsigned short, vector bool short);
9172 int vec_all_gt (vector unsigned short, vector unsigned short);
9173 int vec_all_gt (vector bool short, vector signed short);
9174 int vec_all_gt (vector signed short, vector bool short);
9175 int vec_all_gt (vector signed short, vector signed short);
9176 int vec_all_gt (vector bool int, vector unsigned int);
9177 int vec_all_gt (vector unsigned int, vector bool int);
9178 int vec_all_gt (vector unsigned int, vector unsigned int);
9179 int vec_all_gt (vector bool int, vector signed int);
9180 int vec_all_gt (vector signed int, vector bool int);
9181 int vec_all_gt (vector signed int, vector signed int);
9182 int vec_all_gt (vector float, vector float);
9184 int vec_all_in (vector float, vector float);
9186 int vec_all_le (vector bool char, vector unsigned char);
9187 int vec_all_le (vector unsigned char, vector bool char);
9188 int vec_all_le (vector unsigned char, vector unsigned char);
9189 int vec_all_le (vector bool char, vector signed char);
9190 int vec_all_le (vector signed char, vector bool char);
9191 int vec_all_le (vector signed char, vector signed char);
9192 int vec_all_le (vector bool short, vector unsigned short);
9193 int vec_all_le (vector unsigned short, vector bool short);
9194 int vec_all_le (vector unsigned short, vector unsigned short);
9195 int vec_all_le (vector bool short, vector signed short);
9196 int vec_all_le (vector signed short, vector bool short);
9197 int vec_all_le (vector signed short, vector signed short);
9198 int vec_all_le (vector bool int, vector unsigned int);
9199 int vec_all_le (vector unsigned int, vector bool int);
9200 int vec_all_le (vector unsigned int, vector unsigned int);
9201 int vec_all_le (vector bool int, vector signed int);
9202 int vec_all_le (vector signed int, vector bool int);
9203 int vec_all_le (vector signed int, vector signed int);
9204 int vec_all_le (vector float, vector float);
9206 int vec_all_lt (vector bool char, vector unsigned char);
9207 int vec_all_lt (vector unsigned char, vector bool char);
9208 int vec_all_lt (vector unsigned char, vector unsigned char);
9209 int vec_all_lt (vector bool char, vector signed char);
9210 int vec_all_lt (vector signed char, vector bool char);
9211 int vec_all_lt (vector signed char, vector signed char);
9212 int vec_all_lt (vector bool short, vector unsigned short);
9213 int vec_all_lt (vector unsigned short, vector bool short);
9214 int vec_all_lt (vector unsigned short, vector unsigned short);
9215 int vec_all_lt (vector bool short, vector signed short);
9216 int vec_all_lt (vector signed short, vector bool short);
9217 int vec_all_lt (vector signed short, vector signed short);
9218 int vec_all_lt (vector bool int, vector unsigned int);
9219 int vec_all_lt (vector unsigned int, vector bool int);
9220 int vec_all_lt (vector unsigned int, vector unsigned int);
9221 int vec_all_lt (vector bool int, vector signed int);
9222 int vec_all_lt (vector signed int, vector bool int);
9223 int vec_all_lt (vector signed int, vector signed int);
9224 int vec_all_lt (vector float, vector float);
9226 int vec_all_nan (vector float);
9228 int vec_all_ne (vector signed char, vector bool char);
9229 int vec_all_ne (vector signed char, vector signed char);
9230 int vec_all_ne (vector unsigned char, vector bool char);
9231 int vec_all_ne (vector unsigned char, vector unsigned char);
9232 int vec_all_ne (vector bool char, vector bool char);
9233 int vec_all_ne (vector bool char, vector unsigned char);
9234 int vec_all_ne (vector bool char, vector signed char);
9235 int vec_all_ne (vector signed short, vector bool short);
9236 int vec_all_ne (vector signed short, vector signed short);
9237 int vec_all_ne (vector unsigned short, vector bool short);
9238 int vec_all_ne (vector unsigned short, vector unsigned short);
9239 int vec_all_ne (vector bool short, vector bool short);
9240 int vec_all_ne (vector bool short, vector unsigned short);
9241 int vec_all_ne (vector bool short, vector signed short);
9242 int vec_all_ne (vector pixel, vector pixel);
9243 int vec_all_ne (vector signed int, vector bool int);
9244 int vec_all_ne (vector signed int, vector signed int);
9245 int vec_all_ne (vector unsigned int, vector bool int);
9246 int vec_all_ne (vector unsigned int, vector unsigned int);
9247 int vec_all_ne (vector bool int, vector bool int);
9248 int vec_all_ne (vector bool int, vector unsigned int);
9249 int vec_all_ne (vector bool int, vector signed int);
9250 int vec_all_ne (vector float, vector float);
9252 int vec_all_nge (vector float, vector float);
9254 int vec_all_ngt (vector float, vector float);
9256 int vec_all_nle (vector float, vector float);
9258 int vec_all_nlt (vector float, vector float);
9260 int vec_all_numeric (vector float);
9262 int vec_any_eq (vector signed char, vector bool char);
9263 int vec_any_eq (vector signed char, vector signed char);
9264 int vec_any_eq (vector unsigned char, vector bool char);
9265 int vec_any_eq (vector unsigned char, vector unsigned char);
9266 int vec_any_eq (vector bool char, vector bool char);
9267 int vec_any_eq (vector bool char, vector unsigned char);
9268 int vec_any_eq (vector bool char, vector signed char);
9269 int vec_any_eq (vector signed short, vector bool short);
9270 int vec_any_eq (vector signed short, vector signed short);
9271 int vec_any_eq (vector unsigned short, vector bool short);
9272 int vec_any_eq (vector unsigned short, vector unsigned short);
9273 int vec_any_eq (vector bool short, vector bool short);
9274 int vec_any_eq (vector bool short, vector unsigned short);
9275 int vec_any_eq (vector bool short, vector signed short);
9276 int vec_any_eq (vector pixel, vector pixel);
9277 int vec_any_eq (vector signed int, vector bool int);
9278 int vec_any_eq (vector signed int, vector signed int);
9279 int vec_any_eq (vector unsigned int, vector bool int);
9280 int vec_any_eq (vector unsigned int, vector unsigned int);
9281 int vec_any_eq (vector bool int, vector bool int);
9282 int vec_any_eq (vector bool int, vector unsigned int);
9283 int vec_any_eq (vector bool int, vector signed int);
9284 int vec_any_eq (vector float, vector float);
9286 int vec_any_ge (vector signed char, vector bool char);
9287 int vec_any_ge (vector unsigned char, vector bool char);
9288 int vec_any_ge (vector unsigned char, vector unsigned char);
9289 int vec_any_ge (vector signed char, vector signed char);
9290 int vec_any_ge (vector bool char, vector unsigned char);
9291 int vec_any_ge (vector bool char, vector signed char);
9292 int vec_any_ge (vector unsigned short, vector bool short);
9293 int vec_any_ge (vector unsigned short, vector unsigned short);
9294 int vec_any_ge (vector signed short, vector signed short);
9295 int vec_any_ge (vector signed short, vector bool short);
9296 int vec_any_ge (vector bool short, vector unsigned short);
9297 int vec_any_ge (vector bool short, vector signed short);
9298 int vec_any_ge (vector signed int, vector bool int);
9299 int vec_any_ge (vector unsigned int, vector bool int);
9300 int vec_any_ge (vector unsigned int, vector unsigned int);
9301 int vec_any_ge (vector signed int, vector signed int);
9302 int vec_any_ge (vector bool int, vector unsigned int);
9303 int vec_any_ge (vector bool int, vector signed int);
9304 int vec_any_ge (vector float, vector float);
9306 int vec_any_gt (vector bool char, vector unsigned char);
9307 int vec_any_gt (vector unsigned char, vector bool char);
9308 int vec_any_gt (vector unsigned char, vector unsigned char);
9309 int vec_any_gt (vector bool char, vector signed char);
9310 int vec_any_gt (vector signed char, vector bool char);
9311 int vec_any_gt (vector signed char, vector signed char);
9312 int vec_any_gt (vector bool short, vector unsigned short);
9313 int vec_any_gt (vector unsigned short, vector bool short);
9314 int vec_any_gt (vector unsigned short, vector unsigned short);
9315 int vec_any_gt (vector bool short, vector signed short);
9316 int vec_any_gt (vector signed short, vector bool short);
9317 int vec_any_gt (vector signed short, vector signed short);
9318 int vec_any_gt (vector bool int, vector unsigned int);
9319 int vec_any_gt (vector unsigned int, vector bool int);
9320 int vec_any_gt (vector unsigned int, vector unsigned int);
9321 int vec_any_gt (vector bool int, vector signed int);
9322 int vec_any_gt (vector signed int, vector bool int);
9323 int vec_any_gt (vector signed int, vector signed int);
9324 int vec_any_gt (vector float, vector float);
9326 int vec_any_le (vector bool char, vector unsigned char);
9327 int vec_any_le (vector unsigned char, vector bool char);
9328 int vec_any_le (vector unsigned char, vector unsigned char);
9329 int vec_any_le (vector bool char, vector signed char);
9330 int vec_any_le (vector signed char, vector bool char);
9331 int vec_any_le (vector signed char, vector signed char);
9332 int vec_any_le (vector bool short, vector unsigned short);
9333 int vec_any_le (vector unsigned short, vector bool short);
9334 int vec_any_le (vector unsigned short, vector unsigned short);
9335 int vec_any_le (vector bool short, vector signed short);
9336 int vec_any_le (vector signed short, vector bool short);
9337 int vec_any_le (vector signed short, vector signed short);
9338 int vec_any_le (vector bool int, vector unsigned int);
9339 int vec_any_le (vector unsigned int, vector bool int);
9340 int vec_any_le (vector unsigned int, vector unsigned int);
9341 int vec_any_le (vector bool int, vector signed int);
9342 int vec_any_le (vector signed int, vector bool int);
9343 int vec_any_le (vector signed int, vector signed int);
9344 int vec_any_le (vector float, vector float);
9346 int vec_any_lt (vector bool char, vector unsigned char);
9347 int vec_any_lt (vector unsigned char, vector bool char);
9348 int vec_any_lt (vector unsigned char, vector unsigned char);
9349 int vec_any_lt (vector bool char, vector signed char);
9350 int vec_any_lt (vector signed char, vector bool char);
9351 int vec_any_lt (vector signed char, vector signed char);
9352 int vec_any_lt (vector bool short, vector unsigned short);
9353 int vec_any_lt (vector unsigned short, vector bool short);
9354 int vec_any_lt (vector unsigned short, vector unsigned short);
9355 int vec_any_lt (vector bool short, vector signed short);
9356 int vec_any_lt (vector signed short, vector bool short);
9357 int vec_any_lt (vector signed short, vector signed short);
9358 int vec_any_lt (vector bool int, vector unsigned int);
9359 int vec_any_lt (vector unsigned int, vector bool int);
9360 int vec_any_lt (vector unsigned int, vector unsigned int);
9361 int vec_any_lt (vector bool int, vector signed int);
9362 int vec_any_lt (vector signed int, vector bool int);
9363 int vec_any_lt (vector signed int, vector signed int);
9364 int vec_any_lt (vector float, vector float);
9366 int vec_any_nan (vector float);
9368 int vec_any_ne (vector signed char, vector bool char);
9369 int vec_any_ne (vector signed char, vector signed char);
9370 int vec_any_ne (vector unsigned char, vector bool char);
9371 int vec_any_ne (vector unsigned char, vector unsigned char);
9372 int vec_any_ne (vector bool char, vector bool char);
9373 int vec_any_ne (vector bool char, vector unsigned char);
9374 int vec_any_ne (vector bool char, vector signed char);
9375 int vec_any_ne (vector signed short, vector bool short);
9376 int vec_any_ne (vector signed short, vector signed short);
9377 int vec_any_ne (vector unsigned short, vector bool short);
9378 int vec_any_ne (vector unsigned short, vector unsigned short);
9379 int vec_any_ne (vector bool short, vector bool short);
9380 int vec_any_ne (vector bool short, vector unsigned short);
9381 int vec_any_ne (vector bool short, vector signed short);
9382 int vec_any_ne (vector pixel, vector pixel);
9383 int vec_any_ne (vector signed int, vector bool int);
9384 int vec_any_ne (vector signed int, vector signed int);
9385 int vec_any_ne (vector unsigned int, vector bool int);
9386 int vec_any_ne (vector unsigned int, vector unsigned int);
9387 int vec_any_ne (vector bool int, vector bool int);
9388 int vec_any_ne (vector bool int, vector unsigned int);
9389 int vec_any_ne (vector bool int, vector signed int);
9390 int vec_any_ne (vector float, vector float);
9392 int vec_any_nge (vector float, vector float);
9394 int vec_any_ngt (vector float, vector float);
9396 int vec_any_nle (vector float, vector float);
9398 int vec_any_nlt (vector float, vector float);
9400 int vec_any_numeric (vector float);
9402 int vec_any_out (vector float, vector float);
9405 @node SPARC VIS Built-in Functions
9406 @subsection SPARC VIS Built-in Functions
9408 GCC supports SIMD operations on the SPARC using both the generic vector
9409 extensions (@pxref{Vector Extensions}) as well as built-in functions for
9410 the SPARC Visual Instruction Set (VIS). When you use the @option{-mvis}
9411 switch, the VIS extension is exposed as the following built-in functions:
9414 typedef int v2si __attribute__ ((vector_size (8)));
9415 typedef short v4hi __attribute__ ((vector_size (8)));
9416 typedef short v2hi __attribute__ ((vector_size (4)));
9417 typedef char v8qi __attribute__ ((vector_size (8)));
9418 typedef char v4qi __attribute__ ((vector_size (4)));
9420 void * __builtin_vis_alignaddr (void *, long);
9421 int64_t __builtin_vis_faligndatadi (int64_t, int64_t);
9422 v2si __builtin_vis_faligndatav2si (v2si, v2si);
9423 v4hi __builtin_vis_faligndatav4hi (v4si, v4si);
9424 v8qi __builtin_vis_faligndatav8qi (v8qi, v8qi);
9426 v4hi __builtin_vis_fexpand (v4qi);
9428 v4hi __builtin_vis_fmul8x16 (v4qi, v4hi);
9429 v4hi __builtin_vis_fmul8x16au (v4qi, v4hi);
9430 v4hi __builtin_vis_fmul8x16al (v4qi, v4hi);
9431 v4hi __builtin_vis_fmul8sux16 (v8qi, v4hi);
9432 v4hi __builtin_vis_fmul8ulx16 (v8qi, v4hi);
9433 v2si __builtin_vis_fmuld8sux16 (v4qi, v2hi);
9434 v2si __builtin_vis_fmuld8ulx16 (v4qi, v2hi);
9436 v4qi __builtin_vis_fpack16 (v4hi);
9437 v8qi __builtin_vis_fpack32 (v2si, v2si);
9438 v2hi __builtin_vis_fpackfix (v2si);
9439 v8qi __builtin_vis_fpmerge (v4qi, v4qi);
9441 int64_t __builtin_vis_pdist (v8qi, v8qi, int64_t);
9444 @node Target Format Checks
9445 @section Format Checks Specific to Particular Target Machines
9447 For some target machines, GCC supports additional options to the
9449 (@pxref{Function Attributes,,Declaring Attributes of Functions}).
9452 * Solaris Format Checks::
9455 @node Solaris Format Checks
9456 @subsection Solaris Format Checks
9458 Solaris targets support the @code{cmn_err} (or @code{__cmn_err__}) format
9459 check. @code{cmn_err} accepts a subset of the standard @code{printf}
9460 conversions, and the two-argument @code{%b} conversion for displaying
9461 bit-fields. See the Solaris man page for @code{cmn_err} for more information.
9464 @section Pragmas Accepted by GCC
9468 GCC supports several types of pragmas, primarily in order to compile
9469 code originally written for other compilers. Note that in general
9470 we do not recommend the use of pragmas; @xref{Function Attributes},
9471 for further explanation.
9476 * RS/6000 and PowerPC Pragmas::
9479 * Symbol-Renaming Pragmas::
9480 * Structure-Packing Pragmas::
9482 * Diagnostic Pragmas::
9483 * Visibility Pragmas::
9487 @subsection ARM Pragmas
9489 The ARM target defines pragmas for controlling the default addition of
9490 @code{long_call} and @code{short_call} attributes to functions.
9491 @xref{Function Attributes}, for information about the effects of these
9496 @cindex pragma, long_calls
9497 Set all subsequent functions to have the @code{long_call} attribute.
9500 @cindex pragma, no_long_calls
9501 Set all subsequent functions to have the @code{short_call} attribute.
9503 @item long_calls_off
9504 @cindex pragma, long_calls_off
9505 Do not affect the @code{long_call} or @code{short_call} attributes of
9506 subsequent functions.
9510 @subsection M32C Pragmas
9513 @item memregs @var{number}
9514 @cindex pragma, memregs
9515 Overrides the command line option @code{-memregs=} for the current
9516 file. Use with care! This pragma must be before any function in the
9517 file, and mixing different memregs values in different objects may
9518 make them incompatible. This pragma is useful when a
9519 performance-critical function uses a memreg for temporary values,
9520 as it may allow you to reduce the number of memregs used.
9524 @node RS/6000 and PowerPC Pragmas
9525 @subsection RS/6000 and PowerPC Pragmas
9527 The RS/6000 and PowerPC targets define one pragma for controlling
9528 whether or not the @code{longcall} attribute is added to function
9529 declarations by default. This pragma overrides the @option{-mlongcall}
9530 option, but not the @code{longcall} and @code{shortcall} attributes.
9531 @xref{RS/6000 and PowerPC Options}, for more information about when long
9532 calls are and are not necessary.
9536 @cindex pragma, longcall
9537 Apply the @code{longcall} attribute to all subsequent function
9541 Do not apply the @code{longcall} attribute to subsequent function
9545 @c Describe c4x pragmas here.
9546 @c Describe h8300 pragmas here.
9547 @c Describe sh pragmas here.
9548 @c Describe v850 pragmas here.
9550 @node Darwin Pragmas
9551 @subsection Darwin Pragmas
9553 The following pragmas are available for all architectures running the
9554 Darwin operating system. These are useful for compatibility with other
9558 @item mark @var{tokens}@dots{}
9559 @cindex pragma, mark
9560 This pragma is accepted, but has no effect.
9562 @item options align=@var{alignment}
9563 @cindex pragma, options align
9564 This pragma sets the alignment of fields in structures. The values of
9565 @var{alignment} may be @code{mac68k}, to emulate m68k alignment, or
9566 @code{power}, to emulate PowerPC alignment. Uses of this pragma nest
9567 properly; to restore the previous setting, use @code{reset} for the
9570 @item segment @var{tokens}@dots{}
9571 @cindex pragma, segment
9572 This pragma is accepted, but has no effect.
9574 @item unused (@var{var} [, @var{var}]@dots{})
9575 @cindex pragma, unused
9576 This pragma declares variables to be possibly unused. GCC will not
9577 produce warnings for the listed variables. The effect is similar to
9578 that of the @code{unused} attribute, except that this pragma may appear
9579 anywhere within the variables' scopes.
9582 @node Solaris Pragmas
9583 @subsection Solaris Pragmas
9585 The Solaris target supports @code{#pragma redefine_extname}
9586 (@pxref{Symbol-Renaming Pragmas}). It also supports additional
9587 @code{#pragma} directives for compatibility with the system compiler.
9590 @item align @var{alignment} (@var{variable} [, @var{variable}]...)
9591 @cindex pragma, align
9593 Increase the minimum alignment of each @var{variable} to @var{alignment}.
9594 This is the same as GCC's @code{aligned} attribute @pxref{Variable
9595 Attributes}). Macro expansion occurs on the arguments to this pragma
9596 when compiling C and Objective-C. It does not currently occur when
9597 compiling C++, but this is a bug which may be fixed in a future
9600 @item fini (@var{function} [, @var{function}]...)
9601 @cindex pragma, fini
9603 This pragma causes each listed @var{function} to be called after
9604 main, or during shared module unloading, by adding a call to the
9605 @code{.fini} section.
9607 @item init (@var{function} [, @var{function}]...)
9608 @cindex pragma, init
9610 This pragma causes each listed @var{function} to be called during
9611 initialization (before @code{main}) or during shared module loading, by
9612 adding a call to the @code{.init} section.
9616 @node Symbol-Renaming Pragmas
9617 @subsection Symbol-Renaming Pragmas
9619 For compatibility with the Solaris and Tru64 UNIX system headers, GCC
9620 supports two @code{#pragma} directives which change the name used in
9621 assembly for a given declaration. These pragmas are only available on
9622 platforms whose system headers need them. To get this effect on all
9623 platforms supported by GCC, use the asm labels extension (@pxref{Asm
9627 @item redefine_extname @var{oldname} @var{newname}
9628 @cindex pragma, redefine_extname
9630 This pragma gives the C function @var{oldname} the assembly symbol
9631 @var{newname}. The preprocessor macro @code{__PRAGMA_REDEFINE_EXTNAME}
9632 will be defined if this pragma is available (currently only on
9635 @item extern_prefix @var{string}
9636 @cindex pragma, extern_prefix
9638 This pragma causes all subsequent external function and variable
9639 declarations to have @var{string} prepended to their assembly symbols.
9640 This effect may be terminated with another @code{extern_prefix} pragma
9641 whose argument is an empty string. The preprocessor macro
9642 @code{__PRAGMA_EXTERN_PREFIX} will be defined if this pragma is
9643 available (currently only on Tru64 UNIX)@.
9646 These pragmas and the asm labels extension interact in a complicated
9647 manner. Here are some corner cases you may want to be aware of.
9650 @item Both pragmas silently apply only to declarations with external
9651 linkage. Asm labels do not have this restriction.
9653 @item In C++, both pragmas silently apply only to declarations with
9654 ``C'' linkage. Again, asm labels do not have this restriction.
9656 @item If any of the three ways of changing the assembly name of a
9657 declaration is applied to a declaration whose assembly name has
9658 already been determined (either by a previous use of one of these
9659 features, or because the compiler needed the assembly name in order to
9660 generate code), and the new name is different, a warning issues and
9661 the name does not change.
9663 @item The @var{oldname} used by @code{#pragma redefine_extname} is
9664 always the C-language name.
9666 @item If @code{#pragma extern_prefix} is in effect, and a declaration
9667 occurs with an asm label attached, the prefix is silently ignored for
9670 @item If @code{#pragma extern_prefix} and @code{#pragma redefine_extname}
9671 apply to the same declaration, whichever triggered first wins, and a
9672 warning issues if they contradict each other. (We would like to have
9673 @code{#pragma redefine_extname} always win, for consistency with asm
9674 labels, but if @code{#pragma extern_prefix} triggers first we have no
9675 way of knowing that that happened.)
9678 @node Structure-Packing Pragmas
9679 @subsection Structure-Packing Pragmas
9681 For compatibility with Win32, GCC supports a set of @code{#pragma}
9682 directives which change the maximum alignment of members of structures
9683 (other than zero-width bitfields), unions, and classes subsequently
9684 defined. The @var{n} value below always is required to be a small power
9685 of two and specifies the new alignment in bytes.
9688 @item @code{#pragma pack(@var{n})} simply sets the new alignment.
9689 @item @code{#pragma pack()} sets the alignment to the one that was in
9690 effect when compilation started (see also command line option
9691 @option{-fpack-struct[=<n>]} @pxref{Code Gen Options}).
9692 @item @code{#pragma pack(push[,@var{n}])} pushes the current alignment
9693 setting on an internal stack and then optionally sets the new alignment.
9694 @item @code{#pragma pack(pop)} restores the alignment setting to the one
9695 saved at the top of the internal stack (and removes that stack entry).
9696 Note that @code{#pragma pack([@var{n}])} does not influence this internal
9697 stack; thus it is possible to have @code{#pragma pack(push)} followed by
9698 multiple @code{#pragma pack(@var{n})} instances and finalized by a single
9699 @code{#pragma pack(pop)}.
9702 Some targets, e.g. i386 and powerpc, support the @code{ms_struct}
9703 @code{#pragma} which lays out a structure as the documented
9704 @code{__attribute__ ((ms_struct))}.
9706 @item @code{#pragma ms_struct on} turns on the layout for structures
9708 @item @code{#pragma ms_struct off} turns off the layout for structures
9710 @item @code{#pragma ms_struct reset} goes back to the default layout.
9714 @subsection Weak Pragmas
9716 For compatibility with SVR4, GCC supports a set of @code{#pragma}
9717 directives for declaring symbols to be weak, and defining weak
9721 @item #pragma weak @var{symbol}
9722 @cindex pragma, weak
9723 This pragma declares @var{symbol} to be weak, as if the declaration
9724 had the attribute of the same name. The pragma may appear before
9725 or after the declaration of @var{symbol}, but must appear before
9726 either its first use or its definition. It is not an error for
9727 @var{symbol} to never be defined at all.
9729 @item #pragma weak @var{symbol1} = @var{symbol2}
9730 This pragma declares @var{symbol1} to be a weak alias of @var{symbol2}.
9731 It is an error if @var{symbol2} is not defined in the current
9735 @node Diagnostic Pragmas
9736 @subsection Diagnostic Pragmas
9738 GCC allows the user to selectively enable or disable certain types of
9739 diagnostics, and change the kind of the diagnostic. For example, a
9740 project's policy might require that all sources compile with
9741 @option{-Werror} but certain files might have exceptions allowing
9742 specific types of warnings. Or, a project might selectively enable
9743 diagnostics and treat them as errors depending on which preprocessor
9747 @item #pragma GCC diagnostic @var{kind} @var{option}
9748 @cindex pragma, diagnostic
9750 Modifies the disposition of a diagnostic. Note that not all
9751 diagnostics are modifyiable; at the moment only warnings (normally
9752 controlled by @samp{-W...}) can be controlled, and not all of them.
9753 Use @option{-fdiagnostics-show-option} to determine which diagnostics
9754 are controllable and which option controls them.
9756 @var{kind} is @samp{error} to treat this diagnostic as an error,
9757 @samp{warning} to treat it like a warning (even if @option{-Werror} is
9758 in effect), or @samp{ignored} if the diagnostic is to be ignored.
9759 @var{option} is a double quoted string which matches the command line
9763 #pragma GCC diagnostic warning "-Wformat"
9764 #pragma GCC diagnostic error "-Walways-true"
9765 #pragma GCC diagnostic ignored "-Walways-true"
9768 Note that these pragmas override any command line options. Also,
9769 while it is syntactically valid to put these pragmas anywhere in your
9770 sources, the only supported location for them is before any data or
9771 functions are defined. Doing otherwise may result in unpredictable
9772 results depending on how the optimizer manages your sources. If the
9773 same option is listed multiple times, the last one specified is the
9774 one that is in effect. This pragma is not intended to be a general
9775 purpose replacement for command line options, but for implementing
9776 strict control over project policies.
9780 @node Visibility Pragmas
9781 @subsection Visibility Pragmas
9784 @item #pragma GCC visibility push(@var{visibility})
9785 @itemx #pragma GCC visibility pop
9786 @cindex pragma, visibility
9788 This pragma allows the user to set the visibility for multiple
9789 declarations without having to give each a visibility attribute
9790 @xref{Function Attributes}, for more information about visibility and
9791 the attribute syntax.
9793 In C++, @samp{#pragma GCC visibility} affects only namespace-scope
9794 declarations. Class members and template specializations are not
9795 affected; if you want to override the visibility for a particular
9796 member or instantiation, you must use an attribute.
9800 @node Unnamed Fields
9801 @section Unnamed struct/union fields within structs/unions
9805 For compatibility with other compilers, GCC allows you to define
9806 a structure or union that contains, as fields, structures and unions
9807 without names. For example:
9820 In this example, the user would be able to access members of the unnamed
9821 union with code like @samp{foo.b}. Note that only unnamed structs and
9822 unions are allowed, you may not have, for example, an unnamed
9825 You must never create such structures that cause ambiguous field definitions.
9826 For example, this structure:
9837 It is ambiguous which @code{a} is being referred to with @samp{foo.a}.
9838 Such constructs are not supported and must be avoided. In the future,
9839 such constructs may be detected and treated as compilation errors.
9841 @opindex fms-extensions
9842 Unless @option{-fms-extensions} is used, the unnamed field must be a
9843 structure or union definition without a tag (for example, @samp{struct
9844 @{ int a; @};}). If @option{-fms-extensions} is used, the field may
9845 also be a definition with a tag such as @samp{struct foo @{ int a;
9846 @};}, a reference to a previously defined structure or union such as
9847 @samp{struct foo;}, or a reference to a @code{typedef} name for a
9848 previously defined structure or union type.
9851 @section Thread-Local Storage
9852 @cindex Thread-Local Storage
9853 @cindex @acronym{TLS}
9856 Thread-local storage (@acronym{TLS}) is a mechanism by which variables
9857 are allocated such that there is one instance of the variable per extant
9858 thread. The run-time model GCC uses to implement this originates
9859 in the IA-64 processor-specific ABI, but has since been migrated
9860 to other processors as well. It requires significant support from
9861 the linker (@command{ld}), dynamic linker (@command{ld.so}), and
9862 system libraries (@file{libc.so} and @file{libpthread.so}), so it
9863 is not available everywhere.
9865 At the user level, the extension is visible with a new storage
9866 class keyword: @code{__thread}. For example:
9870 extern __thread struct state s;
9871 static __thread char *p;
9874 The @code{__thread} specifier may be used alone, with the @code{extern}
9875 or @code{static} specifiers, but with no other storage class specifier.
9876 When used with @code{extern} or @code{static}, @code{__thread} must appear
9877 immediately after the other storage class specifier.
9879 The @code{__thread} specifier may be applied to any global, file-scoped
9880 static, function-scoped static, or static data member of a class. It may
9881 not be applied to block-scoped automatic or non-static data member.
9883 When the address-of operator is applied to a thread-local variable, it is
9884 evaluated at run-time and returns the address of the current thread's
9885 instance of that variable. An address so obtained may be used by any
9886 thread. When a thread terminates, any pointers to thread-local variables
9887 in that thread become invalid.
9889 No static initialization may refer to the address of a thread-local variable.
9891 In C++, if an initializer is present for a thread-local variable, it must
9892 be a @var{constant-expression}, as defined in 5.19.2 of the ANSI/ISO C++
9895 See @uref{http://people.redhat.com/drepper/tls.pdf,
9896 ELF Handling For Thread-Local Storage} for a detailed explanation of
9897 the four thread-local storage addressing models, and how the run-time
9898 is expected to function.
9901 * C99 Thread-Local Edits::
9902 * C++98 Thread-Local Edits::
9905 @node C99 Thread-Local Edits
9906 @subsection ISO/IEC 9899:1999 Edits for Thread-Local Storage
9908 The following are a set of changes to ISO/IEC 9899:1999 (aka C99)
9909 that document the exact semantics of the language extension.
9913 @cite{5.1.2 Execution environments}
9915 Add new text after paragraph 1
9918 Within either execution environment, a @dfn{thread} is a flow of
9919 control within a program. It is implementation defined whether
9920 or not there may be more than one thread associated with a program.
9921 It is implementation defined how threads beyond the first are
9922 created, the name and type of the function called at thread
9923 startup, and how threads may be terminated. However, objects
9924 with thread storage duration shall be initialized before thread
9929 @cite{6.2.4 Storage durations of objects}
9931 Add new text before paragraph 3
9934 An object whose identifier is declared with the storage-class
9935 specifier @w{@code{__thread}} has @dfn{thread storage duration}.
9936 Its lifetime is the entire execution of the thread, and its
9937 stored value is initialized only once, prior to thread startup.
9941 @cite{6.4.1 Keywords}
9943 Add @code{__thread}.
9946 @cite{6.7.1 Storage-class specifiers}
9948 Add @code{__thread} to the list of storage class specifiers in
9951 Change paragraph 2 to
9954 With the exception of @code{__thread}, at most one storage-class
9955 specifier may be given [@dots{}]. The @code{__thread} specifier may
9956 be used alone, or immediately following @code{extern} or
9960 Add new text after paragraph 6
9963 The declaration of an identifier for a variable that has
9964 block scope that specifies @code{__thread} shall also
9965 specify either @code{extern} or @code{static}.
9967 The @code{__thread} specifier shall be used only with
9972 @node C++98 Thread-Local Edits
9973 @subsection ISO/IEC 14882:1998 Edits for Thread-Local Storage
9975 The following are a set of changes to ISO/IEC 14882:1998 (aka C++98)
9976 that document the exact semantics of the language extension.
9980 @b{[intro.execution]}
9982 New text after paragraph 4
9985 A @dfn{thread} is a flow of control within the abstract machine.
9986 It is implementation defined whether or not there may be more than
9990 New text after paragraph 7
9993 It is unspecified whether additional action must be taken to
9994 ensure when and whether side effects are visible to other threads.
10000 Add @code{__thread}.
10003 @b{[basic.start.main]}
10005 Add after paragraph 5
10008 The thread that begins execution at the @code{main} function is called
10009 the @dfn{main thread}. It is implementation defined how functions
10010 beginning threads other than the main thread are designated or typed.
10011 A function so designated, as well as the @code{main} function, is called
10012 a @dfn{thread startup function}. It is implementation defined what
10013 happens if a thread startup function returns. It is implementation
10014 defined what happens to other threads when any thread calls @code{exit}.
10018 @b{[basic.start.init]}
10020 Add after paragraph 4
10023 The storage for an object of thread storage duration shall be
10024 statically initialized before the first statement of the thread startup
10025 function. An object of thread storage duration shall not require
10026 dynamic initialization.
10030 @b{[basic.start.term]}
10032 Add after paragraph 3
10035 The type of an object with thread storage duration shall not have a
10036 non-trivial destructor, nor shall it be an array type whose elements
10037 (directly or indirectly) have non-trivial destructors.
10043 Add ``thread storage duration'' to the list in paragraph 1.
10048 Thread, static, and automatic storage durations are associated with
10049 objects introduced by declarations [@dots{}].
10052 Add @code{__thread} to the list of specifiers in paragraph 3.
10055 @b{[basic.stc.thread]}
10057 New section before @b{[basic.stc.static]}
10060 The keyword @code{__thread} applied to a non-local object gives the
10061 object thread storage duration.
10063 A local variable or class data member declared both @code{static}
10064 and @code{__thread} gives the variable or member thread storage
10069 @b{[basic.stc.static]}
10074 All objects which have neither thread storage duration, dynamic
10075 storage duration nor are local [@dots{}].
10081 Add @code{__thread} to the list in paragraph 1.
10086 With the exception of @code{__thread}, at most one
10087 @var{storage-class-specifier} shall appear in a given
10088 @var{decl-specifier-seq}. The @code{__thread} specifier may
10089 be used alone, or immediately following the @code{extern} or
10090 @code{static} specifiers. [@dots{}]
10093 Add after paragraph 5
10096 The @code{__thread} specifier can be applied only to the names of objects
10097 and to anonymous unions.
10103 Add after paragraph 6
10106 Non-@code{static} members shall not be @code{__thread}.
10110 @node C++ Extensions
10111 @chapter Extensions to the C++ Language
10112 @cindex extensions, C++ language
10113 @cindex C++ language extensions
10115 The GNU compiler provides these extensions to the C++ language (and you
10116 can also use most of the C language extensions in your C++ programs). If you
10117 want to write code that checks whether these features are available, you can
10118 test for the GNU compiler the same way as for C programs: check for a
10119 predefined macro @code{__GNUC__}. You can also use @code{__GNUG__} to
10120 test specifically for GNU C++ (@pxref{Common Predefined Macros,,
10121 Predefined Macros,cpp,The GNU C Preprocessor}).
10124 * Volatiles:: What constitutes an access to a volatile object.
10125 * Restricted Pointers:: C99 restricted pointers and references.
10126 * Vague Linkage:: Where G++ puts inlines, vtables and such.
10127 * C++ Interface:: You can use a single C++ header file for both
10128 declarations and definitions.
10129 * Template Instantiation:: Methods for ensuring that exactly one copy of
10130 each needed template instantiation is emitted.
10131 * Bound member functions:: You can extract a function pointer to the
10132 method denoted by a @samp{->*} or @samp{.*} expression.
10133 * C++ Attributes:: Variable, function, and type attributes for C++ only.
10134 * Namespace Association:: Strong using-directives for namespace association.
10135 * Java Exceptions:: Tweaking exception handling to work with Java.
10136 * Deprecated Features:: Things will disappear from g++.
10137 * Backwards Compatibility:: Compatibilities with earlier definitions of C++.
10141 @section When is a Volatile Object Accessed?
10142 @cindex accessing volatiles
10143 @cindex volatile read
10144 @cindex volatile write
10145 @cindex volatile access
10147 Both the C and C++ standard have the concept of volatile objects. These
10148 are normally accessed by pointers and used for accessing hardware. The
10149 standards encourage compilers to refrain from optimizations
10150 concerning accesses to volatile objects that it might perform on
10151 non-volatile objects. The C standard leaves it implementation defined
10152 as to what constitutes a volatile access. The C++ standard omits to
10153 specify this, except to say that C++ should behave in a similar manner
10154 to C with respect to volatiles, where possible. The minimum either
10155 standard specifies is that at a sequence point all previous accesses to
10156 volatile objects have stabilized and no subsequent accesses have
10157 occurred. Thus an implementation is free to reorder and combine
10158 volatile accesses which occur between sequence points, but cannot do so
10159 for accesses across a sequence point. The use of volatiles does not
10160 allow you to violate the restriction on updating objects multiple times
10161 within a sequence point.
10163 In most expressions, it is intuitively obvious what is a read and what is
10164 a write. For instance
10167 volatile int *dst = @var{somevalue};
10168 volatile int *src = @var{someothervalue};
10173 will cause a read of the volatile object pointed to by @var{src} and stores the
10174 value into the volatile object pointed to by @var{dst}. There is no
10175 guarantee that these reads and writes are atomic, especially for objects
10176 larger than @code{int}.
10178 Less obvious expressions are where something which looks like an access
10179 is used in a void context. An example would be,
10182 volatile int *src = @var{somevalue};
10186 With C, such expressions are rvalues, and as rvalues cause a read of
10187 the object, GCC interprets this as a read of the volatile being pointed
10188 to. The C++ standard specifies that such expressions do not undergo
10189 lvalue to rvalue conversion, and that the type of the dereferenced
10190 object may be incomplete. The C++ standard does not specify explicitly
10191 that it is this lvalue to rvalue conversion which is responsible for
10192 causing an access. However, there is reason to believe that it is,
10193 because otherwise certain simple expressions become undefined. However,
10194 because it would surprise most programmers, G++ treats dereferencing a
10195 pointer to volatile object of complete type in a void context as a read
10196 of the object. When the object has incomplete type, G++ issues a
10201 struct T @{int m;@};
10202 volatile S *ptr1 = @var{somevalue};
10203 volatile T *ptr2 = @var{somevalue};
10208 In this example, a warning is issued for @code{*ptr1}, and @code{*ptr2}
10209 causes a read of the object pointed to. If you wish to force an error on
10210 the first case, you must force a conversion to rvalue with, for instance
10211 a static cast, @code{static_cast<S>(*ptr1)}.
10213 When using a reference to volatile, G++ does not treat equivalent
10214 expressions as accesses to volatiles, but instead issues a warning that
10215 no volatile is accessed. The rationale for this is that otherwise it
10216 becomes difficult to determine where volatile access occur, and not
10217 possible to ignore the return value from functions returning volatile
10218 references. Again, if you wish to force a read, cast the reference to
10221 @node Restricted Pointers
10222 @section Restricting Pointer Aliasing
10223 @cindex restricted pointers
10224 @cindex restricted references
10225 @cindex restricted this pointer
10227 As with the C front end, G++ understands the C99 feature of restricted pointers,
10228 specified with the @code{__restrict__}, or @code{__restrict} type
10229 qualifier. Because you cannot compile C++ by specifying the @option{-std=c99}
10230 language flag, @code{restrict} is not a keyword in C++.
10232 In addition to allowing restricted pointers, you can specify restricted
10233 references, which indicate that the reference is not aliased in the local
10237 void fn (int *__restrict__ rptr, int &__restrict__ rref)
10244 In the body of @code{fn}, @var{rptr} points to an unaliased integer and
10245 @var{rref} refers to a (different) unaliased integer.
10247 You may also specify whether a member function's @var{this} pointer is
10248 unaliased by using @code{__restrict__} as a member function qualifier.
10251 void T::fn () __restrict__
10258 Within the body of @code{T::fn}, @var{this} will have the effective
10259 definition @code{T *__restrict__ const this}. Notice that the
10260 interpretation of a @code{__restrict__} member function qualifier is
10261 different to that of @code{const} or @code{volatile} qualifier, in that it
10262 is applied to the pointer rather than the object. This is consistent with
10263 other compilers which implement restricted pointers.
10265 As with all outermost parameter qualifiers, @code{__restrict__} is
10266 ignored in function definition matching. This means you only need to
10267 specify @code{__restrict__} in a function definition, rather than
10268 in a function prototype as well.
10270 @node Vague Linkage
10271 @section Vague Linkage
10272 @cindex vague linkage
10274 There are several constructs in C++ which require space in the object
10275 file but are not clearly tied to a single translation unit. We say that
10276 these constructs have ``vague linkage''. Typically such constructs are
10277 emitted wherever they are needed, though sometimes we can be more
10281 @item Inline Functions
10282 Inline functions are typically defined in a header file which can be
10283 included in many different compilations. Hopefully they can usually be
10284 inlined, but sometimes an out-of-line copy is necessary, if the address
10285 of the function is taken or if inlining fails. In general, we emit an
10286 out-of-line copy in all translation units where one is needed. As an
10287 exception, we only emit inline virtual functions with the vtable, since
10288 it will always require a copy.
10290 Local static variables and string constants used in an inline function
10291 are also considered to have vague linkage, since they must be shared
10292 between all inlined and out-of-line instances of the function.
10296 C++ virtual functions are implemented in most compilers using a lookup
10297 table, known as a vtable. The vtable contains pointers to the virtual
10298 functions provided by a class, and each object of the class contains a
10299 pointer to its vtable (or vtables, in some multiple-inheritance
10300 situations). If the class declares any non-inline, non-pure virtual
10301 functions, the first one is chosen as the ``key method'' for the class,
10302 and the vtable is only emitted in the translation unit where the key
10305 @emph{Note:} If the chosen key method is later defined as inline, the
10306 vtable will still be emitted in every translation unit which defines it.
10307 Make sure that any inline virtuals are declared inline in the class
10308 body, even if they are not defined there.
10310 @item type_info objects
10313 C++ requires information about types to be written out in order to
10314 implement @samp{dynamic_cast}, @samp{typeid} and exception handling.
10315 For polymorphic classes (classes with virtual functions), the type_info
10316 object is written out along with the vtable so that @samp{dynamic_cast}
10317 can determine the dynamic type of a class object at runtime. For all
10318 other types, we write out the type_info object when it is used: when
10319 applying @samp{typeid} to an expression, throwing an object, or
10320 referring to a type in a catch clause or exception specification.
10322 @item Template Instantiations
10323 Most everything in this section also applies to template instantiations,
10324 but there are other options as well.
10325 @xref{Template Instantiation,,Where's the Template?}.
10329 When used with GNU ld version 2.8 or later on an ELF system such as
10330 GNU/Linux or Solaris 2, or on Microsoft Windows, duplicate copies of
10331 these constructs will be discarded at link time. This is known as
10334 On targets that don't support COMDAT, but do support weak symbols, GCC
10335 will use them. This way one copy will override all the others, but
10336 the unused copies will still take up space in the executable.
10338 For targets which do not support either COMDAT or weak symbols,
10339 most entities with vague linkage will be emitted as local symbols to
10340 avoid duplicate definition errors from the linker. This will not happen
10341 for local statics in inlines, however, as having multiple copies will
10342 almost certainly break things.
10344 @xref{C++ Interface,,Declarations and Definitions in One Header}, for
10345 another way to control placement of these constructs.
10347 @node C++ Interface
10348 @section #pragma interface and implementation
10350 @cindex interface and implementation headers, C++
10351 @cindex C++ interface and implementation headers
10352 @cindex pragmas, interface and implementation
10354 @code{#pragma interface} and @code{#pragma implementation} provide the
10355 user with a way of explicitly directing the compiler to emit entities
10356 with vague linkage (and debugging information) in a particular
10359 @emph{Note:} As of GCC 2.7.2, these @code{#pragma}s are not useful in
10360 most cases, because of COMDAT support and the ``key method'' heuristic
10361 mentioned in @ref{Vague Linkage}. Using them can actually cause your
10362 program to grow due to unnecessary out-of-line copies of inline
10363 functions. Currently (3.4) the only benefit of these
10364 @code{#pragma}s is reduced duplication of debugging information, and
10365 that should be addressed soon on DWARF 2 targets with the use of
10369 @item #pragma interface
10370 @itemx #pragma interface "@var{subdir}/@var{objects}.h"
10371 @kindex #pragma interface
10372 Use this directive in @emph{header files} that define object classes, to save
10373 space in most of the object files that use those classes. Normally,
10374 local copies of certain information (backup copies of inline member
10375 functions, debugging information, and the internal tables that implement
10376 virtual functions) must be kept in each object file that includes class
10377 definitions. You can use this pragma to avoid such duplication. When a
10378 header file containing @samp{#pragma interface} is included in a
10379 compilation, this auxiliary information will not be generated (unless
10380 the main input source file itself uses @samp{#pragma implementation}).
10381 Instead, the object files will contain references to be resolved at link
10384 The second form of this directive is useful for the case where you have
10385 multiple headers with the same name in different directories. If you
10386 use this form, you must specify the same string to @samp{#pragma
10389 @item #pragma implementation
10390 @itemx #pragma implementation "@var{objects}.h"
10391 @kindex #pragma implementation
10392 Use this pragma in a @emph{main input file}, when you want full output from
10393 included header files to be generated (and made globally visible). The
10394 included header file, in turn, should use @samp{#pragma interface}.
10395 Backup copies of inline member functions, debugging information, and the
10396 internal tables used to implement virtual functions are all generated in
10397 implementation files.
10399 @cindex implied @code{#pragma implementation}
10400 @cindex @code{#pragma implementation}, implied
10401 @cindex naming convention, implementation headers
10402 If you use @samp{#pragma implementation} with no argument, it applies to
10403 an include file with the same basename@footnote{A file's @dfn{basename}
10404 was the name stripped of all leading path information and of trailing
10405 suffixes, such as @samp{.h} or @samp{.C} or @samp{.cc}.} as your source
10406 file. For example, in @file{allclass.cc}, giving just
10407 @samp{#pragma implementation}
10408 by itself is equivalent to @samp{#pragma implementation "allclass.h"}.
10410 In versions of GNU C++ prior to 2.6.0 @file{allclass.h} was treated as
10411 an implementation file whenever you would include it from
10412 @file{allclass.cc} even if you never specified @samp{#pragma
10413 implementation}. This was deemed to be more trouble than it was worth,
10414 however, and disabled.
10416 Use the string argument if you want a single implementation file to
10417 include code from multiple header files. (You must also use
10418 @samp{#include} to include the header file; @samp{#pragma
10419 implementation} only specifies how to use the file---it doesn't actually
10422 There is no way to split up the contents of a single header file into
10423 multiple implementation files.
10426 @cindex inlining and C++ pragmas
10427 @cindex C++ pragmas, effect on inlining
10428 @cindex pragmas in C++, effect on inlining
10429 @samp{#pragma implementation} and @samp{#pragma interface} also have an
10430 effect on function inlining.
10432 If you define a class in a header file marked with @samp{#pragma
10433 interface}, the effect on an inline function defined in that class is
10434 similar to an explicit @code{extern} declaration---the compiler emits
10435 no code at all to define an independent version of the function. Its
10436 definition is used only for inlining with its callers.
10438 @opindex fno-implement-inlines
10439 Conversely, when you include the same header file in a main source file
10440 that declares it as @samp{#pragma implementation}, the compiler emits
10441 code for the function itself; this defines a version of the function
10442 that can be found via pointers (or by callers compiled without
10443 inlining). If all calls to the function can be inlined, you can avoid
10444 emitting the function by compiling with @option{-fno-implement-inlines}.
10445 If any calls were not inlined, you will get linker errors.
10447 @node Template Instantiation
10448 @section Where's the Template?
10449 @cindex template instantiation
10451 C++ templates are the first language feature to require more
10452 intelligence from the environment than one usually finds on a UNIX
10453 system. Somehow the compiler and linker have to make sure that each
10454 template instance occurs exactly once in the executable if it is needed,
10455 and not at all otherwise. There are two basic approaches to this
10456 problem, which are referred to as the Borland model and the Cfront model.
10459 @item Borland model
10460 Borland C++ solved the template instantiation problem by adding the code
10461 equivalent of common blocks to their linker; the compiler emits template
10462 instances in each translation unit that uses them, and the linker
10463 collapses them together. The advantage of this model is that the linker
10464 only has to consider the object files themselves; there is no external
10465 complexity to worry about. This disadvantage is that compilation time
10466 is increased because the template code is being compiled repeatedly.
10467 Code written for this model tends to include definitions of all
10468 templates in the header file, since they must be seen to be
10472 The AT&T C++ translator, Cfront, solved the template instantiation
10473 problem by creating the notion of a template repository, an
10474 automatically maintained place where template instances are stored. A
10475 more modern version of the repository works as follows: As individual
10476 object files are built, the compiler places any template definitions and
10477 instantiations encountered in the repository. At link time, the link
10478 wrapper adds in the objects in the repository and compiles any needed
10479 instances that were not previously emitted. The advantages of this
10480 model are more optimal compilation speed and the ability to use the
10481 system linker; to implement the Borland model a compiler vendor also
10482 needs to replace the linker. The disadvantages are vastly increased
10483 complexity, and thus potential for error; for some code this can be
10484 just as transparent, but in practice it can been very difficult to build
10485 multiple programs in one directory and one program in multiple
10486 directories. Code written for this model tends to separate definitions
10487 of non-inline member templates into a separate file, which should be
10488 compiled separately.
10491 When used with GNU ld version 2.8 or later on an ELF system such as
10492 GNU/Linux or Solaris 2, or on Microsoft Windows, G++ supports the
10493 Borland model. On other systems, G++ implements neither automatic
10496 A future version of G++ will support a hybrid model whereby the compiler
10497 will emit any instantiations for which the template definition is
10498 included in the compile, and store template definitions and
10499 instantiation context information into the object file for the rest.
10500 The link wrapper will extract that information as necessary and invoke
10501 the compiler to produce the remaining instantiations. The linker will
10502 then combine duplicate instantiations.
10504 In the mean time, you have the following options for dealing with
10505 template instantiations:
10510 Compile your template-using code with @option{-frepo}. The compiler will
10511 generate files with the extension @samp{.rpo} listing all of the
10512 template instantiations used in the corresponding object files which
10513 could be instantiated there; the link wrapper, @samp{collect2}, will
10514 then update the @samp{.rpo} files to tell the compiler where to place
10515 those instantiations and rebuild any affected object files. The
10516 link-time overhead is negligible after the first pass, as the compiler
10517 will continue to place the instantiations in the same files.
10519 This is your best option for application code written for the Borland
10520 model, as it will just work. Code written for the Cfront model will
10521 need to be modified so that the template definitions are available at
10522 one or more points of instantiation; usually this is as simple as adding
10523 @code{#include <tmethods.cc>} to the end of each template header.
10525 For library code, if you want the library to provide all of the template
10526 instantiations it needs, just try to link all of its object files
10527 together; the link will fail, but cause the instantiations to be
10528 generated as a side effect. Be warned, however, that this may cause
10529 conflicts if multiple libraries try to provide the same instantiations.
10530 For greater control, use explicit instantiation as described in the next
10534 @opindex fno-implicit-templates
10535 Compile your code with @option{-fno-implicit-templates} to disable the
10536 implicit generation of template instances, and explicitly instantiate
10537 all the ones you use. This approach requires more knowledge of exactly
10538 which instances you need than do the others, but it's less
10539 mysterious and allows greater control. You can scatter the explicit
10540 instantiations throughout your program, perhaps putting them in the
10541 translation units where the instances are used or the translation units
10542 that define the templates themselves; you can put all of the explicit
10543 instantiations you need into one big file; or you can create small files
10550 template class Foo<int>;
10551 template ostream& operator <<
10552 (ostream&, const Foo<int>&);
10555 for each of the instances you need, and create a template instantiation
10556 library from those.
10558 If you are using Cfront-model code, you can probably get away with not
10559 using @option{-fno-implicit-templates} when compiling files that don't
10560 @samp{#include} the member template definitions.
10562 If you use one big file to do the instantiations, you may want to
10563 compile it without @option{-fno-implicit-templates} so you get all of the
10564 instances required by your explicit instantiations (but not by any
10565 other files) without having to specify them as well.
10567 G++ has extended the template instantiation syntax given in the ISO
10568 standard to allow forward declaration of explicit instantiations
10569 (with @code{extern}), instantiation of the compiler support data for a
10570 template class (i.e.@: the vtable) without instantiating any of its
10571 members (with @code{inline}), and instantiation of only the static data
10572 members of a template class, without the support data or member
10573 functions (with (@code{static}):
10576 extern template int max (int, int);
10577 inline template class Foo<int>;
10578 static template class Foo<int>;
10582 Do nothing. Pretend G++ does implement automatic instantiation
10583 management. Code written for the Borland model will work fine, but
10584 each translation unit will contain instances of each of the templates it
10585 uses. In a large program, this can lead to an unacceptable amount of code
10589 @node Bound member functions
10590 @section Extracting the function pointer from a bound pointer to member function
10592 @cindex pointer to member function
10593 @cindex bound pointer to member function
10595 In C++, pointer to member functions (PMFs) are implemented using a wide
10596 pointer of sorts to handle all the possible call mechanisms; the PMF
10597 needs to store information about how to adjust the @samp{this} pointer,
10598 and if the function pointed to is virtual, where to find the vtable, and
10599 where in the vtable to look for the member function. If you are using
10600 PMFs in an inner loop, you should really reconsider that decision. If
10601 that is not an option, you can extract the pointer to the function that
10602 would be called for a given object/PMF pair and call it directly inside
10603 the inner loop, to save a bit of time.
10605 Note that you will still be paying the penalty for the call through a
10606 function pointer; on most modern architectures, such a call defeats the
10607 branch prediction features of the CPU@. This is also true of normal
10608 virtual function calls.
10610 The syntax for this extension is
10614 extern int (A::*fp)();
10615 typedef int (*fptr)(A *);
10617 fptr p = (fptr)(a.*fp);
10620 For PMF constants (i.e.@: expressions of the form @samp{&Klasse::Member}),
10621 no object is needed to obtain the address of the function. They can be
10622 converted to function pointers directly:
10625 fptr p1 = (fptr)(&A::foo);
10628 @opindex Wno-pmf-conversions
10629 You must specify @option{-Wno-pmf-conversions} to use this extension.
10631 @node C++ Attributes
10632 @section C++-Specific Variable, Function, and Type Attributes
10634 Some attributes only make sense for C++ programs.
10637 @item init_priority (@var{priority})
10638 @cindex init_priority attribute
10641 In Standard C++, objects defined at namespace scope are guaranteed to be
10642 initialized in an order in strict accordance with that of their definitions
10643 @emph{in a given translation unit}. No guarantee is made for initializations
10644 across translation units. However, GNU C++ allows users to control the
10645 order of initialization of objects defined at namespace scope with the
10646 @code{init_priority} attribute by specifying a relative @var{priority},
10647 a constant integral expression currently bounded between 101 and 65535
10648 inclusive. Lower numbers indicate a higher priority.
10650 In the following example, @code{A} would normally be created before
10651 @code{B}, but the @code{init_priority} attribute has reversed that order:
10654 Some_Class A __attribute__ ((init_priority (2000)));
10655 Some_Class B __attribute__ ((init_priority (543)));
10659 Note that the particular values of @var{priority} do not matter; only their
10662 @item java_interface
10663 @cindex java_interface attribute
10665 This type attribute informs C++ that the class is a Java interface. It may
10666 only be applied to classes declared within an @code{extern "Java"} block.
10667 Calls to methods declared in this interface will be dispatched using GCJ's
10668 interface table mechanism, instead of regular virtual table dispatch.
10672 See also @xref{Namespace Association}.
10674 @node Namespace Association
10675 @section Namespace Association
10677 @strong{Caution:} The semantics of this extension are not fully
10678 defined. Users should refrain from using this extension as its
10679 semantics may change subtly over time. It is possible that this
10680 extension will be removed in future versions of G++.
10682 A using-directive with @code{__attribute ((strong))} is stronger
10683 than a normal using-directive in two ways:
10687 Templates from the used namespace can be specialized and explicitly
10688 instantiated as though they were members of the using namespace.
10691 The using namespace is considered an associated namespace of all
10692 templates in the used namespace for purposes of argument-dependent
10696 The used namespace must be nested within the using namespace so that
10697 normal unqualified lookup works properly.
10699 This is useful for composing a namespace transparently from
10700 implementation namespaces. For example:
10705 template <class T> struct A @{ @};
10707 using namespace debug __attribute ((__strong__));
10708 template <> struct A<int> @{ @}; // @r{ok to specialize}
10710 template <class T> void f (A<T>);
10715 f (std::A<float>()); // @r{lookup finds} std::f
10720 @node Java Exceptions
10721 @section Java Exceptions
10723 The Java language uses a slightly different exception handling model
10724 from C++. Normally, GNU C++ will automatically detect when you are
10725 writing C++ code that uses Java exceptions, and handle them
10726 appropriately. However, if C++ code only needs to execute destructors
10727 when Java exceptions are thrown through it, GCC will guess incorrectly.
10728 Sample problematic code is:
10731 struct S @{ ~S(); @};
10732 extern void bar(); // @r{is written in Java, and may throw exceptions}
10741 The usual effect of an incorrect guess is a link failure, complaining of
10742 a missing routine called @samp{__gxx_personality_v0}.
10744 You can inform the compiler that Java exceptions are to be used in a
10745 translation unit, irrespective of what it might think, by writing
10746 @samp{@w{#pragma GCC java_exceptions}} at the head of the file. This
10747 @samp{#pragma} must appear before any functions that throw or catch
10748 exceptions, or run destructors when exceptions are thrown through them.
10750 You cannot mix Java and C++ exceptions in the same translation unit. It
10751 is believed to be safe to throw a C++ exception from one file through
10752 another file compiled for the Java exception model, or vice versa, but
10753 there may be bugs in this area.
10755 @node Deprecated Features
10756 @section Deprecated Features
10758 In the past, the GNU C++ compiler was extended to experiment with new
10759 features, at a time when the C++ language was still evolving. Now that
10760 the C++ standard is complete, some of those features are superseded by
10761 superior alternatives. Using the old features might cause a warning in
10762 some cases that the feature will be dropped in the future. In other
10763 cases, the feature might be gone already.
10765 While the list below is not exhaustive, it documents some of the options
10766 that are now deprecated:
10769 @item -fexternal-templates
10770 @itemx -falt-external-templates
10771 These are two of the many ways for G++ to implement template
10772 instantiation. @xref{Template Instantiation}. The C++ standard clearly
10773 defines how template definitions have to be organized across
10774 implementation units. G++ has an implicit instantiation mechanism that
10775 should work just fine for standard-conforming code.
10777 @item -fstrict-prototype
10778 @itemx -fno-strict-prototype
10779 Previously it was possible to use an empty prototype parameter list to
10780 indicate an unspecified number of parameters (like C), rather than no
10781 parameters, as C++ demands. This feature has been removed, except where
10782 it is required for backwards compatibility @xref{Backwards Compatibility}.
10785 G++ allows a virtual function returning @samp{void *} to be overridden
10786 by one returning a different pointer type. This extension to the
10787 covariant return type rules is now deprecated and will be removed from a
10790 The G++ minimum and maximum operators (@samp{<?} and @samp{>?}) and
10791 their compound forms (@samp{<?=}) and @samp{>?=}) have been deprecated
10792 and will be removed in a future version. Code using these operators
10793 should be modified to use @code{std::min} and @code{std::max} instead.
10795 The named return value extension has been deprecated, and is now
10798 The use of initializer lists with new expressions has been deprecated,
10799 and is now removed from G++.
10801 Floating and complex non-type template parameters have been deprecated,
10802 and are now removed from G++.
10804 The implicit typename extension has been deprecated and is now
10807 The use of default arguments in function pointers, function typedefs and
10808 and other places where they are not permitted by the standard is
10809 deprecated and will be removed from a future version of G++.
10811 G++ allows floating-point literals to appear in integral constant expressions,
10812 e.g. @samp{ enum E @{ e = int(2.2 * 3.7) @} }
10813 This extension is deprecated and will be removed from a future version.
10815 G++ allows static data members of const floating-point type to be declared
10816 with an initializer in a class definition. The standard only allows
10817 initializers for static members of const integral types and const
10818 enumeration types so this extension has been deprecated and will be removed
10819 from a future version.
10821 @node Backwards Compatibility
10822 @section Backwards Compatibility
10823 @cindex Backwards Compatibility
10824 @cindex ARM [Annotated C++ Reference Manual]
10826 Now that there is a definitive ISO standard C++, G++ has a specification
10827 to adhere to. The C++ language evolved over time, and features that
10828 used to be acceptable in previous drafts of the standard, such as the ARM
10829 [Annotated C++ Reference Manual], are no longer accepted. In order to allow
10830 compilation of C++ written to such drafts, G++ contains some backwards
10831 compatibilities. @emph{All such backwards compatibility features are
10832 liable to disappear in future versions of G++.} They should be considered
10833 deprecated @xref{Deprecated Features}.
10837 If a variable is declared at for scope, it used to remain in scope until
10838 the end of the scope which contained the for statement (rather than just
10839 within the for scope). G++ retains this, but issues a warning, if such a
10840 variable is accessed outside the for scope.
10842 @item Implicit C language
10843 Old C system header files did not contain an @code{extern "C" @{@dots{}@}}
10844 scope to set the language. On such systems, all header files are
10845 implicitly scoped inside a C language scope. Also, an empty prototype
10846 @code{()} will be treated as an unspecified number of arguments, rather
10847 than no arguments, as C++ demands.