* Conditionals:: Omitting the middle operand of a @samp{?:} expression.
* Long Long:: Double-word integers---@code{long long int}.
* Complex:: Data types for complex numbers.
-* Decimal Float:: Decimal Floating Point.
+* Decimal Float:: Decimal Floating Types.
* Hex Floats:: Hexadecimal floating-point constants.
* Zero Length:: Zero-length arrays.
* Variable Length:: Arrays whose length is computed at run time.
examine and set these two fictitious variables with your debugger.
@node Decimal Float
-@section Decimal Floating Point
-@cindex decimal floating point
+@section Decimal Floating Types
+@cindex decimal floating types
@cindex @code{_Decimal32} data type
@cindex @code{_Decimal64} data type
@cindex @code{_Decimal128} data type
@cindex @code{DD} integer suffix
@cindex @code{DL} integer suffix
-GNU C supports decimal floating point types in addition to the
-standard floating-point types. This extension supports decimal
-floating-point arithmetic as defined in IEEE-754R, the proposed
-revision of IEEE-754. The C language extension is defined in ISO/IEC
-DTR 24732, Draft 5. Support for this functionality will change when
-it is accepted into the C standard and might change for new drafts
-of the proposal. Calling conventions for any target might also change.
-Not all targets support decimal floating point.
+As an extension, the GNU C compiler supports decimal floating types as
+defined in the N1176 draft of ISO/IEC WDTR24732. Support for decimal
+floating types in GCC will evolve as the draft technical report changes.
+Calling conventions for any target might also change. Not all targets
+support decimal floating types.
-Support for decimal floating point includes the arithmetic operators
+The decimal floating types are @code{_Decimal32}, @code{_Decimal64}, and
+@code{_Decimal128}. They use a radix of ten, unlike the floating types
+@code{float}, @code{double}, and @code{long double} whose radix is not
+specified by the C standard but is usually two.
+
+Support for decimal floating types includes the arithmetic operators
add, subtract, multiply, divide; unary arithmetic operators;
relational operators; equality operators; and conversions to and from
-integer and other floating-point types. Use a suffix @samp{df} or
+integer and other floating types. Use a suffix @samp{df} or
@samp{DF} in a literal constant of type @code{_Decimal32}, @samp{dd}
or @samp{DD} for @code{_Decimal64}, and @samp{dl} or @samp{DL} for
@code{_Decimal128}.
-Passing a decimal floating-point value as an argument to a function
-without a prototype is undefined.
+GCC support of decimal float as specified by the draft technical report
+is incomplete:
+
+@itemize @bullet
+@item
+Translation time data type (TTDT) is not supported.
+
+@item
+Characteristics of decimal floating types are defined in header file
+@file{decfloat.h} rather than @file{float.h}.
+
+@item
+When the value of a decimal floating type cannot be represented in the
+integer type to which it is being converted, the result is undefined
+rather than the result value specified by the draft technical report.
+@end itemize
Types @code{_Decimal32}, @code{_Decimal64}, and @code{_Decimal128}
are supported by the DWARF2 debug information format.
to be possibly unused. GCC will not produce a warning for this
variable.
+@item used
+This attribute, attached to a variable, means that the variable must be
+emitted even if it appears that the variable is not referenced.
+
@item vector_size (@var{bytes})
This attribute specifies the vector size for the variable, measured in
bytes. For example, the declaration:
@subsection PowerPC Variable Attributes
-Two attributes are currently defined for PowerPC configurations:
-@code{ms_struct} and @code{gcc_struct}.
+Three attributes currently are defined for PowerPC configurations:
+@code{altivec}, @code{ms_struct} and @code{gcc_struct}.
-For full documentation of these attributes please see the documentation
-in the @xref{i386 Variable Attributes}, section.
+For full documentation of the struct attributes please see the
+documentation in the @xref{i386 Variable Attributes}, section.
+
+For documentation of @code{altivec} attribute please see the
+documentation in the @xref{PowerPC Type Attributes}, section.
@subsection Xstormy16 Variable Attributes
above in recent GCC versions.
@item visibility
-
In C++, attribute visibility (@pxref{Function Attributes}) can also be
applied to class, struct, union and enum types. Unlike other type
attributes, the attribute must appear between the initial keyword and
@code{__attribute__} instead of @code{__declspec} if you prefer, but
most Symbian OS code uses @code{__declspec}.)
+@anchor{i386 Type Attributes}
@subsection i386 Type Attributes
Two attributes are currently defined for i386 configurations:
double parentheses: for example, @samp{__attribute__ ((aligned (16),
packed))}.
+@anchor{PowerPC Type Attributes}
+@subsection PowerPC Type Attributes
+
+Three attributes currently are defined for PowerPC configurations:
+@code{altivec}, @code{ms_struct} and @code{gcc_struct}.
+
+For full documentation of the struct attributes please see the
+documentation in the @xref{i386 Type Attributes}, section.
+
+The @code{altivec} attribute allows one to declare AltiVec vector data
+types supported by the AltiVec Programming Interface Manual. The
+attribute requires an argument to specify one of three vector types:
+@code{vector__}, @code{pixel__} (always followed by unsigned short),
+and @code{bool__} (always followed by unsigned).
+
+@smallexample
+__attribute__((altivec(vector__)))
+__attribute__((altivec(pixel__))) unsigned short
+__attribute__((altivec(bool__))) unsigned
+@end smallexample
+
+These attributes mainly are intended to support the @code{__vector},
+@code{__pixel}, and @code{__bool} AltiVec keywords.
+
@node Inline
@section An Inline Function is As Fast As a Macro
@cindex inline functions
@smallexample
#define foo(x) \
(@{ \
- typeof (x) tmp; \
+ typeof (x) tmp = (x); \
if (__builtin_types_compatible_p (typeof (x), long double)) \
tmp = foo_long_double (tmp); \
else if (__builtin_types_compatible_p (typeof (x), double)) \
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