+2004-09-03 Jan Beulich <jbeulich@novell.com>
+
+ PR c/7054
+ * defaults.h (TARGET_DEFAULT_PACK_STRUCT): Provide default.
+ * tree.h (initial_max_fld_align): Declare
+ * stor-layout.c (initial_max_fld_align): Define and initialize.
+ (maximum_field_alignment): Initialize to the same value.
+ * common.opt: Add -fpack-struct= variant of switch.
+ * opts.c: Handle -fpack-struct= variant of switch.
+ * c-pragma.c: Change #pragma pack() handling so that it becomes
+ compatible to other compilers: accept individual 'push' argument,
+ make final pop restore (command line) default, correct interaction
+ of push/pop and sole specification of a new alignment (so that the
+ sequence #pragma pack(push) - #pragma pack(<n>) becomes identical
+ to #pragma pack(push, <n>).
+ * doc/extend.texi: New node "Structure-Packing Pragmas" under
+ "Pragmas", describing #pragma pack.
+ * doc/invoke.texi: Document -fpack-struct=<n> variant of switch.
+ * doc/tm.texi: Adjust description for HANDLE_PRAGMA_PACK_PUSH_POP.
+ Document new TARGET_DEFAULT_PACK_STRUCT.
+
2004-09-03 Devang Patel <dpatel@apple.com>
* dwarf2out.c (gen_field_die). Equate decl number to die.
typedef struct align_stack GTY(())
{
int alignment;
- unsigned int num_pushes;
tree id;
struct align_stack * prev;
} align_stack;
happens, we restore the value to this, not to a value of 0 for
maximum_field_alignment. Value is in bits. */
static int default_alignment;
-#define SET_GLOBAL_ALIGNMENT(ALIGN) \
- (default_alignment = maximum_field_alignment = (ALIGN))
+#define SET_GLOBAL_ALIGNMENT(ALIGN) (maximum_field_alignment = *(alignment_stack == NULL \
+ ? &default_alignment \
+ : &alignment_stack->alignment) = (ALIGN))
static void push_alignment (int, tree);
static void pop_alignment (tree);
static void
push_alignment (int alignment, tree id)
{
- if (alignment_stack == NULL
- || alignment_stack->alignment != alignment
- || id != NULL_TREE)
- {
- align_stack * entry;
+ align_stack * entry;
- entry = ggc_alloc (sizeof (* entry));
+ entry = ggc_alloc (sizeof (* entry));
- entry->alignment = alignment;
- entry->num_pushes = 1;
- entry->id = id;
- entry->prev = alignment_stack;
-
- /* The current value of maximum_field_alignment is not necessarily
- 0 since there may be a #pragma pack(<n>) in effect; remember it
- so that we can restore it after the final #pragma pop(). */
- if (alignment_stack == NULL)
- default_alignment = maximum_field_alignment;
-
- alignment_stack = entry;
+ entry->alignment = alignment;
+ entry->id = id;
+ entry->prev = alignment_stack;
+
+ /* The current value of maximum_field_alignment is not necessarily
+ 0 since there may be a #pragma pack(<n>) in effect; remember it
+ so that we can restore it after the final #pragma pop(). */
+ if (alignment_stack == NULL)
+ default_alignment = maximum_field_alignment;
+
+ alignment_stack = entry;
- maximum_field_alignment = alignment;
- }
- else
- alignment_stack->num_pushes ++;
+ maximum_field_alignment = alignment;
}
/* Undo a push of an alignment onto the stack. */
align_stack * entry;
if (alignment_stack == NULL)
- {
- warning ("\
-#pragma pack (pop) encountered without matching #pragma pack (push, <n>)"
- );
- return;
- }
+ GCC_BAD("#pragma pack (pop) encountered without matching #pragma pack (push)");
/* If we got an identifier, strip away everything above the target
entry so that the next step will restore the state just below it. */
for (entry = alignment_stack; entry; entry = entry->prev)
if (entry->id == id)
{
- entry->num_pushes = 1;
alignment_stack = entry;
break;
}
if (entry == NULL)
warning ("\
-#pragma pack(pop, %s) encountered without matching #pragma pack(push, %s, <n>)"
+#pragma pack(pop, %s) encountered without matching #pragma pack(push, %s)"
, IDENTIFIER_POINTER (id), IDENTIFIER_POINTER (id));
}
- if (-- alignment_stack->num_pushes == 0)
- {
- entry = alignment_stack->prev;
+ entry = alignment_stack->prev;
- if (entry == NULL)
- maximum_field_alignment = default_alignment;
- else
- maximum_field_alignment = entry->alignment;
+ maximum_field_alignment = entry ? entry->alignment : default_alignment;
- alignment_stack = entry;
- }
+ alignment_stack = entry;
}
#else /* not HANDLE_PRAGMA_PACK_PUSH_POP */
#define SET_GLOBAL_ALIGNMENT(ALIGN) (maximum_field_alignment = (ALIGN))
/* #pragma pack ()
#pragma pack (N)
+ #pragma pack (push)
#pragma pack (push, N)
+ #pragma pack (push, ID)
#pragma pack (push, ID, N)
#pragma pack (pop)
#pragma pack (pop, ID) */
if (token == CPP_CLOSE_PAREN)
{
action = set;
- align = 0;
+ align = initial_max_fld_align;
}
else if (token == CPP_NUMBER)
{
}
else if (token == CPP_NAME)
{
-#define GCC_BAD_ACTION do { if (action == push) \
- GCC_BAD ("malformed '#pragma pack(push[, id], <n>)' - ignored"); \
+#define GCC_BAD_ACTION do { if (action != pop) \
+ GCC_BAD ("malformed '#pragma pack(push[, id][, <n>])' - ignored"); \
else \
GCC_BAD ("malformed '#pragma pack(pop[, id])' - ignored"); \
} while (0)
else
GCC_BAD2 ("unknown action '%s' for '#pragma pack' - ignored", op);
- token = c_lex (&x);
- if (token != CPP_COMMA && action == push)
- GCC_BAD_ACTION;
-
- if (token == CPP_COMMA)
+ while ((token = c_lex (&x)) == CPP_COMMA)
{
token = c_lex (&x);
- if (token == CPP_NAME)
+ if (token == CPP_NAME && id == 0)
{
id = x;
- if (action == push && c_lex (&x) != CPP_COMMA)
- GCC_BAD_ACTION;
- token = c_lex (&x);
}
-
- if (action == push)
+ else if (token == CPP_NUMBER && action == push && align == -1)
{
- if (token == CPP_NUMBER)
- {
- align = TREE_INT_CST_LOW (x);
- token = c_lex (&x);
- }
- else
- GCC_BAD_ACTION;
+ align = TREE_INT_CST_LOW (x);
+ if (align == -1)
+ action = set;
}
+ else
+ GCC_BAD_ACTION;
}
if (token != CPP_CLOSE_PAREN)
if (c_lex (&x) != CPP_EOF)
warning ("junk at end of '#pragma pack'");
+ if (flag_pack_struct)
+ GCC_BAD ("#pragma pack has no effect with -fpack-struct - ignored");
+
if (action != pop)
switch (align)
{
case 16:
align *= BITS_PER_UNIT;
break;
+ case -1:
+ if (action == push)
+ {
+ align = maximum_field_alignment;
+ break;
+ }
default:
GCC_BAD2 ("alignment must be a small power of two, not %d", align);
}
Common Report Var(flag_pack_struct)
Pack structure members together without holes
+fpack-struct=
+Common RejectNegative Joined UInteger
+-fpack-struct=<number> Set initial maximum structure member alignment
+
fpcc-struct-return
Common Report Var(flag_pcc_struct_return,1) VarExists
Return small aggregates in memory, not registers
#define PREFERRED_STACK_BOUNDARY STACK_BOUNDARY
#endif
+#ifndef TARGET_DEFAULT_PACK_STRUCT
+#define TARGET_DEFAULT_PACK_STRUCT 0
+#endif
+
/* By default, the C++ compiler will use function addresses in the
vtable entries. Setting this nonzero tells the compiler to use
function descriptors instead. The value of this macro says how
* Darwin Pragmas::
* Solaris Pragmas::
* Symbol-Renaming Pragmas::
+* Structure-Packing Pragmas::
@end menu
@node ARM Pragmas
way of knowing that that happened.)
@end enumerate
+@node Structure-Packing Pragmas
+@subsection Structure-Packing Pragmas
+
+For compatibility with Win32, GCC supports as set of @code{#pragma}
+directives which change the maximum alignment of members of structures,
+unions, and classes subsequently defined. The @var{n} value below always
+is required to be a small power of two and specifies the new alignment
+in bytes.
+
+@enumerate
+@item @code{#pragma pack(@var{n})} simply sets the new alignment.
+@item @code{#pragma pack()} sets the alignment to the one that was in
+effect when compilation started (see also command line option
+@option{-fpack-struct[=<n>]} @pxref{Code Gen Options}).
+@item @code{#pragma pack(push[,@var{n}])} pushes the current alignment
+setting on an internal stack and then optionally sets the new alignment.
+@item @code{#pragma pack(pop)} restores the alignment setting to the one
+saved at the top of the internal stack (and removes that stack entry).
+Note that @code{#pragma pack([@var{n}])} does not influence this internal
+stack; thus it is possible to have @code{#pragma pack(push)} followed by
+multiple @code{#pragma pack(@var{n})} instances and finalized by a single
+@code{#pragma pack(pop)}.
+@end enumerate
+
@node Unnamed Fields
@section Unnamed struct/union fields within structs/unions.
@cindex struct
-fpcc-struct-return -fpic -fPIC -fpie -fPIE @gol
-freg-struct-return -fshared-data -fshort-enums @gol
-fshort-double -fshort-wchar @gol
--fverbose-asm -fpack-struct -fstack-check @gol
+-fverbose-asm -fpack-struct[=@var{n}] -fstack-check @gol
-fstack-limit-register=@var{reg} -fstack-limit-symbol=@var{sym} @gol
-fargument-alias -fargument-noalias @gol
-fargument-noalias-global -fleading-underscore @gol
This flag does not have a negative form, because it specifies a
three-way choice.
-@item -fpack-struct
+@item -fpack-struct[=@var{n}]
@opindex fpack-struct
-Pack all structure members together without holes.
+Without a value specified, pack all structure members together without
+holes. When a value is specified (which must be a small power of two), pack
+structure members according to this value, representing the maximum
+alignment (that is, objects with default alignment requirements larger than
+this will be output potentially unaligned at the next fitting location.
@strong{Warning:} the @option{-fpack-struct} switch causes GCC to generate
code that is not binary compatible with code generated without that switch.
@findex pragma
@defmac HANDLE_PRAGMA_PACK_PUSH_POP
Define this macro (to a value of 1) if you want to support the Win32
-style pragmas @samp{#pragma pack(push,@var{n})} and @samp{#pragma
-pack(pop)}. The @samp{pack(push,@var{n})} pragma specifies the maximum alignment
-(in bytes) of fields within a structure, in much the same way as the
-@samp{__aligned__} and @samp{__packed__} @code{__attribute__}s do. A
+style pragmas @samp{#pragma pack(push[,@var{n}])} and @samp{#pragma
+pack(pop)}. The @samp{pack(push,[@var{n}])} pragma specifies the maximum
+alignment (in bytes) of fields within a structure, in much the same way as
+the @samp{__aligned__} and @samp{__packed__} @code{__attribute__}s do. A
pack value of zero resets the behavior to the default. Successive
invocations of this pragma cause the previous values to be stacked, so
that invocations of @samp{#pragma pack(pop)} will return to the previous
value.
@end defmac
+@defmac TARGET_DEFAULT_PACK_STRUCT
+If your target requires a structure packing default other than 0 (meaning
+the machine default), define this macro the the necessary value (in bytes).
+This must be a value that would also valid to be used with
+@samp{#pragma pack()} (that is, a small power of two).
+@end defmac
+
@defmac DOLLARS_IN_IDENTIFIERS
Define this macro to control use of the character @samp{$} in
identifier names for the C family of languages. 0 means @samp{$} is
pp_set_line_maximum_length (global_dc->printer, value);
break;
+ case OPT_fpack_struct_:
+ if (value <= 0 || (value & (value - 1)) || value > 16)
+ error("structure alignment must be a small power of two, not %d", value);
+ else
+ {
+ initial_max_fld_align = value;
+ maximum_field_alignment = value * BITS_PER_UNIT;
+ }
+ break;
+
case OPT_fpeel_loops:
flag_peel_loops_set = true;
break;
/* If nonzero, this is an upper limit on alignment of structure fields.
The value is measured in bits. */
-unsigned int maximum_field_alignment;
+unsigned int maximum_field_alignment = TARGET_DEFAULT_PACK_STRUCT * BITS_PER_UNIT;
+/* ... and its original value in bytes, specified via -fpack-struct=<value>. */
+unsigned int initial_max_fld_align = TARGET_DEFAULT_PACK_STRUCT;
/* If nonzero, the alignment of a bitstring or (power-)set value, in bits.
May be overridden by front-ends. */
+2004-09-03 Jan Beulich <jbeulich@novell.com>
+
+ * gcc.dg/pack-test-2.c: Adjust to permit and check #pragma pack(push).
+ * gcc.dg/c99-flex-array-4.c: Add -fpack-struct=8 to provide a
+ deterministic starting point for the alignment of structure fields.
+ * gcc.dg/Wpadded.c: Dito.
+ * g++.dg/abi/vbase10.C: Dito.
+
2004-09-03 Devang Patel <dpatel@apple.com>
* g++.dg/debug/pr15736.cc: New test.
// { dg-do compile }
-// { dg-options "-Wabi -fabi-version=1" }
+// -fpack-struct is necessary because the code below assumes the initial
+// packing is larger than 1, which cannot ge guaranteed for all targets.
+// { dg-options "-Wabi -fabi-version=1 -fpack-struct=8" }
// On ARM processors, the alignment of B will be 4 even though it
// contains only a single "char". That would avoids the situation
// that the warning below is designed to catch. We therefore
/* Source: EMC. */
/* { dg-do compile } */
-/* { dg-options "-Wpadded" } */
+/* -fpack-struct is necessary because the warning expected requires the initial
+ packing to be larger than 1, which cannot ge guaranteed for all targets. */
+/* { dg-options "-Wpadded -fpack-struct=8" } */
struct foo {
char bar;
from Tony Finch <dot@dotat.at>, adapted to a testcase by Joseph Myers
<jsm28@cam.ac.uk>. See also WG14 reflector messages 9571-3. */
/* { dg-do compile } */
-/* { dg-options "-std=iso9899:1999 -pedantic-errors" } */
+/* -fpack-struct is necessary because the code below assumes the initial
+ packing is larger than 1, which cannot ge guaranteed for all targets. */
+/* { dg-options "-std=iso9899:1999 -fpack-struct=8 -pedantic-errors" } */
#include <stddef.h>
/* { dg-do compile { target *-*-linux* *-*-cygwin* powerpc*-*-eabi* } } */
-#pragma pack(push) /* { dg-error "malformed" } */
#pragma pack(pop) /* { dg-error "without matching" } */
+#pragma pack(push)
+#pragma pack(pop) /* reset */
+
#pragma pack(push, foo, 1)
#pragma pack(pop, foo, 1) /* { dg-error "malformed" } (/
#pragma pack(pop) /* reset */
+ (BITS_PER_UNIT > 8) + (BITS_PER_UNIT > 16) + (BITS_PER_UNIT > 32) \
+ (BITS_PER_UNIT > 64) + (BITS_PER_UNIT > 128) + (BITS_PER_UNIT > 256))
-/* If nonzero, an upper limit on alignment of structure fields, in bits. */
+/* If nonzero, an upper limit on alignment of structure fields, in bits, */
extern unsigned int maximum_field_alignment;
+/* and its original value in bytes, specified via -fpack-struct=<value>. */
+extern unsigned int initial_max_fld_align;
/* If nonzero, the alignment of a bitstring or (power-)set value, in bits. */
extern unsigned int set_alignment;
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