[Bug c/38845] New: aligned attribute not working on ms-extensions anonymous struct

acalando at free dot fr gcc-bugzilla@gcc.gnu.org
Wed Jan 14 18:23:00 GMT 2009


The alignment of an anonymous structure defined as a member
of another structure (thanks to -fms-extensions) cannot be
forced with __attribute__((aligned)).

This problem occurs on cygwin with default gcc packages:
gcc version 4.3.2 20080827 (alpha-testing) 1 (GCC)
and:
gcc version 3.4.4 (cygming special, gdc 0.12, using dmd 0.125)

The code below show the exact problem by comparing the sizes and alignments
of a named struct and an anonynous one.


----------------------------------------------------------------------------
#include <stdio.h>

struct nested
{
    char a;
    char b;
};

struct unaligned
{
    char misalign;
    struct nested __attribute__((aligned(4)));
};

struct aligned
{
    char misalign;
    struct nested name __attribute__((aligned(4)));
};

int main(int argc, char * argv[])
{
    printf("%d %d - %d %d\n",
        sizeof(struct unaligned), sizeof(struct aligned),
        __alignof__(struct unaligned), __alignof__(struct aligned));
}
----------------------------------------------------------------------------
options:
gcc-4 -std=c99 -fms-extensions align.c
----------------------------------------------------------------------------
output:
3 8 - 1 4
----------------------------------------------------------------------------


-- 
           Summary: aligned attribute not working on ms-extensions anonymous
                    struct
           Product: gcc
           Version: 4.3.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: acalando at free dot fr


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38845



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