[Bug c/52769] New: Unspecified designated initializer might not set to zero in some cases

["hudson at osresearch dot net" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52769

             Bug #: 52769
           Summary: Unspecified designated initializer might not set to
                    zero in some cases
    Classification: Unclassified
           Product: gcc
           Version: 4.4.1
            Status: UNCONFIRMED
          Severity: major
          Priority: P3
         Component: c
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: hudson@osresearch.net


#include <stdio.h>

typedef struct
{
    int should_be_zero;
    char s[6];
    int x;
} foo_t;

int main(void)
{
    const foo_t foo = {
        .s = "123456",
        .x = 2
    };

    if (foo.should_be_zero != 0)
        printf("FAIL: %p val=%d\n", &foo, foo.should_be_zero);

    return 0;
}

If s is not fully filled (with room for the terminating nul), the test passes. 
If x is not set in the designated initializer, the test passes.

Fails gcc-4.4.1 with both -m32 and -m64:

gcc-4.4 -m64 -std=c99  -O3 initializer-bug.c  && ./a.out
FAIL: 0x7fffaf867950 val=-1350141376

gcc-4.4 -m32 -std=c99  -O3 initializer-bug.c  && ./a.out
FAIL: 0xffc7df90 val=-144136635

Also fails with 4.3.4, but passes with 4.2.4.