[Bug c/58303] New: C99 union initializers new union members clobber earlier data

[darrenrjenkins at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58303

            Bug ID: 58303
           Summary: C99 union initializers new union members clobber
                    earlier data
           Product: gcc
           Version: 4.6.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: darrenrjenkins at gmail dot com

If using C99 initializers on a union, and using different union members.
The later members seem to clobber the previous members data.
I haven't looked at the standards with respect to this, but it seems wrong.

#include <stdio.h>

typedef struct
{
    int a;
    int b;
} a_t;

typedef struct
{
    int c;
    int d;
} b_t;

typedef union
{
    a_t a;
    b_t b;

} c_t;

void main( int argc, char *argv[] )
{
    c_t var = { .a.a = 4, .b.d = 7 };

    printf( ".a.a = %d .b.d = %d\n", var.a.a, var.b.d );
}