Nested and unnamed unions and structures do not compile in gcc-4.6.

The code compiles under gcc 4.4 with the following command

gcc -fms-extensions experiment.c

Under gcc 4.6 I get errors

#include <stdio.h>

typedef unsigned char          uint8_t;
typedef unsigned short         uint16_t;

typedef signed char            sint8_t;
typedef signed short           sint16_t;

/*
** Decomposition of 16 bis
** in 8 bits
*/
typedef union raw_16_bits_entry
{
   uint16_t raw;
   sint16_t sraw;
   uint8_t  byte[2];

   /* H/L byte access */
   struct
   {
      uint8_t blow;
      uint8_t bhigh;

   } __attribute__((packed));

} __attribute__((packed)) raw16_t;

typedef union raw_msr_entry
{
   struct
   {
      uint8_t  eax;
      uint8_t  edx;

   } __attribute__((packed));

   raw16_t;

} __attribute__((packed)) msr_t;



typedef union amd_syscfg_msr
{
   struct
   {
      uint16_t   rsv0:4;
      uint16_t   mfde:1;
      uint16_t   mfdm:1;
      uint16_t   mvdm:1;
      uint16_t   tom2:1;

   } __attribute__((packed));

   msr_t;
   raw16_t;

} __attribute__((packed)) amd_syscfg_msr_t;

int main()
{

    amd_syscfg_msr_t q;
    q.rsv0=5;
    q.raw=7;
    printf("hello world!");
};

Under gcc 4.6 I get errors with -fms-extensions

exp1.c:15:13: error: duplicate member ‘raw’
exp1.c:16:13: error: duplicate member ‘sraw’
exp1.c:17:13: error: duplicate member ‘byte’
exp1.c:22:15: error: duplicate member ‘blow’
exp1.c:23:15: error: duplicate member ‘bhigh’
exp1.c: In function ‘main’:
exp1.c:66:6: error: ‘amd_syscfg_msr_t’ has no member named ‘raw’

without -fms-extensions

exp1.c:38:11: warning: declaration does not declare anything [enabled by default]
exp1.c:56:9: warning: declaration does not declare anything [enabled by default]
exp1.c:57:11: warning: declaration does not declare anything [enabled by default]
exp1.c: In function ‘main’:
exp1.c:66:6: error: ‘amd_syscfg_msr_t’ has no member named ‘raw’

I can not find any compiler options that will help.

Tags: C, GCC, Compilation