C Semantics in K Framework

[John Regehr <regehr AT cs.utah.edu>]

This seemed interesting enough to pass along.

CompCert and KCC give 0 for the program below but GCC and Clang give 1.

This is all on x86.

The C99 standard seems to make it clear that structs may contain unnamed 
members.  This argues that KCC and CompCert are correct.

Both Clang and GCC (even when given the --std=c99 flag) complain that 
line 5 does not declare anything, and their output is consistent with 
this claim.

Anyone know what's going on?

Thanks,

John



int printf (const char *, ...);

struct S0
{
  int;
  int f1;
};

struct S3
{
  int f2;
  int f3;
};

union U4
{
  struct S3 f0;
  struct S0 f3;
};

union U4 g_110;

int main (void)
{
  g_110.f3.f1 = 1;
  printf ("%d\n", g_110.f0.f2);
  return 0;
}