C Semantics in K Framework

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

GCC and KCC give one answer, ICC and Clang give another -- all with 
optimizations disabled.  Can any of the C experts here tell me who is wrong?

I'm pretty sure the test case is well-defined (but never 100% sure with 
this kind of thing).

John



[regehr@babel
 ~]$ cat small.c
int printf (const char *, ...);

struct S0
{
  unsigned f1:1;
};

struct S2
{
  struct S0 f2;
};

struct S2 g_791;

int main (void)
{
  int l_45 = -3;
  int t = l_45 >= (0, g_791.f2.f1);
  printf ("%d\n", t);
  return 0;
}
[regehr@babel
 ~]$ gcc small.c
[regehr@babel
 ~]$ ./a.out
0
[regehr@babel
 ~]$ kcc small.c
[regehr@babel
 ~]$ ./a.out
0
[regehr@babel
 ~]$ clang small.c
small.c:18:20: warning: expression result unused [-Wunused-value]
  int t = l_45 >= (0, g_791.f2.f1);
                   ^
1 warning generated.
[regehr@babel
 ~]$ ./a.out
1
[regehr@babel
 ~]$ icc small.c
[regehr@babel
 ~]$ ./a.out
1