gcc/testsuite/gcc.dg/bitfld-19.c

/* Test for bit-field widths not integer constant expressions but
   folding to integer constants: PR 42439.  */
/* { dg-do compile } */
/* { dg-options "-O2" } */

void
f (void)
{
  const int m = 1;
  ((void)(sizeof(struct { int i:!!m; })));
}