gcc/gcc/testsuite/gcc.dg/compat/struct-layout-1_test.h

#if (__SIZEOF_INT__ >= 4) 
T(0,enum E2 a:31;,B(0,a,e2_m1,e2_0))
#else
T(0,enum E2 a:15;,B(0,a,e2_m1,e2_0))
#endif