/* This test checks promotion of bitfields. Bitfields should be promoted very much like chars and shorts: Bitfields (signed or unsigned) should be promoted to signed int if their value will fit in a signed int, otherwise to an unsigned int if their value will fit in an unsigned int, otherwise we don't promote them (ANSI/ISO does not specify the behavior of bitfields larger than an unsigned int). We test the behavior by subtracting two from the promoted value: this will result in a negitive value for signed types, a positive value for unsigned types. This test (of course) assumes that the compiler is correctly implementing signed and unsigned arithmetic. */ struct X { unsigned int u3:3; signed long int s31:31; signed long int s32:32; unsigned long int u31:31; unsigned long int u32:32; unsigned long long ull3 :3; unsigned long long ull35:35; unsigned u15:15; }; struct X x; main () { if ((x.u3 - 2) >= 0) /* promoted value should be signed */ abort (); if ((x.s31 - 2) >= 0) /* promoted value should be signed */ abort (); if ((x.s32 - 2) >= 0) /* promoted value should be signed */ abort (); if ((x.u15 - 2) >= 0) /* promoted value should be signed */ abort (); /* Conditionalize check on whether integers are 4 bytes or larger, i.e. larger than a 31 bit bitfield. */ if (sizeof (int) >= 4) { if ((x.u31 - 2) >= 0) /* promoted value should be signed */ abort (); } else { if ((x.u31 - 2) < 0) /* promoted value should be UNsigned */ abort (); } if ((x.u32 - 2) < 0) /* promoted value should be UNsigned */ abort (); if ((x.ull3 - 2) >= 0) /* promoted value should be signed */ abort (); if ((x.ull35 - 2) < 0) /* promoted value should be UNsigned */ abort (); exit (0); }