__builtin_sub_overflow_p  287 lib/intprops-internal.h #define _GL_INT_NEGATE_OVERFLOW(a) __builtin_sub_overflow_p (0, a, (__typeof__ (-(a))) 0)
__builtin_sub_overflow_p  160 lib/intprops.h     __builtin_sub_overflow_p (a, b, (__typeof__ ((a) - (b))) 0)