__builtin_sub_overflow_p  290 lib/intprops-internal.h #    define _GL_INT_NEGATE_OVERFLOW(a) __builtin_sub_overflow_p (0, a, (__typeof__ (-(a))) 0)
__builtin_sub_overflow_p  161 lib/intprops.h         __builtin_sub_overflow_p (a, b, (__typeof__ ((a) - (b))) 0)