Erik Faye-Lund wrote: > +++ b/git-compat-util.h > @@ -28,6 +28,15 @@ > #define ARRAY_SIZE(x) (sizeof(x)/sizeof(x[0])) > #define bitsizeof(x) (CHAR_BIT * sizeof(x)) > > +/* > + * Signed integer overflow is undefined in C, so here's a helper macro > + * to detect if the sum of two integers will overflow. The bitsize to > + * overflow at is taken from the first parameter, which must be zero > + * or positive. > + */ > +#define signed_add_overflows(a, b) \ > + ((b) > ((INTMAX_MAX >> (bitsizeof(intmax_t) - bitsizeof(a))) - (a))) Yes, I still like it. This could be made closer to self-documenting like so: #define maximum_signed_value_of_type(a) \ (INTMAX_MAX >> (bitsizeof(intmax_t) - bitsizeof(a))) /* * Signed overflow is undefined in C, so here's a helper macro * to detect if the sum of two signed integers will overflow. * * Requires: a >= 0, typeof(a) equals typeof(b) */ #define signed_add_overflows(a, b) \ ((b) > maximum_signed_value_of_type(a) - (a)) -- To unsubscribe from this list: send the line "unsubscribe git" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html