Re: [PATCH] do not depend on undefined signed integer overflow

On Mon, Oct 4, 2010 at 9:43 PM, Erik Faye-Lund [off-list ref] wrote:

+/*
+ * Signed integer overflow is undefined in C and some compilers take
+ * advantage of this when optimizing, so here's a helper macro to force
+ * wrapping when adding two integers. The size to wrap to is taken from
+ * the first parameter.
+ */
+#define signed_add_overflows(a, b) \
+    ((b) > ((INTMAX_MAX >> (bitsizeof(uintmax_t) - bitsizeof(a))) - (a)))
+

*Sigh*, I already see that this comment is out of date (I did a
different approach before this one). Sorry, I will fix up this comment
for the next round.