Re: [PATCH] do not depend on undefined signed integer overflow
- From
Erik Faye-Lund <kusmabite@gmail.com>
- Date
- Oct 4, 2010, 19:47 UTC
- Message-ID
- <AANLkTimx0PbyTPgwq8=VoE2Ldihf44c2UkDGYom4TAcf@mail.gmail.com>
- In-Reply-To
- <1286221388-4908-1-git-send-email-kusmabite@gmail.com>
On Mon, Oct 4, 2010 at 9:43 PM, Erik Faye-Lund <kusmabite@gmail.com> wrote:
Show 9 quoted lines
> +/* > + * 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*Sigh*, I already see that this comment is out of date (I did a different approach before this one).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.