From: Erik Faye-Lund <kusmabite@gmail.com>
Date: Mon, 04 Oct 2010 19:47:01 GMT
Subject: Re: [PATCH] do not depend on undefined signed integer overflow
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:
> +/*
> + * 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*Sigh*, I already see that this comment is out of date (I did a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.