[Mesa-dev] [PATCH 00/13] Avoid double promotion

[Matt Turner]

On Tue, Jul 14, 2015 at 4:32 AM, Daniel Stone <daniel at fooishbar.org> wrote:
> Hi,
>
> On 14 July 2015 at 00:22, Matt Turner <mattst88 at gmail.com> wrote:
> but it's not really
>> useful in general because float arguments are always cast to double
>> when passed as arguments to varargs functions like printf (why?), and
>> it warns about that, generating a lot of noise.
>
> It might shock you to learn that the answer is awful historical
> reasons. Or maybe not.
>
> Some types undergo unconditional promotion, similar to pre-prototype
> functions, when used in vararg calls: float is promoted to double, and
> char/short are promoted to int.
>
> http://c-faq.com/~scs/cgi-bin/faqcat.cgi?sec=ansi#argpromos

Eesh! Thanks for the information.