__builtin_clzll and uintmax_t

[Marc Glisse]

Hello,

the following question came up for a libstdc++ patch. We have a variable 
of type uintmax_t and want to count the leading zeros. Can we just call 
__builtin_clzll on it?

In particular, can uintmax_t be larger than unsigned long long in gcc? Is 
__builtin_clzll available on all platforms? Is there a good reason to use 
__builtin_clzl instead on platforms where long and long long have the same 
size?

In case it matters, this is strictly for compile-time computations 
(templates, constexpr).

--
Marc Glisse