Re: [boost] [type_traits] Rewrite and dependency free version

Subject: Re: [boost] [type_traits] Rewrite and dependency free version
From: Tim Blechmann (tim_at_[hidden])
Date: 2015-02-01 07:26:37

>>> While looking at this, I also noticed that
>>> BOOST_NO_CXX11_HDR_TYPE_TRAITS is set for g++ and clang, even though
>>> they do have <type_traits>. The config test fails because they don't
>>> have is_trivially_* and aligned_union. Fair enough, but the rest of the
>>> traits are there and usable, so I'm not entirely sure about this.
>>
>> Me neither.  Basically no one's complained so I've left it set.  <shrug>
>> I guess.  Could go either way on that.   John.
> 
> AFAIR, by convention we set HDR macros when the header is fully usable. I 
> think that's fair. We could introduce other sub-feature macros for finer 
> grained checks, like BOOST_NO_CXX11_TYPE_INSPECTION_TRAITS, 
> BOOST_NO_CXX11_TYPE_TRANSFORM_TRAITS, etc.

not sure: with <atomic> BOOST_NO_CXX11_HDR_ATOMIC is not defined for
some configurations which do not provide a complete implementation of
std::atomic<>: clang/libc++ only very recently managed to provide a
completely usable atomic<>, while other toolchains only provided a
partial implementation for quite some time ...

however it would definitely be a good convention only to define this
macro once a header is fully implemented.

tim