Re: [boost] [TypeTraits] A patch for clang's intrinsics (was: [type_traits] is_enum on scoped enums doesn't works as expected)

Subject: Re: [boost] [TypeTraits] A patch for clang's intrinsics (was: [type_traits] is_enum on scoped enums doesn't works as expected)
From: Vicente J. Botet Escriba (vicente.botet_at_[hidden])
Date: 2011-09-01 13:47:44

Le 01/09/11 19:39, John Maddock a écrit :
>>> OK I'm curious - why would a compiler intrinsic work when used with 
>>> one std
>>> lib, not not when used with another?
>>
>> Here is the details:
>>
>> libstdc++ (of gcc-4.2) defines `struct __is_pod` in some header file. 
>> To deal
>> with this, clang disables __is_pod intrinsics when finding `struct 
>> __is_pod`;
>> then, __is_pod is not treated as keyword and it becomes just an 
>> identifier.
>> However, even in this case, old clang sets __has_feature(is_pod) to 1.
>> So we cannot rely on `#if __has_feature(is_pod)` to check the 
>> availability of
>> __is_pod intrinsics.
>>
>> libc++ does not define `struct __is_pod`, so we can safely check
>> the availability of __is_pod intrinsics by `#if __has_feature(is_pod)`.
>>
>>
>> Ditto for __is_empty.
>
> Got it, that's just plain nasty isn't it?
Yes. It seems that C++ compiler and C++ standard library providers 
shouldn't use the same prefix for the intrinsics and the internals.

Best,
Vicente