Re: [Boost-users] [geometry][typeof][type_traits] Using Boost with Clang/LLVM & VC14

Subject: Re: [Boost-users] [geometry][typeof][type_traits] Using Boost with Clang/LLVM & VC14
From: Adam Wulkiewicz (adam.wulkiewicz_at_[hidden])
Date: 2016-03-15 13:20:36

Hi,

Degski wrote:
>
>
> The problems arose while compiling the minimal example from the get 
> started tutorial.
> Below I pasted some compiler (Clang-Cl.exe) output. It has all to do 
> with MSVC compiler bugs workarounds.
>
<snip>

The name of a macro is _MSC_VER, not __MSVC_VER. With MSC+Clang 
_MSC_VER, __clang__ and BOOST_CLANG are defined after inclusion of 
Boost.Config.

When I compile the Boost.Geometry Quick Start example with MSC+Clang I 
only get errors in other libraries, i.e. TypeOf and TypeTraits (master 
branch). I'm still going to replace _MSC_VER checks in Geometry with 
BOOST_MSVC checks but this will not fix the issues you have.

Side note: If you'd like to have this platform fully supported the best 
way would be to run the regression tests so the maintainers of all 
liberaries would be able to see the errors. Or you could try to convince 
people already running the tests on Windows to add one more compiler.

Boost.TypeOf

> 1>z:\vc\x64\include\boost/typeof/msvc/typeof_impl.hpp(150,31): error : 
> template specialization or definition requires a template parameter 
> list corresponding to the nested type 'base_type' (aka 
> 'msvc_extract_type<ID>')
> 1>              struct base_type::id2type // This uses nice VC6.5 and 
> VC7.1 bugfeature
> 1>                     ~~~~~~~~~  ^
> 1>z:\vc\x64\include\boost/typeof/msvc/typeof_impl.hpp(150,20): error : 
> nested name specifier for a declaration cannot depend on a template 
> parameter
> 1>              struct base_type::id2type // This uses nice VC6.5 and 
> VC7.1 bugfeature
> 1>                     ^~~~~~~~~~~

https://github.com/boostorg/typeof/blob/boost-1.60.0/include/boost/typeof/msvc/typeof_impl.hpp#L150
This code is enabled when BOOST_MSVC is NOT defined or version is lesser 
than 1300.
And the file is included if _MSC_VER is defined:
https://github.com/boostorg/typeof/blob/boost-1.60.0/include/boost/typeof/typeof.hpp#L102

If BOOST_MSVC is checked instead then the code compiles but then 
BOOST_TYPEOF_EMULATION is defined and I'm guessing this is not correct. 
With Clang probably native __typeof__ should be used. So either 
BOOST_CLANG/__clang__ should be checked here as a special case with 
_MSC_VER or it should be checked above as a standalone case, or together 
with __GNUC__. What would be prefered?

Boost.TypeTraits

1>D:\lib\modular-boost\boost/type_traits/has_nothrow_assign.hpp(64,7): 
error : no template named 'is_assignable'; did you mean 
'std::is_assignable'?
1>        BOOST_HAS_NOTHROW_ASSIGN(T)
1>        ^
1>  D:\lib\modular-boost\boost/type_traits/intrinsics.hpp(199,96) :  
note: expanded from macro 'BOOST_HAS_NOTHROW_ASSIGN'
1>  #     define BOOST_HAS_NOTHROW_ASSIGN(T) (__has_nothrow_assign(T) && 
!is_volatile<T>::value && is_assignable<T&, const T&>::value)
1> ^
1>  C:\Program Files (x86)\Microsoft Visual Studio 
14.0\VC\include\type_traits(577,9) :  note: 'std::is_assignable' 
declared here
1>          struct is_assignable
1>                 ^

1>D:\lib\modular-boost\boost/type_traits/has_nothrow_constructor.hpp(26,84): 
error : no template named 'is_default_constructible'; did you mean 
'std::is_default_constructible'?
1>  template <class T> struct has_nothrow_constructor : public 
integral_constant<bool, BOOST_HAS_NOTHROW_CONSTRUCTOR(T)>{};
1> ^
1>  D:\lib\modular-boost\boost/type_traits/intrinsics.hpp(193,80) :  
note: expanded from macro 'BOOST_HAS_NOTHROW_CONSTRUCTOR'
1>  #     define BOOST_HAS_NOTHROW_CONSTRUCTOR(T) 
(__has_nothrow_constructor(T) && is_default_constructible<T>::value)
1> ^
1>  C:\Program Files (x86)\Microsoft Visual Studio 
14.0\VC\include\type_traits(539,9) :  note: 
'std::is_default_constructible' declared here
1>          struct is_default_constructible
1>                 ^

I'm guessing that more type traits suffer from this.

Regards,
Adam

P.S. In both cases you could create a pull request with proposed change 
on GitHub or create a ticket: https://svn.boost.org/trac/boost/newticket 
if maintainers of those libraries didn't answer here.