Boost usage of __int128 when compiled with clang-cl

[Yaron Keren <yaron.keren@…>]

Boost compiled with clang-cl targetting MSVC toolchain should not probably use int128 as the support functions umodti3 and friends, usually available from libgcc are not available from the MSVC libs leading to error LNK2019: unresolved external symbol umodti3.

This may be solved either by using compiler-rt along with the MSVC libs or by not defining BOOST_HAS_INT128 in clang.hpp:

#if defined(SIZEOF_INT128) && !defined(CUDACC) && !defined(_MSC_VER) # define BOOST_HAS_INT128 #endif

I'm not sure which is the right way to go here, but this should be at least be documented.

[Yaron Keren <yaron.keren@…>]

Just noticed all the double underscore symbols turned to underline, oh well.

[anonymous]

I'll make the change but this should be reported as a bug to clang as int128 clearly isn't supported and yet they still define the GCC macro __SIZEOF_INT128__

[John Maddock]

Fixed in ​https://github.com/boostorg/config/commit/05d55111e487002ac772d87931890265262eedc9