[boost] ABI issues with -std

Subject: [boost] ABI issues with -std
From: Peter Dimov (lists_at_[hidden])
Date: 2018-08-19 15:17:41

At some point, we'll need to acknowledge the problem which results from 
building Boost with one -std and user code with another, and deal with it 
somehow, if just by documenting.

Most of our libraries don't suffer from it at the moment but Boost.System 
does, because of my changes; its ABI changes between 03/11/14. So I'm going 
to take the initial hit. :-)

POSIX platforms have long been able to ignore ABI issues so we don't mangle 
the library names there at all, but now whether one builds Boost for C++03, 
C++11 or C++14 matters, and there's nothing to prevent linking C++xx to 
C++yy. Even with --layout=versioned, the cxxstd level is not encoded.

The fact that the default C++ standard differs between g++ and clang++ 
doesn't help; when following the instructions of doing "b2 install", with 
g++6 and above you get C++14, but with g++5 or clang++ you get C++03. The 
latter is very rarely what one wants today.