> On Jul 9, 2020, at 04:25, Mathias Gaunard <mathias.gaun...@ens-lyon.org> 
> wrote:
> 
> On Thu, 9 Jul 2020 at 08:07, DV Henkel-Wallace via Boost-users
> <boost-users@lists.boost.org> wrote:
> 
>> We build with clang++-10 w/libc++.a and g++-10 w/libstdc++.a, so build a 
>> copy of boost in each configuration as well.  This works great on the Mac 
>> development machines but the clang case doesn't generate the correct linkage 
>> on the Linux deployment machines.  The correct clang linkage is 
>> std::__1::basic_string... but boost builds with std::__cxx11::basic_string
> 
> libc++ is not binary compatible with libstdc++.
> You need to use either libstdc++ or libc++ with both compilers if you
> want binary compatibility.
> 
> This doesn't have anything to do with Boost.

Thanks Mathias.  I did not express my problem clearly.  This is a b2 issue; I 
doubt any _library source code_ has any direct interaction with this and I'm 
sorry if I accidentally gave that impression.  Is there a way to get b2 to 
disgorge the environment and tool invocation of each step (basically what is 
passed to system() or exec())?

The background, perhaps clarified:

We have our own code, some third party code (like Boost) and of course 
different runtime platforms (Mac, iOS, Linux...).  Since different platforms 
use different compilers/runtimes as their "native" stack, our development 
system builds everything end-to-end with both gcc and clang to catch problems 
as early as possible.  All compilation is with c++14 or later, post the C++11 
ABI break, hence the naming issues.  This process isolates us from any system 
libraries that don't have C linkage.

Therefore g++ is used to compile libstdc++, boost, other third party code, and 
our code.  Symbols are generated that use __c++11:: in their name.
And clang++ is used to compile libc++, boost, other third party code, and our 
code.  Symbols are generated that use use __1:: in their name.

But boost itself is compiled via b2 and what is passed to the compiler (and 
which compiler b2 chooses) is quite opaque.  Despite my attempts to force the 
use of clang it appears that b2 is either calling g++ or otherwise asking clang 
to use g++-style symbol linkage on Linux. On the Mac the same invocation 
behaves as expected.

I'm compiling boost this way:

export CC=clang CXX="clang++ -stdlib=libc++" CXXSTD=c++20 ; ./b2 stdlib=libc++ 
toolset=clang boost.locale.icu=off boost.locale.std=off --with-atomic 
--with-chrono --with-date_time --with-headers --with-locale --with-log 
--with-program_options --with-random --with-regex --with-system --with-thread 
threading=multi -sNO_COMPRESSION=1 link=static install

Any thoughts on how to debug this?
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