[Boost-build] Runtime-Link and windows/gcc

Subject: [Boost-build] Runtime-Link and windows/gcc
From: Artyom Beilis (artyomtnk_at_[hidden])
Date: 2011-07-25 03:14:23

Hello All,

There is a problem with runtime-link options on mingw/gcc compiler for Windows,
some gcc/mingw link by default with shared libraries (libgcc/libstdc++)
and some versions with static ones.

- Cygwin/gcc-cross-compiler - 4.5.3; default: shared link
- tdm-gcc: 4.5.2; default: static link
- Mingw-gcc 4.5.0 AFAIR: shared link

More then that BB does not provide flags: -shared-libgcc and -shared-libstdc++
for case of shared runtime-link and -static-libgcc and -static-libstdc++
for case of static runtime-link.

This makes it very problematic for DLL's build with gcc that may use
difference instances of the runtime library. This is very critical
to thous who for example accesses some global objects form DLL and main
progam - which are very common in case of iostreams.

Notice: not all gcc versions support -(static|shared)-lib(gcc|stdc++) however
if they are not supported they just warn about them so I'd recommend:

1. Add -shared-libgcc and -shared-libstdc++ to both cxxflags and linkflags
   for gcc/windows when runtime-link=shared
2. Add -static-libgcc and -static-libstdc++ to both cxxflags and linkflags
   for gcc/windows when runtime-link=static

And not rely on defaults.


Also some gcc versions/builds may not honor these flags but this is the best
we can do and it should work well with latest gcc compilers.


I've added the shared flags in Boost.Locale mingw build because
it is VERY critical for Boost.Locale to have correct runtime to
be selected (because std::locale and iostream relate on global
objects that Boost.Locale uses)

But I think the solution should be global and not library 

specific.


Artyom Beilis
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