> On Sep 25, 2016, at 8:29 AM, Ken Cunningham <ken.cunningham.web...@gmail.com> > wrote: > > What is happening exactly on my MacPros running 10.11, I wonder? > Software installed by macports on 10.11 is using clang++ (mostly) and > g++ (sometimes).
What MacPorts-provided software is using g++? It should not be doing that. > clang++ is linking against libc++, and g++ is presumably linking > against libstdc++ as that is what it does > > Why exactly is the situation different on a LibCxxOnOlderSystems > installation? As Chris said, it's easier to get lucky and avoid conflicts mixing two libstdc++/libsupc++ than it is mixing libstdc++ and libc++. There is no fundamental difference, just an increase in visibility. >> As far as I know, you can use the C or Fortran compilers as much as >> you'd like. Several ports do this for various reasons. > > But not easily to link c++ code against libc++. Right. >> These dependencies are coming from the +gfortran variants, which >> instruct the builds to use the Fortran compiler from gcc6. This is >> fine and expected. > > but won't work on LibCxxOnOlderSystems, if it links the binaries > against lilbstdc++ Why would the Fortran compiler link its build products against libstdc++? Are you seeing this behavior? >> What links against libstdc++, specifically? > > gcc6 itself, at least. This is not a problem unless GCC provides C++ API. > It would appear there are a few choices. > > 1. give up and accept it's an either / or situation > 2. just let it go on, and see how it works with cross linking -- is this > what 10.11 macports does? No. No MacPorts-provided software should be compiling with MacPorts-provided FSF g++. We consider such behavior a bug. > 3. figure out how to make this work: > <http://libcxx.llvm.org/docs/UsingLibcxx.html#using-libc-with-gcc>, > possibly by wrapping g++ in a shell script that does it for every use. I don't think it's worth accommodating g++ at all. MacPorts should not be using it, and anyone who wants to use it for their own projects might not appreciate us hijacking its default C++ standard library. Apple handled this in their olde tyme libstdc++ by fixing it to use libc++abi instead of libsupc++. > 4. a parallel installation of macports with libstdc++ and gcc, to > install gimp, octave, qemu, and whatever other similar gcc-requiring > ports come along. Please provide evidence that these ports are actually using g++. If they are, then they should be fixed to not do so. If they are not and are only using gcc and/or gfortran, then *there is no problem*. FWIW, I have py35-numpy+gcc6 installed, and none of its object files link to libstdc++, although many of them do link to MacPorts' libgcc_s.1.dylib. % port -q contents py35-numpy | xargs otool -L | fgrep 'libstdc++' % echo $? 1 vq _______________________________________________ macports-users mailing list macports-users@lists.macosforge.org https://lists.macosforge.org/mailman/listinfo/macports-users
