>what's the benefit of having clang compile software against gcc's libstdc++ >vs. gcc6 compiling it.
The only benefit is that clang handles objc and macos SDK-heavy ports when gcc6 will not. >And what's the relation of all this to the magic -D_GLIBCXX_USE_CXX11_ABI=0 flag. This flag lets libgcc's stdlibc++ speak the same "c++ dialect" as the built-in system stdlibc++, making the built libraries and executables compatible with each other >have this enabled for all versions of clang Only clang-3.9 or newer can do the libgcc trick. It will not be ported to clang-3.7 or clang-3.8. > And we should finally address binary builds for libc++. I agree. The buildbot issue is driving this. I addition to the buildbot problem, there are two other reasons why this libgcc stdlibc++ thing might be interesting. 1. xcode built ports will always build against stdlibc++, and fixing them to build against libc++ is hard. 2. libgcc's stdlibc++ allows thread-local storage on < 10.9, which allows some ports to build that will not build against libc++
