When is it necessary to use the flag -stdlib=libstdc++?

Question

When is it necessary to use use the flag -stdlib=libstdc++ for the compiler and linker when compiling with gcc?

Does the compiler automatically use libstdc++?

I am using gcc4.8.2 on Ubuntu 13.10 and I would like to use the c++11 standard. I already pass -std=c++11 to the compiler.

Answer 1

On Linux: In general, all commonly available linux distributions will use libstdc++ by default, and all modern versions of GCC come with a libstdc++ that supports C++11. If you want to compile c++11 code here, use one of:

• g++ -std=c++11 input.cxx -o a.out (usually GNU compiler)
• g++ -std=gnu++11 input.cxx -o a.out

On OS X before Mavericks: g++ was actually an alias for clang++ and Apple's old version of libstdc++ was the default. You could use libc++ (which included c++11 library support) by passing -stdlib=libc++. If you want to compile c++11 code here, use one of:

• g++ -std=c++11 -stdlib=libc++ input.cxx -o a.out (clang, not GNU compiler!)
• g++ -std=gnu++11 -stdlib=libc++ input.cxx -o a.out (clang, not GNU compiler!)
• clang++ -std=c++11 -stdlib=libc++ input.cxx -o a.out
• clang++ -std=gnu++11 -stdlib=libc++ input.cxx -o a.out

On OS X since Mavericks: libc++ is the default and you should not pass any -stdlib=<...> flag. Since Xcode 10, building against libstdc++ is not supported at all anymore. Existing code built against libstdc++ will keep working because libstdc++.6.dylib is still provided, but compiling new code against libstdc++ is not supported.

• clang++ -std=c++11 input.cxx -o a.out
• clang++ -std=gnu++11 input.cxx -o a.out