Default to lib=stdlibc++ for clang++ on Mac OS Mavericks with Xcode?

Question

I'm running MacOS X Mavericks with Xcode 5.1.1 including the command line tools. I'm compiling simple C++ programs using clang++ supplied with Xcode, the version info is: Apple LLVM version 5.1 (clang-503.0.40) (based on LLVM 3.4svn)

What I find is that if I try to run the following command

clang++ -o hello.out hello.cpp

I get the following errors:

Undefined symbols for architecture x86_64:
"std::ios_base::Init::Init()", referenced from:
___cxx_global_var_init in hello-2ad0da.o
"std::ios_base::Init::~Init()", referenced from:
___cxx_global_var_init in hello-2ad0da.o
"std::cout", referenced from:
_main in hello-2ad0da.o
"std::basic_ostream<char, std::char_traits<char> >& std::operator<<<std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&, char const*)", referenced from:
_main in hello-2ad0da.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

If I change the command to

clang++ -o hello.out -stdlib=libstdc++ hello.cpp

I don't get any errors.

Is there a way to make "-stdlib=libstdc++" the default for clang++, either with some configuration setting or some environment variable? Also, just for my information, why do I get the error?

Answer 1

MACOSX_DEPLOYMENT_TARGET may be what you are looking for.

export MACOSX_DEPLOYMENT_TARGET=10.8 should make clang to default to libstdc++ instead of libc++.

Answer 2

Before OS X 10.9.x:

The default was libstdc++ (using clang++ -o hello.out hello.cpp) would have worked fine.

OS X 10.9.x:

The default is libc++ (as you know the including flag -stdlib=libstdc++ links your project correctly).

Since you're trying to compile code that uses symbols that are not within the design of the newer LLVM libc++ standard library you receive errors. As for changing the default that clang uses you'd likely have to patch it's ToolChains.cpp (docs) with something such as:

-     DAL->AddJoinedArg(0, Opts.getOption(options::OPT_stdlib_EQ), "libc++");
+     DAL->AddJoinedArg(0, Opts.getOption(options::OPT_stdlib_EQ), "libstdc++");

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