In Xcode 4.5, what is "Compiler Default" for "C++ Standard Library" and "C++ Language Dialect"?

Question

What is the value of "Compiler Default" for "C++ Standard Library" and "C++ Language Dialect" in Xcode 4.5?

My guess is libstdc++ and GNU++98, but it would be nice to have clarification.

From the Xcode 4.5 release notes:

Projects created using this Xcode release use the new libc++ implementation of the standard C++ library. The libc++ library is available only on iOS 5.0 and later and OS X 10.7 and later. 12221787

To enable deployment on earlier releases of iOS and OS X in your project, set the C++ Standard Library build setting to libstdc++ (Gnu C++ standard library).

I notice that creating a new project explicitly sets GNU++11 and libc++, but "Compiler Default" is probably something else.

Solution

Here is the best way to find out:

 #include <iostream>

int main()
{
#ifdef _LIBCPP_VERSION
    std::cout << "Using libc++\n";
#else
    std::cout << "Using libstdc++\n";
#endif
#ifdef __GXX_EXPERIMENTAL_CXX0X__
#if __cplusplus == 1
    std::cout << "Language mode = gnu++11\n";
#else
    std::cout << "Language mode = c++11\n";
#endif
#else
#if __cplusplus == 1
    std::cout << "Language mode = gnu++98\n";
#else
    std::cout << "Language mode = c++98\n";
#endif
#endif
}

Just build a test project with the compiler defaults and run it.

Comments

[ribbonwind]

Great, thanks for that useful snippet. The answer is as I thought: "libstdc++" and "gnu++98".

[bames53]

@ribbonwind that's strange; for me the result is libc++ and gnu++11.

[Howard Hinnant]

There is some confusion here as to what was asked and answered. I assumed that ribbonwind was asking what "compiler default" meant when chosen in the build settings. Others are asking/answering what the default build settings are. These are two different things.

[Iulian Onofrei]

I get libstdc++ and gnu++98 even though I set the C++ Standard Library option to libc++ (...) in Xcode 8. Does these macros still apply?

[Howard Hinnant]

@IulianOnofrei: I just ran a HelloWorld with the Xcode 8 command line tools using -E -dM and it output #define _LIBCPP_VERSION 3700. I did not confirm that the IDE does not have a bug with the way it presents options in the GUI.

[Iulian Onofrei]

@HowardHinnant, can you show me the command in order to run it against my project too?

[Howard Hinnant]

@IulianOnofrei: Create a test.cpp that includes any standard header (e.g. <type_traits>). The compile with clang++ test.cpp -E -dM. I like to pipe that to my editor: clang++ test.cpp -E -dM | edit for easer searching. The -E says "preprocess only". The -dM says list all macro definitions.