CMAKE, Clang and C++v11 on OS X 10.8

Question

OS X 1.8

CMAKE 2.8.9

Clang $ clang -v Apple clang version 4.0 (tags/Apple/clang-421.10.60) (based on LLVM 3.1svn) Target: x86_64-apple-darwin12.0.0 Thread model: posix

CMAKELists.txt:

cmake_minimum_required (VERSION 2.8.9)
project (Test)
add_executable(Test main.cpp)

main.cpp

//Create a C++11 thread from the main program
#include <iostream>
#include <thread>

//This function will be called from a thread
void call_from_thread() {
    std::cout << "Hello, World!" << std::endl;
}

int main() {
    //Launch a thread
    std::thread t1(call_from_thread);

    //Join the thread with the main thread
    t1.join();

    return 0;
}

My error:

$ make
Scanning dependencies of target Test
[100%] Building CXX object CMakeFiles/Test.dir/main.cpp.o
test/main.cpp:4:10: fatal error: 'thread' file not found
#include <thread>
     ^
1 error generated.
make[2]: *** [CMakeFiles/Test.dir/main.cpp.o] Error 1
make[1]: *** [CMakeFiles/Test.dir/all] Error 2
make: *** [all] Error 2

So does the version of Clang not support C++v11 features? This same program does compile under gcc-4.7.1 on OSX 10.8

This reference says it should work http://www.cpprocks.com/a-comparison-of-c11-language-support-in-vs2012-g-4-7-and-clang-3-1/

What am I doing wrong?

Solution

You need to provide the -std=c++11 and -stdlib=libc++ flags to the compiler in order to fully activate its C++11 support. This can be done through ccmake (turn on advanced mode (with t), and set CMAKE_CXX_FLAGS to -std=c++11 -stdlib=libc++), or through an equivalent directive in your CMakeLists.txt:

cmake_minimum_required(VERSION 2.8.9)
set(CMAKE_CXX_FLAGS "-std=c++11 -stdlib=libc++")
project(Test)
add_executable(Test main.cpp)

Comments

[Jasmine]

Thanks: set(CMAKE_CXX_FLAGS "-std=c++11 -stdlib=libc++")

[Michael]

That still doesn't work. The options are passed to the compiler, "make VERBOSE=1" verified that, but C++11 classes such as std::thread or std::function are undefined, despite <thread> and <functional> being included.

[aledalgrande]

@Michael did you find a solution?

[Mankarse]

@aledalgrande: Perhaps you also need set(CMAKE_EXE_LINKER_FLAGS "-stdlib=libc++")?

[aledalgrande]

set(CMAKE_CXX_FLAGS "-stdlib=libc++") was what worked for me

[redcurry]

set(CMAKE_CXX_FLAGS "-std=c++11 -stdlib=libc++") and set(CMAKE_EXE_LINKER_FLAGS "-stdlib=libc++") together worked for me. I was running OS X 10.7.5 and LLVM version 4.2 (clang-425.0.28).