clang-omp in Xcode under El Capitan

Question

I like to use openmp in a c++ project using Xcode as IDE. Unfortunately, Apple's Clang compiler does not support openmp (see here), so I installed clang-omp. I exactly followed the instructions given on that website to use it within Xcode, but I get the error message can't exec '/usr/local/bin/clang++-omp' (No such file or directory). I tried to compile the simple example given on their website via terminal and I got it to work when I compile it via clang-omp++ -fopenmp file.cpp. For me it looks like Xcode should search for /usr/local/bin/clang-omp++ (which exists in contrast to /usr/local/bin/clang++-omp). After making a symlink as suggested in the comments I get another error message: library not found for -liomp5. How can I fix this?

Solution 1

In case anyone else is trying to get clang-omp under Xcode to work, the correct way is (following the official instructions):

1. Install clang-omp using homebrew: brew install clang-omp
2. Create a new Xcode project
3. Add a new user-defined setting CC with the value /usr/local/bin/clang-omp under the project's build settings
4. Add -fopenmp to Other C Flags under the project's build settings
5. Add /usr/local/include to Header Search Paths under the project's build settings
6. Add /usr/local/lib to Library Search Paths under the project's build settings
7. Set Enable Modules (C and Objective-C) to No under the project's build settings
8. Add /usr/local/lib/libiomp5.dylib to Link Binary With Libraries under the project's build phases
9. Make a symbolic link via sudo ln -s /usr/local/bin/clang-omp++ /usr/local/bin/clang++-omp using the terminal
10. Use #include <libiomp/omp.h> to be able to use openmp in your project

Solution 2

OpemMP runtimes are usually not delivered with clang, you can download and install from: https://www.openmprtl.org

Comments

[David Ganster]

@JosephK I know it's a little late, but try running brew update before brew install.

[Adriweb]

Note (July 2016): clang-omp has been "removed" from brew, OpenMP now being directly supported by upstream LLVM (available on brew as well). Regarding Xcode integration now, though, I'm not sure.

[DoDo]

I've installed llvm38 from homebrew and while -fopenmp flag now correctly gets recognizer, I get a compile error stating that omp.h does not exists. I searched for the file and it really does not exist. What to do now?

[Bhargav Rao]

Whilst this may theoretically answer the question, it would be preferable to include the essential parts of the answer here, and provide the link for reference.

[eborisch]

If you install clang-3.8 and above from MacPorts, -fopenmp "just works."

[eborisch]

To use in Xcode from MacPorts and then, similar to above: [1] sudo port install clang-3.8 ld64 +ld64_xcode [2] User-defined setting CC /opt/local/bin/clang-mp/3.8 [3] Other C Flags: -fopenmp [4] Other Linker Flags: -fopenmp [5] Enable Modules (C and Objective-C): No [6] And done. The include and library search paths and linking requirements are baked into clang-mp-3.8. You will need #include <omp.h> as always. (Inspired by Jan-Michael Tressler's openmp-dev post.)

[Royi]

What about newer XCode? Is there a simple way?