How do I enable C++17 in Xcode for Mac OSX?

Question

How do I enable C++17 in Xcode (9.4.1) on OSX High Sierra (10.13.5)?

Answer 1

Steps to use C++17 in Xcode (9.4.1) on OSX High Sierra (10.13.5):

1. Open existing or create a new C++ project in Xcode
2. Click on the "show project navigator" button. It is located on the top-left section of Xcode window just below the minimize/maximize/close window buttons. It is the left-most icon and looks like a folder.
3. Click on "Build Settings" and scroll down to find and expand the section "Apple LLVM 9.0 - Language - C++"
4. Change the C++ Language Dialect combobox selection to "C++17 [-std=c++17]"

Verification steps:

Now when I output __cplusplus, I see 201703, and I am able to compile C++17 features, such as if constexpr.

template<class T> int compute(T x) {     if constexpr( supportsAPI(T{}) ) {         // only gets compiled if the condition is true         return x.Method();     } else {         return 0;     } }  int main(){     cout << __cplusplus << endl;     return 0; } 

Output:

201703 Program ended with exit code: 0 

Answer 2

When using development CocoaPods (writing a C++ library) I had also to update podspec of this library containing c++ 17 code to make compile host application which included this pod.

So I added these flags to library's podspec

  spec.xcconfig = {      "CLANG_CXX_LANGUAGE_STANDARD" => "c++17",     "CLANG_CXX_LIBRARY" => "libc++"   }