cmake detect which library libc++ or libstdc++ is configured to be used against g++ or clang++

Question

I wrote an CMakeLists.txt to build a project with either g++ or clang++.

To catch as many as possible bugs I use both libc++

Answer 1

I think you can safely just pass both defines for each library.

But if you really want to do this conditionally, I'd recommend using CheckCXXSourceCompiles module with following code:

#include <iostream>

int a =
#ifdef __GLIBCXX__
    1;
#else
    fgsfds;
#endif

int main(int argc, char* argv[])
{
return 0;
}

If that code compiles, then you are using libstdc++.