C++17 filesystem support for x86_64-apple-darwin14-clang++

[peremato]

While trying to upgrade to latest version Geant4 I encountered the following problem. The code snippet to check the availability of filesystem library fails with the error:

# /opt/bin/x86_64-apple-darwin14-libgfortran5-cxx11/x86_64-apple-darwin14-clang++ -std=c++17 /workspace/srcdir/geant4-v11.1.1/cmake/Modules/check_cxx_filesystem.cc 
Undefined symbols for architecture x86_64:
  "__ZNSt3__14__fs10filesystem11__canonicalERKNS1_4pathEPNS_10error_codeE", referenced from:
      __ZNSt3__14__fs10filesystem9canonicalERKNS1_4pathE in check_cxx_filesystem-acb0f7.o
ld: symbol(s) not found for architecture x86_64
clang-13: error: linker command failed with exit code 1 (use -v to see invocation)

the file is:

# cat  /workspace/srcdir/geant4-v11.1.1/cmake/Modules/check_cxx_filesystem.cc 
// Check that trivial use of <filesystem> works
// - https://en.cppreference.com/w/cpp/filesystem
#include <iostream>
#include <filesystem>

namespace fs = std::filesystem;

int main( int argc, char* argv[] ) {
  fs::path p{ argv[0] };
  std::cout << p << ", " << fs::canonical( p ) << std::endl;
}

The compiler x86_64-apple-darwin14-clang++ does support c++17 standard however filesystem seems to be missing from the libc++ library. Any suggestion to overcome the problem?

[giordano]

Substantially duplicate of #863 and all other issues referencing that one.

However there's a work around, manually use a newer SDK: https://github.com/JuliaPackaging/Yggdrasil/blob/4533b19ff5314ecc9de92b63f48f05ac5ceba3c0/C/Ccache/build_tarballs.jl#L13-L14 and
https://github.com/JuliaPackaging/Yggdrasil/blob/4533b19ff5314ecc9de92b63f48f05ac5ceba3c0/C/Ccache/build_tarballs.jl#L21-L29. This isn't pretty and in the not-so-distant future we should have a solution to make this more straightforward, but it does the job for the time being.

[peremato]

Thanks very much @giordano . But following the recipe I get tons of errors if I delete/modify anything in /opt/${target}/${target}/sys-root. It seems that the filesystem is readonly. Did I miss anything?

[giordano]

Not sure what you're doing, we use that trick extensively.

I don't know your setup (are you using Docker on macOS by any chance? I'm not familiar with that setup), you may want to consider using GitHub Codespaces: https://docs.binarybuilder.org/stable/#GitHub-Codespaces

[peremato]

Yes, I am using Docker on MacOS. I'll use a Linux system later.