Clang 18.1.5 and the support of std::println

Question

I have recently upgraded my Clang compiler on my M1 Mini Mac from Clang 17.0.6 to Clang 18.1.5 through brew package manager. I had few test programmes that had the std::println which worked fine with the Clang 17.0.6. Now with Clang 18.1.5 I get the below error message:

Undefined symbols for architecture arm64:
  "std::__1::__is_posix_terminal(__sFILE*)", referenced from:
      std::__1::__print::__is_terminal[abi:ne180100](__sFILE*) in main.cpp.o
ld: symbol(s) not found for architecture arm64
clang++: error: linker command failed with exit code 1 (use -v to see invocation)`

I am not sure if the support of std::println or the <print> header library was removed from Clang 18.1.6? I have tried to search the release notes but did not find anything related to this topic. I am by the way specifying the C++ standard as 23 in my CMakeLists.txt

Answer 1

It was a linker issue to the proper libc++. I am not sure what happened with the brew update that it changed installation locations without having the symbolic links. I have reinstalled llvm via brew and got the below messages:

To use the bundled libc++ please add the following LDFLAGS:
  LDFLAGS="-L/opt/homebrew/opt/llvm/lib/c++ -Wl,-rpath,/opt/homebrew/opt/llvm/lib/c++"
llvm is keg-only, which means it was not symlinked into /opt/homebrew,
because macOS already provides this software and installing another version in
parallel can cause all kinds of trouble.
If you need to have llvm first in your PATH, run:
  echo 'export PATH="/opt/homebrew/opt/llvm/bin:$PATH"' >> ~/.zshrc

For compilers to find llvm you may need to set:
  export LDFLAGS="-L/opt/homebrew/opt/llvm/lib"
  export CPPFLAGS="-I/opt/homebrew/opt/llvm/include"

So, I have added the below line to my CMakeLists.txt, and everything then worked as it is supposed to with std::println

set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -L/opt/homebrew/opt/llvm/lib/c++ -Wl,-rpath,/opt/homebrew/opt/llvm/lib/c++")