[SOLVED] How to get path to the compiler libs from the CmakeLists.txt using presets?

Issue

I use cmake 3.22 and presets to configure and build my project. I have a few presets for different compilers defined like below.

How can I get the compiler libraries dir in the CMakeLists.txt file? I can get ${CMAKE_CXX_COMPILER} - full path to the compiler, but is it possible to retrieve the path to its libs?

Why can't I read ${GCC_DIR} at least?

   ...
   "configurePresets": [
    {
      "name": "tools",
      "hidden": true,
      "environment": {
        "BINUTILS": "/gnu/binutils/binutils-2.37",
        "GCC_DIR": "/gnu/gcc/gcc-11.2.0-rh6",
        "LLVM_DIR": "/llvm/llvm-14.0",
        "NINJA_DIR": "/ninja/ninja-1.7.2"
      },
      "generator": "Ninja"
    },
...
    {
      "name": "gcc",
      "hidden": true,
      "inherits": ["tools", "common_settings"],
      "environment": {
        "PATH": "$env{BINUTILS}/bin:$env{GCC_DIR}/bin:$env{NINJA_DIR}/bin",
        "LD_LIBRARY_PATH": "$env{GCC_DIR}/lib64",
        "CC": "gcc",
        "CXX": "g++"
      }
    },
...
  "buildPresets": [
    {
      "name": "gcc_debug",
      "configurePreset": "gcc_debug"
    },
...

Solution

Why can't I read ${GCC_DIR} at least?

Because you set GCC_DIR as an environment variable, not a CMake (cache) variable. That syntax only considers CMake variables (both "normal" and cache).

You could write $ENV{GCC_DIR} to read the environment variable, but I would recommend immediately caching it so that incremental builds don't have to run under the exact same environment as the first configure:

cmake_minimum_required(VERSION 3.21)  # for sane cache behavior
project(example)

# ...

set(GCC_DIR "$ENV{GCC_DIR}"
    CACHE PATH "Path to GCC libraries")

# ... use ${GCC_DIR} freely ...

Answered By - Alex Reinking

Answer Checked By - Marilyn (WPSolving Volunteer)