CMake: how to set -B parameter (path-to-build) inside CMakeLists.txt?

Question

Is there some system variable in CMakeLists.txt to set all build temporary files to specified dir (CMakeCache, CMakeFiles, build artifacts, etc)? This can be done using command line parameter -B (path-to-build), but I need it inside CMakeLists.txt to set default dir for all files, which are not-tracked with git

Answer 1

If you specify a build directory via command line, it always overwrites any values from other sources.

You can achieve something similar to the effect you desire using cmake presets, but it's a relatively new addition (= version 3.19) to the cmake features and it doesn't specify the build directory inside the CMakeLists.txt file, but inside a CMakePresets.json file.

The presence of the file won't break the project for older cmake versions, but the initial configuration becomes less convenient.

CMakePresets.json (place next to the toplevel CMakeLists.txt)

{
  "version": 1,
  "cmakeMinimumRequired": {
    "major": 3,
    "minor": 19,
    "patch": 0
  },
  "configurePresets": [
    {
      "name": "makefiles",
      "displayName": "Default configuration",
      "description": "Default config",
      "generator": "Unix Makefiles",
      "binaryDir": "../build"
    }
  ]
}

This allows you to choose the default build location as a sibling directory of the source dir using

cmake --preset makefiles .

This uses the sibling directory build of the source directory as the binary directory.

Answer 2

You can use CMake presets for it. You use the binaryDir property and never again you need to provide the -B argument as long as you use presets to generate your project files and/or build your project.