CMake presets: `inherit` makes it hard to include toolchain file

Chardrazle · August 8, 2025, 11:16am

We just ran into this issue. We “solved” it by using an environment variable that is under control of the presets.
For example, in the “BasePresets.json”:

{
  "version": 8,
  "configurePresets": [
    {
      "name": "default",
      "hidden": true,
      "binaryDir": "$env{BASE_ROOT}/.build/${sourceDirName}",
      "toolchainFile": "$env{BASE_ROOT}/where_we_keep_common_stuff/toolchain.cmake",
      "environment": {
        "BASE_ROOT": "${fileDir}"
      }
    }
  ]
}

Then in the project-specific presets we specify “where” the root is from this file by overriding the env-var.
So if it is located one subdirectory away:

{
  "version": 8,
  "include": ["../BasePresets.json"],
  "configurePresets": [
    {
      "name": "default-inherited",
      "inherits": ["default"],
      "hidden": true,
      "environment": {
        "BASE_ROOT": "${fileDir}/.."
      }
    },
    {
      "name": "an-actual-preset-for-the-project",
      "inherits": ["default-inherited"]
    }
  ]
}