CMP0180 — CMake 4.2.6 Documentation

# CMP0180

Added in version 3.31.

`project()` always sets `<PROJECT-NAME>_*` as normal variables.

In CMake 3.29 and below, the `project()` command set `<PROJECT-NAME>_SOURCE_DIR`, `<PROJECT-NAME>_BINARY_DIR`, and `<PROJECT-NAME>_IS_TOP_LEVEL` as cache entries, but not as normal variables. CMake 3.30 started setting them as normal variables, but only if they are already set as normal variables. This was needed to preserve support for some `FetchContent` use cases under policy `CMP0169`'s NEW behavior, while also preserving behavior of nested directories that call `project()` with the same project name. See release notes for 3.30.3, 3.30.4, and 3.30.5 for details.

CMake 3.31 and later prefer to always set `<PROJECT-NAME>_SOURCE_DIR`, `<PROJECT-NAME>_BINARY_DIR`, and `<PROJECT-NAME>_IS_TOP_LEVEL`, as both cache entries and normal variables, regardless of what cache or normal variables already exist. This policy provides compatibility for projects that have not been updated to expect this behavior.

The `OLD` behavior for this policy will only set normal variables for `<PROJECT-NAME>_SOURCE_DIR`, `<PROJECT-NAME>_BINARY_DIR`, and `<PROJECT-NAME>_IS_TOP_LEVEL` if there is already a normal variable by that name when `project()` is called. The `NEW` behavior for this policy will always set normal variables for `<PROJECT-NAME>_SOURCE_DIR`, `<PROJECT-NAME>_BINARY_DIR`, and `<PROJECT-NAME>_IS_TOP_LEVEL` when `project()` is called.

This policy was introduced in CMake version 3.31. It may be set by `cmake_policy()` or `cmake_minimum_required()`. If it is not set, CMake does not warn, and uses `OLD` behavior.

Note

The `OLD` behavior of a policy is `deprecated by definition` and may be removed in a future version of CMake.