# CMP0041

Error on relative include with generator expression.

Diagnostics in CMake 2.8.12 and lower silently ignored an entry in the `INTERFACE_INCLUDE_DIRECTORIES` of a target if it contained a generator expression at any position.

The path entries in that target property should not be relative. High-level API should ensure that by adding either a source directory or a install directory prefix, as appropriate.

As an additional diagnostic, the `INTERFACE_INCLUDE_DIRECTORIES` generated on an `IMPORTED` target for the install location should not contain paths in the source directory or the build directory.

The `OLD` behavior for this policy is to ignore relative path entries if they contain a generator expression. The `NEW` behavior for this policy is to report an error if a generator expression appears in another location and the path is relative.

This policy was introduced in CMake version 3.0. CMake version 3.21.4 warns when the policy is not set and uses `OLD` behavior. Use the `cmake_policy()` command to set it to `OLD` or `NEW` explicitly.

Note

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