FetchContent compatibility: Use PROJECT_SOURCE_DIR instead of CMAKE_SOURCE_DIR

[michael545]

Hi Enrico, thanks for the great library!

I'm integrating Clothoids into a larger CMake project using FetchContent and ran into an issue where the submodule resolution fails during the configure step.

The problem stems from cmake_utils/CMakeLists-utilities.txt:134:
if (EXISTS "${CMAKE_SOURCE_DIR}/submodules/${MODULE_DIR}")

Because CMAKE_SOURCE_DIR always points to the top-level project root, it searches for submodules/ in the parent project rather than inside the Clothoids directory. This causes the build to fail with Neither quarticRootsFlocke nor quarticRootsFlocke exist in submodules when included via FetchContent or add_subdirectory.

Replacing ${CMAKE_SOURCE_DIR} with ${PROJECT_SOURCE_DIR} fixes the issue perfectly, as it correctly resolves to the directory where project(Clothoids) was declared.

I'm currently patching this on the fly using sed in my FetchContent block, but it would be awesome to get this fixed upstream so it's fully compatible with modern CMake dependency management out of the box.

Thanks!

[ebertolazzi]

Hi,

thanks for the suggestion. I have applied the patch you proposed.

I should also mention that, with the help of a couple of friends who know CMake better than I do, I am currently working on modernizing the library, also using FetchContent and related modern CMake features.

You can find this work in the Clothoids3.0 branch. Once it has been tested thoroughly, it will become the new main branch.

Feel free to try it already and let me know if you have any feedback.

Thanks again!