Having trouble adding autodiff and Eigen to a project

[EmmanuelMess]

Turns out there is a (sort of) library "autodiff" inside Eigen 3.4.0.

I added Eigen and autodiff like this:

 cpmaddpackage("https://gitlab.com/libeigen/eigen/-/archive/3.4.0/eigen-3.4.0.zip")
 cpmaddpackage("gh:autodiff/autodiff@1.0.3")

It returns the error:

CMake Error at cmake-build-debug-gcc-10/_deps/tools-src/cmake/SystemLink.cmake:65 (target_link_libraries):
  Target "autodiff" of type UTILITY may not be linked into another target.
  One may link only to INTERFACE, OBJECT, STATIC or SHARED libraries, or to
  executables with the ENABLE_EXPORTS property set.

The problem is that the linked library is eigen's autodiff (inside unsupported/test), not autodiff/autodiff.

[EmmanuelMess]

Here is a workaround:

set(EIGEN_BUILD_DOC OFF)
set(BUILD_TESTING OFF) # This removes the tests and makes autodiff test not collide with autodiff/autodiff
set(EIGEN_BUILD_PKGCONFIG OFF)
cpmaddpackage("https://gitlab.com/libeigen/eigen/-/archive/3.4.0/eigen-3.4.0.zip")

cpmaddpackage("gh:autodiff/autodiff@1.0.3")