Cmake find_package 未检测到 Windows 中的路径

Question

I am trying to build the ceres sovler using Cmake_gui and Visual Studio

I have ceres-solver cloned to E:\\Code\\libs\\ceres-solver and the required library Eigen3 cloned to E:\\Code\\libs\\eigen-3.3.9

When I run cmake-gui on ceres-solver, I get the following error:

-- Detected available Ceres threading models: [CXX_THREADS, OPENMP, NO_THREADS]
-- Building with C++14
CMake Error at CMakeLists.txt:242 (find_package):
  By not providing "FindEigen3.cmake" in CMAKE_MODULE_PATH this project has
  asked CMake to find a package configuration file provided by "Eigen3", but
  CMake did not find one.

  Could not find a package configuration file provided by "Eigen3" (requested
  version 3.3) with any of the following names:

    Eigen3Config.cmake
    eigen3-config.cmake

  Add the installation prefix of "Eigen3" to CMAKE_PREFIX_PATH or set
  "Eigen3_DIR" to a directory containing one of the above files.  If "Eigen3"
  provides a separate development package or SDK, be sure it has been
  installed.

I modified ceres CMakeLists.txt line 241 from:

find_package(Eigen3 3.3 REQUIRED)

to

find_package(Eigen3 3.3 REQUIRED PATH "E:/Code/libs/eigen-3.3.9")

But I still get this error above

I also tried

list(APPEND CMAKE_PREFIX_PATH "E:/Code/libs/eigen-3.3.9")

set(Eigen3_DIR "E:/Code/libs/eigen-3.3.9")

My questions are:

1. What is the correct way to specify the path for find_package? Do I need to use path environment variable within windows or modify CMakeLists.txt?

2. Am I specifying this path correctly in Windows? Do I need to link to some internal directory of Eigen3? Like E:\\Code\\libs\\eigen-3.3.9\\cmake , use forward slashes instead of back slashes, or use quotation marks for the path? I tried all of these things without success.

3. Does find_package recursively search for the package within the directories specified? Or do I need to point to the exact directory?

Thanks

Answer 1

According to comments:

I must run Cmake-Gui on Eigen3 first, to generate a Build directory. However, it does not necessarily need to be built in VS afterwards,

Then setting on line 240 in CMakeLists.txt for ceres-solver

list(APPEND CMAKE_PREFIX_PATH "E:/Code/libs/eigen-3.3.9/build")

Was sufficient for Cmake-Gui to find the Eigen3Config.cmake file

Notes:

1. Eigen3 does not have any required dependencies it seems, but it does throw a lot of warnings when generating with Cmake-Gui, I ignored these
2. glog library or any other libraries are not required, but I did have to check "Enable mini-glog" option and re-run config for ceres-solver.