How can I make a library find Eigen with CMake in macOS?

Question

I am trying to compile my project with CMake which includes the Ceres Solver library. I'm using macOS Sierra with Xcode 8.1 dev tools.

I installed the library with Homebrew (brew install ceres-solver). I downloaded and tested the binary manually ( http://ceres-solver.org/building.html#mac-os-x ), and that works just fine. But I can't include it in my own project because it can't seem to find Eigen. Here is a complete example:

ceres-test/CMakeLists.txt:

cmake_minimum_required(VERSION 2.8)                                                                                            
project(CeresTest)                                                                                                             
find_package(ceres REQUIRED)                                                                                                   
add_executable(                                                                                                                
  TestCeres                                                                                                                    
  src/test_ceres.cpp                                                                                                           
)                                                                                                                              
target_link_libraries(                                                                                                         
  TestCeres                                                                                                                    
  ceres                                                                                                                        
)

ceres-test/src/test_ceres.cpp

#include <iostream>

#include "ceres/ceres.h"

int main(int argc, char** argv) {
  std::cout << "Works." << std::endl;
  return 0;
}

How I compile it:

mkdir build
cd build
cmake ..
make

Full output:

me: ceres-test $ mkdir build
me: ceres-test $ cd build/

cmake

me: build $ cmake ..
-- The C compiler identification is AppleClang 8.0.0.8000042
-- The CXX compiler identification is AppleClang 8.0.0.8000042
-- Check for working C compiler: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/cc
-- Check for working C compiler: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/cc -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Detecting C compile features
-- Detecting C compile features - done
-- Check for working CXX compiler: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/c++
-- Check for working CXX compiler: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/c++ -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Found required Ceres dependency: Eigen version 3.2.10 in /usr/local/include/eigen3
-- Found required Ceres dependency: Glog in /usr/local/include
-- Found Ceres version: 1.11.0 installed in: /usr/local
-- Configuring done
-- Generating done
-- Build files have been written to: /Users/me/Tests/ceres-test/build

make

me: build $ make
Scanning dependencies of target TestCeres
[ 50%] Building CXX object CMakeFiles/TestCeres.dir/src/test_ceres.cpp.o
In file included from /Users/me/Tests/ceres-test/src/test_ceres.cpp:3:
In file included from /usr/local/include/ceres/ceres.h:37:
In file included from /usr/local/include/ceres/autodiff_cost_function.h:132:
In file included from /usr/local/include/ceres/internal/autodiff.h:145:
/usr/local/include/ceres/jet.h:165:10: fatal error: 'Eigen/Core' file not found
#include "Eigen/Core"
         ^
1 error generated.
make[2]: *** [CMakeFiles/TestCeres.dir/src/test_ceres.cpp.o] Error 1
make[1]: *** [CMakeFiles/TestCeres.dir/all] Error 2
make: *** [all] Error 2

I have no idea how to resolve this. None of the solutions I found online helped. CMake seems to be finding the Eigen library just fine, so I'm not sure how to add it in.

On a side note I cannot include "Eigen/Core" directly either, but the tests that I was able to compile do include it and those are fine. I'm not familiar how to deal with these kinds of problems with CMake.

Edit: I can get it to compile if I include it as "eigen3/Eigen/Core" but I can't change the source code for Ceres.

Answer 1

Fixed with

include_directories(${EIGEN_INCLUDE_DIR})

in the CMakeLists....