eigen3_cmake_module

On Ubuntu Bionic, the Eigen3 CMake package offers exported targets and non-standard CMake variables. This is a problem for packages using ament_cmake.

Targets using ament_target_dependencies(my_target Eigen3) will fail to find Eigen3 headers at compile time. Downstream packages will also fail to find Eigen3 headers at compile time, even if your package uses ament_export_dependencies(Eigen3).

This package adds a CMake find module for Eigen3 that sets standard CMake variables. ROS 2 packages using Eigen3 should use this package to avoid these problems.

Using this package

Edit your CMakeLists.txt

In your CMakeLists.txt, call find_package() on this package using REQUIRED. Afterwards, find Eigen3 with or without REQUIRED as appropriate for your package.

find_package(eigen3_cmake_module REQUIRED)
find_package(Eigen3)

Using with ament_cmake

If your package uses ament_cmake, then use ament_target_dependencies() to give your library or executable targets access to the Eigen3 headers.

# add_library(my_thing ...)
# # OR
# add_executable(my_thing ...)
# ...
ament_target_dependencies(my_thing Eigen3)

If Eigen3 appears in headers installed by your package, then downstream packages will need the Eigen3 headers too. Call ament_export_dependencies() on this package, and afterwards do the same for Eigen3.

ament_export_dependencies(eigen3_cmake_module)
ament_export_dependencies(Eigen3)

Using without ament_cmake

If your package does not use ament_cmake, then use target_include_directories() to give your targets access to the Eigen3 headers.

target_include_directories(my_target PUBLIC "${Eigen3_INCLUDE_DIRS}")

If Eigen3 is used in headers installed by your package, then your <project>-config.cmake must find both this package and Eigen3. Afterwards the Eigen3 headers should be added to your package’s include variable.

find_package(eigen3_cmake_module)
if (NOT eigen3_cmake_module_FOUND)
  set(your_package_name_FOUND 0)
  return()
endif()

find_package(Eigen3)
if (NOT Eigen3_FOUND)
  set(your_package_name_FOUND 0)
  return()
endif()

list(APPEND your_package_name_INCLUDE_DIRS ${Eigen3_INCLUDE_DIRS})

Edit your package.xml

Add a buildtool dependency to this package, and a build dependency to Eigen3 to your package.xml.

<buildtool_depend>eigen3_cmake_module</buildtool_depend>
<build_depend>eigen</build_depend>

If your package uses Eigen3 in public headers, then also add these tags so downstream packages also depend on this package and Eigen3.

<buildtool_export_depend>eigen3_cmake_module</buildtool_export_depend>
<build_export_depend>eigen</build_export_depend>

<exec_depend> is not necessary because Eigen3 is a header only library.

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