Prefer Eigen installs over exported build directories.
- Use the same logic as per gflags & glog whereby we perform (up to)
two find_package() calls such that installed packages are preferred
to exported build directories across all platforms.
Change-Id: Ifb9a7ba322ee43ed18c5774633e4bb527ce7cd75
diff --git a/cmake/FindEigen.cmake b/cmake/FindEigen.cmake
index af141ef..348f043 100644
--- a/cmake/FindEigen.cmake
+++ b/cmake/FindEigen.cmake
@@ -116,9 +116,57 @@
endif()
if (EIGEN_PREFER_EXPORTED_EIGEN_CMAKE_CONFIGURATION)
- find_package(Eigen3 QUIET)
+ # Try to find an exported CMake configuration for Eigen.
+ #
+ # We search twice, s/t we can invert the ordering of precedence used by
+ # find_package() for exported package build directories, and installed
+ # packages (found via CMAKE_SYSTEM_PREFIX_PATH), listed as items 6) and 7)
+ # respectively in [1].
+ #
+ # By default, exported build directories are (in theory) detected first, and
+ # this is usually the case on Windows. However, on OS X & Linux, the install
+ # path (/usr/local) is typically present in the PATH environment variable
+ # which is checked in item 4) in [1] (i.e. before both of the above, unless
+ # NO_SYSTEM_ENVIRONMENT_PATH is passed). As such on those OSs installed
+ # packages are usually detected in preference to exported package build
+ # directories.
+ #
+ # To ensure a more consistent response across all OSs, and as users usually
+ # want to prefer an installed version of a package over a locally built one
+ # where both exist (esp. as the exported build directory might be removed
+ # after installation), we first search with NO_CMAKE_PACKAGE_REGISTRY which
+ # means any build directories exported by the user are ignored, and thus
+ # installed directories are preferred. If this fails to find the package
+ # we then research again, but without NO_CMAKE_PACKAGE_REGISTRY, so any
+ # exported build directories will now be detected.
+ #
+ # To prevent confusion on Windows, we also pass NO_CMAKE_BUILDS_PATH (which
+ # is item 5) in [1]), to not preferentially use projects that were built
+ # recently with the CMake GUI to ensure that we always prefer an installed
+ # version if available.
+ #
+ # [1] http://www.cmake.org/cmake/help/v2.8.11/cmake.html#command:find_package
+ find_package(Eigen3 QUIET
+ NO_MODULE
+ NO_CMAKE_PACKAGE_REGISTRY
+ NO_CMAKE_BUILDS_PATH)
if (EIGEN3_FOUND)
message(STATUS "Found installed version of Eigen: ${Eigen3_DIR}")
+ else()
+ # Failed to find an installed version of Eigen, repeat search allowing
+ # exported build directories.
+ message(STATUS "Failed to find installed Eigen CMake configuration, "
+ "searching for Eigen build directories exported with CMake.")
+ # Again pass NO_CMAKE_BUILDS_PATH, as we know that Eigen is exported and
+ # do not want to treat projects built with the CMake GUI preferentially.
+ find_package(Eigen3 QUIET
+ NO_MODULE
+ NO_CMAKE_BUILDS_PATH)
+ if (EIGEN3_FOUND)
+ message(STATUS "Found exported Eigen build directory: ${Eigen3_DIR}")
+ endif()
+ endif()
+ if (EIGEN3_FOUND)
set(FOUND_INSTALLED_EIGEN_CMAKE_CONFIGURATION TRUE)
set(EIGEN_FOUND ${EIGEN3_FOUND})
set(EIGEN_INCLUDE_DIR "${EIGEN3_INCLUDE_DIR}" CACHE STRING
