From ec3d6b36da7edc2718d7509b82e48c0746888ccd Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Gonzalve?=
 <sebastien.gonzalve@aliceadsl.fr>
Date: Wed, 5 Oct 2022 20:15:39 +0200
Subject: [PATCH] Use cannonical library name for eigen

---
 CMakeLists.txt          |  2 --
 cmake/HandleEigen.cmake | 26 +++++++++++++++++++++-----
 gtsam/CMakeLists.txt    |  7 ++-----
 3 files changed, 23 insertions(+), 12 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 74433f333..39d1e4307 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -101,8 +101,6 @@ if(GTSAM_BUILD_PYTHON OR GTSAM_INSTALL_MATLAB_TOOLBOX)
     # Copy matlab.h to the correct folder.
     configure_file(${PROJECT_SOURCE_DIR}/wrap/matlab.h
                ${PROJECT_BINARY_DIR}/wrap/matlab.h COPYONLY)
-    # Add the include directories so that matlab.h can be found
-    include_directories("${PROJECT_BINARY_DIR}" "${GTSAM_EIGEN_INCLUDE_FOR_BUILD}")
 
     add_subdirectory(wrap)
     list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_LIST_DIR}/wrap/cmake")
diff --git a/cmake/HandleEigen.cmake b/cmake/HandleEigen.cmake
index c49eb4f8e..887ae1748 100644
--- a/cmake/HandleEigen.cmake
+++ b/cmake/HandleEigen.cmake
@@ -16,8 +16,14 @@ endif()
 if(GTSAM_USE_SYSTEM_EIGEN)
     find_package(Eigen3 REQUIRED) # need to find again as REQUIRED
 
-    # Use generic Eigen include paths e.g. <Eigen/Core>
-    set(GTSAM_EIGEN_INCLUDE_FOR_INSTALL "${EIGEN3_INCLUDE_DIR}")
+    add_library(Eigen3::Eigen INTERFACE IMPORTED)
+
+    set_target_properties(Eigen3::Eigen PROPERTIES
+            INTERFACE_INCLUDE_DIRECTORIES ${EIGEN3_INCLUDE_DIR}
+            )
+
+    # The actual include directory (for BUILD cmake target interface):
+    set(GTSAM_EIGEN_INCLUDE_FOR_BUILD "${EIGEN3_INCLUDE_DIR}/")
 
     # check if MKL is also enabled - can have one or the other, but not both!
     # Note: Eigen >= v3.2.5 includes our patches
@@ -30,9 +36,6 @@ if(GTSAM_USE_SYSTEM_EIGEN)
     if(EIGEN_USE_MKL_ALL AND (EIGEN3_VERSION VERSION_EQUAL 3.3.4))
         message(FATAL_ERROR "MKL does not work with Eigen 3.3.4 because of a bug in Eigen. See http://eigen.tuxfamily.org/bz/show_bug.cgi?id=1527. Disable GTSAM_USE_SYSTEM_EIGEN to use GTSAM's copy of Eigen, disable GTSAM_WITH_EIGEN_MKL, or upgrade/patch your installation of Eigen.")
     endif()
-
-    # The actual include directory (for BUILD cmake target interface):
-    set(GTSAM_EIGEN_INCLUDE_FOR_BUILD "${EIGEN3_INCLUDE_DIR}")
 else()
     # Use bundled Eigen include path.
     # Clear any variables set by FindEigen3
@@ -46,6 +49,19 @@ else()
 
     # The actual include directory (for BUILD cmake target interface):
     set(GTSAM_EIGEN_INCLUDE_FOR_BUILD "${GTSAM_SOURCE_DIR}/gtsam/3rdparty/Eigen/")
+
+    add_library(gtsam_eigen3 INTERFACE)
+
+    target_include_directories(gtsam_eigen3 INTERFACE
+      $<BUILD_INTERFACE:${GTSAM_EIGEN_INCLUDE_FOR_BUILD}>
+      $<INSTALL_INTERFACE:${GTSAM_EIGEN_INCLUDE_FOR_INSTALL}>
+    )
+    add_library(Eigen3::Eigen ALIAS gtsam_eigen3)
+
+    install(TARGETS gtsam_eigen3 EXPORT GTSAM-exports PUBLIC_HEADER DESTINATION ${CMAKE_INSTALL_INCLUDEDIR})
+
+    list(APPEND GTSAM_EXPORTED_TARGETS gtsam_eigen3)
+    set(GTSAM_EXPORTED_TARGETS "${GTSAM_EXPORTED_TARGETS}" PARENT_SCOPE)
 endif()
 
 # Detect Eigen version:
diff --git a/gtsam/CMakeLists.txt b/gtsam/CMakeLists.txt
index 09f1ea806..d3408ee7f 100644
--- a/gtsam/CMakeLists.txt
+++ b/gtsam/CMakeLists.txt
@@ -117,12 +117,9 @@ set_target_properties(gtsam PROPERTIES
     VERSION             ${gtsam_version}
     SOVERSION           ${gtsam_soversion})
 
-# Append Eigen include path, set in top-level CMakeLists.txt to either
 # system-eigen, or GTSAM eigen path
-target_include_directories(gtsam PUBLIC
-  $<BUILD_INTERFACE:${GTSAM_EIGEN_INCLUDE_FOR_BUILD}>
-  $<INSTALL_INTERFACE:${GTSAM_EIGEN_INCLUDE_FOR_INSTALL}>
-)
+target_link_libraries(gtsam PUBLIC Eigen3::Eigen)
+
 # MKL include dir:
 if (GTSAM_USE_EIGEN_MKL)
   target_include_directories(gtsam PUBLIC ${MKL_INCLUDE_DIR})