CMake: Support a FindMPI.cmake of CMake version 3.10 and later

This change should also be backward compatible to older CMake versions.
(Fingers crossed.)

diff --git a/cmake/macros/macro_deal_ii_package_handle.cmake b/cmake/macros/macro_deal_ii_package_handle.cmake
index bedef00f0d81705b5f23d31a37ad4879e45ed57c..be6ff875f3243d937a93aaadd35e96eb36596157 100644 (file)
--- a/cmake/macros/macro_deal_ii_package_handle.cmake
+++ b/cmake/macros/macro_deal_ii_package_handle.cmake
@@ -51,7 +51,14 @@ MACRO(DEAL_II_PACKAGE_HANDLE _feature _var)
     MESSAGE(STATUS "  ${_feature}_VERSION: ${${_feature}_VERSION}")
   ENDIF()
 
-  SET(${_feature}_FOUND TRUE)
+  #
+  # Respect a possible ${_feature}_FOUND variable that is set to a truth
+  # value. We need this for modern™ MPI detection where CMake's
+  # FindMPI.cmake might only set MPI_FOUND to true and nothing else.
+  #
+  IF(NOT DEFINED ${_feature}_FOUND)
+    SET(${_feature}_FOUND TRUE)
+  ENDIF()
 
   SET(_variable ${_var})
   SET(${_feature}_${_variable} "")

diff --git a/cmake/modules/FindMPI.cmake b/cmake/modules/FindMPI.cmake
index 863dc66a4a12e08a46121726a45c0fdd9818e5e7..ec229c1f48f71c69b06208b65cda73c5f463be19 100644 (file)
--- a/cmake/modules/FindMPI.cmake
+++ b/cmake/modules/FindMPI.cmake
@@ -130,14 +130,11 @@ ENDIF()
 
 DEAL_II_PACKAGE_HANDLE(MPI
   LIBRARIES
-    REQUIRED MPI_CXX_LIBRARIES
-    OPTIONAL MPI_Fortran_LIBRARIES MPI_C_LIBRARIES
+    OPTIONAL MPI_CXX_LIBRARIES MPI_Fortran_LIBRARIES MPI_C_LIBRARIES
   INCLUDE_DIRS
-    REQUIRED MPI_CXX_INCLUDE_PATH
-    OPTIONAL MPI_C_INCLUDE_PATH
+    OPTIONAL MPI_CXX_INCLUDE_PATH MPI_C_INCLUDE_PATH
   USER_INCLUDE_DIRS
-    REQUIRED MPI_CXX_INCLUDE_PATH
-    OPTIONAL MPI_C_INCLUDE_PATH
+    OPTIONAL MPI_CXX_INCLUDE_PATH MPI_C_INCLUDE_PATH
   CXX_FLAGS OPTIONAL MPI_CXX_COMPILE_FLAGS
   LINKER_FLAGS OPTIONAL MPI_CXX_LINK_FLAGS
   CLEAR