fixed some Fortran related bugs

CMakeLists.txt

@@ -15,15 +15,16 @@ option(CM_ALL_AUTO_DOC "Enables creation of auto-documentation")
 cmake_policy(SET CMP0004 OLD)
 
 enable_language(CXX)
+enable_language(C)
 
+if (CM_ALL_USE_F08)
     if (CM_ALL_FORTRAN)
-    enable_language(Fortran)
+        message(FATAL_ERROR "Flag for Fortran 08 MPI interface set, while Fortran interface is not enabled!")
     endif (CM_ALL_FORTRAN)
+endif (CM_ALL_USE_F08)
 
-# set standards compliance flags
-set(CMAKE_CXX_STANDARD 11)
-set(CMAKE_CXX_STANDARD_REQUIRED ON)
-set(CMAKE_CXX_EXTENSIONS OFF)
+if (CM_ALL_FORTRAN)
+    enable_language(Fortran)
 # todo(s.schulz): This should be extended for other compilers, if they
 #                 support standard checking. The Intel Fortran compiler
 #                 does not.
@@ -34,7 +35,15 @@ else()
     endif()
     add_compile_options($<$<AND:$<COMPILE_LANGUAGE:Fortran>,$<Fortran_COMPILER_ID:GNU>>:-fbacktrace>)
     add_compile_options($<$<AND:$<COMPILE_LANGUAGE:Fortran>,$<Fortran_COMPILER_ID:Intel>>:-traceback>)
+endif (CM_ALL_FORTRAN)
+
+# set standards compliance flags
+set(CMAKE_CXX_STANDARD 11)
+set(CMAKE_CXX_STANDARD_REQUIRED ON)
+set(CMAKE_CXX_EXTENSIONS OFF)
+if (CM_ALL_FORTRAN)
     add_compile_options("$<$<AND:$<CONFIG:Debug>,$<COMPILE_LANGUAGE:Fortran>,$<Fortran_COMPILER_ID:GNU>>:-Wall;-Wextra>")
+endif (CM_ALL_FORTRAN)
 add_compile_options("$<$<AND:$<CONFIG:Debug>,$<COMPILE_LANGUAGE:C>,$<C_COMPILER_ID:GNU>>:-Wall;-Wextra>")
 add_compile_options("$<$<AND:$<CONFIG:Debug>,$<COMPILE_LANGUAGE:CXX>,$<CXX_COMPILER_ID:GNU>>:-Wall;-Wextra>")
 
@@ -46,7 +55,12 @@ project(ALL
 # add custom find-scripts to module path
 set(CMAKE_MODULE_PATH "${PROJECT_SOURCE_DIR}/cmake" ${CMAKE_MODULE_PATH})
 
-find_package(MPI REQUIRED)
+if (CM_ALL_FORTRAN)
+    find_package(MPI REQUIRED COMPONENTS CXX Fortran)
+else()
+    find_package(MPI REQUIRED COMPONENTS CXX)
+endif (CM_ALL_FORTRAN)
+
 
 if(CM_ALL_VTK_OUTPUT)
     message("Using VTK output")