Fortran fixes (LLNL#108)

* Enable GTest by default only when CXX is enabled

 - If GTest is enabled without CXX we throw a `FATAL_ERROR` and explain to the
   user that enabling CXX is a hard requirement for using GTest.
 - Fixes LLNL#105

* Default 2 enabling Fortran if use already detected

 - If user explicitly enables Fortran via `project()` or `enable_language()`
   they should not have to reenable it again.

* Remove BLT Fortran format setting

 - Fixes LLNL#106
 - Users should explicitly set the `CMAKE_Fortran_FORMAT` variable for
   the project themselves, or set the target property as appropriate.

* Use more canonical Fortran file naming convention

 - Move `blt_fruit_smoke.f` to `blt_fruit_smoke.f90`

SetupBLT.cmake

@@ -75,7 +75,7 @@ if (NOT BLT_LOADED)
   endif()
 
   ################################
-  # Enable ctest support 
+  # Enable ctest support
   ################################
   if(ENABLE_TESTS)
       enable_testing()

cmake/BLTOptions.cmake

@@ -53,8 +53,14 @@ option(ENABLE_COVERAGE   "Enables code coverage support" OFF)
 ################################
 # Build Options
 ################################
+get_property(_languages GLOBAL PROPERTY ENABLED_LANGUAGES)
+if(_languages MATCHES "Fortran")
+    set(_fortran_already_enabled TRUE)
+else()
+    set(_fortran_already_enabled FALSE)
+endif()
 option(ENABLE_COPY_HEADERS "Copy headers to build directory" OFF)
-option(ENABLE_FORTRAN      "Enables Fortran compiler support" OFF)
+option(ENABLE_FORTRAN      "Enables Fortran compiler support" ${_fortran_already_enabled})
 option(ENABLE_SHARED_LIBS  "Enables shared libraries." OFF)
 
 option(ENABLE_MPI          "Enables MPI support" OFF)
@@ -72,10 +78,20 @@ mark_as_advanced(BLT_CLANG_CUDA_ARCH)
 #
 # Google Mock requires and always builds Google Test, so ENABLE_GMOCK=ON implies ENABLE_GTEST=ON.
 #
-option(ENABLE_GTEST        "Enable Google Test testing support (if ENABLE_TESTS=ON)" ON)
+get_property(_languages GLOBAL PROPERTY ENABLED_LANGUAGES)
+if(_languages MATCHES "CXX")
+  set(_CXX_enabled ON)
+else()
+  set(_CXX_enabled OFF)
+endif()
+option(ENABLE_GTEST        "Enable Google Test testing support (if ENABLE_TESTS=ON)" ${_CXX_enabled})
 option(ENABLE_GMOCK        "Enable Google Mock testing support (if ENABLE_TESTS=ON)" OFF)
 option(ENABLE_FRUIT        "Enable Fruit testing support (if ENABLE_TESTS=ON and ENABLE_FORTRAN=ON)" ON)
-
+
+if( (NOT _CXX_enabled) AND ENABLE_GTEST )
+  message( FATAL_ERROR
+    "You must have CXX enabled in your project to use GTEST!" )
+endif()
 
 ################################
 # Compiler Options

cmake/SetupCompilerOptions.cmake

@@ -334,9 +334,6 @@ if(ENABLE_FORTRAN)
         message(FATAL_ERROR "Fortran support selected, but no Fortran compiler was found.")
     endif()
 
-    # default property to free form
-    set(CMAKE_Fortran_FORMAT FREE)
-
     list(APPEND langFlags "CMAKE_Fortran_FLAGS")
 else()
     message(STATUS  "Fortran support disabled.")

tests/CMakeLists.txt

@@ -93,7 +93,7 @@ endif()
 ################
 if (ENABLE_FORTRAN AND ENABLE_FRUIT)
     blt_add_executable(NAME blt_fruit_smoke
-                       SOURCES blt_fruit_smoke.f
+                       SOURCES blt_fruit_smoke.f90
                        OUTPUT_DIR ${TEST_OUTPUT_DIRECTORY}
                        DEPENDS_ON fruit
                        FOLDER blt/tests )

tests/blt_fruit_smoke.f → tests/blt_fruit_smoke.f90

@@ -43,7 +43,7 @@
 
 !------------------------------------------------------------------------------
 !
-! blt_fruit_smoke.f
+! blt_fruit_smoke.f90
 !
 !------------------------------------------------------------------------------
 module fruit_smoke