CMake check system for underscore requirements between C and Fortran

CMakeLists.txt

@@ -893,6 +893,12 @@ else()
   list( APPEND PROJECT_COMPILE_DEFINITIONS_CONFCHECK FSEEK_OK )
 endif()
 
+if ( ${NOUNDERSCORE_SYMBOL} )
+  list( APPEND PROJECT_COMPILE_DEFINITIONS_CONFCHECK NOUNDERSCORE )
+elseif( ${UNDERSCORE_SYMBOL} )
+  list( APPEND PROJECT_COMPILE_DEFINITIONS_CONFCHECK UNDERSCORE )
+endif()
+
 # I don't believe these are used anymore...
 # $<$<BOOL:${MPI2_SUPPORT}>:MPI2_SUPPORT=$<BOOL:${MPI2_SUPPORT}>>
 # $<$<BOOL:${MPI2_THREAD_SUPPORT}>:MPI2_THREAD_SUPPORT=$<BOOL:${MPI2_THREAD_SUPPORT}>>

arch/configure_reader.py

@@ -161,13 +161,18 @@ def sanitize( self ) :
     # # Now deref
     self.dereference( "FCBASEOPTS" )
 
+    definesToRemove = [ "-DUNDERSCORE", "-DNOUNDERSCORE" ]
+
     # Remove rogue compile commands that should *NOT* even be here
     for keyToSan in self.kvPairs_.keys() :
+      # It's easier to do this first
+      for cppDef in definesToRemove :
+        self.kvPairs_[ keyToSan ] = self.kvPairs_[ keyToSan ].replace( cppDef, "" )
+
       self.kvPairs_[ keyToSan ] = configureRepl.sub( r"\1\2", self.kvPairs_[ keyToSan ] ).strip()
       self.kvPairs_[ keyToSan ] = compileObject.sub( r"\1\2", self.kvPairs_[ keyToSan ] ).strip()
       self.kvPairs_[ keyToSan ] =    defineRepl.sub( r"\1",   self.kvPairs_[ keyToSan ] ).strip()
 
-
     # Now fix certain ones that are mixing programs with flags all mashed into one option
     self.splitIntoFieldAndFlags( "SFC" )
     self.splitIntoFieldAndFlags( "SCC" )

cmake/confcheck.cmake

@@ -26,7 +26,7 @@ function( wrf_conf_check )
 
   message( STATUS "Performing Check ${WRF_CFG_RESULT_VAR}" )
 
-  if ( DEFINED WRF_CFG_RUN )
+  if ( DEFINED WRF_CFG_RUN AND "${WRF_CFG_RUN}" )
     try_run( 
             ${WRF_CFG_RESULT_VAR}
             WRF_CFG_COMPILE_RESULT_VAR
@@ -61,9 +61,9 @@ function( wrf_conf_check )
     endif()
 
     if ( DEFINED WRF_CFG_MESSAGE )
-      message( ${WRF_CFG_MSG_TYPE} "${WRF_CFG_MESSAGE}" )
+      message( ${WRF_CFG_MSG_TYPE} "  ${WRF_CFG_MESSAGE}" )
     else()
-      message( ${WRF_CFG_MSG_TYPE} "${WRF_CFG_RESULT_VAR} marked as required, check failed" )
+      message( ${WRF_CFG_MSG_TYPE} "  ${WRF_CFG_RESULT_VAR} check failed" )
     endif()
   else()
     message( STATUS "Performing Check ${WRF_CFG_RESULT_VAR} - Success" )

confcheck/CMakeLists.txt

@@ -65,6 +65,31 @@ if ( NOT "${FSEEKO64}" )
   set(FSEEKO ${FSEEKO} PARENT_SCOPE)
 endif()
 
+
+# Check if underscores are needed for implicit c-Fortran interfacing functions that
+# don't use ISO C binding to map symbols
+wrf_conf_check(
+                # try_run() with more than one source was introduced in CMake 3.25+
+                # so we won't use it here until we see reasonable need to increase the 
+                # version requirements
+                RESULT_VAR             NOUNDERSCORE_SYMBOL
+                SOURCES                ${CMAKE_CURRENT_SOURCE_DIR}/check_underscore.c ${CMAKE_CURRENT_SOURCE_DIR}/check_underscore.f90
+                OPTIONS
+                  COMPILE_DEFINITIONS -DNOUNDERSCORE
+                MESSAGE                "Implicit symbol usage between C and Fortran are not identical, checking with underscores"
+              )
+if ( NOT ${NOUNDERSCORE_SYMBOL} )
+  # If the above fails we NEED the following to work
+  wrf_conf_check(
+                  RESULT_VAR             UNDERSCORE_SYMBOL
+                  SOURCES                ${CMAKE_CURRENT_SOURCE_DIR}/check_underscore.c ${CMAKE_CURRENT_SOURCE_DIR}/check_underscore.f90
+                  OPTIONS
+                    COMPILE_DEFINITIONS -DUNDERSCORE
+                  MESSAGE                "Implicit symbol usage between C with underscores and Fortran did not link!"
+                  REQUIRED
+                )
+endif()
+
 # Unsure if this is even necessary. Defines littered throughout configure.defaults
 # if ( ${USE_MPI} )
 #   wrf_conf_check(

confcheck/check_underscore.c

@@ -0,0 +1,8 @@
+#include <stdio.h>
+#ifdef UNDERSCORE 
+#  define foo foo_
+#endif
+void foo( void )
+{
+  printf( "Hello World!\n" );
+}

confcheck/check_underscore.f90

@@ -0,0 +1,5 @@
+
+program test
+  write( *, * ) "Calling foo() from Fortran"
+  call foo()
+end program test