Gaurd new descriptor component w/ ifdef GCC >= 8

Author: zbeekman

CMakeLists.txt

@@ -165,6 +165,9 @@ endif()
   if ( gfortran_compiler AND ( NOT CMAKE_Fortran_COMPILER_VERSION VERSION_LESS 7.0.0 ) )
     add_definitions(-DGCC_GE_7) # Tell library to build against GFortran 7.x bindings b/c we might be using clang for C
   endif()
+  if ( gfortran_compiler AND ( NOT CMAKE_Fortran_COMPILER_VERSION VERSION_LESS 8.0.0 ) )
+    add_definitions(-DGCC_GE_8) # Tell library to build against GFortran 8.x bindings w/ descriptor change
+  endif()
 
 if(gfortran_compiler)
   set(OLD_REQUIRED_FLAGS ${CMAKE_REQUIRED_FLAGS})

src/libcaf-gfortran-descriptor.h

@@ -51,7 +51,9 @@ typedef struct gfc_descriptor_t {
   void *base_addr;
   size_t offset;
   ptrdiff_t dtype;
+#ifdef GCC_GE_8
   ptrdiff_t span;
+#endif
   descriptor_dimension dim[];
 } gfc_descriptor_t;