How to make Fortran program with [REFERENCE] compatible with gfortran?

Question

I am working on compiling an old piece of Fortran code written sometime in the early 2000s. In this code base there are functions designed to interface with C code and have the following structure:

SUBROUTINE F_LIB_FOO(MY_VAR)
   !DEC$ ATTRIBUTES DLLEXPORT,STDCALL :: F_LIB_FOO
   REAL(8), INTENT(IN) :: MY_VAR [REFERENCE]
   LIB_FOO(MY_VAR) !This calls the function implemented internally

However, when I try to compile it using gfortran 4.4.7 I get the following error

REAL(8), INTENT(IN) :: MY_VAR  [REFERENCE]
                             1
Error: Syntax error in data declaration at (1)

My belief is that REFERENCE indicates that the MY_VAR is passed by reference. However, I can't find any examples that use this sort of syntax.

According to this answer, this syntax is supported in Visual Studios. I want to know if there is a similar way to do this in a Linux machine and if there isn't, how can I change the code to compile with gfortran and have the same functionality.

It is sort of implied there that you can just delete it, but to understand that you must know what STDCALL is... — Vladimir F Героям слава, Jan 19 '18 at 18:48

score 0 · Accepted Answer · answered Jan 19 '18 at 19:37

As the linked answer says, the [REFERENCE] attribute is a highly non-standard thing that changes the behaviour for STDCALL calling conventions. Stdcall is the standard calling convention for the Microsoft Win32 API and for Open Watcom C++.

You can safely delete it for Linux programs and for 64-bit Windows as well.

For situations (Win32), where it might be necessary, GCC uses !GCC$ ATTRIBUTES STDCALL, but I am not sure how to specify REFERENCE there.

How to make Fortran program with [REFERENCE] compatible with gfortran?

1 Answers1