Re: Compile antiquated fortran?

[Steve Kargl <sgk@troutmask.apl.washington.edu>]

On Thu, Jul 27, 2023 at 01:36:46PM -0400, Allin Cottrell via Fortran wrote:
> I have old fortran source code (not my own work) for a specialized
> statistical program that I and others find quite useful.
> 
> A few years ago I was able to compile it on Linux using gfortran with
> std=legacy (and also cross-compile it for Windows an Mac). Now I'd like to
> rebuild it, but with recent gfortran (I've tried 12.2.1 on Fedora and 13.1.1
> on Arch) it's a no-go. I get lots of errors of the following sort:
> 
> ansub9.f:151:44:
> 
>   151 |    INTEGER ITYPE,INIT,LAM,IMEAN,IP,ID,Q,BP,BD,BQ,SQG,MQ,L,M,
>       |                                       1
> Error: Symbol ‘q’ at (1) already has basic type of REAL
> 
> I can understand this complaint. The code contains this sort of thing within
> a given subroutine:
> 
>        IMPLICIT  REAL*8 (A-H,O-Z)
> 
> then some lines later on:
> 
>        INTEGER ITYPE,INIT,LAM,IMEAN,P,D,Q,...
> 
> I guess the author was assuming that an explicit type-assignment just
> overrides an implicit one. Older gfortran apparently played along with that.
> 
> My question: Given that I'm already using -std=legacy, are there any other
> flags that I could add to get the code to compile?
> 
> (I know I could tackle this by renaming a bunch of variables, but in context
> that would be an extremely fiddly job.)
> 

I'm afraid we'll need to see some actual code.  The following compiles
without a problem.

       SUBROUTINE FOO(Q)
       IMPLICIT REAL*8 (A-H,O-Z)
       INTEGER Q
       Q = 1
       END

Hmmm, are DATA statements in the code?

       SUBROUTINE FOO
       IMPLICIT REAL*8 (A-H,O-Z)
       DATA Q/1/
       INTEGER Q
       Q = 1
       END

% gfortran12 -c -Wall a.f
a.f:4:16:

    4 |        INTEGER Q
      |                1
Error: Symbol 'q' at (1) already has basic type of REAL

gfortran is correct to complain here.  The DATA statement give
Q a REAL type due to the implicit statement.  Q can only appear
in a later declaration statement that re-affirms that type.

-- 
Steve