Program on old fortran IV

[Tim Prince]

On 4/29/2020 9:37 AM, Joao Martins Correia wrote:
> Dear Gcc Helpers
>
> I recovered an old scientific program code written in Fortran IV.
> Still using hollerith assignments - which I think I understand, I can compile it with the many warnings
> regarding essentially 3 things
>
> 1- hollerith
>
> 2- “do" cycles indexed to an active command line instead of “enddo" or “continue”, e.g.
>
> do	10 i=1,n
>  		x=x+1
> 10	y=y+1
>
> 3-“if” of the type
>
>  If (n) 10,20,30
>
> All of this can be cleaned, but I have the feeling that in spite of the warnings the compiler still treats these 3 warnings correctly, since I could test it
> with coherent results.
>
> The program starts running, properly, reads input files and execute some routines, but then gets stuck with strange huge
> numbers that have no apparent reason to be there.
> The problem is in fact that there are no assignment of variable types and there are many commons with different variable names
> that contribute to the confusion when debugging. Setting “implicit none” creates too many errors, since sometimes is not easy
> to assign the type of the variable on a code with 30 routines and more than 5000 lines.
>
> I am considering reviewing it fully, but first would like to know if there is some options that could help emulating
> an older compiler for fortran IV. In the moment the fortran routines have type .f 
>
> Thanks anyway
>
> Cheers
>
> João Correia

Those old programs often made assumptions such as those covered by
gfortran -fno-automatic -finit-local-zero .  There was no portability or
standards checking in most compilers, and chances are your program was
never analyzed for those.  I don't think gfortran carried over the
-fone-trip option from g77, another assumption which many people
considered erroneously to be part of f66 standard.   You may be stuck
with setting implicit none and weeding out errors.


-- 
Tim Prince