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From: Thomas Koenig <tkoenig@netcologne.de>
Newsgroups: comp.lang.fortran
Subject: Re: in gfortran, is it faster compile times with *.mod files ?
Date: Thu, 14 Nov 2024 06:48:47 -0000 (UTC)
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Lynn McGuire <lynnmcguire5@gmail.com> schrieb:
> On 11/12/2024 2:59 PM, Thomas Koenig wrote:

>> Hm... maybe another point. If you want to find discrepancies in
>> argument lists, you could concatenate all your Fortran source files
>> into one (which will be large, I presume) and then run "gfortran
>> -fsyntax-only" on it.  You could then get error messages like
>> 
>> $ cat mismatch.f
>>        subroutine foo(a)
>>        real a
>>        end
>> 
>>        subroutine bar
>>        call foo(42)
>>        end
>> $ gfortran -fsyntax-only mismatch.f
>> mismatch.f:6:72:
>> 
>>      6 |       call foo(42)
>>        |                                                                        1
>> Error: Type mismatch in argument 'a' at (1); passed INTEGER(4) to REAL(4)
>> 
>> which you could then investigate.
>
> Yeah, I really do not want to do that as it will be only a special run. 
> I want the errors to show up during each compile so that the programmer 
> will fix them right then and there.

Then modules are your best choice, I think.

On the other hand, -fsyntax-only is very fast because it does not
do code generation at all.  It might be worth a try to see how
long it takes on your whole codebase, and if it can be integrated
into your normal compilation process.

> And we had a user run into an unbalanced argument call to a subroutine 
> on Monday.  One of us had changed a subroutine argument list and fixed 8 
> out of the 9 calls.  No telling how many of those land mines are sitting 
> in our software.

You will find out with -fsyntax-only.  Another possibility is -flto, but
then the final "linking" step will take a very long time.  Might speed
up things in the resulting executable, though.