[Bug fortran/72798] Module (.mod) file changes even when interface does not

["dominiq at lps dot ens.fr" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=72798

Dominique d'Humieres <dominiq at lps dot ens.fr> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |WAITING
   Last reconfirmed|                            |2016-08-04
     Ever confirmed|0                           |1

--- Comment #3 from Dominique d'Humieres <dominiq at lps dot ens.fr> ---
> If I compile the attached module ('gfortran -c test_mod.f90') with and without
> the print statement commented out, I get .mod files which not only differ
> in contents, but also in size.

Why do you expect the .mod files be the same with or without a print statement?
IMO if two files differ in contents, it is likely they also differ in size.

AFAICT compiling several time the attached test does not regenerate the
test_mod.mod file unless I do some modification in the module. So you probably
need a more complex test to expose the behavior you are complaining about.

> Is there a way to force gfortran to treat all routines as being
> (internally) impure, unless explicitly declared as pure?

You can always give the IMPURE attribute to the routines, but I have no idea if
it helps.