[Bug fortran/81615] New: save-temps and gfortran produces *.f90 files instead of *.i or *i90 files

["barrowes at alum dot mit.edu" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81615

            Bug ID: 81615
           Summary: save-temps and gfortran produces *.f90 files instead
                    of *.i or *i90 files
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
          Assignee: unassigned at gcc dot gnu.org
          Reporter: barrowes at alum dot mit.edu
  Target Milestone: ---

If I have a file test1.f:

      program test2
      real x
      x=3.0
C#ifdef DDD
C      x=2.0
C#endif
      print *,'x=',x
      end

and I compile it with:

gfortran -save-temps -o test0 test0.f

I get two temporary files, test0.o and test0.s.

If I uncomment the directive:

      program test2
      real x
      x=3.0
#ifdef MPI
      x=2.0
#endif
      print *,'x=',x
      end

and compile with:

gfortran -cpp -save-temps -o test0 test0.f

In addition to the two temporary files above, a test0.f90 is produced that
looks like:

# 1 "test0.f"
# 1 "<built-in>"
# 1 "<command-line>"
# 1 "test0.f"
      program test2
      real x
      x=3.0
      print *,'x=',x
      end


I was under the impression that I would get a test0.i file since the only
documentation of using -save-temps I can find comes from the gcc docs:
https://gcc.gnu.org/onlinedocs/gcc/Developer-Options.html#index-save-temps
which mentions *.i files in their example.


And if I have a file test1.f90:

program test1
real x
x=3.0
#ifdef MPI
x=2.0
#endif
print *,'x=',x
end

and I compile with:

gfortran -cpp -save-temps -o test1 test1.f90

The test1.o and test1.s files are produced, but no preprocessed fortran source
file is produced (I suppose because the source file already has the f90
extension).

How can I get a preprocessed source file in this case? Where is this behavior
of -save-temps producing *.f90 files documented? Can I change the f90 extension
of the preprocessed temporary files to i or i90 instead of f90?