Re: [Patch, Fortran] PR32980 - Add GAMMA and LGAMMA intrinsics

[Tobias Schlüter <tobias dot schlueter at physik dot uni-muenchen dot de>]

Tobias Burnus wrote:
> Tobias Schlüter wrote:
> > I'm worried that this will lead to surprising results for people that
> > have their own GAMMA functions defined.  Maybe a new std class is
> > appropriate?  What's the opposite of "legacy"?  Maybe "incompatible",
> > as in "even incompatible extensions"?
>
> Are you suggest that GAMMA is only available with -std=f2008 and
> -std=incompatible? I would find it extremely surprising if -std=f2003
> and -std=gnu give a different result than -std=f2008! (Not that we have
> Fortran 2008 yet, but it will come rather sooner than later.)
>
> A proper Fortran program already uses "EXTERNAL GAMMA" or better an
> explicit interface for nonintrinsic functions. Additionally, GAMMA is
> present in several other compilers such as IBM lf95, g95 or openf95,
> which thus have the same problem.
>
> (When we have whole-file checks, one should put in a check whether a
> user routine has the same name as an intrinsic procedure when no
> intrinsic or external has been used, in which case a warning should be
> printed.)

Ok, since you and Steve agree on this, I have a suggestion that I think 
we all could live with: if the user defines a function that has the same 
name as an intrinsic available with the selected standard, issue a 
warning, perhaps only with -Wall.  Bonus points for a command line 
option that allows disabling intrinsics by name.

Thus,
      FUNCTION GAMMA(x)
        ...
      END FUNCTION

      PRINT *, GAMMA(x)
      END
will not call the function the user intended, but at least he will be 
able to understand why because the compiler told him something akin to
      FUNCTION GAMMA(x)
               1
Warning: 'GAMMA' declared at (1) is also the name of an intrinsic.  It 
can only be called via an explicit interface or if declared EXTERNAL.

If gamma is declared in a module the warning could be something like

Warning: 'GAMMA' declared at (1) may shadow the intrinsic of the same 
name.  In order to call the intrinsic, explicit INTRINSIC declarations 
may be required.

Cheers,
- Tobi