[Bug fortran/51638] gfortran optimization breaks a single variable used as both input and output for subroutine call

[kargl at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51638

--- Comment #4 from kargl at gcc dot gnu.org 2012-01-03 19:05:27 UTC ---
(In reply to comment #3)
> (In reply to comment #1)
> > 
> > I can reproduce it with
> >   -O -m32
> > on x86-64-linux.
> 
> Fine you can reproduce it easily.
> 
> 
> > In terms of code validity, there are two other issues:
> 
> I definitely agree this code is not latest-Fortran-standard, but it implements
> a few F77 tricks which, from my view, are not really broken by the latest
> Fortran requirements. Or at least the other compilers and the other gfortran
> modes did not need to break these tricks yet. So I will hurry not to change
> anything in my code until you have a clear diagnostic of this bug. ;-)
> 
> Thanks for your help.

See comment #3 in the audit trail of this PR.  Your
Fortran code is invalid.  We have a clear diagnostic.
The bug is in your code not the Fortran compiler.