Hi!

On Wed, 4 Nov 2015 18:21:36 +0100, Jakub Jelinek <jakub@redhat.com> wrote:
> On Wed, Nov 04, 2015 at 06:15:14PM +0100, Thomas Schwinge wrote:
> > > --- a/gcc/fortran/openmp.c
> > > +++ b/gcc/fortran/openmp.c
> > 
> > > @@ -3028,6 +3015,22 @@ resolve_omp_clauses (gfc_code *code, gfc_omp_clauses *omp_clauses,
> > >  	n->sym->mark = 1;
> > >      }
> > >  
> > > +  /* OpenACC reductions.  */
> > > +  if (openacc)
> > > +    {
> > > +      for (n = omp_clauses->lists[OMP_LIST_REDUCTION]; n; n = n->next)
> > > +	n->sym->mark = 0;
> > 
> > Maybe I'm just confugsed, but if setting all these to zero here...
> > 
> > > +
> > > +      for (n = omp_clauses->lists[OMP_LIST_REDUCTION]; n; n = n->next)
> > > +	{
> > > +	  if (n->sym->mark)
> > > +	    gfc_error ("Symbol %qs present on multiple clauses at %L",
> > > +		       n->sym->name, &n->where);
> > > +	  else
> > > +	    n->sym->mark = 1;
> > 
> > ... won't this just always run into the "else" branch?
> 
> The point is to check if some symbol isn't present multiple times in
> reduction clause(s).  So the first loop clears the flag as it could have
> arbitrary values, and the second loop will diagnose an error if n->sym
> is present multiple times in the list.  reduction(+: a, b, a) and the like.
> In C/C++ FE we use bitmaps for this, in Fortran FE we have mark
> field for those purposes.

Thanks for the explanation -- I'd missed the fact that several "n" might
refer to the same "sym"...  ;-)


Grüße
 Thomas