[Bug c/70688] New: bogus OpenACC data clause errors involving reductions

[cesar at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70688

            Bug ID: 70688
           Summary: bogus OpenACC data clause errors involving reductions
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Keywords: openacc
          Severity: normal
          Priority: P3
         Component: c
          Assignee: cesar at gcc dot gnu.org
          Reporter: cesar at gcc dot gnu.org
                CC: tschwinge at gcc dot gnu.org
  Target Milestone: ---

Created attachment 38285
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=38285&action=edit
test case

Here is the output of the attached test case when it is build with -fopenacc:

tr1.c: In function ‘sum’:
tr1.c:12:9: error: ‘s’ appears both in data and map clauses
 #pragma acc parallel num_gangs (10) copy (s) reduction (+:s)
         ^~~

There are two problems with this. 1) the c FE should not be reporting a data
map clause error on a reduction variable. 2) That error only gets detected some
of the time, depending on the ordering of the clauses (e.g. a data clause
involving variable 'v' appears before a reduction clause involving 'v' in the
clause list). A third problem would be that this error message is not specific
to OpenACC.

The c++ FE also has a similar problem.