[Bug fortran/56007] New: Remarkably bad error message with DO array=1,2

[Bug fortran/56007] New: Remarkably bad error message with DO array=1,2

[tobi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56007

             Bug #: 56007
           Summary: Remarkably bad error message with DO array=1,2
    Classification: Unclassified
           Product: gcc
           Version: 4.7.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: tobi@gcc.gnu.org


$ cat t3.f90
real iw1(90)
do iw1=1,2
end do
END 
$ gfortran t3.f90
t3.f90:2.6:

do iw1=1,2
      1
Error: Loop variable at (1) cannot be a sub-component
t3.f90:3.3:

end do
   1
Error: Expecting END PROGRAM statement at (1)
$ 

match.c has the following check in gfc_match_iterator:
  if (var->ref != NULL)
    {
      gfc_error ("Loop variable at %C cannot be a sub-component");
      goto cleanup;
    }
This assumes that all ref's are component ref's.  I verified that the bug
happens with 4.7.2, but looking at the code I would assume that this also
happens with the trunk.

This error message was mildly confusing, as I ran into this in a Fortran 77
codebase where there are no components.

[Bug fortran/56007] Remarkably bad error message with DO array=1,2

[dominiq at lps dot ens.fr]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56007

Dominique d'Humieres <dominiq at lps dot ens.fr> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2013-01-16
     Ever Confirmed|0                           |1

--- Comment #1 from Dominique d'Humieres <dominiq at lps dot ens.fr> 2013-01-16 17:11:48 UTC ---
I get the same error with gcc version 4.4.6 and trunk.

[Bug fortran/56007] Remarkably bad error message with DO array=1,2

[anlauf at gmx dot de]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56007

Harald Anlauf <anlauf at gmx dot de> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |anlauf at gmx dot de

--- Comment #2 from Harald Anlauf <anlauf at gmx dot de> 2013-01-16 17:40:00 UTC ---
(In reply to comment #1)
> I get the same error with gcc version 4.4.6 and trunk.

It dates back to g95, so "no regression".

[Bug fortran/56007] Remarkably bad error message with DO array=1,2

[tobi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56007

--- Comment #3 from Tobias Schlüter <tobi at gcc dot gnu.org> 2013-01-22 12:56:26 UTC ---
Just for the fun of it, another confusing way this error message appears:
$ cat t3.f90
character c(5)

do c=2,3
end do

END 
$ gfortran t3.f90
t3.f90:3.4:

do c=2,3
    1
Error: Loop variable at (1) cannot be a sub-component
t3.f90:4.3:

end do
   1
Error: Expecting END PROGRAM statement at (1)
$ 

Of course this behavior is expected once you look at the code.


Another related error message that's not really helpful:
$ cat t3.f90
real iw1(90) ! same for integer

do iw1(1)=1,2
end do

END 
$ gfortran t3.f90
t3.f90:3:

do iw1(1)=1,2
1
Error: Unclassifiable statement at (1)
t3.f90:4.3:

end do
   1
Error: Expecting END PROGRAM statement at (1)
tobi@tobias-schluters-computer src$

This latter error message is an artefact of fixed-form, where
 doiw1(90)=1,2
cannot be distinguished from an assignment to an array-valued variable (though
it could catch that the variable is not declared).

Here's a fixed-form example showing the various possibilities that involve
arrays:
$ cat t3.f
         integer iw1(90), doiw1(90)
         do iw1(1)=1,2
         end do
         do iw1(1)=1
         do iw1=1
         do iw1=1,2
         end do
         END 
$ gfortran t3.f
t3.f:2.9:

         do iw1(1)=1,2                                                  
         1
Error: Unclassifiable statement at (1)
t3.f:3.12:

         end do                                                         
            1
Error: Expecting END PROGRAM statement at (1)
t3.f:6.15:

         do iw1=1,2                                                     
               1
Error: Loop variable at (1) cannot be a sub-component
t3.f:7.12:

         end do                                                         
            1
Error: Expecting END PROGRAM statement at (1)
$