[Bug fortran/30973] undetected name conflict: variables may be named like modules

[burnus at gcc dot gnu dot org]

------- Comment #3 from burnus at gcc dot gnu dot org  2007-02-26 21:36 -------
> Tobias, the same happens if the MODULE foo contains anything and the ONLY part
> actually lists something. I omitted this to keep the testcase short.

Good news. That means that indicates that my patch does the right thing and is
not too kludgy.

In read_module, p = find_use_name_n (name, &j);  is used to find renamed
symbols. If a symbol is not in in the only list, p == NULL. Since the module
name is never in the only list, we have "p = NULL".

Index: module.c
===================================================================
--- module.c    (Revision 122328)
+++ module.c
@@ -3438,6 +3438,9 @@
          /* Get the jth local name for this symbol.  */
          p = find_use_name_n (name, &j);

+         if (p == NULL && strcmp (name, module_name) == 0)
+           p = name;
+
          /* Skip symtree nodes not in an ONLY clause, unless there
             is an existing symtree loaded from another USE
             statement.  */


Another related bug: "use foo, only: foo" gives no error.
------------- test case -------
MODULE foo
  integer :: i
END MODULE

PROGRAM test_foo
  use foo, only: foo  ! { dg-error "been used as an external module name" }
  USE foo, ONLY: i => foo! { dg-error "been used as an external module name" }
  USE foo, ONLY: foo => i! { dg-error "been used as an external module name" }
END PROGRAM
--------------------------

Possible patch below; note: Even with the patch
  use bar, only foo => j
  use foo
is possible. But as soon as one accesses foo, e.g. "foo = 5", an error is
given.
This is in the line with other compilers.

Index: module.c
===================================================================
*** module.c    (revision 122328)
--- module.c    (working copy)
*************** gfc_match_use (void)
*** 619,624 ****
--- 619,632 ----
                goto cleanup;
            }

+         if (strcmp (new->use_name, module_name) == 0
+             || strcmp (new->local_name, module_name) == 0)
+           {
+             gfc_error ("The name '%s' at %C has already been used as "
+                        "an external module name.", module_name);
+             goto cleanup;
+           }
+
          break;

        case INTERFACE_USER_OP:


-- 

burnus at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |burnus at gcc dot gnu dot
                   |                            |org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30973