[Bug fortran/50536] an input item shall not appear as the do-variable of any io-implied-do

["burnus at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50536

Tobias Burnus <burnus at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |accepts-invalid,
                   |                            |diagnostic, patch
                 CC|                            |burnus at gcc dot gnu.org

--- Comment #5 from Tobias Burnus <burnus at gcc dot gnu.org> ---
Simple - and completely untested - patch. I am not quite sure whether nested
io-implied-dos can appear - if they can, the patch would be insufficient.
However, I cannot come up with any nested io-implied-do for READ (which
requires the items to be variables). Hence, the patch is presumably sufficient.

--- a/gcc/fortran/io.c
+++ b/gcc/fortran/io.c
@@ -3057,2 +3057,12 @@ match_io_iterator (io_kind k, gfc_code **result)

+  if (k == M_READ)
+    for (new_code = head; new_code; new_code = head->next)
+      if (iter->var->symtree == new_code->expr1->symtree)
+       {
+         gfc_error ("In a READ statement, the input item at %L shall not "
+                    "be the do-variable of any io-implied-do");
+         m = MATCH_ERROR;
+         goto cleanup;
+       }
+
   new_code = gfc_get_code ();