[Bug fortran/51208] [OOP] ALLOCATE with SOURCE= or MOLD=: Diagnose if variable occurs twice

[sgk at troutmask dot apl.washington.edu]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51208

--- Comment #3 from Steve Kargl <sgk at troutmask dot apl.washington.edu> 2011-11-18 18:40:31 UTC ---
On Fri, Nov 18, 2011 at 04:03:04PM +0000, burnus at gcc dot gnu.org wrote:
> 
> Well, it is not. One can restrict one to the common case of expr->expr_type ==
> EXPR_VARIABLE and just do the same as for STAT=: Checking whether the variable
> is the same.
> 
> Will that catch all wrong usage? No, but it will catch the most common mistake
> of choosing the wrong variable. That's as illustrated above the same with
> STAT=.
> 
> I am sure that Intel's compiler does not do anything more advanced - and it
> would have found the mistake I made in PR 51207.
> 

Although I think this is equilavent to putting a bandaid
on a AK-47 bullet hole, here you go

troutmask:sgk[246] cat foo.f90

program foo
  use bar
  allocate(x(2), source=x)
end program foo


troutmask:sgk[245] gfc4x -o z -Wall -Wextra foo.f90
foo.f90:4.11-24:

  allocate(x(2), source=x)
           1            2
Error: Allocate-object at (1) shall not appear in a source-expr or mold-expr at
(2)


Index: resolve.c
===================================================================
--- resolve.c    (revision 181489)
+++ resolve.c    (working copy)
@@ -7173,6 +7173,38 @@ resolve_allocate_deallocate (gfc_code *c
       }
     }

+  /* If source-expr or mold-expr is a variable, check that it
+     is not an alloc-object.  */
+  if (code->expr3 && code->expr3->expr_type == EXPR_VARIABLE)
+    {
+      for (p = code->ext.alloc.list; p; p = p->next)
+    if (p->expr->symtree->n.sym->name == code->expr3->symtree->n.sym->name)
+      {
+        gfc_ref *ref1, *ref2;
+        bool found = true;
+
+        for (ref1 = p->expr->ref, ref2 = code->expr3->ref; ref1 && ref2;
+         ref1 = ref1->next, ref2 = ref2->next)
+          {
+        if (ref1->type != REF_COMPONENT || ref2->type != REF_COMPONENT)
+          continue;
+        if (ref1->u.c.component->name != ref2->u.c.component->name)
+          {
+            found = false;
+            break;
+          }
+          }
+
+        if (found)
+          {
+        gfc_error ("Allocate-object at %L shall not appear in a "
+               "source-expr or mold-expr at %L",
+                &p->expr->where, &code->expr3->where);
+        break;
+          }
+      }
+    }
+
   /* Check that an allocate-object appears only once in the statement.  
      FIXME: Checking derived types is disabled.  */
   for (p = code->ext.alloc.list; p; p = p->next)