check.c (gfc_check_move_alloc): Introduce error to prevent aliasing between to and from arguments.

2016-11-05  Paul Thomas  <pault@gcc.gnu.org>

	* check.c (gfc_check_move_alloc): Introduce error to prevent
	aliasing between to and from arguments.

2016-11-05  Paul Thomas  <pault@gcc.gnu.org>

	* gfortran.dg/move_alloc_17.f03: New test.

From-SVN: r241872

gcc/fortran/ChangeLog

+2016-11-05  Paul Thomas  <pault@gcc.gnu.org>
+
+	* check.c (gfc_check_move_alloc): Introduce error to prevent
+	aliasing between to and from arguments.
+
 2016-11-05  Janus Weil  <janus@gcc.gnu.org>
 	    Manuel Lopez-Ibanez  <manu@gcc.gnu.org>
 

gcc/fortran/check.c

@@ -3342,6 +3342,16 @@ gfc_check_move_alloc (gfc_expr *from, gfc_expr *to)
       return false;
     }
 
+  /*  F2003 12.4.1.7  */
+  if (to->expr_type == EXPR_VARIABLE && from->expr_type ==EXPR_VARIABLE
+      && !strcmp (to->symtree->n.sym->name, from->symtree->n.sym->name))
+    {
+      gfc_error ("The FROM and TO arguments at %L are either the same object "
+		 "or subobjects thereof and so violate aliasing restrictions "
+		 "(F2003 12.4.1.7)", &to->where);
+      return false;
+    }
+
   /* CLASS arguments: Make sure the vtab of from is present.  */
   if (to->ts.type == BT_CLASS && !UNLIMITED_POLY (from))
     gfc_find_vtab (&from->ts);

gcc/testsuite/ChangeLog

+2016-11-05  Paul Thomas  <pault@gcc.gnu.org>
+
+	* gfortran.dg/move_alloc_17.f03: New test.
+
 2016-11-05  Richard Biener  <rguenther@suse.de>
 
 	PR bootstrap/78188

gcc/testsuite/gfortran.dg/move_alloc_17.f90

+! { dg-do compile }
+!
+! The call to MOVE_ALLOC below caused a seg fault in runtime.
+! This was discussed in:
+! https://groups.google.com/forum/#!topic/comp.lang.fortran/ZVLqXFYDZ0M
+! Richard Maine proposed that the code violated the restrictions on
+! actual arguments in F2003 12.4.1.7 and so the fix asserts that the
+! TO and FROM arguments cannot be the same object or subobjects thereof.
+!
+!
+program test_move_alloc
+  type :: linked_list
+     type(linked_list), allocatable :: link
+     integer :: value
+  end type linked_list
+  type(linked_list) :: test
+
+  allocate(test % link)
+  allocate(test % link % link)
+  call move_alloc(test % link, test % link % link) ! { dg-error "aliasing restrictions" }
+end program test_move_alloc