Fix ICE in gfc_trans_subcomponent_assign due to NULL components.

	PR fortran/78259
	* gcc/fortran/trans-expr.c (gfc_trans_subcomponent_assign): Guard
	against NULL values.

	PR fortran/78259
	* gcc/testsuite/gfortran.dg/pr78259.f90: New test.

From-SVN: r242010

gcc/fortran/ChangeLog

+2016-11-09  Fritz O. Reese <fritzoreese@gmail.com>
+
+	PR fortran/78259
+	* trans-expr.c (gfc_trans_subcomponent_assign): Guard against NULL
+	values.
+
 2016-11-09  Steve Kargl <kargl@gcc.gnu.org>
 	    Janus Weil  <janus@gcc.gnu.org>
 

gcc/fortran/trans-expr.c

@@ -7327,7 +7327,8 @@ gfc_trans_subcomponent_assign (tree dest, gfc_component * cm, gfc_expr * expr,
       gfc_constructor *c = gfc_constructor_first (expr->value.constructor);
       /* We mark that the entire union should be initialized with a contrived
          EXPR_NULL expression at the beginning.  */
-      if (c->n.component == NULL && c->expr->expr_type == EXPR_NULL)
+      if (c != NULL && c->n.component == NULL
+	  && c->expr != NULL && c->expr->expr_type == EXPR_NULL)
         {
           tmp = build2_loc (input_location, MODIFY_EXPR, void_type_node,
 		            dest, build_constructor (TREE_TYPE (dest), NULL));

gcc/testsuite/ChangeLog

+2016-11-09  Fritz O. Reese <fritzoreese@gmail.com>
+
+	PR fortran/78259
+	* gfortran.dg/pr78259.f90: New test.
+
 2016-11-09  Janus Weil  <janus@gcc.gnu.org>
 
 	PR fortran/60777

gcc/testsuite/gfortran.dg/pr78259.f90

+! { dg-do "compile" }
+! { dg-options "-fdec-structure" }
+!
+! PR fortran/78259
+!
+! ICE in gfc_trans_subcomponent_assign
+!
+
+subroutine sub
+  structure /s/
+    union
+      map
+        integer n(2)
+      end map
+      map
+        integer(8) m /2/
+      end map
+    end union
+  end structure
+  record /s/ r
+  r.n(1) = 1
+end