Index: gcc/testsuite/gfortran.dg/typebound_override_1.f90
===================================================================
--- gcc/testsuite/gfortran.dg/typebound_override_1.f90	(revision 177733)
+++ gcc/testsuite/gfortran.dg/typebound_override_1.f90	(working copy)
@@ -23,7 +23,7 @@ module m
      procedure, nopass :: b => b2  ! { dg-error "should have matching result types and ranks" }
      procedure, nopass :: c => c2  ! { dg-warning "Possible character length mismatch" }
      procedure, nopass :: d => d2  ! valid, check for commutativity (+,*)
-     procedure, nopass :: e => e2  ! { dg-warning "Possible character length mismatch" }
+     procedure, nopass :: e => e2  ! { dg-error "Character length mismatch" }
   end type
 
 contains
Index: gcc/fortran/interface.c
===================================================================
--- gcc/fortran/interface.c	(revision 177733)
+++ gcc/fortran/interface.c	(working copy)
@@ -3574,7 +3574,8 @@ gfc_check_typebound_override (gfc_symtree* proc, g
 	  switch (compval)
 	  {
 	    case -1:
-	    case 1:
+	    case  1:
+	    case -3:
 	      gfc_error ("Character length mismatch between '%s' at '%L' and "
 			 "overridden FUNCTION", proc->name, &where);
 	      return FAILURE;
Index: gcc/fortran/frontend-passes.c
===================================================================
--- gcc/fortran/frontend-passes.c	(revision 177733)
+++ gcc/fortran/frontend-passes.c	(working copy)
@@ -682,7 +682,7 @@ optimize_comparison (gfc_expr *e, gfc_intrinsic_op
 	  && op1->ts.type != BT_COMPLEX && op2->ts.type != BT_COMPLEX))
     {
       eq = gfc_dep_compare_expr (op1, op2);
-      if (eq == -2)
+      if (eq <= -2)
 	{
 	  /* Replace A // B < A // C with B < C, and A // B < C // B
 	     with A < C.  */
Index: gcc/fortran/dependency.c
===================================================================
--- gcc/fortran/dependency.c	(revision 177733)
+++ gcc/fortran/dependency.c	(working copy)
@@ -230,8 +230,12 @@ gfc_dep_compare_functions (gfc_expr *e1, gfc_expr
 	return -2;      
 }
 
-/* Compare two values.  Returns 0 if e1 == e2, -1 if e1 < e2, +1 if e1 > e2,
-   and -2 if the relationship could not be determined.  */
+/* Compare two expressions.  Return values:
+   * +1 if e1 > e2
+   * 0 if e1 == e2
+   * -1 if e1 < e2
+   * -2 if the relationship could not be determined
+   * -3 if e1 /= e2, but we cannot tell which one is larger.  */
 
 int
 gfc_dep_compare_expr (gfc_expr *e1, gfc_expr *e2)
@@ -304,9 +308,9 @@ gfc_dep_compare_expr (gfc_expr *e1, gfc_expr *e2)
 	  r = gfc_dep_compare_expr (e1->value.op.op2, e2->value.op.op2);
 	  if (l == 0 && r == 0)
 	    return 0;
-	  if (l == 0 && r != -2)
+	  if (l == 0 && r > -2)
 	    return r;
-	  if (l != -2 && r == 0)
+	  if (l > -2 && r == 0)
 	    return l;
 	  if (l == 1 && r == 1)
 	    return 1;
@@ -317,9 +321,9 @@ gfc_dep_compare_expr (gfc_expr *e1, gfc_expr *e2)
 	  r = gfc_dep_compare_expr (e1->value.op.op2, e2->value.op.op1);
 	  if (l == 0 && r == 0)
 	    return 0;
-	  if (l == 0 && r != -2)
+	  if (l == 0 && r > -2)
 	    return r;
-	  if (l != -2 && r == 0)
+	  if (l > -2 && r == 0)
 	    return l;
 	  if (l == 1 && r == 1)
 	    return 1;
@@ -354,9 +358,9 @@ gfc_dep_compare_expr (gfc_expr *e1, gfc_expr *e2)
 	  r = gfc_dep_compare_expr (e1->value.op.op2, e2->value.op.op2);
 	  if (l == 0 && r == 0)
 	    return 0;
-	  if (l != -2 && r == 0)
+	  if (l > -2 && r == 0)
 	    return l;
-	  if (l == 0 && r != -2)
+	  if (l == 0 && r > -2)
 	    return -r;
 	  if (l == 1 && r == -1)
 	    return 1;
@@ -375,8 +379,8 @@ gfc_dep_compare_expr (gfc_expr *e1, gfc_expr *e2)
       l = gfc_dep_compare_expr (e1->value.op.op1, e2->value.op.op1);
       r = gfc_dep_compare_expr (e1->value.op.op2, e2->value.op.op2);
 
-      if (l == -2)
-	return -2;
+      if (l <= -2)
+	return l;
 
       if (l == 0)
 	{
@@ -387,7 +391,7 @@ gfc_dep_compare_expr (gfc_expr *e1, gfc_expr *e2)
 	  if (e1_left->expr_type == EXPR_CONSTANT
 	      && e2_left->expr_type == EXPR_CONSTANT
 	      && e1_left->value.character.length
-	        != e2_left->value.character.length)
+		 != e2_left->value.character.length)
 	    return -2;
 	  else
 	    return r;
@@ -411,7 +415,7 @@ gfc_dep_compare_expr (gfc_expr *e1, gfc_expr *e2)
     }
 
   if (e1->expr_type != e2->expr_type)
-    return -2;
+    return -3;
 
   switch (e1->expr_type)
     {
@@ -434,7 +438,7 @@ gfc_dep_compare_expr (gfc_expr *e1, gfc_expr *e2)
       if (are_identical_variables (e1, e2))
 	return 0;
       else
-	return -2;
+	return -3;
 
     case EXPR_OP:
       /* Intrinsic operators are the same if their operands are the same.  */
@@ -1406,7 +1410,7 @@ gfc_check_element_vs_section( gfc_ref *lref, gfc_r
       if (!start || !end)
 	return GFC_DEP_OVERLAP;
       s = gfc_dep_compare_expr (start, end);
-      if (s == -2)
+      if (s <= -2)
 	return GFC_DEP_OVERLAP;
       /* Assume positive stride.  */
       if (s == -1)
@@ -1553,7 +1557,7 @@ gfc_check_element_vs_element (gfc_ref *lref, gfc_r
   if (contains_forall_index_p (r_start) || contains_forall_index_p (l_start))
     return GFC_DEP_OVERLAP;
 
-  if (i != -2)
+  if (i > -2)
     return GFC_DEP_NODEP;
   return GFC_DEP_EQUAL;
 }
