Index: frontend-passes.c
===================================================================
--- frontend-passes.c	(Revision 164618)
+++ frontend-passes.c	(Arbeitskopie)
@@ -165,10 +165,10 @@ optimize_assignment (gfc_code * c)
   lhs = c->expr1;
   rhs = c->expr2;
 
-  /* Optimize away a = trim(b), where a is a character variable.  */
-
   if (lhs->ts.type == BT_CHARACTER)
     {
+      /* Optimize away a = trim(b), where a is a character variable.  */
+
       if (rhs->expr_type == EXPR_FUNCTION &&
 	  rhs->value.function.isym &&
 	  rhs->value.function.isym->id == GFC_ISYM_TRIM)
@@ -177,8 +177,69 @@ optimize_assignment (gfc_code * c)
 	  optimize_assignment (c);
 	  return;
 	}
+
+      /* Fill up blanks on the right-hand side on assignment, if they extend
+	 the length by less than 8 bytes.  This is an arbitrary limit.*/
+
+#define STRING_PAD_LIMIT 8
+
+      if (rhs->expr_type == EXPR_CONSTANT)
+	{
+	  mpz_t lhs_l, diff;
+	  bool valid_lhs = false;
+
+	  mpz_init (lhs_l);
+	  mpz_init (diff);
+
+	  if (lhs->ref && lhs->ref->type == REF_SUBSTRING)
+	    {
+	      if (lhs->ref->u.ss.start->expr_type == EXPR_CONSTANT
+		  && lhs->ref->u.ss.end->expr_type == EXPR_CONSTANT)
+		{
+		  mpz_sub (lhs_l, lhs->ref->u.ss.end->value.integer,
+			   lhs->ref->u.ss.start->value.integer);
+		  mpz_add_ui (lhs_l, lhs_l, 1u);
+		  valid_lhs = true;
+		}
+	    }
+	  else if (lhs->ts.u.cl->length)
+	    {
+	      mpz_set (lhs_l, lhs->ts.u.cl->length->value.integer);
+	      valid_lhs = true;
+	    }
+
+	  if (valid_lhs)
+	    {
+	      mpz_sub_ui (diff, lhs_l, rhs->value.character.length);
+	      if (mpz_cmp_si (diff, 0) > 0
+		  && mpz_cmp_si (diff, STRING_PAD_LIMIT) < 0)
+		{
+		  long int sz;
+		  int i;
+		  gfc_char_t *v;
+
+		  sz = mpz_get_si (lhs_l);
+		  v = gfc_get_wide_string (sz);
+
+		  memcpy (v, rhs->value.character.string,
+			  rhs->value.character.length*sizeof(gfc_char_t));
+
+		  for (i=rhs->value.character.length; i<sz; i++)
+		    v[i] = ' ';
+
+		  gfc_free (rhs->value.character.string);
+		  rhs->value.character.string = v;
+		  rhs->value.character.length = sz;
+		}
+	    }
+
+	  mpz_clear (lhs_l);
+	  mpz_clear(diff);
+	}
     }
 
+#undef STRING_PAD_LIMIT
+
   if (lhs->rank > 0 && gfc_check_dependency (lhs, rhs, true) == 0)
     optimize_binop_array_assignment (c, &rhs, false);
 }