Fortran: Fix fn spec for character-returning functions

gcc/fortran/ChangeLog
	* trans-types.c (create_fn_spec): For character-returning functions,
	set the hidden string-length argument to 'R' only when the "len=:",
	i.e. deferred length which goes alongside with allocatable/pointer.

diff --git a/gcc/fortran/trans-types.c b/gcc/fortran/trans-types.c
index 220976babb8..637d2c71d01 100644
--- a/gcc/fortran/trans-types.c
+++ b/gcc/fortran/trans-types.c
@@ -3008,7 +3008,14 @@ create_fn_spec (gfc_symbol *sym, tree fntype)
 	}
       if (sym->ts.type == BT_CHARACTER)
 	{
-	  spec[spec_len++] = 'R';
+	  if (!sym->ts.u.cl->length
+	      && ((sym->attr.allocatable && sym->attr.target)
+		  || sym->attr.pointer))
+	    spec[spec_len++] = '.';
+	  if (!sym->ts.u.cl->length && sym->attr.allocatable)
+	    spec[spec_len++] = 'w';
+	  else
+	    spec[spec_len++] = 'R';
 	  spec[spec_len++] = ' ';
 	}
     }