re PR c++/47783 (Warning 'set but not used' [-Wunused-but-set-parameter]…

re PR c++/47783 (Warning 'set but not used' [-Wunused-but-set-parameter] incorrectly issued for update through reference wrapper)

	PR c++/47783
	* cvt.c (convert_from_reference): Call mark_exp_read.

	* g++.dg/warn/Wunused-parm-4.C: New test.

From-SVN: r170255

gcc/cp/ChangeLog

+2011-02-17  Jakub Jelinek  <jakub@redhat.com>
+
+	PR c++/47783
+	* cvt.c (convert_from_reference): Call mark_exp_read.
+
 2011-02-11  Dodji Seketeli  <dodji@redhat.com>
 
 	PR c++/47172

gcc/cp/cvt.c

@@ -512,6 +512,7 @@ convert_from_reference (tree val)
       tree t = TREE_TYPE (TREE_TYPE (val));
       tree ref = build1 (INDIRECT_REF, t, val);
 
+      mark_exp_read (val);
        /* We *must* set TREE_READONLY when dereferencing a pointer to const,
 	  so that we get the proper error message if the result is used
 	  to assign to.  Also, &* is supposed to be a no-op.  */

gcc/testsuite/ChangeLog

+2011-02-17  Jakub Jelinek  <jakub@redhat.com>
+
+	PR c++/47783
+	* g++.dg/warn/Wunused-parm-4.C: New test.
+
 2011-02-17  Alexandre Oliva  <aoliva@redhat.com>
 	    Jan Hubicka  <jh@suse.cz>
 

gcc/testsuite/g++.dg/warn/Wunused-parm-4.C

+// PR c++/47783
+// { dg-do compile }
+// { dg-options "-Wunused -W" }
+
+struct R
+{
+  int &i;
+};
+
+void
+foo (R r, int &s)
+{
+  r.i = 7;
+  s = 8;
+}
+
+int
+bar ()
+{
+  int x = 1, y = 1;
+  R r = { x };
+  foo (r, y);
+  return x + y;
+}