re PR c++/44444 (-Wunused-but-set-variable problem with field references)

	PR c++/44444
	* expr.c (mark_exp_read): Handle INDIRECT_REF.
	* cvt.c (convert_to_void): Handle INDIRECT_REF like
	handled_component_p.

	* g++.dg/warn/Wunused-var-12.C: New test.

From-SVN: r160388

gcc/cp/ChangeLog

 2010-06-07  Jakub Jelinek  <jakub@redhat.com>
 
+	PR c++/44444
+	* expr.c (mark_exp_read): Handle INDIRECT_REF.
+	* cvt.c (convert_to_void): Handle INDIRECT_REF like
+	handled_component_p.
+
 	PR c++/44443
 	* decl.c (initialize_local_var): If TREE_USED is set on the type,
 	set also DECL_READ_P on the decl.

gcc/cp/cvt.c

@@ -834,7 +834,9 @@ convert_to_void (tree expr, const char *implicit, tsubst_flags_t complain)
 
       while (TREE_CODE (exprv) == COMPOUND_EXPR)
 	exprv = TREE_OPERAND (exprv, 1);
-      if (DECL_P (exprv) || handled_component_p (exprv))
+      if (DECL_P (exprv)
+	  || handled_component_p (exprv)
+	  || TREE_CODE (exprv) == INDIRECT_REF)
 	/* Expr is not being 'used' here, otherwise we whould have
 	   called mark_{rl}value_use use here, which would have in turn
 	   called mark_exp_read.  Rather, we call mark_exp_read directly

gcc/cp/expr.c

 /* Convert language-specific tree expression to rtl instructions,
    for GNU compiler.
    Copyright (C) 1988, 1992, 1993, 1994, 1995, 1996, 1997, 1998,
-   2000, 2001, 2002, 2003, 2004, 2007 Free Software Foundation, Inc.
+   2000, 2001, 2002, 2003, 2004, 2007, 2010 Free Software Foundation, Inc.
 
 This file is part of GCC.
 
@@ -132,6 +132,7 @@ mark_exp_read (tree exp)
     case IMAGPART_EXPR:
     CASE_CONVERT:
     case ADDR_EXPR:
+    case INDIRECT_REF:
       mark_exp_read (TREE_OPERAND (exp, 0));
       break;
     case COMPOUND_EXPR:

gcc/testsuite/ChangeLog

 2010-06-07  Jakub Jelinek  <jakub@redhat.com>
 
+	PR c++/44444
+	* g++.dg/warn/Wunused-var-12.C: New test.
+
 	PR c++/44443
 	* c-c++-common/Wunused-var-11.c: New test.
 

gcc/testsuite/g++.dg/warn/Wunused-var-12.C

+// PR c++/44444
+// { dg-do compile }
+// { dg-options "-Wunused" }
+
+struct S
+{
+  const int &u;
+  const int &v;
+  S (const int &a, const int &b) : u(a), v(b) { }
+};
+
+bool
+f1 ()
+{
+  bool t = false;
+  S z = S (1, 2);
+  t |= z.u == 1;
+  t |= z.v == 2;
+  return t;
+}
+
+void
+f2 ()
+{
+  S z = S (1, 2);
+  z.u;		// { dg-warning "no effect" }
+}
+
+int i;
+
+void
+f3 ()
+{
+  S z = S (1, 2);
+  i++, z.u;	// { dg-warning "no effect" }
+}