re PR c/50179 (wrong "set but not used" warning)

	PR c/50179
	* c-typeck.c (c_process_expr_stmt): Skip over nops and
	call mark_exp_read even if exprv is ADDR_EXPR.

	* c-c++-common/Wunused-var-14.c: New test.

From-SVN: r178110

gcc/ChangeLog

+2011-08-26  Jakub Jelinek  <jakub@redhat.com>
+
+	PR c/50179
+	* c-typeck.c (c_process_expr_stmt): Skip over nops and
+	call mark_exp_read even if exprv is ADDR_EXPR.
+
 2011-08-26  Richard Sandiford  <richard.sandiford@linaro.org>
 
 	* df-problems.c (df_note_bb_compute): Pass uses rather than defs

gcc/c-typeck.c

@@ -9109,7 +9109,11 @@ c_process_expr_stmt (location_t loc, tree expr)
   exprv = expr;
   while (TREE_CODE (exprv) == COMPOUND_EXPR)
     exprv = TREE_OPERAND (exprv, 1);
-  if (DECL_P (exprv) || handled_component_p (exprv))
+  while (CONVERT_EXPR_P (exprv))
+    exprv = TREE_OPERAND (exprv, 0);
+  if (DECL_P (exprv)
+      || handled_component_p (exprv)
+      || TREE_CODE (exprv) == ADDR_EXPR)
     mark_exp_read (exprv);
 
   /* If the expression is not of a type to which we cannot assign a line

gcc/testsuite/ChangeLog

+2011-08-26  Jakub Jelinek  <jakub@redhat.com>
+
+	PR c/50179
+	* c-c++-common/Wunused-var-14.c: New test.
+
 2011-08-26  Tom de Vries  <tom@codesourcery.com>
 
 	* gcc.dg/tree-ssa/ivopts-lt.c: New test.

gcc/testsuite/c-c++-common/Wunused-var-14.c

+/* PR c/50179 */
+/* { dg-options "-Wunused" } */
+/* { dg-do compile } */
+
+void bar (int, ...);
+
+char *
+foo (void)
+{
+  bar (1, (__extension__ ({ static char b[2]; b[0] = 1; b; })));
+  bar (1, ({ static char c[2]; c[0] = 1; c; }));
+  return ({ static char d[2]; d[0] = 1; d; });
+}