re PR middle-end/30729 (value computed is not used warning with unused result of va_arg)

2007-02-15  Andrew Pinski  <andrew_pinski@playstation.sony.com>

        PR middle-end/30729
        * stmt.c (warn_if_unused_value): VA_ARG_EXPR has side
        effects unknown to this function, return early.

2007-02-15  Andrew Pinski  <andrew_pinski@playstation.sony.com>

        PR middle-end/30729
        * gcc.dg/Wunused-value-2.c: New testcase.

From-SVN: r122027

gcc/ChangeLog

+2007-02-15  Andrew Pinski  <andrew_pinski@playstation.sony.com>
+
+	PR middle-end/30729
+	* stmt.c (warn_if_unused_value): VA_ARG_EXPR has side
+	effects unknown to this function, return early.
+
 2007-02-15  Ian Lance Taylor  <iant@google.com>
 
 	* lower-subreg.c (move_eh_region_note): New static function.

gcc/stmt.c

@@ -1425,6 +1425,7 @@ warn_if_unused_value (tree exp, location_t locus)
     case TRY_CATCH_EXPR:
     case WITH_CLEANUP_EXPR:
     case EXIT_EXPR:
+    case VA_ARG_EXPR:
       return 0;
 
     case BIND_EXPR:

gcc/testsuite/ChangeLog

+2007-02-15  Andrew Pinski  <andrew_pinski@playstation.sony.com>
+
+	PR middle-end/30729
+	* gcc.dg/Wunused-value-2.c: New testcase.
+
 2007-02-15  Ian Lance Taylor  <iant@google.com>
 
 	* g++.dg/eh/subreg-1.C: New test.

gcc/testsuite/gcc.dg/Wunused-value-2.c

+/* Test -Wunused-value.  Bug 30729.  */
+/* { dg-do compile } */
+/* { dg-options "-Wunused-value" } */
+/* Make sure va_arg does not cause a value computed is not used warning
+   because it has side effects.   */
+#include <stdarg.h>
+
+int f(int t, ...)
+{
+  va_list a;
+  va_start (a, t);
+  va_arg(a, int);/* { dg-bogus "value computed is not used" } */
+  int t1 = va_arg(a, int);
+  va_end(a);
+  return t1;
+}
+
+