clang/test/SemaCXX/warn-unused-value-cxx11.cpp

   1 // RUN: %clang_cc1 -std=c++11 -fsyntax-only -verify -Wunused-value %s
   2
   3 void f() __attribute__((const));
   4
   5 namespace PR18571 {
   6 // Unevaluated contexts should not trigger unused result warnings.
   7 template <typename T>
   8 auto foo(T) -> decltype(f(), bool()) { // Should not warn.
   9   return true;
  10 }
  11
  12 void g() {
  13   foo(1);
  14 }
  15
  16 void h() {
  17   int i = 0;
  18   (void)noexcept(++i); // expected-warning {{expression with side effects has no effect in an unevaluated context}}
  19   decltype(i++) j = 0; // expected-warning {{expression with side effects has no effect in an unevaluated context}}
  20 }
  21
  22 struct S {
  23   S operator++(int);
  24   S(int i);
  25   S();
  26
  27   int& f();
  28   S g();
  29 };
  30
  31 void j() {
  32   S s;
  33   int i = 0;
  34   (void)noexcept(s++); // Ok
  35   (void)noexcept(i++); // expected-warning {{expression with side effects has no effect in an unevaluated context}}
  36   (void)noexcept(i = 5); // expected-warning {{expression with side effects has no effect in an unevaluated context}}
  37   (void)noexcept(s = 5); // Ok
  38
  39   (void)sizeof(s.f()); // Ok
  40   (void)sizeof(s.f() = 5); // expected-warning {{expression with side effects has no effect in an unevaluated context}}
  41   (void)noexcept(s.g() = 5); // Ok
  42 }
  43
  44 }
  45
  46 namespace volatile_array {
  47 void test() {
  48   char a[10];
  49   volatile char b[10];
  50   a; // expected-warning-re {{expression result unused{{$}}}}
  51   b; // expected-warning-re {{expression result unused{{$}}}}
  52 }
  53 }