clang/test/SemaCXX/libcxx_move_hack.cpp

   1 // RUN: %clang_cc1 -fsyntax-only %s -std=c++98 -verify
   2 // expected-no-diagnostics
   3
   4 // This is a test for a hack in Clang that works around an issue with libc++
   5 // 3.1's std::move and std::forward implementation. When emulating these
   6 // functions in C++98 mode, libc++ 3.1 has a "fake rvalue reference" type, and
   7 // std::move will return by value when given an instance of that type.
   8
   9 namespace std {
  10   struct rv {};
  11
  12   template<bool B, typename T> struct enable_if;
  13   template<typename T> struct enable_if<true, T> { typedef T type; };
  14
  15   template<typename T> typename enable_if<__is_convertible(T, rv), T>::type move(T &);
  16   template<typename T> typename enable_if<!__is_convertible(T, rv), T&>::type move(T &);
  17
  18   template<typename U, typename T> typename enable_if<__is_convertible(T, rv), U>::type forward(T &);
  19   template<typename U, typename T> typename enable_if<!__is_convertible(T, rv), U&>::type forward(T &);
  20 }
  21
  22 struct A {};
  23 void f(A a, std::rv rv) {
  24   a = std::move(a);
  25   rv = std::move(rv);
  26
  27   a = std::forward<A>(a);
  28   rv = std::forward<std::rv>(rv);
  29
  30   a = std::forward<A&>(a);
  31   rv = std::forward<std::rv&>(rv);
  32 }