File: libcxx_move_hack.cpp

package info (click to toggle)
llvm-toolchain-20 1%3A20.1.8-1~exp1
  • links: PTS, VCS
  • area: main
  • in suites: experimental
  • size: 2,111,388 kB
  • sloc: cpp: 7,438,767; ansic: 1,393,871; asm: 1,012,926; python: 241,728; f90: 86,635; objc: 75,411; lisp: 42,144; pascal: 17,286; sh: 10,027; ml: 5,082; perl: 4,730; awk: 3,523; makefile: 3,349; javascript: 2,251; xml: 892; fortran: 672
file content (32 lines) | stat: -rw-r--r-- 1,130 bytes parent folder | download | duplicates (24)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
// RUN: %clang_cc1 -fsyntax-only %s -std=c++98 -verify
// expected-no-diagnostics

// This is a test for a hack in Clang that works around an issue with libc++
// 3.1's std::move and std::forward implementation. When emulating these
// functions in C++98 mode, libc++ 3.1 has a "fake rvalue reference" type, and
// std::move will return by value when given an instance of that type.

namespace std {
  struct rv {};

  template<bool B, typename T> struct enable_if;
  template<typename T> struct enable_if<true, T> { typedef T type; };

  template<typename T> typename enable_if<__is_convertible(T, rv), T>::type move(T &);
  template<typename T> typename enable_if<!__is_convertible(T, rv), T&>::type move(T &);

  template<typename U, typename T> typename enable_if<__is_convertible(T, rv), U>::type forward(T &);
  template<typename U, typename T> typename enable_if<!__is_convertible(T, rv), U&>::type forward(T &);
}

struct A {};
void f(A a, std::rv rv) {
  a = std::move(a);
  rv = std::move(rv);

  a = std::forward<A>(a);
  rv = std::forward<std::rv>(rv);

  a = std::forward<A&>(a);
  rv = std::forward<std::rv&>(rv);
}