LWG2442: call_once() shouldn't DECAY_COPY(). Patch from K-Ballo.

This patch fixes LWG issue 2422 by removing the DECAY_COPY from call once.
The review can be found here: http://reviews.llvm.org/D10191

llvm-svn: 239654
This commit is contained in:
Eric Fiselier 2015-06-13 02:23:00 +00:00
parent 678ad2f9da
commit 793f59e767
3 changed files with 79 additions and 23 deletions

View File

@ -442,7 +442,11 @@ void call_once(once_flag&, _Callable&&, _Args&&...);
template<class _Callable>
_LIBCPP_INLINE_VISIBILITY
void call_once(once_flag&, _Callable);
void call_once(once_flag&, _Callable&);
template<class _Callable>
_LIBCPP_INLINE_VISIBILITY
void call_once(once_flag&, const _Callable&);
#endif // _LIBCPP_HAS_NO_VARIADICS
@ -465,7 +469,11 @@ private:
#else // _LIBCPP_HAS_NO_VARIADICS
template<class _Callable>
friend
void call_once(once_flag&, _Callable);
void call_once(once_flag&, _Callable&);
template<class _Callable>
friend
void call_once(once_flag&, const _Callable&);
#endif // _LIBCPP_HAS_NO_VARIADICS
};
@ -474,15 +482,10 @@ private:
template <class _Fp>
class __call_once_param
{
_Fp __f_;
_Fp& __f_;
public:
#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
_LIBCPP_INLINE_VISIBILITY
explicit __call_once_param(_Fp&& __f) : __f_(_VSTD::move(__f)) {}
#else
_LIBCPP_INLINE_VISIBILITY
explicit __call_once_param(const _Fp& __f) : __f_(__f) {}
#endif
explicit __call_once_param(_Fp& __f) : __f_(__f) {}
_LIBCPP_INLINE_VISIBILITY
void operator()()
@ -496,7 +499,7 @@ private:
_LIBCPP_INLINE_VISIBILITY
void __execute(__tuple_indices<_Indices...>)
{
__invoke(_VSTD::move(_VSTD::get<0>(__f_)), _VSTD::move(_VSTD::get<_Indices>(__f_))...);
__invoke(_VSTD::get<0>(_VSTD::move(__f_)), _VSTD::get<_Indices>(_VSTD::move(__f_))...);
}
};
@ -505,15 +508,10 @@ private:
template <class _Fp>
class __call_once_param
{
_Fp __f_;
_Fp& __f_;
public:
#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
_LIBCPP_INLINE_VISIBILITY
explicit __call_once_param(_Fp&& __f) : __f_(_VSTD::move(__f)) {}
#else
_LIBCPP_INLINE_VISIBILITY
explicit __call_once_param(const _Fp& __f) : __f_(__f) {}
#endif
explicit __call_once_param(_Fp& __f) : __f_(__f) {}
_LIBCPP_INLINE_VISIBILITY
void operator()()
@ -543,9 +541,9 @@ call_once(once_flag& __flag, _Callable&& __func, _Args&&... __args)
{
if (__flag.__state_ != ~0ul)
{
typedef tuple<typename decay<_Callable>::type, typename decay<_Args>::type...> _Gp;
__call_once_param<_Gp> __p(_Gp(__decay_copy(_VSTD::forward<_Callable>(__func)),
__decay_copy(_VSTD::forward<_Args>(__args))...));
typedef tuple<_Callable&&, _Args&&...> _Gp;
_Gp __f(_VSTD::forward<_Callable>(__func), _VSTD::forward<_Args>(__args)...);
__call_once_param<_Gp> __p(__f);
__call_once(__flag.__state_, &__p, &__call_once_proxy<_Gp>);
}
}
@ -555,7 +553,7 @@ call_once(once_flag& __flag, _Callable&& __func, _Args&&... __args)
template<class _Callable>
inline _LIBCPP_INLINE_VISIBILITY
void
call_once(once_flag& __flag, _Callable __func)
call_once(once_flag& __flag, _Callable& __func)
{
if (__flag.__state_ != ~0ul)
{
@ -564,6 +562,18 @@ call_once(once_flag& __flag, _Callable __func)
}
}
template<class _Callable>
inline _LIBCPP_INLINE_VISIBILITY
void
call_once(once_flag& __flag, const _Callable& __func)
{
if (__flag.__state_ != ~0ul)
{
__call_once_param<const _Callable> __p(__func);
__call_once(__flag.__state_, &__p, &__call_once_proxy<const _Callable>);
}
}
#endif // _LIBCPP_HAS_NO_VARIADICS
_LIBCPP_END_NAMESPACE_STD

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@ -14,7 +14,7 @@
// struct once_flag;
// template<class Callable, class ...Args>
// void call_once(once_flag& flag, Callable func, Args&&... args);
// void call_once(once_flag& flag, Callable&& func, Args&&... args);
#include <mutex>
#include <thread>
@ -153,6 +153,35 @@ public:
}
};
class NonCopyable
{
#if !defined(__clang__)
// GCC 4.8 complains about the following being private
public:
NonCopyable(const NonCopyable&)
{
}
#else
NonCopyable(const NonCopyable&);
#endif
public:
NonCopyable() {}
void operator()(int&) {}
};
#if __cplusplus >= 201103L
// reference qualifiers on functions are a C++11 extension
struct RefQual
{
int lv_called, rv_called;
RefQual() : lv_called(0), rv_called(0) {}
void operator()() & { ++lv_called; }
void operator()() && { ++rv_called; }
};
#endif
#endif
int main()
@ -204,5 +233,22 @@ int main()
std::once_flag f;
std::call_once(f, MoveOnly(), MoveOnly());
}
// check LWG2442: call_once() shouldn't DECAY_COPY()
{
std::once_flag f;
int i = 0;
std::call_once(f, NonCopyable(), i);
}
#if __cplusplus >= 201103L
// reference qualifiers on functions are a C++11 extension
{
std::once_flag f1, f2;
RefQual rq;
std::call_once(f1, rq);
assert(rq.lv_called == 1);
std::call_once(f2, std::move(rq));
assert(rq.rv_called == 1);
}
#endif
#endif // _LIBCPP_HAS_NO_VARIADICS
}

View File

@ -127,7 +127,7 @@
<tr><td><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/lwg-defects.html#2438">2438</td><td>std::iterator inheritance shouldn't be mandated</td><td>Lenexa</td><td>Complete</td></tr>
<tr><td><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/lwg-defects.html#2439">2439</td><td>unique_copy() sometimes can't fall back to reading its output</td><td>Lenexa</td><td></td></tr>
<tr><td><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/lwg-defects.html#2440">2440</td><td>seed_seq::size() should be noexcept</td><td>Lenexa</td><td>Complete</td></tr>
<tr><td><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/lwg-defects.html#2442">2442</td><td>call_once() shouldn't DECAY_COPY()</td><td>Lenexa</td><td></td></tr>
<tr><td><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/lwg-defects.html#2442">2442</td><td>call_once() shouldn't DECAY_COPY()</td><td>Lenexa</td><td>Complete</td></tr>
<tr><td><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/lwg-defects.html#2448">2448</td><td>Non-normative Container destructor specification</td><td>Lenexa</td><td>Complete</td></tr>
<tr><td><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/lwg-defects.html#2454">2454</td><td>Add raw_storage_iterator::base() member</td><td>Lenexa</td><td>Complete</td></tr>
<tr><td><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/lwg-defects.html#2455">2455</td><td>Allocator default construction should be allowed to throw</td><td>Lenexa</td><td>Complete</td></tr>