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Fix PR34298 - Allow std::function with an incomplete return type.

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This patch fixes llvm.org/PR34298. Previously libc++ incorrectly evaluated
the __invokable trait via the converting constructor `function(Tp)` [with Tp = std::function]
whenever the copy constructor or copy assignment operator
was required. This patch further constrains that constructor to short
circut before evaluating the troublesome SFINAE when `Tp` matches
std::function.

The original patch is from Alex Lorenz.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@312890 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Eric Fiselier
2017-09-10 23:12:33 +00:00
parent 11762b4acd
commit f83132a4d1
3 changed files with 55 additions and 27 deletions
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36
include/functional
View File

@@ -1597,9 +1597,11 @@ class _LIBCPP_TEMPLATE_VIS function<_Rp(_ArgTypes...)>
return reinterpret_cast<__base*>(p);
}
template <class _Fp, bool = !is_same<_Fp, function>::value &&
__invokable<_Fp&, _ArgTypes...>::value>
struct __callable;
template <class _Fp, bool = __lazy_and<
integral_constant<bool, !is_same<__uncvref_t<_Fp>, function>::value>,
__invokable<_Fp&, _ArgTypes...>
>::value>
struct __callable;
template <class _Fp>
struct __callable<_Fp, true>
{
@@ -1612,6 +1614,9 @@ class _LIBCPP_TEMPLATE_VIS function<_Rp(_ArgTypes...)>
{
static const bool value = false;
};
template <class _Fp>
using _EnableIfCallable = typename enable_if<__callable<_Fp>::value>::type;
public:
typedef _Rp result_type;
@@ -1622,9 +1627,7 @@ public:
function(nullptr_t) _NOEXCEPT : __f_(0) {}
function(const function&);
function(function&&) _NOEXCEPT;
template<class _Fp, class = typename enable_if<
__callable<_Fp>::value && !is_same<_Fp, function>::value
>::type>
template<class _Fp, class = _EnableIfCallable<_Fp>>
function(_Fp);
#if _LIBCPP_STD_VER <= 14
@@ -1638,21 +1641,15 @@ public:
function(allocator_arg_t, const _Alloc&, const function&);
template<class _Alloc>
function(allocator_arg_t, const _Alloc&, function&&);
template<class _Fp, class _Alloc, class = typename enable_if<__callable<_Fp>::value>::type>
template<class _Fp, class _Alloc, class = _EnableIfCallable<_Fp>>
function(allocator_arg_t, const _Alloc& __a, _Fp __f);
#endif
function& operator=(const function&);
function& operator=(function&&) _NOEXCEPT;
function& operator=(nullptr_t) _NOEXCEPT;
template<class _Fp>
typename enable_if
<
__callable<typename decay<_Fp>::type>::value &&
!is_same<typename remove_reference<_Fp>::type, function>::value,
function&
>::type
operator=(_Fp&&);
template<class _Fp, class = _EnableIfCallable<_Fp>>
function& operator=(_Fp&&);
~function();
@@ -1854,13 +1851,8 @@ function<_Rp(_ArgTypes...)>::operator=(nullptr_t) _NOEXCEPT
}
template<class _Rp, class ..._ArgTypes>
template <class _Fp>
typename enable_if
<
function<_Rp(_ArgTypes...)>::template __callable<typename decay<_Fp>::type>::value &&
!is_same<typename remove_reference<_Fp>::type, function<_Rp(_ArgTypes...)>>::value,
function<_Rp(_ArgTypes...)>&
>::type
template <class _Fp, class>
function<_Rp(_ArgTypes...)>&
function<_Rp(_ArgTypes...)>::operator=(_Fp&& __f)
{
function(_VSTD::forward<_Fp>(__f)).swap(*this);