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[libcxx] Fix PR22771 - Support access control SFINAE in the library version of is_convertible.

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Summary:
Currently the conversion check does not take place in a context where access control SFINAE is applied. This patch changes the context of the test expression so that SFINAE occurs if access control does not permit the conversion.

Related bug: https://llvm.org/bugs/show_bug.cgi?id=22771

Reviewers: mclow.lists, rsmith, dim

Reviewed By: dim

Subscribers: dim, rodrigc, emaste, cfe-commits

Differential Revision: http://reviews.llvm.org/D8461

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@233552 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Eric Fiselier 2015-03-30 15:22:20 +00:00
parent 4f274d0633
commit 4bd15469a9
2 changed files with 18 additions and 5 deletions
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17
include/type_traits
View File

@ -848,7 +848,16 @@ template <class _T1, class _T2> struct _LIBCPP_TYPE_VIS_ONLY is_convertible
namespace __is_convertible_imp
{
template <class _Tp> char __test(_Tp);
template <class _Tp> void __test_convert(_Tp);
template <class _From, class _To, class = void>
struct __is_convertible_test : public false_type {};
template <class _From, class _To>
struct __is_convertible_test<_From, _To,
decltype(__test_convert<_To>(_VSTD::declval<_From>()))> : public true_type
{};
template <class _Tp> __two __test(...);
#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
template <class _Tp> _Tp&& __source();
@ -883,10 +892,8 @@ template <class _T1, class _T2,
unsigned _T2_is_array_function_or_void = __is_convertible_imp::__is_array_function_or_void<_T2>::value>
struct __is_convertible
: public integral_constant<bool,
#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
sizeof(__is_convertible_imp::__test<_T2>(__is_convertible_imp::__source<_T1>())) == 1
#else
sizeof(__is_convertible_imp::__test<_T2>(__is_convertible_imp::__source<_T1>())) == 1
__is_convertible_imp::__is_convertible_test<_T1, _T2>::value
#if defined(_LIBCPP_HAS_NO_RVALUE_REFERENCES)
&& !(!is_function<_T1>::value && !is_reference<_T1>::value && is_reference<_T2>::value
&& (!is_const<typename remove_reference<_T2>::type>::value
|| is_volatile<typename remove_reference<_T2>::type>::value)

6
test/std/utilities/meta/meta.rel/is_convertible.pass.cpp
View File

@ -186,4 +186,10 @@ int main()
static_assert((std::is_convertible<volatile NonCopyable&, const volatile NonCopyable&>::value), "");
static_assert((std::is_convertible<const volatile NonCopyable&, const volatile NonCopyable&>::value), "");
static_assert((!std::is_convertible<const NonCopyable&, NonCopyable&>::value), "");
// This test requires Access control SFINAE which we only have in C++11 or when
// we are using the compiler builtin for is_convertible.
#if __cplusplus >= 201103L || !defined(_LIBCPP_USE_IS_CONVERTIBLE_FALLBACK)
test_is_not_convertible<NonCopyable&, NonCopyable>();
#endif
}