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[libc++] Tweak how we check constraints on shared_ptr(nullptr_t) (#94996)

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This avoids breaking code that should arguably be valid but technically
isn't after enforcing the constraints on shared_ptr's constructors. A
new LWG issue was filed to fix this in the Standard.

This patch applies the expected resolution of this issue to avoid
flip-flopping users whose code should always be considered valid.

See #93071 for more context.
This commit is contained in:
Louis Dionne
2024-06-11 16:45:12 -04:00
committed by GitHub
parent 982b4b6f4d
commit 16f2aa1a2d
5 changed files with 28 additions and 9 deletions
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2
libcxx/include/__memory/shared_ptr.h
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@@ -404,7 +404,7 @@ struct __shared_ptr_deleter_ctor_reqs {
};
template <class _Dp, class _Tp>
using __shared_ptr_nullptr_deleter_ctor_reqs = _And<is_move_constructible<_Dp>, __well_formed_deleter<_Dp, nullptr_t> >;
using __shared_ptr_nullptr_deleter_ctor_reqs = _And<is_move_constructible<_Dp>, __well_formed_deleter<_Dp, _Tp*> >;
#if defined(_LIBCPP_ABI_ENABLE_SHARED_PTR_TRIVIAL_ABI)
# define _LIBCPP_SHARED_PTR_TRIVIAL_ABI __attribute__((__trivial_abi__))

7
libcxx/test/std/utilities/memory/util.smartptr/util.smartptr.shared/util.smartptr.shared.const/nullptr_t_deleter.pass.cpp
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@@ -32,17 +32,16 @@ int A::count = 0;
// LWG 3233. Broken requirements for shared_ptr converting constructors
// https://cplusplus.github.io/LWG/issue3233
static_assert( std::is_constructible<std::shared_ptr<int>, std::nullptr_t, test_deleter<int> >::value, "");
static_assert(!std::is_constructible<std::shared_ptr<int>, std::nullptr_t, bad_deleter>::value, "");
static_assert(!std::is_constructible<std::shared_ptr<int>, std::nullptr_t, no_nullptr_deleter>::value, "");
static_assert(!std::is_constructible<std::shared_ptr<int>, std::nullptr_t, bad_deleter>::value, "");
static_assert(!std::is_constructible<std::shared_ptr<int>, std::nullptr_t, no_move_deleter>::value, "");
#if TEST_STD_VER >= 17
static_assert( std::is_constructible<std::shared_ptr<int[]>, std::nullptr_t, test_deleter<int> >::value, "");
static_assert(std::is_constructible<std::shared_ptr<int[]>, std::nullptr_t, test_deleter<int[]> >::value, "");
static_assert(!std::is_constructible<std::shared_ptr<int[]>, std::nullptr_t, bad_deleter>::value, "");
static_assert(!std::is_constructible<std::shared_ptr<int[]>, std::nullptr_t, no_nullptr_deleter>::value, "");
static_assert(!std::is_constructible<std::shared_ptr<int[]>, std::nullptr_t, no_move_deleter>::value, "");
static_assert( std::is_constructible<std::shared_ptr<int[5]>, std::nullptr_t, test_deleter<int> >::value, "");
static_assert(std::is_constructible<std::shared_ptr<int[5]>, std::nullptr_t, test_deleter<int[5]> >::value, "");
static_assert(!std::is_constructible<std::shared_ptr<int[5]>, std::nullptr_t, bad_deleter>::value, "");
static_assert(!std::is_constructible<std::shared_ptr<int[5]>, std::nullptr_t, no_nullptr_deleter>::value, "");
static_assert(!std::is_constructible<std::shared_ptr<int[5]>, std::nullptr_t, no_move_deleter>::value, "");

12
libcxx/test/std/utilities/memory/util.smartptr/util.smartptr.shared/util.smartptr.shared.const/nullptr_t_deleter_allocator.pass.cpp
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@@ -33,17 +33,21 @@ int A::count = 0;
// LWG 3233. Broken requirements for shared_ptr converting constructors
// https://cplusplus.github.io/LWG/issue3233
static_assert( std::is_constructible<std::shared_ptr<int>, std::nullptr_t, test_deleter<int>, test_allocator<int> >::value, "");
static_assert(!std::is_constructible<std::shared_ptr<int>, std::nullptr_t, bad_deleter, test_allocator<int> >::value, "");
static_assert(!std::is_constructible<std::shared_ptr<int>, std::nullptr_t, no_nullptr_deleter, test_allocator<int> >::value, "");
static_assert(!std::is_constructible<std::shared_ptr<int>, std::nullptr_t, bad_deleter, test_allocator<int> >::value,
"");
static_assert(!std::is_constructible<std::shared_ptr<int>, std::nullptr_t, no_move_deleter, test_allocator<int> >::value, "");
#if TEST_STD_VER >= 17
static_assert( std::is_constructible<std::shared_ptr<int[]>, std::nullptr_t, test_deleter<int>, test_allocator<int> >::value, "");
static_assert(
std::is_constructible<std::shared_ptr<int[]>, std::nullptr_t, test_deleter<int[]>, test_allocator<int> >::value,
"");
static_assert(!std::is_constructible<std::shared_ptr<int[]>, std::nullptr_t, bad_deleter, test_allocator<int> >::value, "");
static_assert(!std::is_constructible<std::shared_ptr<int[]>, std::nullptr_t, no_nullptr_deleter, test_allocator<int> >::value, "");
static_assert(!std::is_constructible<std::shared_ptr<int[]>, std::nullptr_t, no_move_deleter, test_allocator<int> >::value, "");
static_assert( std::is_constructible<std::shared_ptr<int[5]>, std::nullptr_t, test_deleter<int>, test_allocator<int> >::value, "");
static_assert(
std::is_constructible<std::shared_ptr<int[5]>, std::nullptr_t, test_deleter<int[5]>, test_allocator<int> >::value,
"");
static_assert(!std::is_constructible<std::shared_ptr<int[5]>, std::nullptr_t, bad_deleter, test_allocator<int> >::value, "");
static_assert(!std::is_constructible<std::shared_ptr<int[5]>, std::nullptr_t, no_nullptr_deleter, test_allocator<int> >::value, "");
static_assert(!std::is_constructible<std::shared_ptr<int[5]>, std::nullptr_t, no_move_deleter, test_allocator<int> >::value, "");

8
libcxx/test/std/utilities/memory/util.smartptr/util.smartptr.shared/util.smartptr.shared.const/pointer_deleter.pass.cpp
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@@ -115,6 +115,14 @@ int main(int, char**)
}
#endif // TEST_STD_VER >= 11
#if TEST_STD_VER >= 14
{
// See https://github.com/llvm/llvm-project/pull/93071#issuecomment-2158494851
auto deleter = [](auto pointer) { delete pointer; };
std::shared_ptr<int> p(new int, deleter);
}
#endif
test_function_type();
return 0;
}

8
libcxx/test/std/utilities/memory/util.smartptr/util.smartptr.shared/util.smartptr.shared.const/pointer_deleter_allocator.pass.cpp
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@@ -165,5 +165,13 @@ int main(int, char**)
test_allocator<Derived[4]> >::value, "");
}
#if TEST_STD_VER >= 14
{
// See https://github.com/llvm/llvm-project/pull/93071#issuecomment-2158494851
auto deleter = [](auto pointer) { delete pointer; };
std::shared_ptr<int> p(new int, deleter, std::allocator<int>());
}
#endif
return 0;
}