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[libc++] Fix padding calculation for function reference types #142125

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Merged
merged 1 commit into from
Jun 3, 2025
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[libc++] Fix padding calculation for function reference types #142125

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15 changes: 11 additions & 4 deletions libcxx/include/__memory/compressed_pair.h
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Original file line number Diff line number Diff line change
Expand Up @@ -15,7 +15,6 @@
#include <__type_traits/datasizeof.h>
#include <__type_traits/is_empty.h>
#include <__type_traits/is_final.h>
#include <__type_traits/is_reference.h>

#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
# pragma GCC system_header
Expand Down Expand Up @@ -63,9 +62,17 @@ inline const size_t __compressed_pair_alignment = _LIBCPP_ALIGNOF(_Tp);
template <class _Tp>
inline const size_t __compressed_pair_alignment<_Tp&> = _LIBCPP_ALIGNOF(void*);

template <class _ToPad,
bool _Empty = ((is_empty<_ToPad>::value && !__libcpp_is_final<_ToPad>::value) ||
is_reference<_ToPad>::value || sizeof(_ToPad) == __datasizeof_v<_ToPad>)>
template <class _ToPad>
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Do this have to be updated as well?

llvm-project/lldb/packages/Python/lldbsuite/test/make/libcxx-simulators-common/compressed_pair.h

Lines 75 to 81 in 18e5131

template <class _ToPad> class __compressed_pair_padding {
char __padding_[((is_empty<_ToPad>::value &&
!__lldb_is_final<_ToPad>::value) ||
is_reference<_ToPad>::value)
? 0
: sizeof(_ToPad) - __datasizeof_v<_ToPad>];
};

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Looks like that changes in lldbsuite should belong to another PR. I've opened #142516.

inline const bool __is_reference_or_unpadded_object =
(is_empty<_ToPad>::value && !__libcpp_is_final<_ToPad>::value) || sizeof(_ToPad) == __datasizeof_v<_ToPad>;

template <class _Tp>
inline const bool __is_reference_or_unpadded_object<_Tp&> = true;

template <class _Tp>
inline const bool __is_reference_or_unpadded_object<_Tp&&> = true;

template <class _ToPad, bool _Empty = __is_reference_or_unpadded_object<_ToPad> >
class __compressed_pair_padding {
char __padding_[sizeof(_ToPad) - __datasizeof_v<_ToPad>] = {};
};
Expand Down
19 changes: 19 additions & 0 deletions ...d/utilities/smartptr/unique.ptr/unique.ptr.class/unique.ptr.ctor/pointer_deleter.pass.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -32,6 +32,8 @@ bool my_free_called = false;

void my_free(void*) { my_free_called = true; }

TEST_CONSTEXPR_CXX23 void deleter_function(A*) {}

#if TEST_STD_VER >= 11
struct DeleterBase {
TEST_CONSTEXPR_CXX23 void operator()(void*) const {}
Expand Down Expand Up @@ -325,20 +327,37 @@ TEST_CONSTEXPR_CXX23 void test_nullptr() {
#endif
}

template <bool IsArray>
TEST_CONSTEXPR_CXX23 void test_function_reference() {
typedef typename std::conditional<!IsArray, A, A[]>::type VT;
{
std::unique_ptr<VT, void (&)(A*)> u(nullptr, deleter_function);
assert(u.get() == nullptr);
assert(u.get_deleter() == deleter_function);
}
{
std::unique_ptr<VT, void (&)(A*)> u(nullptr, deleter_function);
assert(u.get() == nullptr);
assert(u.get_deleter() == deleter_function);
}
}

TEST_CONSTEXPR_CXX23 bool test() {
{
test_basic</*IsArray*/ false>();
test_nullptr<false>();
test_basic_single();
test_sfinae<false>();
test_noexcept<false>();
test_function_reference<false>();
}
{
test_basic</*IsArray*/ true>();
test_nullptr<true>();
test_sfinae<true>();
test_sfinae_runtime();
test_noexcept<true>();
test_function_reference<true>();
}

return true;
Expand Down
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