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[libc++] Remove alignment attributes from _LIBCPP_COMPRESSED_PAIR #158595

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Merged
merged 1 commit into from
Sep 25, 2025
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[libc++] Remove alignment attributes from _LIBCPP_COMPRESSED_PAIR #158595

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14 changes: 7 additions & 7 deletions libcxx/include/__memory/compressed_pair.h
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Original file line number Diff line number Diff line change
Expand Up @@ -28,8 +28,8 @@ _LIBCPP_BEGIN_NAMESPACE_STD
// understand how it works). //
// ================================================================================================================== //

// The first member is aligned to the alignment of the second member to force padding in front of the compressed pair
// in case there are members before it.
// On GCC, the first member is aligned to the alignment of the second member to force padding in front of the compressed
// pair in case there are members before it.
//
// For example:
// (assuming x86-64 linux)
Expand All @@ -53,6 +53,9 @@ _LIBCPP_BEGIN_NAMESPACE_STD
// Furthermore, that alignment must be the same as what was used in the old __compressed_pair layout, so we must
// handle reference types specially since alignof(T&) == alignof(T).
// See https://llvm.org/PR118559.
//
// On Clang, this is unnecessary, since we use anonymous structs instead, which automatically handle the alignment
// correctly.

#ifndef _LIBCPP_ABI_NO_COMPRESSED_PAIR_PADDING

Expand Down Expand Up @@ -104,18 +107,15 @@ class __compressed_pair_padding<_ToPad, true> {};
# else
# define _LIBCPP_COMPRESSED_PAIR(T1, Initializer1, T2, Initializer2) \
struct { \
_LIBCPP_NO_UNIQUE_ADDRESS \
__attribute__((__aligned__(::std::__compressed_pair_alignment<T2>))) T1 Initializer1; \
_LIBCPP_NO_UNIQUE_ADDRESS T1 Initializer1; \
_LIBCPP_NO_UNIQUE_ADDRESS ::std::__compressed_pair_padding<T1> _LIBCPP_CONCAT3(__padding1_, __LINE__, _); \
_LIBCPP_NO_UNIQUE_ADDRESS T2 Initializer2; \
_LIBCPP_NO_UNIQUE_ADDRESS ::std::__compressed_pair_padding<T2> _LIBCPP_CONCAT3(__padding2_, __LINE__, _); \
}

# define _LIBCPP_COMPRESSED_TRIPLE(T1, Initializer1, T2, Initializer2, T3, Initializer3) \
struct { \
_LIBCPP_NO_UNIQUE_ADDRESS \
__attribute__((__aligned__(::std::__compressed_pair_alignment<T2>), \
__aligned__(::std::__compressed_pair_alignment<T3>))) T1 Initializer1; \
_LIBCPP_NO_UNIQUE_ADDRESS T1 Initializer1; \
_LIBCPP_NO_UNIQUE_ADDRESS ::std::__compressed_pair_padding<T1> _LIBCPP_CONCAT3(__padding1_, __LINE__, _); \
_LIBCPP_NO_UNIQUE_ADDRESS T2 Initializer2; \
_LIBCPP_NO_UNIQUE_ADDRESS ::std::__compressed_pair_padding<T2> _LIBCPP_CONCAT3(__padding2_, __LINE__, _); \
Expand Down
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