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[cpp23] Remove use of std::aligned_storage in webrtc

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std::aligned_storage is deprecated in C++23, see linked bug. The only
webrtc usage (VoidUnion::inline_storage) employed the default Align
parameter (i.e. std::aligned_storage<Len>, not std::aligned_storage<Len,
Alignment>), which is defined as the largest alignment <= Len.

This patch replaces the usage with a char buffer of same size and
alignment alignof(std::max_align_t). In theory, this might increase
alignment and use more memory. In practice, local testing in my
machines showed no behavior change, since Len =
kInlineStorageWords * sizeof(uintptr_t) = 32 > 16 (maximum alignment
on linux x86_64) > 8 (maximum alignment on mac arm64).


Bug: chromium:388068052
Change-Id: If08b69f7a5ff7b716a66c8703e31eb5d4de14431
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/373800
Commit-Queue: Victor Vianna <victorvianna@google.com>
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Auto-Submit: Victor Vianna <victorvianna@google.com>
Reviewed-by: Tomas Gunnarsson <tommi@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#43842}
This commit is contained in:
Victor Hugo Vianna Silva 2025-02-03 10:43:14 +00:00 committed by WebRTC LUCI CQ
parent c262375415
commit a6f35491d6
1 changed files with 3 additions and 2 deletions
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5
rtc_base/untyped_function.h
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@ -30,8 +30,9 @@ enum : size_t { kInlineStorageWords = 4 };
union VoidUnion {
void* void_ptr;
FunVoid* fun_ptr;
typename std::aligned_storage<kInlineStorageWords * sizeof(uintptr_t)>::type
inline_storage;
// std::max_align_t satisfies alignment requirements for every type.
alignas(std::max_align_t) char inline_storage[kInlineStorageWords *
sizeof(uintptr_t)];
};
// Returns the number of elements of the `inline_storage` array required to