<algorithm>: Stable sorting algorithms don't accept element types of large alignments by default #5800
Description
Describe the bug
Currently, _Optimistic_temporary_buffer used for stable sorting algorithms relies on _Aligned_storage_t, which doesn't accept overaligned element types by default due to ABI compatibility issues.
Line 491 in eb024e0
Lines 1246 to 1266 in eb024e0
Command-line test case
#include <algorithm>
#include <array>
#include <iterator>
struct alignas(32) large_element {
std::array<unsigned char, 32> elems;
friend auto operator<=>(const large_element&, const large_element&) = default;
};
int main() {
large_element arr[42]{};
std::stable_sort(std::begin(arr), std::end(arr));
std::stable_partition(std::begin(arr), std::end(arr), [](const auto&) { return true; });
std::inplace_merge(std::begin(arr), std::begin(arr), std::end(arr));
std::ranges::stable_sort(arr);
std::ranges::stable_partition(arr, [](const auto&) { return true; });
std::ranges::inplace_merge(arr, std::ranges::begin(arr));
}Expected behavior
This program correctly compiles and runs.
STL version
Probably all versions with default error set for aligned_storage_t.
Additional context
As _Optimistic_temporary_buffer is only internally used and only used on the stack, perhaps it's safe to change the size and/or the alignment of the buffer with its name changed.