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Unconditionally lower std::string's alignment requirement from 16 to 8. #68925

Merged
merged 1 commit into from
Jan 24, 2024
Merged

Unconditionally lower std::string's alignment requirement from 16 to 8. #68925

merged 1 commit into from
Jan 24, 2024

Commits on Jan 23, 2024

  1. Unconditionally change std::string's alignment to 8. 

        Save memory by providing the allocator more freedom to allocate the most
    efficient size class by dropping the alignment requirements for std::string's
    pointer from 16 to 8. This changes the output of std::string::max_size,
    which makes it ABI breaking.

    That said, the discussion concluded that we don't care about this ABI
    break and would like this change enabled universally.

    The ABI break isn't one of layout or "class size", but rather the value of
    "max_size()" changes, which in turn changes whether std::bad_alloc or
    std::length_error is thrown for large allocations.

    This change is the child of PR llvm#68807, which enabled the change behind an ABI
    flag.
    @EricWF
    EricWF committed Jan 23, 2024
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