[all-commits] [llvm/llvm-project] 979e93: [libc++] Fix improper static_cast in std::deque an...

[Peng Liu via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 979e9361f0e0426e555c94cb8b1a64c655805765
      https://github.com/llvm/llvm-project/commit/979e9361f0e0426e555c94cb8b1a64c655805765
  Author: Peng Liu <winner245 at hotmail.com>
  Date:   2024-12-13 (Fri, 13 Dec 2024)

  Changed paths:
    M libcxx/include/__split_buffer
    M libcxx/include/deque

  Log Message:
  -----------
  [libc++] Fix improper static_cast in std::deque and __split_buffer (#119106)

This PR addresses the improper use of `static_cast` to `size_t` where
`size_type` is intended. Although the `size_type` member type of STL
containers is usually a synonym of `std::size_t`, there is no guarantee
that they are always equivalent. The C++ standard does not mandate this
equivalence.

In libc++'s implementations of `std::deque`, `std::vector`, and
`__split_buffer`, the `size_type` member type is defined as
`std::allocator_traits<allocator_type>::size_type`, which is either
`allocator_type::size_type` if available or
`std::make_unsigned<difference_type>::type`. While it is true for
`std::allocator` that the `size_type` member type is `std::size_t`, for
user-defined allocator types, they may mismatch. This justifies the need
to replace `static_cast<size_t>` with `static_cast<size_type>` in this
PR.



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