[all-commits] [llvm/llvm-project] efa287: [libc++] Slightly simplify max_size and add new te...

[Peng Liu via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: efa287dd8a0920b20c3fe69253d8438ec8944383
      https://github.com/llvm/llvm-project/commit/efa287dd8a0920b20c3fe69253d8438ec8944383
  Author: Peng Liu <winner245 at hotmail.com>
  Date:   2025-02-05 (Wed, 05 Feb 2025)

  Changed paths:
    M libcxx/include/__vector/vector_bool.h
    A libcxx/test/std/containers/sequences/vector.bool/max_size.pass.cpp
    M libcxx/test/std/containers/sequences/vector/vector.capacity/max_size.pass.cpp

  Log Message:
  -----------
  [libc++] Slightly simplify max_size and add new tests for vector (#119990)

This PR slightly simplifies the implementation of `vector<bool>::max_size`
and adds extensive tests for the `max_size()` function for both `vector<bool>`
and `vector<T>`. The main purposes of the new tests include:

- Verify correctness of `max_size()` under various `size_type` and
  `difference_type` definitions: check that `max_size()` works properly
  with allocators that have custom `size_type` and `difference_type`. This
  is particularly useful for `vector<bool>`, as different `size_type` lead
  to different `__storage_type` of different word lengths, resulting in
  varying `max_size()` values for `vector<bool>`. Additionally, different
  `difference_type` also sets different upper limit of `max_size()` for
  both `vector<bool>` and `std::vector`. These tests were previously
  missing.

- Eliminate incorrect implementations: Special tests are added to identify and
  reject incorrect implementations of `vector<bool>::max_size` that unconditionally
  return `std::min<size_type>(size-max, __internal_cap_to_external(allocator-max-size))`.
  This can cause overflow in the `__internal_cap_to_external()` call and lead
  to incorrect results. The new tests ensure that such incorrect
  implementations are identified.



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