[all-commits] [llvm/llvm-project] 155fd9: [libc++] `flat_meow` transparent comparator string...

[Hui via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 155fd97a66349926026f05e3fe2fba55abd894be
      https://github.com/llvm/llvm-project/commit/155fd97a66349926026f05e3fe2fba55abd894be
  Author: Hui <hui.xie1990 at gmail.com>
  Date:   2025-06-06 (Fri, 06 Jun 2025)

  Changed paths:
    M libcxx/include/__flat_map/flat_map.h
    M libcxx/include/__flat_map/flat_multimap.h
    M libcxx/include/__flat_set/flat_set.h
    M libcxx/test/std/containers/container.adaptors/flat.map/flat.map.access/at_transparent.pass.cpp
    M libcxx/test/std/containers/container.adaptors/flat.map/flat.map.access/index_transparent.pass.cpp
    M libcxx/test/std/containers/container.adaptors/flat.map/flat.map.modifiers/erase_key_transparent.pass.cpp
    M libcxx/test/std/containers/container.adaptors/flat.map/flat.map.modifiers/insert_or_assign_transparent.pass.cpp
    M libcxx/test/std/containers/container.adaptors/flat.map/flat.map.modifiers/insert_transparent.pass.cpp
    M libcxx/test/std/containers/container.adaptors/flat.map/flat.map.modifiers/try_emplace_transparent.pass.cpp
    M libcxx/test/std/containers/container.adaptors/flat.map/flat.map.operations/contains_transparent.pass.cpp
    M libcxx/test/std/containers/container.adaptors/flat.map/flat.map.operations/count_transparent.pass.cpp
    M libcxx/test/std/containers/container.adaptors/flat.map/flat.map.operations/equal_range_transparent.pass.cpp
    M libcxx/test/std/containers/container.adaptors/flat.map/flat.map.operations/find_transparent.pass.cpp
    M libcxx/test/std/containers/container.adaptors/flat.map/flat.map.operations/lower_bound_transparent.pass.cpp
    M libcxx/test/std/containers/container.adaptors/flat.map/flat.map.operations/upper_bound_transparent.pass.cpp
    M libcxx/test/std/containers/container.adaptors/flat.multimap/flat.multimap.modifiers/erase_key_transparent.pass.cpp
    M libcxx/test/std/containers/container.adaptors/flat.multimap/flat.multimap.modifiers/insert_transparent.pass.cpp
    M libcxx/test/std/containers/container.adaptors/flat.multimap/flat.multimap.operations/contains_transparent.pass.cpp
    M libcxx/test/std/containers/container.adaptors/flat.multimap/flat.multimap.operations/count_transparent.pass.cpp
    M libcxx/test/std/containers/container.adaptors/flat.multimap/flat.multimap.operations/equal_range_transparent.pass.cpp
    M libcxx/test/std/containers/container.adaptors/flat.multimap/flat.multimap.operations/find_transparent.pass.cpp
    M libcxx/test/std/containers/container.adaptors/flat.multimap/flat.multimap.operations/lower_bound_transparent.pass.cpp
    M libcxx/test/std/containers/container.adaptors/flat.multimap/flat.multimap.operations/upper_bound_transparent.pass.cpp
    M libcxx/test/std/containers/container.adaptors/flat.set/flat.set.modifiers/erase_key_transparent.pass.cpp
    M libcxx/test/std/containers/container.adaptors/flat.set/flat.set.modifiers/insert_transparent.pass.cpp
    M libcxx/test/std/containers/container.adaptors/flat.set/flat.set.operations/contains_transparent.pass.cpp
    M libcxx/test/std/containers/container.adaptors/flat.set/flat.set.operations/count_transparent.pass.cpp
    M libcxx/test/std/containers/container.adaptors/flat.set/flat.set.operations/equal_range_transparent.pass.cpp
    M libcxx/test/std/containers/container.adaptors/flat.set/flat.set.operations/find_transparent.pass.cpp
    M libcxx/test/std/containers/container.adaptors/flat.set/flat.set.operations/lower_bound_transparent.pass.cpp
    M libcxx/test/std/containers/container.adaptors/flat.set/flat.set.operations/upper_bound_transparent.pass.cpp

  Log Message:
  -----------
  [libc++] `flat_meow` transparent comparator string literals (#133654)

See discussion in https://cplusplus.github.io/LWG/issue4239

    std::flat_map<std::string, int, std::less<>> m;
    m.try_emplace("abc", 5);  // hard error

The reason is that we specify in 23.6.8.7 [flat.map.modifiers]/p21
the effect to be as if `ranges::upper_bound` is called.

`ranges::upper_bound` requires indirect_strict_weak_order, which
requires the comparator to be invocable for all combinations. In this
case, it requires

    const char (&)[4] < const char (&)[4]

to be well-formed, which is no longer the case in C++26 after
https://wg21.link/P2865R6.

This patch uses `std::upper_bound` instead.



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