[all-commits] [llvm/llvm-project] da827d: [lldb][DataFormatter] Simplify std::unordered_map:...

[Michael Buch via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: da827d0896e5e66fe9130f8f4479537d3bbee1da
      https://github.com/llvm/llvm-project/commit/da827d0896e5e66fe9130f8f4479537d3bbee1da
  Author: Michael Buch <michaelbuch12 at gmail.com>
  Date:   2024-07-08 (Mon, 08 Jul 2024)

  Changed paths:
    M lldb/source/Plugins/Language/CPlusPlus/LibCxxUnorderedMap.cpp
    M lldb/test/API/functionalities/data-formatter/data-formatter-stl/libcxx/iterator/TestDataFormatterLibccIterator.py
    M lldb/test/API/functionalities/data-formatter/data-formatter-stl/libcxx/iterator/main.cpp

  Log Message:
  -----------
  [lldb][DataFormatter] Simplify std::unordered_map::iterator formatter (#97754)

Depends on https://github.com/llvm/llvm-project/pull/97752

This patch changes the way we retrieve the key/value pair in the
`std::unordered_map::iterator` formatter (similar to how we are changing
it for `std::map::iterator` in
https://github.com/llvm/llvm-project/pull/97713, the motivations being
the same).

The old logic was not very easy to follow, and encoded the libc++ layout
in non-obvious ways. But mainly it was also fragile to alignment
miscalculations (https://github.com/llvm/llvm-project/pull/97443); this
would break once the new layout of `std::unordered_map` landed as part
of https://github.com/llvm/llvm-project/issues/93069.

Instead, this patch simply casts the `__hash_iterator` to a
`__node_pointer` (which is what libc++ does too) and uses a
straightforward `GetChildMemberWithName("__value_")` to get to the
key/value we care about.

The `std::unordered_map` already does it this way, so we align the
iterator counterpart to do the same. We can eventually re-use the
core-part of the `std::unordered_map` and `std::unordered_map::iterator`
formatters. But it will be an easier to change to review once both
simplifications landed.



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