(brought to my attention in
https://github.com/llvm/llvm-project/pull/155153#discussion_r2682666325)
This patch removes the `anon_struct_idx` of
`GetValueOrOldCompressedPair`.
The latest `_LIBCPP_COMPRESSED_PAIR` wraps the members in an anonymous
structure. Around the time of the original patch that introduced
`GetValueOrOldCompressedPair`
(https://github.com/llvm/llvm-project/pull/155153),
`GetChildMemberWithName` wasn't capable of "seeing through" anonymous
structures when searching for children. However, around the same time as
https://github.com/llvm/llvm-project/pull/155153 landed, the
`GetChildMemberWithName` behaviour was fixed (in
https://github.com/llvm/llvm-project/pull/138487). So regardless of
whether the the compressed pair is wrapped in an anonymous structure,
simply calling `GetChildMemberWithName` is the right thing to do.
We weren't even using the result of `GetChildAtIndex`, so we were always
calling `GetChildMemberWithName` with the root ValueObject anyways.
Our `libcxx-simulators` already test both compressed pair layouts, so no
extra coverage is needed here.
Since PDB doesn't have template information, we need to get the element
type from somewhere else. I'm using the type of `_Myval` in a list node,
which holds the element type.
Starting with https://github.com/llvm/llvm-project/pull/154686 the
compressed_pair children are now wrapped in an anonymous structure.
This patch adjusts the LLDB data-formatters to support that.
Outstanding questions:
1. Should GetChildMemberWithName look through anonymous structures? That
will break users most likely. But maybe introducing a new API is worth
it? Then we wouldnt have to do this awkward passing around of
`anon_struct_index`
2. Do we support the layout without the anonymous structure? It's not
too much added complexity. And we did release that version of libc++, so
there is code out there compiled against it. But there is no great way
of testing it (some of our macOS matrix bots do test it i suppose, but
not in a targeted way). We have the layout "simulator" tests for some of
the STL types which I will adjust.
Adds synthetic providers for MSVC's `std::forward_list` and `std::list`.
It refactors `LibCxxList` to be generic over the STL type (currently
libc++ or MSVC STL). The libstdc++ synthetic providers use something
similar in Python
[here](3092b765ba/lldb/examples/synthetic/gnu_libstdcpp.py (L134)).
Eventually, this could be ported to C++ as well.
Towards #24834.
