[Bug debug/99178] Emit .debug_names

["dblaikie at gmail dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99178

David Blaikie <dblaikie at gmail dot com> changed:

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--- Comment #4 from David Blaikie <dblaikie at gmail dot com> ---
(In reply to Mark Wielaard from comment #3)
> So if the compiler would emit the .debug_name index would that make any
> link/post-processing steps easier or more efficient?

Right - that's the intent. You can omit the hash table part of .debug_names -
in which case it's just like a newer pubnames/pubtypes - maybe with the
opportunity to have more guaranteed contents (the lack of those guarantees I
think is why debug_gnu_pubnames/types came to be, yeah?).

At least on the lld side, we're working on adding the requisite merging - like
`-Wl,--gdb-index`, except instead of merging debug_gnu_pubnames/pubtypes ->
gdb_index, it merges debug_names -> debug_names.

This is relevant/important/necessary for Split DWARF in particular, where the
linker wouldn't have access to the DWARF to index it anyway (& you don't always
want to run the dwp tool, which would have access to all the DWARF to index it
- but it'd be nice to avoid that in iterative developer scenarios, and save it
only for archival situations) - and even if you do have all the DWARF, it's
certainly faster to merge some tables than to reparse all the DWARF from
scratch.

It'd be great to get GCC/GDB folks take on the name tables - get some practical
experience with their contents, file any bugs about missing elements, etc. It's
possible they're leaning too heavily towards lldb's style of name lookup since
they derived from an existing apple implementation there & it'd be good to
generalize them where needed.