[lld] [lld][ELF] Add --debug-names to create merged .debug_names. (PR #86508)

[via llvm-commits]

cmtice wrote:

> > I tried very hard to craft a test for the error for 'if (locs.EntriesBase > namesExtractor.getData().size())', but was unable to create one; either my changes would cause NameIndex::extract() to error out. before we get to this code; or it would trigger the other ' index entry out of bounds' error , but not this one. I'm open to suggestions.
> 
> Yes, `NameIndex::extract` checks this property:
> 
> https://github.com/llvm/llvm-project/blob/f811d7b50957b801788d7b171ddeb25b1fda415a/llvm/lib/DebugInfo/DWARF/DWARFAcceleratorTable.cpp#L585
> 
> So it'll error if the offsets at least up to the end of the abbrev table are larger than the data available in the section. The only errors not caught by this are offsets to entries themselves (and not the first entry - because that is checked by the above, `NameIndex::extract` will error if there isn't at least one byte after the abbrevs - the first entry)
> 
> So, yes, this particular error case should be an assert with a message that describes basically this ^ that `NameIndex::extract` should've caught this case already.

I've created https://github.com/llvm/llvm-project/pull/88783 to create the Offsets accessor function, to do what you've requested here.

https://github.com/llvm/llvm-project/pull/86508