[PATCH] D40950: [ELF] - Fail when multiple .debug_* sections are used in a single object.

[George Rimar via llvm-commits]

>>Hi,
>>
>>My colleagues and I have actually been doing quite a bit of investigation
>>in the past couple of weeks into what to do about debug data that refers to
>>sections that are discarded due to --gc-sections etc. Currently, LLD treats
>>the references as address zero, but at least on our platform, address zero
>>is a valid address, so we were looking at alternatives. One of the ideas
>>that I personally looked at was based on section E.3 of the DWARF4/5
>>specifications, i.e. having a separate .debug_info section for each
>>subprogram, each of which imports from a "main" .debug_info section
>>containing shared information. I was able to prototype a change to LLVM
>>that did this, without too much effort, given that I hadn't previously
>>looked in that area of code before. I then had to modify LLD to recognise
>>these new info sections as being dependent on the corresponding text
>>section, which was a relatively simple change to make, thanks to the
>>mechanism for dependent sections already being there. It didn't require
>>inspecting the contents of the section, only the section name in my case
>>(the sections in my experiment were named things like .debug_info._Z3foov).
>>I also prototyped changes to llvm-dwarfdump to print the .debug_info for
>>these multiple sections. Again, this was relatively simple, although I
>>certainly didn't experiment beyond a very simply case. Similar
>>investigations are being conducted for having multiple of other .debug_*
>>sections.
>>
>>We haven't yet decided whether this is an approach we'd like to push for,
>>as there are some downsides (e.g. larger debug information) but my point is
>>that I wouldn't be so certain that we won't need to handle multiple
>>.debug_info sections correctly in the relatively near term, so I'd much
>>rather option 2).
>>
>>Regards,
>>
>>James>
>
>Hi James, sorry, only thing I can say atm that I did not see your mail until David replied.
>I suspect something was wrong with our mail server, I'll answer this
>tommorrow.
>
>George.

James, David, given the comments and my feelings, I think we should just support multiple .debug_info* sections.
It anyways not something that will be harmfull given the current latest DWARF specification it seems.

Sorry if I am missing something, but can we just do it ? (I can take this task I believe, FWIW).

George.