[PATCH] D38719: [llvm-dwarfdump] Verify compatible TAG for attributes.

[David Blaikie via llvm-commits]

Ping

On Thu, Aug 12, 2021 at 7:42 PM David Blaikie <dblaikie at gmail.com> wrote:

> On Wed, Oct 11, 2017 at 10:03 AM Adrian Prantl <aprantl at apple.com> wrote:
>
>>
>>
>> > On Oct 11, 2017, at 9:45 AM, David Blaikie <dblaikie at gmail.com> wrote:
>> >
>> > Adrian - could you take a look here & see why
>> DWARFVerifier::handleDebugInfo is creating empty TUSection/CUSection,
>> rather than passing the DCtx's populated sections in? (that's my rough
>> reading of the code, at least)
>>
>> It looks like this was introduced by https://reviews.llvm.org/D35521
>>
>> "This patch modifies the handleDebugInfo() function so that we verify the
>> contents of each unit
>> in the .debug_info section only if its header has been successfully
>> verified."
>>
>> So it looks like the code is trying to avoid parsing the unit if the
>> header didn't verify? At the first glance this does look bit redundant to
>> me but I didn't give it a thorough reading.
>>
>> Jonas, can you make sense of it in the context of that commit? I would
>> not be surprised if this is just compensating for a missing feature in the
>> codebase at that point in time.
>>
>> If we can get away with deleting the redundant code that would definitely
>> be a win.
>>
>
> Resurrecting this thread, since I just came across this issue again -
> while trying to improve the verifier (after seeing a lot of "error:
> invalid DIE reference 0x0000015f. Offset is in between DIEs:" followed
> by  a series of blank lines - caused by
> ReferenceToDIEOffsets being kept and used over multiple sections (when it
> contains section relative offsets without any base section to know which
> section they are relative to) - so you get invalid references from type
> units, and then verifyDebugInfoReferences tries to dump the DIEs in the
> type units that have the "invalid" references and it can't dump those DIEs
> (just ends up with spooky blank lines) because it's looking in the wrong
> section for them).
>
> It seems this code introduced in D35521 is really likely to cause ongoing
> headaches - by creating units that aren't in the DWARFContext's unit lists
> that's going to be a problem for many uses of the libDebugInfoDWARF APIs
> (like the one discussed in this review for navigating DIE to DIE references
> - and I want to add a bunch more of those for reconstructing template names
> (well, at the moment I have them in patches to the verifier, but they'll
> probably more into libDebugInfoDWARF's normal APIs and be used by the
> verifier - but that'll have the same problem)).
>
> Any chance of this getting fixed? Perhaps we need a DWARFContext mode that
> reflects the verifiers needs, while still preserving the usual DWARFContext
> invariants of having the DWARFUnits in the DWARFContext's data structures,
> rather than separately instantiated? (eg: a mode that includes invalid
> headers in the list - so that the verifier can walk them and visit invalid
> headers?)
>
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