Re: [PATCH 0/4] Modernize frame unwinders and add disable feature

Luis Machado
2024-03-11T15:11:03Z

On 3/11/24 15:00, Guinevere Larsen wrote:
> On 11/03/2024 15:56, Luis Machado wrote:
>> Hi,
>>
>> On 3/6/24 12:51, Guinevere Larsen wrote:
>>> This patch series started with me trying to make it easier to test GDB's
>>> ability to unwind using CFI data, to improve a previous patch I sent to
>>> the list. However, once I finished these changes, I realized there was
>>> an unrelated bug I should fix before proposing the CFI test. Since these
>>> changes are significant enough already, and I think would be interesting
>>> on their own, I figured I shoudl submit this patch series as is right
>>> now while I figure out the other bug.
>>>
>>> The first patch is just a minor change, storing frame unwinders in a
>>> vector instead of through an unwinder table accessible using the
>>> registry system. This isn't required (like I originally thought it was),
>>> but it does make the whole system more readable in my opinion.
>>>
>>> Patch 3 has the real meat of the modernization, making GDB use
>>> polymorphism to handle frame unwinders. This is slightly slower than
>>> using function pointers, but much more readable in my opinion.
>>>
>>> As for the unwinder classes, they were chosen somewhat arbitrarily,
>>> mostly based on where I found an unwinder and its name. I almost expect
>>> some unwinders to be mis-categorized, but that should be easy to fix.
>>>
>>> The changes up to patch 3 have been tested with a try-branch, no
>>> regressions as far as I could see.
>>>
>>> Guinevere Larsen (4):
>>>    gdb: make gdbarch store a vector of frame unwinders
>>>    gdb: add "unwinder class" to frame unwinders
>>>    gdb: Migrate frame unwinders to use C++ classes
>>>    GDB: introduce ability to disable frame unwinders
>> I haven't gone through the series in detail, but I thought I'd give it a try on one of the
>> aarch64 machines I have access to. I didn't look particularly healthy:
>>
>>
>> # of unexpected core files      47
>> # of expected passes            116521
>> # of unexpected failures        581
>> # of expected failures          77
>> # of known failures             116
>> # of untested testcases         128
>> # of unresolved testcases       1102
>> # of unsupported tests          458
>> # of duplicate test names       10
>>
>> I see a number of internal errors going on. Mostly like these:
>>
>>          ../../../repos/binutils-gdb/gdbsupport/errors.cc:58
>> 0xaaaad27e7877 check_ptrace_stopped_lwp_gone
>>          ../../../repos/binutils-gdb/gdb/linux-nat.c:1634
>> 0xaaaad27e7877 check_ptrace_stopped_lwp_gone
>>          ../../../repos/binutils-gdb/gdb/linux-nat.c:1630
>> 0xaaaad2ae0fa3 linux_resume_one_lwp
>>
> Oh no! Linaro CI had showed something was wrong, but I wasn't able to grab an aarch64 machine to test yet. I'll check it out when I can, thanks for narrowing it down for me
>

You're welcome. Do let me know if you can't easily find an aarch64 machine to try things on, and I can provide more info
and take a deeper look.