[Lldb-commits] [PATCH] D37651: Fix for bug 34532 - A few rough corners related to post-mortem debugging (core/minidump)

[Zachary Turner via lldb-commits]

On Tue, Sep 12, 2017 at 11:07 AM Greg Clayton <clayborg at gmail.com> wrote:

>
> On Sep 12, 2017, at 10:10 AM, Zachary Turner <zturner at google.com> wrote:
>
>
>
> On Tue, Sep 12, 2017 at 10:03 AM Greg Clayton <clayborg at gmail.com> wrote:
>
>> On Sep 12, 2017, at 9:53 AM, Zachary Turner <zturner at google.com> wrote:
>>
>> If you had just logged it, the bug would still not be fixed because
>> nobody would know about it.  I also can't believe we have to keep saying
>> this :-/
>>
>>
>> By log, I mean Host::SystemLog(...) which would come out in the command
>> line. Not "log enable ...". So users would see the issue and report the
>> bug. Crashing doesn't mean people always report the bug.
>>
> I mentioned earlier in the thread that I assumed Xcode had an automatic
> crash that would handle the crash and automatically upload it to Apple.  Is
> this really not the case?  If core dumps are too big, why not just a stack
> trace?  Surely the Xcode team must have some kind of internal metrics
> system to track stability.
>
>
> They do just upload text crash logs. It doesn't tell us what expression
> triggered the issue though. It shows a crash in an expression, but doesn't
> show the expression text as this violates privacy.
>

So, you do get a bug report when a crash occurs then.  In contrast to the
case where you simply log something, and don't get a crash report.

In some cases, you can look at the code and figure out why it crashed.  In
other cases the bug occurs extremely infrequently (you can build heuristic
matching of call-stacks into your infrastructure that processes the crash
logs).  If it's a high incidence crasher then you do some investigation.
And the good news is, once you fix it, you've *actually* fixed it.  Now
instead of hundreds of thousands of people using something that doesn't
work quite right for presumably the rest of the software's life (since
nobody knows about the bug), they have something that actually works.

There's probably some initial pain associated with this approach since the
test coverage is so low right now (I came up with about ~25% code coverage
in a test I ran a while back).  When you get this higher, your tests start
catching all of the high incidence stuff, and then you're left with only
occasional crashes.

And since you have the out of process stuff, it doesn't even bring down
Xcode anymore.  Just a debugging session.  That's an amazing price to pay
for having instant visibility into a huge class of bugs that LLDB is
currently willfully ignoring.
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