Definitely explore this!

I want us to be very careful/deliberate about the privacy consequences of
this, though. Any values which could be user data need to be tightly
controlled, in the same manner we control access to the minidumps
themselves. So I don't think we should be too generic about this.

As data steward I'd like to be kept in the loop and do a data review of any
changes here.


On Thu, Sep 22, 2016 at 9:28 AM, Nicolas B. Pierron <> wrote:

> On 09/22/2016 04:28 AM, Nicholas Nethercote wrote:
>> I want to highlight a nice case where converting a normal assertion
>> into a release assertion was a win. In bug 1159244 Michael Layzell did
>> this in nsTArray::ElementAt(), to implement a form of always-on array
>> bounds checking. See
>> for
>> discussion of how this is finding real bugs in the wild. (As well as
>> identifying new bugs, it's also helping understand existing crash
>> reports, e.g. see bug 1291082 where the crash signature changed.)
> Independently of the release/debug assertion, I want to raise something
> that I see in the patch above, and in a patch made to investigate some rare
> crashes in the JS engine.
> The patch from the bug above adds instrumentation to attach a dynamically
> computed reason string (snprintf).  In the JS engine Jan De Mooij did
> something similar by dumping content on the stack between 2 magic numbers,
> in order to include this information in crash reports.
> What I see is a recurring pattern where the classical MOZ_CRASH /
> MOZ_ASSERT might not be ergonomic enough.  I think we should add a way to
> annotate our crashes (even in debug builds) with some state, without going
> in the internals of MOZ_CRASHs or requiring privileged access to the
> mini-dump. Maybe something like:
>   MOZ_ASSERT(foo < 0x1000, MOZ_REASON("Unexpected value: %x", foo));
> which could be converted into a lambda doing the snprintf into a
> pre-reserved space.
> --
> Nicolas B. Pierron
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