Re: Firefox and Cliqz tabs crashing at GOV.UK government pages

Graham Perrin <grahamperrin_at_gmail.com> writes:

> On 08/04/2020 20:23, Graham Perrin wrote:
>
>> Firefox 75.0_1,1 tabs crashing or mis-rendering at some www.gov.uk pages
>>
>> Most noticeable today at
>   <https://www.gov.uk/coronavirus>. Screenshots available on request.
>>
>> AFAICT the same types of problem with 75.0_1,1 on both r357746 and
>   r359628.
>
> The problem persists with r359750, is reproducible with a different
> user account, is reproducible with Cliqz browser. As far as I can
> tell, only bugging UK.GOV government pages.

I could reproduce on Nightly, so have reported upstream.
https://bugzilla.mozilla.org/show_bug.cgi?id=1629231

> Occasionally a page will appear OK (e.g. the screen to the left at
> <https://i.imgur.com/ROO9FIN.png>), more often the page will appear 
> wrong (screen to the right, safe mode).

According to backtrace the crash happens in harfbuzz code which is
responsible how text is shaped. If it doesn't crash right away then
scrolling the page usually helps to trigger.

> Most often: the tab will crash before the screen can be read. Crashes
> seem to occur at load time, towards the tail end of content loading or 
> rendering.
>
> More shots of what appears to be mis-rendering, Firefox with a
> refreshed profile in safe mode:
>
> <https://i.imgur.com/rNp20f5.png>
> <https://i.imgur.com/TuqYnAe.png>

Maybe report your findings on upstream bug.

>
> I have .core files from both Firefox and Cliqz, should I report a bug?
>
> (Also I'd like to take this opportunity to learn how to interpret
> parts of a .core file, I'll do what I can with man pages but might
> need to seek help in IRC.)

Try "lldb --core firefox.*.core /usr/local/bin/firefox" then run "bt all"
from (lldb) prompt. core(5) files are not portable across environments,
so after getting some basic info discard the files because they'd
quickly become unusable after rebuilding www/firefox or any of its
library dependencies.