[webkit-dev] CSS Parse error in <link rel> element.

[Atul Sowani]

@Konstantin thanks for the suggestions. I disabled CSS JIT on x85 but there
was no negative impact on the results on x86. So I guess the issue is a
genuine ppc64le problem. I have picked up the starting points mentioned in
this thread earlier and debugging the issue. I have also isolated the issue
to a single CSS file which is causing the problem. Now I am trying to
isolate the exact entry in the CSS file which is causing the trouble.

Thanks!
Atul.

On Tue, Feb 7, 2017 at 3:53 PM, Konstantin Tokarev <annulen at yandex.ru>
wrote:

>
>
> 07.02.2017, 12:55, "Atul Sowani" <sowani at gmail.com>:
> > Thanks Geoffrey, Alex, Yoav for the debugging pointer. I am debugging
> the issue further using this information and will most likely need some
> more help in immediate future as well.
> >
> > Unfortunately, I don't have a stand-alone test case which can be tested
> with qtwebkit. I am trying to load a page using PhantomJS and it's
> crashing. The typical URLs which cause it to crash are http://engadget.com
> and http://cnn.com - both of these load without any issue on x86 platform
> though, so the issue seems to be specific to ppc64le.
>
> A few suggestions:
>
> 1. I suppose you are building with disabled JIT, as WebKit does not
> implement JIT for any PPC variant in official tree. This may introduce
> subtle differences in behavior, for example I once encountered layout test
> that was failing only when CSS JIT was disabled. You can try building
> without JIT on x86_64 and compare.
>
> 2. It might be miscompilation, as your platform may not be as thoroughly
> tested as more mainstream ones. You can try to build with -O0, -O1, -O2
> (default is -O3). Alternatively, try building with different compiler (at
> least GCC and Clang support ppc64le and are fine for WebKit, xlC may not
> work though), or try different version of your compiler.
>
> 3. Note that webkit-qt list is more appropriate for issues specific for
> QtWebKit. Make sure you are using latest release (technology preview 5 at
> the moment [1])
>
> [1] https://github.com/annulen/webkit/releases/tag/qtwebkit-tp5
>
> >
> > Thanks,
> > Atul.
> >
> > On Mon, Feb 6, 2017 at 5:56 PM, Yoav Weiss <yoav at yoav.ws> wrote:
> >> Hi Atul,
> >>
> >> I second Alex's suggestion (perhaps followed by
> HTMLLinkElement::process() and other places in that file that refer to
> `hrefAttr`).
> >> If you have a test case online, I could try to take a look and maybe
> provide more guidance.
> >>
> >> Cheers :)
> >> Yoav
> >>
> >> On Fri, Feb 3, 2017 at 9:19 PM Alex Christensen <achristensen at apple.com>
> wrote:
> >>> I would start looking at HTMLLinkElement::parseAttribute.
> >>> LinkHeader.cpp contains parsers for link headers, which are related.
> Yoav knows more about those.  Those parsers ought to be united more.
> >>>
> >>>> On Feb 3, 2017, at 1:17 AM, Atul Sowani <sowani at gmail.com> wrote:
> >>>> At present I am focusing on CSSParser::findURI() particularly
> and CSSParser::realLex() other related functionality in CSSParser.cpp
> - hope I am on right track. ;-)
> >>>>
> >>>> Please let me know if I should be looking at some other functionality
> as well to resolve this issue.
> >>>>
> >>>> Thanks!
> >>>> Atul.
> >>>>
> >>>> On Fri, Feb 3, 2017 at 2:33 PM, Atul Sowani <sowani at gmail.com> wrote:
> >>>>> Hi,
> >>>>>
> >>>>> I came across an issue in qtwebkit CSS parser while working on a
> PhantomJS crash. The issue seems to be with parsing of <link rel="..."
> href="..."> type elements in an HTML page. What I observed is that the
> parser is trying to interpret the value for href given inside
> double-quotes. The value contains a "-" (e.g. "
> http://some.domain.com/some-page-etc-etc"). The "-" sign is being
> interpreted as minus and then things go wrong. In another case I found that
> "\g" embedded in the value (e.g. "http://some.domain.com/some-
> page/global/something") is also creating issues. In essence, the parser
> is trying to interpret the value, which I believe, it should not.
> >>>>>
> >>>>> I am willing to dive further into it to debug and fix the issue, but
> looking at the complexity and size of WebCore, I think I would benefit a
> lot to expedite a fix, if I could get some tips about which code
> area/functionality I should specifically focus in the WebCore. Looking
> forward to some help in this regard.
> >>>>>
> >>>>> Thanks,
> >>>>> Atul.
> >>>> _______________________________________________
> >>>> webkit-dev mailing list
> >>>> webkit-dev at lists.webkit.org
> >>>> https://lists.webkit.org/mailman/listinfo/webkit-dev
> > ,
> >
> > _______________________________________________
> > webkit-dev mailing list
> > webkit-dev at lists.webkit.org
> > https://lists.webkit.org/mailman/listinfo/webkit-dev
>
>
> --
> Regards,
> Konstantin
>
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