Handle string overflow in DFG graph dump while validating AI.

[Mark Lam]

<rdar://problem/64635620>

[Mark Lam]

Created attachment 402569 [details]
proposed patch.

[Mark Lam]

Thanks for the review.  Landed in r263405: <http://trac.webkit.org/r263405>.

[Darin Adler]

Comment on attachment 402569 [details]
proposed patch.

View in context: https://bugs.webkit.org/attachment.cgi?id=402569&action=review

> Source/JavaScriptCore/ftl/FTLLowerDFGToB3.cpp:563
> +            auto expectedString = out.tryToString();
> +            m_graphDump = expectedString ? expectedString.value() : String("<out of memory while dumping graph>"_s);

I would have written this using valueOr. I think it possibly be this one-liner:

    m_graphDump = out.tryToString().valueOr("<out of memory while dumping graph>"_s);

[Mark Lam]

(In reply to Darin Adler from comment #3)
> Comment on attachment 402569 [details]
> proposed patch.
> 
> View in context:
> https://bugs.webkit.org/attachment.cgi?id=402569&action=review
> 
> > Source/JavaScriptCore/ftl/FTLLowerDFGToB3.cpp:563
> > +            auto expectedString = out.tryToString();
> > +            m_graphDump = expectedString ? expectedString.value() : String("<out of memory while dumping graph>"_s);
> 
> I would have written this using valueOr. I think it possibly be this
> one-liner:
> 
>     m_graphDump = out.tryToString().valueOr("<out of memory while dumping
> graph>"_s);

Nice.  Will apply this (except with Expected::value_or(); there's no valueOr() method).

[Mark Lam]

Landed follow up in r263408: <http://trac.webkit.org/r263408>.