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List:       webkit-dev
Subject:    Re: [webkit-dev] Change WTFCrash to not trash the crash site register state.
From:       Geoffrey Garen <ggaren () apple ! com>
Date:       2016-02-09 19:17:48
Message-ID: AC4D9B83-4000-4D14-B913-08D6F3C47335 () apple ! com
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I like this change.

Perhaps all ports can adopt this behavior. 

Geoff

> On Feb 8, 2016, at 11:55 AM, Mark Lam <mark.lam@apple.com> wrote:
> 
> Hi WebKit folks,
> 
> For non-debug OS(DARWIN) builds, I would like to change WTFCrash()'s implementation \
> into an inlined function that has a single inlined asm statement that issues a \
> breakpoint trap.  The intent is to crash directly in the caller's frame and \
> preserve the register values at the time of the crash.  As a result, for non-debug \
> OS(DARWIN) builds, crashes due to failed RELEASE_ASSERTs will now show up in crash \
> reports as crashing due to EXC_BREAKPOINT (SIGTRAP) instead of a EXC_BAD_ACCESS \
> (SIGSEGV) on address 0xbbadbeef. 
> This is in contrast to the current implementation where WTFCrash() is a function \
> that calls a lot of handler / callback functions before actually crashing.  As a \
> result, by the time it crashes, the caller's register values has most likely been \
> trashed by all the work that the WTFCrash and the handlers / callbacks do.  The \
> register values in the captured crash report will, therefore, no longer be useful \
> for crash site analysis.  
> You can find the patch for this change at \
> https://bugs.webkit.org/show_bug.cgi?id=153996.  This change will only be applied \
> for non-debug OS(DARWIN) builds for now.  I'm leaving all other build build \
> configurations with the existing WTFCrash() implementation and behavior. 
> Does anyone have any opinion / feedback on this change?
> 
> Thanks.
> 
> Regards,
> Mark
> 
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