[webkit-dev] Stability problems involving Javascript GC

[Joe Mason]

> -----Original Message-----
> From: webkit-dev-bounces at lists.webkit.org [mailto:webkit-dev-
> bounces at lists.webkit.org] On Behalf Of Samuel Rivas
> Sent: Thursday, December 16, 2010 3:03 AM
> To: Zoltan Herczeg
> Cc: webkit-dev Development
> Subject: Re: [webkit-dev] Stability problems involving Javascript GC
> 
> On 6 December 2010 22:31, Zoltan Herczeg <zherczeg at inf.u-szeged.hu>
> wrote:
> > Crash in WTF::fastMalloc? Such things only happen if something
> overwrites
> > memory areas belongs to the memory manager (i.e overwrites some bytes
> > before or after a block returned by malloc). Try some valgrind
> equivalent
> > on mac to detect those writings into "red zones".
> 
> How can you use valgrind to help on that? We had some symptoms similar
> to this and also came to the conclusion that probably something is
> overwriting the structures used by fast malloc, but couldn't find
> anything with valgrind. Overwriting in an area that has bee reserved
> is not an error vangrind finds, at least not with any options that I
> know.

It is possible to add macros to the code to help valgrind know which areas are being used by a custom allocator.  (See VALGRIND_MALLOCLIKE_BLOCK and VALGRIND_FREELIKE_BLOCK, for example.)  I'm not sure if they're useful in this situation, but they're worth taking a look at.

Joe 

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