[webkit-dev] Stuck... again (Conserative GC)

Justin Haygood justin at xiondigital.net
Sun Jun 12 09:21:34 PDT 2005

Thank you, I got it fixed.

At least the license of the Boehm GC allows blatent copy/pasting into 
LGPLed sources ;-) .

If it works, expect a patch by the end of the week.

Maciej Stachowiak wrote:

> On Jun 11, 2005, at 3:16 PM, Justin Haygood wrote:
>> the Win32 API simply does not allow getting the base stack address of 
>> a thread, because:
>> 1. not stable.. Windows *WILL* and *DOES* move that base address at will.
> This part seems unlikely - I could imagine moving the physical address 
> of the stack, but what would be the point of moving the virtual 
> address? Further, this would break any code that kept a pointer to 
> anything on the stack.
> But as Darin pointed out, it doesn't matter, because you only need to 
> get it at one particular point in time, it does not need to be stable 
> for all time.
>> 2. Its exclusively chosen and managed by Windows itself.. no ands, 
>> buts, or ors about it.
> It's ok that Windows chooses it - it's chosen by the OS on pretty much 
> all platforms. We don't need to change the stack base, just to get it.
>> What would be an alternative way to implement a conservative GC that 
>> I can use?
> My suggestion for how to research this would be to look at the code 
> for the Boehm garbage collector. This is a portable conservative GC 
> implementation for C++, so they must have some way of getting the 
> range of the stack on windows. I'm not sure if the Boehm GC is 
> threadsafe, but as I pointed out it should be sufficient to just get 
> the stack base for the current thread or for the main thread, and to 
> disable marking of other threads.
> http://www.hpl.hp.com/personal/Hans_Boehm/gc/
> I took a quick peek in the source and it does appear to have a way to 
> get the stack base on win32.
> Regards,
> Maciej

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