Re: [boost] [context] Why does boost::ctx::minimum_stacksize() on Windows return 65536

Subject: Re: [boost] [context] Why does boost::ctx::minimum_stacksize() on Windows return 65536
From: Hartmut Kaiser (hartmut.kaiser_at_[hidden])
Date: 2012-09-02 14:11:14

Oliver,

> > I don't see how that info relates to my question, sorry. Even if I
> > need only 4k of stack space (or 8k, or whatever), I still would like
> > to get the guard page detecting stack overruns.
> My target development platform is POSIX - not Windows; maybe my
> understanding of the related MSDN articles was not correct.

I think you got everything right except for the assumption that everybody
wants to reserve stacks of 64k size or more.

> > But why should I be forced to do so if all I need to change is to
> > remove the check for the minimal stack size. The constraint you're
> > trying to enforce is something belonging into the documentation, not
> > the code.
> You are referring to the precondition in maximum_stacksize()? The
> documentation of maximum_stacksize() contains the info that
> is_stack_unbounded() returns false as precondition.

I'm referring to my initial question: Why does the library enforce a minimum
stack size of 64k on Windows if all I need are 4k + guard page.

> > BTW, on an unrelated note: I think the ctx::minimum_stacksize() and
> > ctx::maximum_stacksize() functions should be tied to the allocator.
> > They should not be global as they will return wrong numbers if a
> > custom allocator is used.
> good point - both functions should be part of the stack_allocator
> interface. I'll change it asap.
> 
> What are the minimum and maximum stacksize on the several Windows versions
> (XP, 7, 8, Ce, R, ...)? I didn't found infos in the MSDN about this issue.
> Maybe pagesize? SUggestions?

Well, I can't answer this question. All I know is that VirtualAlloc does not
allow allocating less than a page, regardless of the (Windows) system. Thus
I assume the minimal stack size in Boost.Context should be a page as well
(well, plus guard page).

Regards Hartmut
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