Re: [boost] [boost::context] reusing stacks

Subject: Re: [boost] [boost::context] reusing stacks
From: Oliver Kowalke (oliver.kowalke_at_[hidden])
Date: 2012-11-27 02:25:10

Am 27.11.2012 00:45 schrieb "Valentin Milea" <valentin.milea_at_[hidden]>:
>
> Hi,
>
> I'm working on a tiny coroutine library based on boost::context. For
> performance reasons I'd rather keep a pool of stacks instead
> allocating/deallocating every time. Is it legal to reuse a stack for a
> different context?

yes, but only one context is allowed to own the stack. If the context is
deallocated you could asign the stack to another context via
make_fcontext() instead to deallocate it.

Therefore your code is not correct (two context's share the same stack at
the same time).

>     int main(int argc, char * argv[])
>     {
>         ctx::guarded_stack_allocator alloc;
>
>         std::size_t size =
ctx::guarded_stack_allocator::default_stacksize();
>         void *sp = alloc.allocate(size);
>
>         fc = ctx::make_fcontext(sp, size, f1);
>         std::cout << "main: jump 1" << std::endl;
>         ctx::jump_fcontext(&fcm, fc, 0);
>
>         fc = ctx::make_fcontext(sp, size, f2); // legal? No
>         std::cout << "main: jump 2" << std::endl;
>         ctx::jump_fcontext(&fcm, fc, 0);
>
>         std::cout << "main: done" << std::endl;
>
>         return 0;
>     }
>
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