Re: [uClinux-dev] brk(2) and stack pointer

["Shaun Jackman" <sjackman at gmail dot com>]

On 4/28/06, Jamie Lokier <jamie@shareable.org> wrote:
> A few programs allocate memory on the heap, and then use that as a
> stack (possibly one of several stacks).  Programs which do that will
> fail your test, unless malloc(3) is implemented by doing anonymous
> mmap(2) instead of brk(2).
>
> Such programs tend to be those doing user-space threading or clever
> things with signals.  Those techniques are relatively portable and
> valid, using "sigaltstack" or "makecontext", so although most programs
> don't use them, a few do that you might want to use (or someone else
> using newlib on ARM might want to use).

Thanks for the explanation.

> What's the reason for the check?

For the typical case where the heap is growing up towards the stack,
which is growing down, I wanted to check that the requested heap
hasn't collided with the stack.

Cheers,
Shaun