Re: kernel programming questions
Joerg Pommnitz (pommnitz@darmstadt.gmd.de)
Tue, 01 Jul 1997 09:46:23 +0200
Richard B. Johnson wrote:
>
> On Mon, 30 Jun 1997, Michael Bruck wrote:
>
> > Ok, two short questions:
> >
> > Is there a arch-independant type available for the
> > save_flags macro ? (flags_t ??)
> >
> > Is there a problem that could prevent one from using memory
> > alloc'd from stack in the kernel like
> >
> > int foo(int bar)
> > {
> > int foo_bar[bar];
> > ...
> > }
>
> Even though that works.... There SHOULD be a problem with it! Don't
> write code like that. For some reason gcc lets you get away with it.
> If you must write code like that it's broken from the start. Automatic
> variables are supposed to be automatic, not dynamic.
This is a gcc extension. Since almost every part of the kernel depends
on these, that's not a problem.
The problem is that every process has just a single page of kernel
stack space (4K for x86). So, better allocate some memory and release
it on function return.