First draft: rewrite of {get|set|swap}context(3)

[Daniel Eischen]

On Sun, 17 Aug 2003, Marcel Moolenaar wrote:

> On Sun, Aug 17, 2003 at 05:12:29PM -0400, Daniel Eischen wrote:
> > On Sun, 17 Aug 2003, Marcel Moolenaar wrote:
> > 
> > > Please review the attached patch and let me know to what extend it
> > > introduces breakages. It is the result of "aggressive engineering"
> > > to provoke comments and further fuel discussion. The reason for this
> > > approach is that we currently do not initialize any fields other than
> > > the mcontext and sigmask and only partially copyin() and copyout()
> > > the contexts (typically only the mcontext and sigmask fields). This
> > > generally is very sensitive to breakages, especially when we intro-
> > > duce flags or need to use any of the spare fields.
> > > 
> > > getcontext(3): the whole ucontext is zeroed before (partially) filled
> > > 	and we copyout() all of it. This means that uc_link can only
> > > 	be set/defined after calling setcontext().
> > 
> > This prevents reuse of the same context without resetting
> > uc_link after every usage.  I don't see any requirement
> > by POSIX that uc_link be left intact after getcontext(),
> > but it might be worth preserving...  It's up to you.
> 
> Yes, it's a tricky issue. I'll begin runtime testing and think about
> it some more. I don't want to rush it...
> 
> BTW: I think we need to preserve uc_stack as well.

Yes, I think that's a good idea.

-- 
Dan Eischen