From: "Gary R. Van Sickle wrote: >In the post you're replying to, I listed the legitimate reasons for wanting >to do it. Here they are again: > >- If you're writing a task switcher.
And what's the difference between a task switcher and switching between co-routines? Basically nothing at all except that a task gets switched whenever the OS wants to, whereas a co-routine gets switched under program control. So why must they be implemented differently? It's nothing new to be writing user space task switchers that switch stacks, I see no reason why a user space co-routine switcher should not do the same. >Do you actually realize that there are far better ways to implement stacks >for interpreters than dinking with esp? I realise there are a dozen ways to suck eggs. But do YOU realise that there are two ways to implement a language with co-routines, whether it be interpreted or compiled, and that is to either have a vm with a fake stack, or to use the machine's real stack. And if you use the machine's real stack you MUST "dink" with esp. You MUST. I don't happen to be writing a VM based interpreter with a fake stack. >I suggest you investigate those alternatives instead of trying to >do something that cannot work, and then getting all pissy when people try to >dissuade you from wasting your time. That's strange. Now that I know that on Windows it likes to use its own stack for system calls, its working fine by just restoring the system stack temporarily. I can switch stacks and co-routines with no problems at all. So much for your bogus "cannot work". I guess you don't know everything after all huh? I do remain curious why Windows actually cares whereas Linux acts sensibly and doesn't carebut it matters little for my purposes. >No, but there is a law that you have to learn to walk before you can run. >You are trying to sprint a marathon before you're even able to stand erect. Meaningless ad-hominem. I guess now that I've got it working, if I can't stand erect, you must not even be crawling. >Christopher Faylor <cgf-no-personal-reply-please at cygwin dot com> wrote: >What you are trying to do is a bad idea. Bad huh? I'm fuzzy on the whole good/bad thing. Care to elaborate? >Btw, have you thought about how to handle stack overflow? What happens >when the program pushes its way to the top of your malloced region? Each Scheme function call has its own environment that is chained to previous environments. Each environment has its own stack. The C code that executes a scheme function uses a small and well-defined amount of stack. Restoring the system stack for external library calls is going to be a good idea anyway, because they can use arbitrary amounts of stack. But for the interpreter itself the exact amount of stack required for one lambda can be calculated by trial and error. The other way to implement it is to copy the entire stack when switching co-routines, but I'm trying to avoid that. ----------------------------------------------------------------- If you have received this transmission in error please notify us immediately by return e-mail and delete all copies. If this e-mail or any attachments have been sent to you in error, that error does not constitute waiver of any confidentiality, privilege or copyright in respect of information in the e-mail or attachments. -- Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple Problem reports: http://cygwin.com/problems.html Documentation: http://cygwin.com/docs.html FAQ: http://cygwin.com/faq/
