From: ts <decoux@...>
Date: 2003-11-27T19:14:44+09:00
Subject: Re: Ruby thread problems

>>>>> "B" == Brad  <BCoish@Dymaxion.ca> writes:

B> Q: Doesn't the setjmp/longjmp maintain the stack information?  Seems to me that
B>    setjmp/longjmp would be quite unusable if it didn't maintain stack 
B>    information.

 longjmp restore the stack registers (%esp on 80x86), not the stack content.
 Say another way, this is valid in C

    int g()
    {
        longjmp(jmp, val);
    }

    int f()
    {
        setjmp(jmp);
        g();
    }

 but this don't work

    int g()
    {
        setjmp(jmp);
    }

    int f()
    {
        g();
        longjmp(jmp, val);
    }



B> Perhaps this is a naive assumption on my part as I have not had opportunity to
B> use setjmp/longjmp before now.

 When a thread is stopped, ruby store the content of the stack in stk_ptr,
 when it want to resume a thread it must restore the stack pointers before
 calling longjmp()


Guy Decoux