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From: "Lawrence Rust" <nospam AT NOsoftsystemSPA DOT coM DOT uk>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: Task switch with SIGALRM
Date: Mon, 17 May 2004 16:44:23 +0200
Organization: Software Systems
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To: djgpp AT delorie DOT com
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Gabriel Zoltan wrote...
> Hi!
>
> Thanks for the code you provided. I'm going to try to use setjmp/longjmp.
> The only thing I don't understand is how you set up the jmp_buf structure
> initially. How do I run a task for the first time? Could someone please
> explain it? (Sadly I'm quite in a rush for trial&error.) Thanks in
> advance.

The jmp_buf is setup by the call to setjmp in MTC_PlatformThreadAlloc().  So
using the code snippet that I posted you would do something like:

struct MTC_Thread* pMain;
struct MTC_Thread* pThread;

/* Create the main thread */
pMain = MTC_PlatformThreadAlloc( 1);

/* Create worker thread */
pThread = MTC_PlatformThreadAlloc( 0); /* This init's the jmp_buf */

/* Switch to worker.
 * This saves main's state in pMain->jbuf and jumps to the point
 * saved in pThread->jbuf i.e. just after the call to setjmp() in
 * MTC_PlatformThreadAlloc() but using the worker's stack.  The
 * worker then calls MTC_ThreadExecute() which would call a thread
 * specific main function.
 */
PlatformThreadSwitch( &pMain->thread, &pThread->thread);


NB The functions shown were intended to be called from a platform
independent scheduler so they don't show how to setup the thread's main
function and how to manage which thread to dispatch, say from your signal
handler.

-- Lawrence Rust, Software Systems, www.softsystem.co.uk