Re: Spawn a process without exec

[John Cupitt <jcupitt gmail com>]

On Fri, 20 Aug 2004 00:22:33 +0000, David Rosal <davidrr menta net> wrote:
> John Cuppit wrote:
> > sounds like you want to start a child thread:
> >
> >   http://developer.gnome.org/doc/API/2.0/glib/glib-Threads.html
>
> Uhrgh! I dreaded something like that. It's (always) time to learn...

It's really pretty easy, very similar to fork(), except that the new
thread runs in the same address space, and it's a function that gets
called rather than one side of an if() that gets taken. The only two
API calls you need are thread create and thread join. Plus a little
commmunication and synchronisation stuff.

> > there are some 'gotchas' if you have several threads all calling the
> > same GTK. It's usually best (IMO) to have all of the GTK calls in one
> > thread and to use something like an asyncqueue for workers to tell the
> > GUI thread what to do.
>
> At the moment I know almost nothing about glib threads, but after
> taking a first look at the API reference I couldn't find any way to
> "kill" a thread from the main thread, which is what I want to do.
> There's g_thread_exit(), but it exits the current thread, and
> g_thread_join() waits for the thread to exit by itself...

Apparently thread cancel is very hard to implement portably. Instead I
usually have a flag somewhere which the main thread sets when it wants
the child to exit.

The good thing about doing it this way is that the child then gets a
chance to clean up. Because the child thread runs in the same address
space, there's no automatic freeing of memory / closing of files /
etc. when the child dies. Thread cancel would (probably) cause
terrible resource leaks.

John