Re: Posix thread exiting and destructors

"James Kanze" <>
11 Apr 2007 06:20:15 -0700
On Apr 10, 11:47 pm, "Boltar" <> wrote:

On Apr 10, 4:49 pm, "James Kanze" <> wrote:

It's also not too clear to me what kind of a class could want to
do an exit in its destructor. pthread_exit has semantics more
or less like throwing an exception, and that's generally
something you want to avoid in a destructor. Please explain
what you're trying to do.

Its a TCP server. Each incoming connection gets its own thread which
is encapsulated in a connection object. I would have just used fork()
but I want the threads to access some global stats and I couldn't be
bothered with the hassle of shared memory and associated locking
issues. When the session is over or the remote client closes the
connection the thread has to exit and the object be destroyed. However
going by my own tests and whats been written here I've now just
created a procedural function which the object calls which deletes the
calling object then exits the thread.

Yes. You need the procedural function anyway, to start the
thread. You might as well delete the object there.

My real question concerning your initial design, I guess, was
who was going to call the destructor. A thread is a function,
an asynchronous function, but a function.

In reponse to another post , I don't need to do a join on an exiting
thread because they're all running detached. The parent thread doesn't
need to care about them , its just a fire and forget dispatcher.

And of course, you never stop the server, so there's no worry
about calling exit with running threads (which can cause various
problems as well):-). If not, for a clean shutdown (especially
given that pthread_cancel doesn't work in C++), you need a
thread counter, and a flag which signals that shutdown is
requested, which the threads poll from time to time. The flag
must be protected by a mutex, and the thread counter by a
condition variable (since it will be decremented at the end of
the procedural function, just before the return). Set the flag,
and wait until the counter is 0, then return from main.

James Kanze (GABI Software)
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