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Call another function when main() exits.

Answer 1

+20 A:

You can register functions to run after main exits using the atexit function.

MSDN has a nice succinct example of how this is done. Basically, the functions registered with atexit are executed in reverse order of when they were registered.

James McNellis 2009-11-21 21:02:02

actually nice answer :)

SjB 2009-11-21 21:08:41

Occasionally a blind squirrel finds a nut...

James McNellis 2009-11-21 21:11:00

just what i needed, thank you!

edarroyo 2009-11-21 21:35:32

atexit() is a frequent source of platform-specific weirdness and unpredictable crashes. For example the OpenBSD manpage advises not to use it. I was looking for some articles I read circa 2003 on the subject, but was unable to find them...

asveikau 2009-11-21 21:51:52

@asveikau: OpenBSD advises not to use it because of races at exit-time. Is it the case that a single-threaded OpenBSD program suffers from weirdness and unpredictable crashes on exit if it has used atexit() naively? If so that's a worry, but I don't see why in principle a non-compliant implementation of the function on one platform should mean you ought not to use it on other platforms. If you write multi-threaded code, then of course you have to look to your platform's treatment of "hidden" global data like the atexit list...

Steve Jessop 2009-11-22 01:59:18

Really,nice examples !!

nthrgeek 2009-11-22 02:07:40

@Steve I wish I could find those old articles on the subject so I could refresh my memory on their particular reasoning. I seem to recall it applied to other systems as well. FWIW, I've experienced a few bugs firsthand because atexit() was called without realizing that the handlers persist on a fork(), or exit() was called from within a signal handler or while a lock is held, or if the handler comes from a shared library that gets unloaded. Similar to signals, you really should be careful where your handler comes from and what it does.

asveikau 2009-11-22 02:31:19

I guess you can be careless about how you call exit, or you can be careless about how you call atexit, but not both. Most programmers prefer the former.

Steve Jessop 2009-11-22 13:15:02

Answer 2

+7 A:

Try the atexit() function:

void myfunc() {
    /* Called when the program ends */
}

int main( int arc, char *argv[] ) {
    atexit( myfunc );
    ...
    return 0;
}

Graeme Perrow 2009-11-21 21:03:17

Answer 3

+2 A:

Great question and answers. Just a side note. Abuse of a similar feature in Delphi libraries led to applications which are annoyingly slow on close.

RocketSurgeon 2009-11-21 21:15:29

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Call another function when main() exits.

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