Date: Mon, 18 Apr 2011 11:24:41 -0400
From: Christopher Faylor <cgf-use-the-mailinglist-please AT cygwin DOT com>
To: cygwin AT cygwin DOT com
Subject: Re: Memory leak in select
Message-ID: <20110418152441.GA12913@ednor.casa.cgf.cx>
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On Mon, Apr 18, 2011 at 04:32:10PM +0200, Peter Rosin wrote:
>Den 2011-04-18 14:23 skrev Peter Rosin:
>> Den 2011-04-18 13:43 skrev Peter Rosin:
>>> Hi!
>>>
>>> Using the following STC, I'm seeing what appears to be a memory
>>> leak in select(2).
>>>
>> ----------------8<---(selectleak.c)---------
>> #include <sys/time.h>
>> #include <fcntl.h>
>> 
>> int
>> main(void)
>> {
>> 	fd_set fdset;
>> 
>> 	long flags = fcntl(0, F_GETFL);
>> 	fcntl(0, F_SETFL, flags | O_NONBLOCK);
>> 
>> 	for (;;) {
>> 		int res;
>> 		char buf[20];
>> 
>> 		FD_ZERO(&fdset);
>> 		FD_SET(0, &fdset);
>> 		res = select(1, &fdset, NULL, NULL, NULL);
>> 		if (!res)
>> 			continue;
>> 		if (res < 0)
>> 			return 1;
>> 		res = read(0, buf, sizeof(buf));
>> 		if (!res)
>> 			break;
>> 		if (res < 0)
>> 			return 1;
>> 	}
>> 
>> 	return 0;
>> }
>> ----------------8<--------------------------
>
>Ok, I'm taking a wild swing at this, and my guess is that the call
>sel.cleanup () in cygwin_select prematurely zeros out the cleanup
>member of the select_record. The call to sel.poll () then adds
>"stuff" to the select_record that really should have been cleaned
>up, but isn't since cleanup has already been executed and then
>zapped (by select_stuff::cleanup).
>
>But what do I know?

How does sel.poll add "stuff" that should be cleaned up?  That function
only looks for bits to set.

cgf


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