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Bug in HTTimer.c

From: Stefan Wiesner <sw@ais-ag.de>
Date: Mon, 26 Feb 2001 15:10:43 +0100
Message-ID: <3A9A63E3.F876552E@ais-ag.de>
To: www-lib@w3.org
Hi,

I think there is a bug in the code of function HTTimer_new if a timer
is already expired when HTTimer_new is called. See description below:


>>> ...
>>>    /*
>>>    **  Sort new element into list
>>>    */
>>>    for (cur = last; 
>>>	    (pres = (HTTimer *) HTList_nextObject(cur)) != NULL && pres->expires < expires; 
>>>	    last = cur);

       last                     cur
   	|                        |
   	|                        |
   	V                        |
     --------                    |
     |object|--->timer1          V
     |      |                 --------
     |next  |---------------->|object|--->timer2
     --------                 |      |
   			      |next  |--->...
   			      --------

>>> ...
>>>    /*
>>>    **	add to list if timer is new
>>>    */
>>>    HTList_addObject(last, (void *)timer);

       last                                               cur
   	|                                                  |
   	|                                                  |
   	V                                                  |
     --------                                              | 
     |object|--->timer1                                    |
     |      |                 --------                     |
     |next  |---------------->|object|--->timer_new        V
     --------                 |      |                  --------
   			      |next  |----------------->|object|--->timer2
   			      --------                  |      |
                                                        |next  |--->...
                                                        --------

>>> ...
>>>    /* Check if the timer object has already expired. If so then dispatch */
>>>    if (timer->expires <= now) Timer_dispatch(cur, last);
>>> ...

If the 'if' evaluates to 'TRUE', function 'Timer_dispatch' is called
with wrong parameters. As the result, the HTList object pointing to
timer_new gets lost and the callback function of timer2 is called.

To fix this, the previous call of function
'HTList_addObject(last, (void *)timer);' should be replaced by
'cur = HTList_addList(last, (void *)timer);'


One other thing to the Timer handling:
Although it is a good idea to dispatch the timer in function
'HTTimer_new'
when it has already expired, (I think) there is no way to get this
information
from the parameter the function returns. This behaviour may lead to
errors in a calling program. (In fact it has in my program.)


Greetings


Stefan Wiesner

-- 
Stefan Wiesner
AIS Automations- und Informationssysteme GmbH
Rheinweg 7, 34131 Kassel, Germany
Telefon: +49-561/30859-24, Telefax: +49-561/30859-39
Received on Monday, 26 February 2001 09:35:52 GMT

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