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RE: Bug fix to HTHost.c

From: Peter Kocks <peter.kocks@baygate.com>
Date: Tue, 23 May 2000 10:51:40 -0700
To: <yovavm@contact.com>
Cc: <www-lib@w3.org>, "'Francois Nicot'" <fnicot@silicom.fr>
Message-ID: <NDBBJBILNGKNBCDAKIJMKEHDCDAA.peter.kocks@baygate.com>
> The problem I will describe does not happen on Win2000 & Win98, but it
> happen all the time when running my application on WinNT.
> Then, when going into the loop, the select statement in HTEventList_loop
> (HTEvtLst.c) returns -1, with a Winsock error of WSAEINVAL since the
> FDArrays are empty (!?)
> This of course causes the EventLoop to exit immediately without performing
> any read/write to/from the socket.
>

This sounds very familiar, but I'm on UNIX (Solaris 2.7)
not on Windows NT.  My problem was that the
HTEventList_unregister() was being called with s=-1
(or socket = -1).  HTEventList_unregister then does
a HASH(s) on the -1 and then later dereferences and crashes.

The solution to my problem was to find where the socket
number gets set to -1.  The reason turns out to be
in HTHost.c where HTChannel_delete(host->channel, status)
and after the delete, host->channel is set to NULL.  While
this appears correct at first (you delete the channel, the
channel should therefore be NULL), it is not because
other pieces of code rely on using the socket number as
an index.

I'm not familiar with the FDArrays stuff.  Is that NT specific?  I doubt
it, but perhaps.

--pk



> Peter,
> Is that the same problem you have faced ?
> I have tried using your fix but it did not solve my problem ?
>
> All others,
> Did anyone see this before ?
> Can anyone give my an idea what is wrong here ?
> Are there some configuration / initialization points I am missing ?
>
> Any help would be appreciated,
> Yovav
>
> ~~~~~~~~~~~~~~~
> Yovav Meydad
> Software Engineer
> Contact Networks
> www.contact.com
> ~~~~~~~~~~~~~~~
>
>
> -----Original Message-----
> From: www-lib-request@w3.org [mailto:www-lib-request@w3.org]On Behalf Of
> Francois Nicot
> Sent: Tuesday, May 23, 2000 6:53 PM
> To: peter.kocks@baygate.com
> Cc: www-lib@w3.org
> Subject: Re: Bug fix to HTHost.c
>
>
> Peter Kocks wrote:
>
> > Hi all,
> >
> > I'm new to this list and have both a
> > bug to report and a solution.
> >
> > I can reproducibly crash a custom webbot program
> > that uses libwww.  The program crashes under a
> > couple of circumstances (gdb stack traces are
> > attached at the bottom of this message), but
> > both are related to two lines of code in HTHost.c
> >
> > In HTHost.c, starting at line 1099 (current cvs)
> > HTChannel_delete(host->channel, status);
> > host->channel = NULL;
> >
> > The second line (host->channel = NULL) is both
> > unnecessary and causes libwww crash under certain
> > conditions.  For  example, any subsequent code that
> > calls HTChannel_socket(host->channel)) will return
> > a socket number of "-1".  This will cause a
> > segfault if something is keyed on socket
> > number.  E.g. HTEventList_unregister().
> >
> > I'm not sure what the procedure is, but I'd
> > like the line host->channel = NULL deleted from
> > the code base because it is causing some
> > of my programs to crash.
> >
> > Thanks in advance
> >
> > Peter Kocks
> >
> > Stack traces follow.
> >
> > -----------------------------------------------------
> >
> > Program received signal SIGSEGV, Segmentation fault.
> > 0xdff47971 in HTEventList_unregister (s=-1, type=HTEvent_READ)
> >     at HTEvtLst.c:457
> > 457         while (cur && (pres = (SockEvents *)
> HTList_nextObject(cur)))
> {
> > (gdb) where
> > #0  0xdff47971 in HTEventList_unregister (s=-1, type=HTEvent_READ)
> >     at HTEvtLst.c:457
> > #1  0xdfeaca8c in HTEvent_unregister (s=-1, type=HTEvent_READ) at
> > HTEvent.c:52
> > #2  0xdfeaf391 in HTHost_recoverPipe (host=0x8074958) at HTHost.c:841
> > #3  0xdfeb38fb in HTNet_delete (net=0x80834b0, status=200) at
> HTNet.c:912
> > #4  0xdff162ee in HTTPCleanup (req=0x8083310, status=200) at HTTP.c:168
> > #5  0xdff183ea in HTTPEvent (soc=9, pVoid=0x80827a0, type=HTEvent_READ)
> >     at HTTP.c:1290
> > #6  0xdfeae58e in HostEvent (soc=9, pVoid=0xffffffff, type=HTEvent_READ)
> >     at HTHost.c:196
> > #7  0xdff475e1 in EventOrder_executeAndDelete () at HTEvtLst.c:321
> > #8  0xdff48045 in HTEventList_loop (theRequest=0x8072b50) at
> HTEvtLst.c:762
> > #9  0x805222c in main (argc=17, argv=0x8047b5c) at RobotMain.c:593
> >
> >
> --------------------------------------------------------------------------
> --
> >
> > #0  redirection_handler (request=0x8072c30, response=0x8077060,
> param=0x0,
> >     status=302) at HTRobot.c:992
> > #1  0xdfab2b3a in HTNetCall_executeAfter (list=0x8073210,
> request=0x8072c30,
> >     status=302) at HTNet.c:314
> > #2  0xdfab2db5 in HTNet_executeAfterAll (request=0x8072c30, status=302)
> >     at HTNet.c:420
> > #3  0xdfab3a8b in HTNet_delete (net=0x8073f48, status=302) at
> HTNet.c:920
> > #4  0xdfb16332 in HTTPCleanup (req=0x8072c30, status=302) at HTTP.c:168
> > #5  0xdfb18452 in HTTPEvent (soc=-1, pVoid=0x8070db0, type=HTEvent_READ)
> >     at HTTP.c:1294
> > #6  0xdfb17b7d in HTLoadHTTP (soc=-1, request=0x8072c30) at HTTP.c:967
> > #7  0xdfab384c in HTNet_newClient (request=0x8072c30) at HTNet.c:808
> > #8  0xdfab7450 in HTLoad (me=0x8072c30, recursive=-8 '') at
> HTReqMan.c:1685
> > #9  0xdfb443e5 in launch_request (request=0x8072c30, recursive=0 '\000')
> >     at HTAccess.c:77
> > #10 0xdfb44742 in HTLoadAnchorToChunk (anchor=0x8072ba0,
> request=0x8072c30)
> >     at HTAccess.c:243
> > #11 0x8050d73 in get_robots_txt (
> >     uri=0x8072970 "http://www.seattletimes.com/robots.txt") at
> > HTRobot.c:1548
> > #12 0x8052063 in main (argc=17, argv=0x8047bc0) at RobotMain.c:527
>
> Peter,
>
> I am happy you have found a work around to fix that bug that
> spoils my days.
>
> but, could anyone  from w3.org confirm that it is ok .
>
> When is the next official libwww  release that might include this patch ?
>
> thanks.
>
> Francois Nicot
>
>
>
>
Received on Tuesday, 23 May 2000 13:53:16 GMT

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