Path: utzoo!mnetor!uunet!husc6!bbn!uwmcsd1!leah!itsgw!imagine!pawl23.pawl.rpi.edu!jesup
From: jesup@pawl23.pawl.rpi.edu (Randell E. Jesup)
Newsgroups: comp.sys.amiga
Subject: Re: a very simple question on DoIO/GetMsg/device drivers
Message-ID: <180@imagine.PAWL.RPI.EDU>
Date: 24 Dec 87 08:01:20 GMT
References: <890@louie.udel.EDU>
Sender: news@imagine.PAWL.RPI.EDU
Reply-To: beowulf!lunge!jesup@steinmetz.UUCP
Distribution: na
Organization: RPI Public Access Workstation Lab - Troy, NY
Lines: 30

In article <890@louie.udel.EDU> rminnich@udel.EDU (Ron Minnich) writes:
>I have a very simple question and i think a very simple problem
>involving internet.device. Here is the scenario:
...
>   Telnet gets the news. It does a CheckIO(Request), which returns
>non-zero value. It also does a WaitIO for grins, and gets a zero
>back. Then the fun begins. The port in this case is called tcpinp.
>If i look at tcpinp->MsgList (not the exact name), the lh_Head
>points to Request, and lh_TailPred points to Request. But a 
>GetMsg(tcpinp) returns a 0! How can this happen?

	Note:  while it is not mentioned in the autodocs (people at C/A also
might want to note for the next autodocs), WaitIO removes the message
from the port, no GetMsg needed (it'll return 0 always).  Beyond that, it
sounds like many errors I've had: They seem absolutely incomprehensible,
to the point of blaming compilers/OS/whatever, until you walk through it or
tweak it for the nth time and the light suddenly dawns.
	A first step: dump the GetMsg and CheckIO, just WaitIO (if you don't
mind waiting, and know it'll be sent back.)  Next step, if it still doesn't
work, triple-check everything, make sure you're not playing with it anywhere
you shouldn't, snapshot the list before and after the WaitIO (Note: the
message will still have pointers to the list in it).  If it still doesn't
work, look at any code that uses messages you can find (like vt100 x.x).

>ron (rminnich@udel.edu)

     //	Randell Jesup			Lunge Software Development
    //	Dedicated Amiga Programmer	13 Frear Ave, Troy, NY 12180
 \\//	lunge!jesup@beowulf.UUCP	(518) 272-2942
  \/    (uunet!steinmetz!beowulf!lunge!jesup)