Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!ucbvax!dewey.soe.berkeley.edu!mkent
From: mkent@dewey.soe.berkeley.edu (Marty Kent)
Newsgroups: comp.sys.mac.programmer
Subject: Globals in Device Drivers, LSC 3.0 ??
Message-ID: <28152@ucbvax.BERKELEY.EDU>
Date: 23 Feb 89 21:12:59 GMT
Sender: usenet@ucbvax.BERKELEY.EDU
Reply-To: mkent@dewey.soe.berkeley.edu (Marty Kent)
Organization: School of Education, UC-Berkeley
Lines: 28

I'm building a device driver to implement journalling (as hinted at in
IM-I), using Think C 3.0.  Things seem to be okay except my globals aren't
working.  The Think manual (pg 76-77) says the driver glue is supposed to
pre-allocate space for the globals in the device control block's
dCtlStorage field, and that the device's Open routine should check to make
sure that's been done properly (i.e. the field should be a handle rather
than 0). When I read this I assumed the implicit possible problem was the
usual one with dynamic storage allocation, i.e. maybe there wasn't enough
space.  

It turns out my Open routine *is* finding a 0 in the dCtlStorage
field. Since I'm running with 8Meg of memory on a Mac II, I know there's
enough memory.  (In fact, when I added an explicit call to NewHandle in my
Open routine, it worked fine.)  Does anyone have any ideas as to what
I might be doing that's causing the driver glue to fail to allocate the
globals?

By the way, if I let the driver open with a null dCtlStorage, the
individual routines work fine, but they can't communicate with each
other. This is all running under MultiFinder, System 4.3, Finder 6.0. Any
clues will be much appreciated!


Marty Kent  	Sixth Sense Research and Development
		415/642 0288	415/548 9129
		MKent@dewey.soe.berkeley.edu
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