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Changes made in release 1.01.1:
- Included the updated assembly source of the 1.01 release. Ooops.
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Changes made in release 1.01:
-ConsoleFix 1.00 failed from time to time if the console.device main task was,
due to some unfortune, not waiting in its main loop. Added a workaround
that checks several times.
-Added a version tag.
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Purpose of this program:
This little patch fixes possible crashes of the console.device task, which,
luckely, do not show up under "normal" circumstances. However, as soon as
the console.device supervisor task takes more stack than usual, or this
stack is filled by more than just zeros, the console device will crash on
window resizes.
The reason for this crash is that the console.device main task uses a
faulty algorithm to traverse an exec style list: The list header is
also processed as a "node". Due to some lucky coincidences, the only data
that gets querried by this faulty node is on the stack of the console device,
and again due to some coincidence, this points to an area of the stack which
is usually set to zero. All provided the stack of the console.device doesn't
grow too much.
For the experts:
The main loop of the console device looks like this:
lea WindowList(a6),a2 ;get the head of the window list
.loop:
bsr ProcessWindow ;re-calcutes the window on a resize
move.l (a2),a2 ;get next node
tst.l (a2) ;end of list?
bne.s .loop
Hence, the list header is processed as a first node. Urgh!
The correct method would have been:
lea WindowList(a6),a2 ;get the head of the window list
bra.s .into
.loop:
bsr ProcessWindow ;re-calcutes the window on a resize
.into:
move.l (a2),a2 ;get next node
tst.l (a2) ;end of list?
bne.s .loop
This program fixes this bug by "hacking in" a new main loop for the console
device, the source code is included.
I'm sorry for the uglyness of this patch, it was designed at 2 a.m. in the
night and I was all than awake. It currently works like it is, but I'd really
prefer if someone could write a "nicer" fix, or if AI would include this fix
in the "SetPatch" program.
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Credits:
Thanks goes to Nils Goers and his StackSnoop program. This console.device
problem showed up while Nils was beta-testing his program, and I was
curious what could have caused the crash. Stack-Snoop fills the application
stack with a "magic cookie" to find out the true stack size a program re-
quires, and this magic cookie caused the buggy code above to get mad.
Always interested in the true reason for a crash, I found the above bug...
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Copyright:
None, this is freeware, public domain. Do whatever you want to do
with it.
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Thomas,
October 1999
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