darkness@altger.UUCP (Stefan Willmeroth) (11/06/90)
Hi fellow Windows-Programmers. Some days ago when my Excel 2.1c was killed apruptly with an unrecoverable application error I wondered if this would be the only way to deal with an GP-Fault. I dont know exactly about the rules and tricks of protected mode, but as far as I remember those GP-violations mostly result when an application adresses an undefined memory location or loads an invalid descriptor into a segment register. Why cant Windows tolerate those faults and map some unused bytes to the referred adress instead of shutting down the application and deleting the users work? The scheme of protected mode seems rather ridicolous to me since an application is allowed to trash another applications data without being shut down. In the case of modifying code segments a shutdown may remain the best way, but for simple memory-problems it seems overkill to me. So let the debug-version of Windows complain and the retail version be tolerant. If the program is too buggy, it will crash the system after all. Now... can such thing be implemented by changing a driver or device? Greetings Stefan Willmeroth -- ------------------------------------------------------------------- Stefan Willmeroth |Write a program even idiots can use, Munich/Germany |and you will see that only idiots will darkness@salyko.doit.sub.org|want to use it. (Murphy)
ed@odi.com (Ed Schwalenberg) (11/07/90)
In article <192@altger.UUCP> darkness@altger.UUCP (Stefan Willmeroth) writes:
Some days ago when my Excel 2.1c was killed apruptly with an unrecoverable
application error I wondered if this would be the only way to deal with
an GP-Fault. I dont know exactly about the rules and tricks of protected
mode, but as far as I remember those GP-violations mostly result when an
application adresses an undefined memory location or loads an invalid
descriptor into a segment register. Why cant Windows tolerate those faults
and map some unused bytes to the referred adress instead of shutting down
the application and deleting the users work?
Windows could do such a thing, but it would be irresponsible. If your
spreadsheet was broken and it just printed wrong answers instead of
crashing, I wouldn't want to drive on the bridge you were designing.
The scheme of protected mode
seems rather ridicolous to me since an application is allowed to trash
another applications data without being shut down.
In order to make Windows run in real mode as well as standard and extended
modes, some compromises were made. A wild reference by a Winapp might
cause that app to fail, but it might simply trash something else instead.
I wouldn't go so far as to call it ridiculous.
Now... can such thing be implemented by changing a driver or device?
It is possible to write a device driver using the DDK to do the sort of thing
you are interested in. More importantly, it is possible to write a driver
that displays a box that says:
General Protection fault by instruction at 105:6969 MOV ES,DX
AX=0000 BX=1234 CX=0001 DX=FFFF SI=0000 DI=0000
CS=0105 SS=087D DS=0785 ES=0000 FS=0000 GS=0000
which would give the programmer a clue as to what was happening.
It is similarly possible to write a driver which would let an application-
defined fault handler gain control and perform application-specific recovery
actions.