At 12:55 AM +0100 2001/07/07, Igor Mozolevsky wrote:
>So, how does one get the OS not to unload the code for a particular function when the
>app quits?
You don't. And you don't leave traps patched after your application exits.
However, there are several methods available to work around this. For example, copy
the patch routine(s) into an allocated [dynamic heap or feature] pointer so that
neither the code nor the allocated memory block is part of your application. Better
yet, write a system extension (not documented, sorry) which loads during the boot
sequence and permanently patches the trap (like System Updates do).
The latter is the best way to avoid problems without using a patch chain manager such
as Hackmaster. To understand why, you merely need to think through the following
[extremely common] situation: A and B are patches to the same trap. A is applied
first. Then B is applied. Then A is removed. The trap can no longer be called without
crashing. Hackmaster (et al.) remap the patch chain to avoid this situation. This is
why patching should *only* be done using one of the third-party trap managers.
Regards,
Jim Schram
Palm Incorporated
Partner Engineering
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