🚀 go-pugleaf

In article <DEVEN.90Feb8035053@netserv2.rpi.edu> deven@rpi.edu (Deven T. Corzine) writes:
>Just curious...  what exactly happens when you SetFunction a library
>call and the library is later expunged?  Is it possible to be notified
>to remove the patch?  (or would you have to patch the Expunge() call
>of the library to do so?)  Or must you make sure you keep the library
>open for the duration of the SetFunction?

Exactly what you think. If you patch a library you MUST hold it in
memory as long as your patch should work. In a library this is easily
done with opening the library. A device (that's a special library) may
refuse to open from more programs at the same time, there you have to
patch the Expunge vector too.

Carolyn Sheppners program CMD (source on some fishdisk) shows this
method. It patches the devices Expunge and BeginIO vectors to catch
all CMD_WRITES to the parallel or serial device. It even checks if
another patch program has done a second SetFunction on these vectors
because this program might call CMD's patches in a daisy chain.

Michael van Elst
uunet!unido!mpirbn!p554mve