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From: gardner@prls.UUCP (Robert Gardner)
Newsgroups: comp.sys.ibm.pc,comp.sys.mac,comp.sys.atari.st
Subject: LSC, function pointers, and segments
Message-ID: <8217@prls.UUCP>
Date: 5 Jan 88 00:29:25 GMT
References: <782@daisy.UUCP> <22358@ucbvax.BERKELEY.EDU>
Reply-To: gardner@prls.UUCP (Robert Gardner)
Organization: Philips Research Labs, Sunnyvale, California
Lines: 19

I started working on segmenting a large program that uses function pointers
rather extensively and got worried about assigning a function pointer
in one segment, unloading that segment, and having it accessed later from
another segment. Is the function pointer still valid?

Interestingly, when I step through the code with TMON I noticed that when
the function pointer is used it is called via JSR (A0), as expected,
but the next function called is something like JMP xx(A5), which is usually
the type of call you see in the jump table for a loaded segment, which
is replaced by _LoadSeg if the segment is unloaded. (I haven't yet had time
to see what it says when the segment is unloaded.)

So, it appears that the function pointer should still be valid, even
if the segment containing the function gets unloaded. I would like to know
if this is true, even for static functions, and if so, what kind of magic
makes it possible.

Thank you,
Robert Gardner