Path: utzoo!attcan!uunet!aplcen!uakari.primate.wisc.edu!brutus.cs.uiuc.edu!usc!ucsd!ucbvax!RAND.ORG!salzman%iris
From: salzman%iris@RAND.ORG (Isaac Salzman)
Newsgroups: comp.soft-sys.andrew
Subject: Re: WP bug on SPARC, new release version?
Message-ID: <8911220012.AA02790@iris.rand.org>
Date: 22 Nov 89 00:12:47 GMT
References: <2657@auspex.auspex.com>
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 30


>(Actually, it's a bug in the WP code, which happens not to prevent it
>from doing what you want on many C implementations, but the SPARC and
>perhaps Pyramid C implementations are not among them; passing an object
>of type "foo" to a routine expecting an object of a union type that
>includes type "foo" is not valid C.)

i didn't think it was valid C. defeinitely not code that i would write :-)
(especially declaring the union as part of the paramater dec's - yech)!  but
since it worked under GCC on SPARC and both Sun's CC and GCC on the sun3....

>Is it ever the case that somebody passes something to "wp_DeAllocate"
>and doesn't know which of the N flavors of things that "wp_DeAllocate"
>can deallocate it is?  If not, perhaps the best long-term fix is to
>replace "wp_DeAllocate" with multiple deallocaters and call the correct
>one in each instance, passing it a pointer to a "wp_PrimeKeySet" or to a
>"struct wp_SrchToken".  (I.e., does all the code that calls it passing
>it a "struct wp_SrchToken *" really truly pass it a pointer to a
>"wp_SrchToken", not a pointer to a "wp_PrimeKeySet" in disguise, and
>*vice versa*?)

i haven't explored the andrew code a whole lot. i do know that andrew uses
(in some places) a classing mechanism. i guess it does not implement any
sort of dynamic binding (aka virtual functions in C++). here's a good case
for using an object system with dynamic binding. you wouldn't need to know
which of the N flavors of an object something is. it's determined at
runtime. just send the DeAllocate message (actually, just "delete" the object
in C++ and the destructors get called automatically)....

		-isaac (salzman@rand.org)