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Article #3319

Re: What's an APTR, BPTR?

#3319
From: Dave Mc Mahan
Date: Fri, 13 Apr 1990 04:41
33 lines
1829 bytes
In article <DEVEN.90Apr12051138@netserv2.rpi.edu> deven@rpi.edu (Deven T. Corzine) writes:
>
>
>So, as you can see, CPTR is a "fixed" APTR typedef.  Unfortunately, it
>is still misdefined.  Properly, APTR should be defined as:
>
>typedef VOID            *APTR;      /* absolute memory pointer */
>
>which is a generic pointer.  The original APTR ended up being an
>unsigned char **, which is clearly wrong.  The "fixed" CPTR is an
>unsigned long, which is actually worse, since APTR is at least a
>pointer.  (just a pointer to a pointer)  CPTR is not a pointer, so if
>the pointers in the machine were, say, 64 bits, a CPTR would be the
>wrong size, but an APTR would not.
>
>All of this is somewhat academic at this point, since all three forms
>work within the present architecture -- they all resolve to a 4-byte
>(longword) value.  Still, both "official" definitions are wrong.
>

The only problem I have run into with this is when doing pointer arithmatic.
Doing things like incrementing a pointer tends to give different results,
depending on if you use APTR, CPTR, or whatever.  I usually just use casts
to keep my compiler from barfing and then make it whatever I want it to be
within the declaration of my program.

>*sigh*
>
>Deven


double sigh,
  -dave
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References: <3421@newton.physics.purdue.edu> <10712@cbmvax.commodore.com> <1990Apr11.103419.29002@bath.ac.uk> <DEVEN.90Apr12051138@netserv2.rpi.edu>

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Path: arc1-ca.pugleaf.net!utzoo!utgpu!watserv1!watmath!att!tut.cis.ohio-state.edu!snorkelwacker!apple!netcom!mcmahan
From: mcmahan@netcom.UUCP (Dave Mc Mahan)
Newsgroups: comp.sys.amiga.tech
Subject: Re: What's an APTR, BPTR?
Message-ID: <10923@netcom.UUCP>
Date: 13 Apr 90 04:41:15 GMT
References: <3421@newton.physics.purdue.edu> <10712@cbmvax.commodore.com> <1990Apr11.103419.29002@bath.ac.uk> <DEVEN.90Apr12051138@netserv2.rpi.edu>
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