Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!wuarchive!usc!ucsd!ucbvax!mtxinu!taniwha!paul
From: paul@taniwha.UUCP (Paul Campbell)
Newsgroups: comp.sys.mac.programmer
Subject: Re: StripAddress...
Message-ID: <478@taniwha.UUCP>
Date: 3 Feb 90 22:12:30 GMT
References: <1990Feb2.010425.28126@oracle.com> <1461@husc6.harvard.edu>
Reply-To: paul@taniwha.UUCP (Paul Campbell)
Organization: Taniwha Systems Design, Oakland
Lines: 37

In article <1461@husc6.harvard.edu> siegel@endor.UUCP (Rich Siegel) writes:
>In article <1990Feb2.010425.28126@oracle.com> gstein@oracle.uucp (Gregory Stein) writes:
>>
>>Geez, it seems like StripAddress needs to be called *everywhere* if
>>you want to be 32-bit clean.  If you maintain any kind of information
>
>	Not quite. You should call StripAddress if you want to be sure
>that the address you get by dereferencing a handle is clear of any
>extra information such as flag bits. This is useful if you're planning to
>do any kind of address arithmetic. However, in the normal case, you
>can double-indirect a locked (or purgeable, or resource) handle and 
>still get the right thing, because the system only uses the low-order
>24 bits of whatever addresses you use.

It is also a problem if you are going to do a SwapMMUMode(1) call to get to
32-bit addressing on a 24-bit system in order to access a board with
more than 1Mb of slot space and then want to work with any indirected
handle, including the address of HLock()ed code - you have to load the
address of code, Stripaddress it and jump to it ie:


	lea	@1, a0
	move.l	a0, d0
	_StripAddress
	move.l	d0, a0
	jmp	(a0)
@1:	
	move.l	#1, d0
	_SwapMMUMode



	Paul

-- 
Paul Campbell    UUCP: ..!mtxinu!taniwha!paul     AppleLink: CAMPBELL.P
"Skifield": N, device to collect and refine assholes