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Re: [objc-improvements] Just remembered something about multiple method


From: Chris Hanson
Subject: Re: [objc-improvements] Just remembered something about multiple method signatures...
Date: Sun, 7 Sep 2003 17:07:09 -0500

On Saturday, September 6, 2003, at 02:54  AM, David Ayers wrote:
It doesn't on my architecture and probably not on the G4, but it would on 64 bit archs where small enums (i.e. NSComparisionResult) are not the same size as id (I'm not sure how the G5 handles small enums).

I've seen a couple of the comments and questions about the G5 so far in this and related threads. I just thought I'd point out how Mac OS X and the G5 behave together.

Apple provides some details for developers here:

  http://developer.apple.com/hardware/g5/

Essentially, right now Mac OS X does not support user-level code with a 64-bit address space (to my knowledge, anyway). Instead, it only supports 64-bit integer operations. Furthermore, it does so without changing the size of existing data types (int, long, void*, etc.).

The reason is compatibility. A developer can release a single executable that supports G3, G4, and G5 without resorting to building a triple-fat executable (one binary for each architecture combined into a single file). Instead, the developer can build a particular source file with PowerPC 970 optimization and PowerPC-64 integer instruction generation, detect which processor the user has at run time, and use the code in that file in that particular case. This is the same way AltiVec & G4 optimization is done.

  -- Chris

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