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Re: About Universal Binaries...




On Jan 31, 2006, at 6:06 PM, Juan P. Pertierra wrote:

From an initial look to the online Apple transition documentation it seems all the differences that have to be addressed span from the difference in byte order i.e. big endian vs little endian.

That's one thing, but there's a lot more than that:

1. On PPC, if some code divides by zero, then the result returned is NaN and the executable will continue running. On Intel, if some code divides by zero, then the executable crashes.

2. On PPC, the scalar values returned by sending a message to a nil argument are technically undefined, but tend to return 0 for all values that are not 64 bits long or longer. I wouldn't rely on this behavior on Intel builds.

3. Watch how you're using Unicode buffers. On PPC builds, -[NSString initWithData:encoding:] with NSUnicodeStringEncoding expects the data to be in big-endian format if there is no BOM; on Intel builds, it'll be expected to be in little-endian format if there is no BOM.

4. If you've got any vector code for PPC, you'll (most likely) have to rewrite it for Intel.

5. A few Carbon data structures (e.g. KeyMap) are very different on Intel than they are on PPC.

There's probably a few more, but that's all I can think of at the moment...

Nick Zitzmann
<http://www.chronosnet.com/>

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References: 
 >Still struggling with Universal Binaries (From: Aram Kudurshian <email@hidden>)
 >Re: Still struggling with Universal Binaries (From: Shawn Erickson <email@hidden>)
 >About Universal Binaries... (From: "Juan P. Pertierra" <email@hidden>)



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