Re: 64 bit addressing

• Subject: Re: 64 bit addressing
• From: Mike Vannorsdel <email@hidden>
• Date: Mon, 30 Jun 2003 03:38:24 -0600

On Saturday, June 28, 2003, at 11:08, Mike Vannorsdel wrote:

Then it sounds like most of Mac OS X will remain 32-bit except for special cases (apps which need the large allocations). It seems like making the libraries 64-bit will cause huge backwards compatibility problems. Unless there are 32 and 64-bit versions of each.

I assume there will need to be an entire stack of libraries for 32 and another for 64 bit, with no mix-n-matching.

What would happen if your 32-bit code linked with a 64-bit lib?

I assume that the upper 32 bits in the general purpose registers in a 32-bit task would always be zeros, since the task wouldn't be putting anything in there itself. However, if the library tried to return something > 32 bits, the 32 bit task won't see the value properly in some way or other. Or, if a pointer to a pointer was being passed in, the 64-bit library might put a 64-bit pointer in the space for a 32-bit pointer that the app is passing a reference to. It's all just trouble waiting to happen.

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