Re: 64-bit, 10.5/10.4, SDK build settings
Re: 64-bit, 10.5/10.4, SDK build settings
- Subject: Re: 64-bit, 10.5/10.4, SDK build settings
- From: Greg Guerin <email@hidden>
- Date: Tue, 2 Jun 2009 14:55:33 -0700
Alex Sheh wrote:
So my understanding is, if I build a 64-bit Objective-C
application, then it can only run on 10.5 or later (since there is
no 64-bit Objective-C runtime on 10.4). And if I want an Objective-
C application to run on 10.4, then it must be compiled as 32-bit.
Correct.
This would mean that I need to ship 2 versions of the software, an
installer containing the 32-bit version of the Objective-C
application to run on 10.4 (Tiger), and another installer
containing the 64-bit version of the Objective-C application to run
on 10.5 (Leopard) or later.
Incorrect.
Universal binaries can be 4-way executable: ppc + ppc64 + i386 + x86_64.
The slice for one arch, say "ppc", need not be compiled for the same
OS version as the slice for another arch, say "ppc64".
... the ppc64 binary would have to be either 32-bit or 64-bit, ...
That's nonsense. There is no such thing as a ppc64 binary that's 32-
bit. It doesn't exist. It can't exist. If it's ppc64, it is always
and only 64-bit.
What can and does exist is a 32-bit binary that runs on a CPU which
can also run the ppc64 arch name, namely a G5. That arch name is
"ppc" or "ppc7400", though, not "ppc64".
Every CPU that can run ppc64 can also run ppc. Likewise, every CPU
that can run x86_64 can also run i386.
You're really confused about this. You should start with what the
hardware is. What CPU does the user have? Once that's been
identified, you can determine which arch names will execute on it.
Next you determine what OS version the user has. This will determine
whether there is or isn't a 64-bit option at all. If there's no 64-
bit option for the OS, then it doesn't matter what the hardware is,
you can't run 64-bit on that OS version.
If that's still confusing, then draw the logic tree as an actual
diagram on a piece of paper, starting with CPU hardware and adding
conditionals for OS version.
-- GG
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