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Mac Forum / Programming / Mac Programming / February 200564-bit apps on Tiger
Does anyone have some practical experience with 64-bit apps on Tiger? The Apple page <http://developer.apple.com/macosx/tiger/64bit.html> mentions a strange limitation: no GUI in a 64 bit address space. Does this mean that Apple just hasn't gotten around to updating the libraries, or is there a more fundamental reason? Are there any other 'gotcha's that detract from the "64 bit experience"? Can an application have full 64-bit math support without the the 64 bit address space? -just curious > Can an application have full 64-bit math support without the the 64 bit > address space? Yes, the two are completely unrelated. You can use 64 bit instructions today on a G5 system running 10.3.x (gcc -mpowerpc64). Paul > The Apple page <http://developer.apple.com/macosx/tiger/64bit.html> > mentions a strange limitation: no GUI in a 64 bit address space. Does > this mean that Apple just hasn't gotten around to updating the > libraries Its probably that. Lots of stuff (parts of Carbon for example) assume pointers are 32 bits. It'll take forever to change. :) > The Apple page <http://developer.apple.com/macosx/tiger/64bit.html> > mentions a strange limitation: no GUI in a 64 bit address space. Does > this mean that Apple just hasn't gotten around to updating the > libraries, or is there a more fundamental reason? The fundemental reason is pretty simple - GUIs do not, as a rule, need to access huge amounts of data, so users are not clamoring for 64 bit pointer access in Cocoa. They are so clamoring for 64 bit underlying libraries. Further, doubling the size of pointers requires, at the least, a redefinition of the base pointer types, and thus a doubling of the ram required (for those pointers). Such binaries would also be incompatible with older systems. So, you get more memory use, and slower access on systems without a 64 bit integer data path, with little benefit. Eventually, this will change. They will have a G5 powerbook, and will decide that backwards incompatibility is a price worth paying for not having to code (slightly) differently when writing big server apps vs GUI apps. The reference documents on 64 bit codinghave advice on how to put a 32 bit GUI on a 64 bit process. Not that difficult, and similar to what we were doing already for our data analysis apps. Frankly, writing command line-style tools to do heavy lifting with a simple gui on top is pretty useful if you ever expect to need it to become a web app. Scott > > The Apple page <http://developer.apple.com/macosx/tiger/64bit.html> > > mentions a strange limitation: no GUI in a 64 bit address space. Does [quoted text clipped - 5 lines] > pointer access in Cocoa. They are so clamoring for 64 bit underlying > libraries. What I want to know, which isn't really answered, is what level of 64-bit support there is in Objective-C and the non-GUI parts of Cocoa (the Foundation classes). Separating an app's GUI from its back-end code is easy enough, but it would be nice to be able to use Obj-C and the foundation classes *in* the back-end code. [snip]  SignatureIs Bush wearing a LifeVest defibrillator? http://nyc.indymedia.org/newswire/display/136872/ In comp.sys.mac.programmer.misc ZnU <znu@fake.invalid> wrote: > What I want to know, which isn't really answered, is what level of > 64-bit support there is in Objective-C and the non-GUI parts of Cocoa > (the Foundation classes). Separating an app's GUI from its back-end code > is easy enough, but it would be nice to be able to use Obj-C and the > foundation classes *in* the back-end code. As far as I am aware, libobjc has not been ported to 64-bit, so you won't be able to write 64-bit ObjC code *at all* at least with the first revision of Tiger. (That's just hedging my bets; as far as I know, Apple may not get libobjc ported over for quite some time, but they might.) In comp.sys.mac.programmer.misc Sam Hutchings <spamBucket@stop.spam.on.the.net> wrote: > Does anyone have some practical experience with 64-bit apps on Tiger? > > The Apple page <http://developer.apple.com/macosx/tiger/64bit.html> > mentions a strange limitation: no GUI in a 64 bit address space. Does > this mean that Apple just hasn't gotten around to updating the > libraries, or is there a more fundamental reason? It's basically just a matter of updating the libraries, but this is a huge undertaking. It's not just a matter of flipping a switch and recompiling, as there's probably a great deal of code in them that relies on the size of pointers being four bytes, and it all has to be tracked down and changed. Since this isn't the primary place where 64-bit support can be useful, Apple hasn't done it yet. Even Tiger's kernel is still 32 bit. > Even Tiger's kernel is still 32 bit. Are you sure? How can a process address 64-bits of virtual memeory if the kernel can only address 32-bits of memory? At least under Solaris, a 64-bit kernel can run both 64- and 32-bit bit binaries. But a 32-bit kernel can only run 32-bit binaires. SignatureDavid Magda <dmagda at ee.ryerson.ca>, http://www.magda.ca/ Because the innovator has for enemies all those who have done well under the old conditions, and lukewarm defenders in those who may do well under the new. -- Niccolo Machiavelli, _The Prince_, Chapter VI In comp.sys.mac.programmer.misc David Magda <dmagda+trace050112@ee.ryerson.ca> wrote: >> Even Tiger's kernel is still 32 bit. > > Are you sure? Positive. > How can a process address 64-bits of virtual memeory if > the kernel can only address 32-bits of memory? Because memory access goes through the processor and MMU, not the kernel. All the kernel has to do is manage paging and be able to read from the memory of 64-bit processes, both of which it can do in 32-bit mode. > At least under Solaris, a 64-bit kernel can run both 64- and 32-bit > bit binaries. But a 32-bit kernel can only run 32-bit binaires. That's because of Solaris's architecture, not something inherent in kernel design. >Does anyone have some practical experience with 64-bit apps on Tiger? > >The Apple page <http://developer.apple.com/macosx/tiger/64bit.html> >mentions a strange limitation: no GUI in a 64 bit address space. Does >this mean that Apple just hasn't gotten around to updating the >libraries, or is there a more fundamental reason? That's fundamental enough, I'd think. >Are there any other 'gotcha's that detract from the "64 bit experience"? > >Can an application have full 64-bit math support without the the 64 bit >address space? Yes, see that same page under "Benefits to 32-bit Applications" SignatureThere's no such thing as a free lunch, but certain accounting practices can result in a fully-depreciated one. |
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