What to target on Mac OS X? 32-bit and/or 64-bit?

[agarny]

Hi,

I currently use the Cocoa: Mac binary package for Mac OS X 10.5 - 10.6 (32-bit and 64-bit) (http://qt.nokia.com/downloads/qt-for-open-source-cpp-development-on-mac-os-x) version of Qt 4.7.3, and I understand that it can be used to build both 32-bit and 64-bit applications.

Now, because Mac OS X 10.5 supports 64-bit applications, I was wondering whether there is still an argument in favour of having both a 32-bit and a 64-bit version of my application, or whether I could get away with just a 64-bit version of my application?

Certainly, Apple seems to be encouraging the development of 64-bit applications, and by default if I compile my application on my MacBook Air running OS X 10.6, I get a 64-bit executable. So, I am kind of inclined to only having a 64-bit version of my application, but because I am no Mac expert, I thought I would seek opinions from you guys here...

Cheers, Alan.

[koan]

If you only intend to support 10.5+ then 64 bit should be fine. Quite likely there will be no advantage to 64 bit over 32 bit AFAIK, the only way is to test performance in both. Some frameworks are not available in 64 bit (and some not in 32 bit) so think ahead to what functionality you might want to add in the future. Personally, I would be happy to be 64 bit only if I don't mind the limitation of 10.5+ only; Lion will be here soon.