Compiling for older versions of Mac OS X

Question

I have recently started producing applications for the Mac, on my most recent release I got overwhelming suggestions to get the app working on OSX 10.5 as I'm working in and compiling for 10.6.

I tried looking for the 10.5 SDK but couldn't find it anywhere to download! How can I go about compiling my app for older versions of Mac OS X using Xcode 2.2 and developing in 10.6?

EDIT: ------ I will mention I don't have the to option to select different SDKs as I don't have any others installed and my problem is more not being able to find where to get those sdks from? then actually not know how to go about compiling for the older sdks

Answer 1

This can be configured in the project or target settings (right-click -> Get Info):

Build -> Base SDK.

Answer 2

Redownload the entire Xcode Tools packages from http://developer.apple.com/mac/. Then, run the installer, and when you get to the screen that says "Standard Install", instead of pressing Continue, press Customize in the bottom left-hand corner. You should have the option to install MacOSX10.5.sdk as well as MacOSX10.4u.sdk.