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Using Cross-Development in Xcode

Using Xcode, you can develop software that can be deployed on, and take advantage of features from, different versions of Mac OS X, including versions different from the one you are developing on.

When you install the developer tools shipped with Mac OS X v10.3, you can also install SDKs, or Software Development Kits, which are complete sets of header files and stub libraries as shipped in previous versions of Mac OS X. In order to take advantage of cross-development, you must install the SDKs for the OS versions you plan on targeting. You then specify which version (or SDK) of Mac OS X headers and libraries to build with. You can also specify the earliest Mac OS X system version on which the software will run.

In some cases, Apple may seed an SDK for an upcoming version of the operating system, allowing you to prepare your application to work with future versions of the Mac OS before they have been released to the general public.

To set up your Xcode project for cross-development, take the following steps:

1. Choose an SDK to develop for. Select your project in the Groups & Files list and open an Info window. In the General pane, choose the SDK—for example, Mac OS X version 10.2.7—from the “Cross-Develop Using Target SDK” pop-up menu. When you choose an SDK, Xcode builds targets in your project against the set of headers corresponding to the specified version of Mac OS X, and links against the stub libraries in that SDK. This allows you to build products on your development machine that can be run on the system targeted by the SDK. Your software can use features available in system versions up to and including the one you select. The default value is to build for the current operating system.

   You can also type a path directly in the text field or click the Choose button to select an SDK other than a Mac OS X SDK, or to choose a Mac OS X SDK that is stored in a nonstandard location.

2. Choose a deployment version of the Mac OS. If your software must run on a range of operating system versions, choose a Mac OS X deployment operating system for each individual target that requires one. The deployment operating system identifies the earliest system version on which the software can run. By default, this is set to the version of Mac OS X corresponding to the SDK version. If no SDK is specified and the Mac OS X Deployment Target build setting is not set, the compiler targets Mac OS X version 10.1 by default.

   To set the deployment version for a target, select the target in the Groups & Files list and open an Info window. Click Build to open the Build pane.

   Find the Mac OS X Deployment Target setting and choose a deployment operating system from the pop-up menu in the “Value” column. If this build setting is not visible, select Deployment from the Collections menu.

3. For each target, supply a prefix file that takes into account the selected SDK. To use an umbrella framework header from an SDK as your prefix file, add the appropriate #include <Framework/Framework.h> directive to your target's prefix file, instead of setting a Prefix Header path to the umbrella framework header directly.

There is a lot more to successfully developing software for multiple versions of the Mac OS. For more information see Cross Development in Tools Documentation.

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