Mac OS X is undergoing a gradual transition to a 64-bit model. An 64-bit executable is a process that can support a 64-bit address space. In a 64-bit world pointers are 64 bits (eight bytes) and some integer types, once 32 bits, are now 64 bits. These fundamental changes required for 64-bit processes impact the programmatic interfaces of many of the frameworks of Mac OS X, including Cocoa, in various ways.
This document explains the rationale for the 64-bit transition and describes the 64-bit related changes to the Cocoa API. It also discusses the steps you must take to convert existing Cocoa applications to a 64-bit model.
This document has the following chapters:
“Moving to 64-Bit Addressing” provides background information about the 64-bit initiative for Mac OS X and offers general advice for developers thinking about moving their Cocoa projects to 64-bit addressing.
“64-Bit Changes To the Cocoa API” describes the changes to data types for integers, floating-point values, enumeration constants, and other types of values in the Cocoa API.
“Converting an Existing Application to 64-Bit” explains how to run the script for converting a Cocoa code base to 64-bit and describes modifications you may have to perform manually after the script is run.
“Optimizing Memory Performance” describes common memory usage patterns in 64-bit applications and how to profile your application to find them.
As a prerequisite to this document, read 64-Bit Transition Guide, which describes in full detail the reasons for the 64-bit transition, the fundamental changes to Mac OS X to support 64-bit addressing, and the general requirements and procedure for building 64-bit executables.
Last updated: 2009-04-30