Apple Darwin User Manual download pdf (Page 8)

As a general rule, in OS X v10.7 and later, the answer is probably yes. A 64-bit executable can provide many

benefits to users and to programmers, depending on the nature of your program.

There are a number of factors to consider when deciding whether to make your application run in 64-bit mode.

These considerations are described in the sections that follow.

Automatic Reference Counting

Applications that target OS X v10.7 and later should take advantage of automatic reference counting (ARC).

This technology frees you from having to manually retain and release objects, and in so doing, often fixes

latent bugs in applications.

ARC is supported only in the new Objective-C runtime, which is supported only in 64-bit applications. For this

reason, most new development should be 64-bit.

Operating System Version

Prior to OS X v10.6, all applications that shipped with the operating system were 32-bit applications. Beginning

in v10.6, applications that ship with the operating system are generally 64-bit applications.

This means that in v10.5 and previous, the first third-party 64-bit application that a user runs causes the entire

64-bit framework stack to be brought into memory, resulting in a launch performance penalty and significant

memory overhead.

Similarly, in v10.6 and later, the first non-64-bit-capable application pays a performance and memory footprint

penalty because OS X must bring in the entire 32-bit framework stack. Thus, if you are primarily targeting OS

X v10.6 and later, you should be 64-bit if at all possible.

Should You Recompile Your Software as a 64-Bit

Executable?

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Apple Darwin User Manual Page 8