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Building a Universal Binary

Architectural differences between Macintosh computers that use Intel and PowerPC microprocessors can cause existing PowerPC code to behave differently when built and run natively on a Macintosh computer that uses an Intel microprocessor. The extent to which architectural differences affect your code depends on the level of your source code. Most existing code is high-level source code that is not specific to the processor. If your application falls into this category, you’ll find that creating a universal binary involves adjusting code in a few places. Cocoa developers may need to make fewer adjustments than Carbon developers whose code was ported from Mac OS 9 to Mac OS X.

Most code that uses high-level frameworks and that builds with GCC 4.0 in Mac OS X v10.4 will build with few, if any, changes on an Intel-based Macintosh computer. The best approach for any developer in that situation is to build the existing code as a universal binary, as described in this chapter, and then see how the application runs on an Intel-based Macintosh. Find the places where the code doesn’t behave as expected and consult the sections in this document that cover those issues.

Developers who use AltiVec instructions in their code or who intentionally exploit architectural differences for optimization or other purposes will need to make the most code adjustments. These developers will probably want to consult the rest of this document before building a universal binary. AltiVec programmers should read “Preparing Vector-Based Code.”

This chapter describes how to use Xcode 2.2 to create a universal binary, provides troubleshooting information, and lists relevant build options. You’ll find that the software development workflow on an Intel-based Macintosh computer is exactly the same as the software development workflow on a PowerPC-based Macintosh.

Contents:

Build Assumptions
Building Your Code
Debugging
Troubleshooting Your Built Application
Determining Whether a Binary Is Universal
Build Options
See Also

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