Building Cocoa Applications: A Step by Step Guide

Debugging Programs with gdb

The GNU debugger is gdb . It was written and is maintained by the Free Software Foundation. gdb is a powerful tool for looking inside a running program and trying to figure out why that program is not behaving as expected. Apple has modified gdb to be aware of Objective-C syntax and objects, and to work together with the PB and Terminal applications.

The gdb tool is located in the directory /usr/bin. If you click the Computer icon in the Finder’s toolbar and then select Macintosh HD, you will not see /usr listed. Mac OS X and the Finder hide many system details from the user, including Unix system directories such as /usr/bin, /bin, and /etc. You can view these directories in the Finder using the Go to Folder sheet, but you cannot see all directories in the Finder (e.g., the .app directories are hidden). You can, however, see all the filesystem directories in a Terminal shell — your vehicle for exploring the guts of Mac OS X.

Using gdb in Project Builder, Step by Step

The easiest way to use the gdb debugger is in PB. We’ll show you how to get started with that in this section. First, we must have an application to work with, so we’ll use a copy of the CircleView example application that is bundled with the Mac OS X developer system.

When you debug a running program within PB, you can access some of the most useful gdb commands graphically. You can set breakpoints by clicking the mouse next to a line of code (a breakpoint is a place where a running ...