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MacsBug is Apple's assembly-level 680x0 and PowerPC debugger for Mac OS. It can be used to debug code running in most execution environments, from applications to drivers and everything in between. It is often used as a bug-reporting tool by many Mac OS software developers.

This Note is directed at quality assurance engineers who do not have any experience with MacsBug.

Installing MacsBug

MacsBug can be downloaded from http://developer.apple.com/tools/debuggers/MacsBug/. The minimal installation requires that you take the file called MacsBug and move it into the System Folder. You need to restart the computer after installing MacsBug.

MacsBug is currently installed on each computer in the ADC Compatibility Labs. When an application crashes it will generally activate MacsBug, which will appear as a white screen with mostly black text. You may manually bring up MacsBug by hitting both the apple and power-on keys in unison. If an application crashes and activates MacsBug, it is a good idea to create a Standard Log and restart the system.

Useful MacsBug Commands

Here is a list of a few MacsBug commands that Mac OS system software developers find extremely useful while doing quality assurance.

Additional Notes & Comments

It is recommended that you restart after a crash that activates MacsBug. Whenever an application crashes, the machine is left in an unstable state and may affect your testing.

The Standard Log that MacsBug generates contains debugging information that is useful to programmers and should be included in your bug reports. It is also a good idea to attach the steps you used to cause the crash so a programmer can retrace your steps.

• Mac Tech Journal article "Getting Results with Macsbug: A Checklist of Techniques" at http://www.mactech.com/articles/mactech/Vol.07/07.09/MacsBugresults/
• "Tips and Tricks for MacsBug" at http://www.goingware.com/tips/macsbug.html
• "Accessing your globals in MacsBug", a Mac Tech Journal article at http://www.mactech.com/articles/mactech/Vol.08/08.07/MacsbugTemplate/

• "MacsBug for Non-Programmers" at http://www.macfixit.com/reports/MacsBug.shtml, a good general introduction to Macsbug and what to do with a crash for non-programmers.
• Macsbug documentation at http://developer.apple.com/tools/debuggers/MacsBug/ This Apple site contains the current release notes and a PDF file of the original "Macsbug Reference and Debugging Guide" for Macsbug 6.2.