RetroTechCollection

MacsBug Reference and Debugging Guide

The MacsBug Reference and Debugging Guide is Apple Computer, Inc.'s developer manual for MacsBug 6.2, published by Apple Developer Press, 1995 (© 1994, 1990 Apple Computer, Inc.). 410 pages, with full bookmarks and a text layer.

MacsBug is Apple's low-level assembly-language debugger for the 68 K Macintosh — the tool that catches a machine at the moment it crashes, below the level any application-level debugger reaches.

Contents

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  • Preface: About This Manual (p. xxi)
  • 1. MacsBug and Low-Level Debugging (p. 1) — error handling on the Macintosh, why low-level debugging, new features in 6.2
  • 2. Getting Started (p. 9) — installing MacsBug, installing under A/UX, displaying MacsBug on a different monitor (System 3.2–6.x and System 7.0 differ), the Debugger Prefs file, the MacsBug display regions (command line, PC, output, status/stack/register), invoking MacsBug — the programmer's switch, an 'FKEY' resource, or DebugStr from source
  • 3. An Assembly-Language Primer (p. 33) — 68 K instruction syntax and every addressing mode
  • 4. Macintosh Memory Organization (p. 65) — the memory map and its regions, using low-memory globals to draw a memory map, memory management under System 7, 32-bit addressing, virtual memory, registers, templates, the heap and heap blocks, and detecting a corrupted heap
  • 5–6 — the stack and A-traps, Macintosh interrupts and code that runs at interrupt time, VBL tasks, the A-trap action table, the file system (drive queue, file control blocks, file I/O queue)
  • 7. Debugging Strategies (p. 163) — before the crash and after it; the named failure modes "The Deep Freeze", "The Restart Surprise", "Nasty Pointers", "No Room to Maneuver"
  • 8 — macros, 'mxbm' resources, dcmds and how to build one
  • 9. MacsBug Commands (p. 207) — the full command reference, alphabetically from ATB

What it is good for on this wiki

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A Macintosh that crashes reproducibly at a known address is diagnosable with this book and a keyboard, without opening the case. Chapter 7 is the part worth reading: it separates a software crash from a hardware fault by what the machine does at the moment of failure, which is exactly the question a repairer needs answered before desoldering anything.

Chapter 4's memory map and low-memory globals are also the reference behind the address interpretation used in Sad Mac Error Codes — though the Sad Mac codes themselves come from the ROM, not from MacsBug.

What it does not contain

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No hardware information of any kind. No schematic, no part number, no component value, no voltage, no connector pinout. It is a software debugger manual. Do not cite it for a hardware figure.

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Download the MacsBug Reference and Debugging Guide here: MacsBug Reference and Debugging Guide.pdf (1.5 MB)

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