17 Bit Software 6: Level 6/17 Bit - Level 6 (1998)(Epic Marketing)[!].iso/quartz/q0705.dms/q0705.adf/Amiga/Appendices/GuruMeditation.doc

Text File | 1992-07-29 | 8KB | 273 lines

6    GURU-MEDITATION

6.1  INTRODUCTION

If you have been programming the Amiga for a while you have
most certainly seen your nice Amiga blow up in front of your
eyes. However, the Amiga is a nice computer, and if it crashes
it will try to do that as neatly as possible. You are usually
(!) allowed to save any important files, and when the Amiga
goes down it will give you a last message, trying to tell you
what went wrong.

Many programmers have not realized how important that last
message is. For them, it is just a collection of strange
numbers. But those numbers can actually tell you what exactly
went wrong, and once you know what went wrong, it is usually
no problem to find the bug.



6.2  AMIGA CRASHING

When the Amiga is crashing it happens that the Exec have
realized that something will go wrong and halted that task.
Exec will then open a System requester with a warning message:

  --------------------------------
  |  Software error - task held  |
  |   Finish all disk activity   |
  | Select CANCEL to reset/debug |
  |                              |
  | ---------         ---------- |
  | | Retry |         | Cancel | |
  | ---------         ---------- |
  --------------------------------

You can then save any important files to a disk before you
answer the requester (once you have pressed CANCEL the Guru
will visit you!). Important, since the Amiga is in trouble
it can crash any second, and if you were saving anything onto
a disk at that moment, the disk may become corrupted, and all
data lost. The best solution is to have an empty emergency
disk that you only use when the Amiga is upset. Sometimes the
Exec have not been able to halt the task, and the Guru will
immediately visit you.



6.3  GURU ALERTS

Once the Amiga really crashes, the powerlight will flash for
some seconds, and an Alert will be activated. For example:

  ----------------------------------------------------------
  | Software failure! Press left mouse button to continue. |
  |          Guru Meditation   #84010007.00C13870          |
  ----------------------------------------------------------

Now you only need to decode the message and you have found
the error. (Advanced programmer can attach a modem to the
Amiga and use a program called ROMWack in order to debug the
computer. But we will not discuss it here.)



6.4  GURU MEDITATION NUMBERS

There exist two different types of Guru Meditation Numbers:
  - CPU Errors (680x0 Processor Traps)
  - System Software Errors



6.5  CPU ERRORS

CPU Errors look like this:

Guru Meditation  #0000000x.yyyyyyyy

x is one of the following values:

2  Bus Error              Hardware error
3  Address Error          Word access on odd byte boundary
4  Illegal Instruction
5  Divide by zero
6  CHK Instruction
7  TRAPV Instruction
8  Privilege Violation
9  Trace
A  Opcode 1010 Emulation  Instruction word with a value
                          between A000-AFFF.
B  Opcode 1111 Emulation  Instruction word with a value
                          between F000-FFFF.

yyyyyyyy is the address of the task which went wrong. (It
is normally your own program that caused the problem.)

If you get a Guru Meditation number like #00000005.00C13870
it means: A program, at the address C13870, tried to devide
a value by zero. Since you now know what the error was you
only need to look at the places where your program can be
forced to devide a value by zero, and it should not take to
long time to find the bug.



6.6  SYSTEM SOFTWARE ERRORS

System Software errors look like this:

Guru Meditation  #aabbcccc.dddddddd

The first field of the number tells us if the error is a
Recoverable Error or if it is a Dead End Alert. If the error
is a Dead End Alert the number will start with 8 otherwise it
is 0. (The total screen will also be black, while on
Recoverable Errors the screen is merely pushed down a bit.)

The first field of the number tells us also which Device,
Library or Resource went wrong:

01  Exec Library         LIBRARIES
02  Graphics Library
03  Layers Library
04  Intuition Library
05  Math Library
06  CList Library
07  AmigaDOS Library
08  RAM Handler Library
09  Icons Library

10  Audio Device         DEVICES
11  Console Device
12  GamePort Device
13  Keyboard Device
14  Trackdisk Device
15  Timer Device

20  CIA Resource         RESOURCES
21  Disk Resource
22  Misc Resource

30  BootStrap            OTHERS
31  Workbench
32  Disk Copy

A number like 04 means: Recoverable Error in the Intuition
Library. While a number like 84 means: Fatal Error in
the Intuition Library.


The second field (bb) of the Guru Meditation number gives
us the general cause of the problem:

01  No Memory
02  Unable to Create Library
03  Unable to Open Library
04  Unable to Open Device
05  Unable to Open Resource
06  Input/Output (I/O) Error
07  No Signal

So a number like 8201cccc means a fatal error in the Graphics
Library, the problem was caused by not enough memory.


The last field (cccc) before the dot gives some more specific
information. Here is a list of some common Guru Meditation
Numbers: (This information is taken form the headerfile
"exec/alerts.h" [V1.3]:)

Exec Library:
  01000000
  81000001  68000 exception vector checksum
  81000002  Execbase checksum
  81000003  Library checksum failure
  81000004  No memory to make library
  81000005  Corrupted memory list
  81000006  No memory for interrupt servers
  81000007  InitStruct() of an APTR source
  81000008  A semaphore is in illegal state
  81000009  Freeing memory already freed
  8100000A  Illegal 68k exception taken


Graphics Library:
  02000000
  82010000  Graphics out of memory
  82010006  Long frame, no memory
  82010007  Short frame, no memory
  02010009  Text, no memory for TmpRas
  8201000A  BltBitMap, no memory
  8201000B  Regions, memory not available
  82010030  MakeVPort, no memory
  82011234  Emergency memory not available *


Layers Library:
  03000000
  83010000  Layers out of memory


Intuition Library:
  04000000
  84000001  Unknown gadet type
  04000001  Recovery form of AN_GadgetType
  84010002  Create port, no memory
  04010003  Item plane alloc, no memory
  04010004  Sub alloc, no memory
  84010005  Plane alloc, no memory
  84000006  Item box top < RelZero
  84010007  Open screen, no memory
  84010008  Open screen, raster alloc, no memory
  84000009  Open sys screen, unknown type
  8401000A  Add SW gadgets, no memory
  8401000B  Open window, no memory
  8400000C  Bad State Return entering Intuition
  8400000D  Bad Message received by IDCMP
  8400000E  Weird echo causing incomprehension
  8400000F  Couldn't open the Console Device


Amiga DOS Library:
  07000000
  07010001  No memory at startup
  07000002  EndTask didn't
  07000003  Qpkt failure
  07000004  Unexpected packet received
  07000005  Freevec failed
  07000006  Disk block sequence error
  07000007  Bitmap corrupt
  07000008  Key already free
  07000009  Invalid checksum
  0700000A  Disk Error
  0700000B  Key out of range
  0700000C  Bad overlay


RAM Library:
  08000000
  08000001  No overlays in library seglists


Trackdisk Device:
  14000000
  14000001  Calibrate: seek error
  14000002  Delay: error on timer wait


Timer Device:
  15000000
  15000001  Bad request
  15000002  Power supply does not supply ticks


Disk Resourcek.resource:
  21000000
  21000001  Get unit: already has disk
  21000002  Interrupt: no active unit


BootStrap:
  30000000
  30000001  Boot code returned an error


The number after the dot (dddddd dd) can be three things:
1. Address of the task which went wrong.
2. If the error occured because of some sort of memory
   allocation/deallocation, it is the address of that memory
   block.
3. If Exec is realy confused the number is 48454C50, which
   stands for HELP. (48=H, 45=E, 4C=L, 50=P)