How to tell if MacsBug is Installed

This is a small snippet of code that can be used to to detect if

macsbug is installed or not. NOTE: This code is intended to only work with

version 6.2 of macsbug. You should refer to your Low Level Debugger's manual

for more information on how they install themselves.

This code is based on information obtained from the MacsBug Reference.

The basic assumptions are that macsbug will install itself in the following

manner:

If you are running in 24 bit mode, then the high -order byte of MacJmp is a flags

byte that contains the following information:

Bit Meaning

--- --------------------------------------

7 - Set if debugger is running

6 - Set if debugger can handle system errors

5 - Set if debugger is installed

4 - Set if debugger can support discipline utility

The lower 3 bytes are used to store the address of the debugger's entry point.

If you are running in 32-bit mode, the flags byte is moved to address 0xBFF and

the long word at MacJmp becomes a full 32-bit address that points to the

debugger's entry point..

ADDENDUM: The above information seems to be incorrect in the reference

manual. I have found through testing etc. that in both modes, the Flag Byte

appears at location 0xBFF. The code reflects these findings.

#include

// Assumes inclusion of

// Proto types

Boolean MacsBugInstalled(void);

#define BYTEMASK 0x20 // Used to detect if bit 5 is set

Boolean MacsBugInstalled()

{

Ptr FlagByte = (Ptr)0xBFF; // This is used only if running in 32 bit mode

return (*FlagByte & BYTEMASK);

}

main()

{

if (MacsBugInstalled())

printf ("MacsBug is installed, go ahead and crash!");

else

printf ("MacsBug is not installed, be careful!");

}