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Ulm's Modula-2 System:
mdb

NAME

mdb - Modula-2 debugger

SYNOPSIS

mdb [-f] [objfile [corefile]]

DESCRIPTION

Mdb is a Modula-2 debugging tool. Objfile is an executable program file (default: a.out). Corefile is assumed to be a core image file produced after executing objfile; the default for corefile is core. Under f-option mdb gives a backtrace and error diagnostics. Otherwise mdb switches to command mode.

WINDOWS

Mdb builds up a tree of windows according to the program found in objfile and the reference files of the modules used in the program. The M-window (i.e. the root) contains the list of all global modules. The D-windows show the contents of all variables of a certain level. The procedure backtrace is shown in the P-window. You can examine parts of your source code by using the T-window. The C-window enables you to read the core dump. For example, you may select a certain procedure shown in the P-window by moving the cursor to it, then change to D-window to examine the variable values. The I-window allows to examine disassembled code.

COMMANDS

The command lines of the mdb are of the following syntax:

	 line	  = cmd	{ ";" cmd }.
	 cmd	  = count letter { arg } .
	 arg	  = intarg | strarg .
	 count	  = intarg .
	 intarg	  = ["-"] digit	{ digit	} [H|B]	.
	 strarg	  = text | "'" text "'"	| '"' text '"' .

q, x: exit
!: shell command
= value ['x'|'d'|'o']: convert value into hexadecimal, decimal (default) or octal format.
e: print run time error messages
h: displays an overview of the commands.
i [address] ['d'|'t']: switches to the I-window at location address in space 't' (a.out-file: default) or 'd' (core-file / current process). If address isn't specified the next instruction after the last 'i' command will be printed.
$m ['x'|'d'|'o']: print map in hexidecimal (default), decimal, or octal format (for further information about maps see adb(1)).
$r ['x'|'d'|'o']: print register contents and the last instruction. If a run time library routine is executed, two instructions will be printed: that of the library routine and the next instruction of the Modula-2 procedure.

Window Switches

p: switch to P-window.
P [pdesc]: Modula-2 process switch. The optional parameter specifies the address of a process descriptor. The address may be omitted if being in a D-window and a process variable have been choosen.
M: Switch to current coroutine. (Useful after 'P' command.)
d: switch to D-window.
m: switch to M-window.
c [address ['x'|'d'|'o'|'c' ['x'|'d'|'o']]]: switch to C-window. The C-window starts at address if specified, else it displays the contents of the current variable. The second parameter determines the data format, the third paramter determines the address format.
t [filename]: switch to T-window.

Positioning

<return>, + [lines]: next line / move lines lines (default: 1) forward.
- [lines]: move lines lines (default: 1) backward.
b: display last page.
n: display next page.
u: print context of current line.
/pattern: search forward for pattern.
?pattern: search backwards for pattern.

Process Control

R: start process
C: continue process
I: continue process and ignore last interrupt

Breakpoints

Breakpoints may be set at the begin and end of every procedure. For each breakpoint a counter has to be specified according to following rule:

0: ignore breakpoint
n > 0: stop when breakpoint is reached the n-th time and delete breakpoint.
-1: stop every time breakpoint is reached.

B [count1 [count2]]: set breakpoints at begin of the procedure (count1) and at the end of the procedure (count2).
D: delete breakpoint

ENVIRONMENT

MODPATH: MODPATH specifies a list of directories separated by colons. This path is used for the search of reference file archives named REF.
SRCPATH: This path is used on the search for source files (T-window!) and reference files.
MDBPS: defines the prompt (default: "> ").

CAVEATS

Avoid commands like "/7" because 7 is interpreted as an integer argument and "/" expects a string argument. The correct solution ist "/'7'" which enforces the "7" to be interpreted as string argument.

SEE

m2c

FILES

`*.r`	reference files
`REF`	archive with reference files
`/usr/local/lib/modula/REF`	Modula-2 library reference files
`a.out`	default object file
`core`	default core file

BUGS

Mdb has not yet been ported to the Solaris2.x/SPARCv8 platform.

Edited by: borchert, last change: 1997/02/24, revision: 1.2, converted to HTML: 1997/04/28