tdb: the TSF debugger

In order to help users to follow the execution of their scripts and to understand problems, a debugger has been developed. This one provides the usual operations that you can expect from a tool of this kind.

The debugger is launched from the main TSF window (menu Options/Debugger). Its invocation starts a new window which corresponds to the console of the debugger. Once started, it reads commands from the terminal until you tell it to exit with the tdb command quit. You can get online help from tdb itself by using the command help.

Here is a description of the tdb commands:

  $\blacktriangleright$ help

[NAME] 
  Show information about tdb command NAME.

  $\blacktriangleright$ cont

[nb] 
  Restart the execution. The optional argument is the number of breakpoints to ignore. $\vartriangleright$ Example 68:

      cont		     : continue the execution


cont 10		  : continue the execution but ignore 10 breakpoints

    

  $\blacktriangleright$ print

[VAR] 
  Display the content of the variable VAR.

  $\blacktriangleright$ quit

 
  Quit the debugger and close the tdbcons window.

  $\blacktriangleright$ break

[SCRIPT] [NAME] 
  Enable the breakpoint NAME in the specified SCRIPT.
SCRIPT:

• The symbol . is a shortcut for the current script.
• The symbol * is a shortcut for all scripts (only with @enter and @exit)

NAME:

• A name must start by the symbol @
• Some breakpoints of names @enter and @exit are implicitaly created at the beginning and at the end of each scripts.

$\vartriangleright$ Example 69:

• break : enable all users breakpoints (not @exit and @enter)
• break test @1 : enable the breakpoint @1 in the script test
• break . : enable all breakpoints in the current script
• break * @exit : enable a breakpoint at the end of each script

  $\blacktriangleright$ delete

[SCRIPT] [NAME] 
  Disable the breakpoint NAME in the specified SCRIPT.

SCRIPT:

• The symbol . is a shortcut for the current script.
• The symbol * is a shortcut for all scripts (only with @enter and @exit)

NAME:

• A name must start by the symbol @
• Some breakpoints of names @enter and @exit are implicitaly created at the beginning and at the end of each scripts.

$\vartriangleright$ Example 70:

         delete		               : disable all users breakpoints (not @exit and @enter)


delete test @1		       : disable the breakpoint @1 in the script test  

delete . 		        : disable all breakpoints in the current script 

delete * @exit		       : disable a breakpoint at the end of each script 
       

  $\blacktriangleright$ list

[SCRIPT] 
  Display the status of the breakpoints.

$\vartriangleright$ Example 71:

      list		     : list all breakpoints


list main		  : list the breakpoints in the function main

      

  $\blacktriangleright$ display

[VAR] 
  Print the content of the variable VAR after each breakpoint. $\vartriangleright$ Example 72:

    display i 
  

  $\blacktriangleright$ trace

[on/off] 
  Activate/desactivate the breakpoint tracing.

  $\blacktriangleright$ dump

 
  Print all variables.

  $\blacktriangleright$ where

 
  Print the position in the stack.

  $\blacktriangleright$ up

 
  Go up in the stack.

  $\blacktriangleright$ down

 
  Go down in the stack.

  $\blacktriangleright$ stack

 
  Display the stack.

  $\blacktriangleright$ go[LEVEL

] 
  Move directly at the specified level in the stack.

  $\blacktriangleright$ undisplay

[VAR] 
  Disable a display command.

$\vartriangleright$ Example 73:

      display i


undisplay i

    

  $\blacktriangleright$ ABORT

 
  When a script is running, the key CTRL-C aborts the execution at the next BREAKPOINT even if it is not activated. A loop without a BREAKPOINT or a script call cannot be stopped.

  $\blacktriangleright$ error

 
  Terminate the script by an error. Warning, you have to execute a cont command after the error command to quit the script.

Breakpoints are set directly in TSF scripts by using the keyword BREAKPOINT. The syntax of the command is the following.

  $\blacktriangleright$ BREAKPOINT

[N] 
   Set a breakpoint in the script. N will be the identifier of the breakpoint and will be used by the tdb commands at the console level.

  

Figure 10: Example of TSF script which use breakpoints

SCRIPT facto(n,res)


xx:="test"


BREAKPOINT(2)


IF (n<=1) THEN  

res:=1


ELSE 

CALL facto(n-1,&res)


res := res*n


ENDIF      

ENDSCRIPT




SCRIPT main()


a:=1 

PRINT a


BREAKPOINT(1)


a:=2  

res:=9999


CALL facto(5,&n)


PRINT n


BREAKPOINT(3)


ENDSCRIPT

The figure 11 illustrates the use of the tdb commands during the execution of the script presented figure 10.

  

Figure 11: Example of use of the tdb commands

Action	tdb commands (in console)	Results
Launch the execution of the script		(tdb) Script is running
		BREAK in script main at @enter
	list	All breakpoints are ON
	cont	BREAK in script main at @1
	cont	BREAK in script facto at @2
	stack	3: <TOPLEVEL>
		2: main
		* 1: facto
	cont 3	BREAK in script facto at @2
	stack	6: <TOPLEVEL>
		5: main
		4: facto
		3: facto
		2: facto
		* 1: facto
	dump	# Symtab facto
		- n = 2 - xx = 'test' - res -> res # Symtab <COMMON> - $cstat = FALSE - $cforlib : TYPE forlib - $verbose = FALSE - $cfile : TYPE flb-file - $version = 1.01 - $csel = FALSE - $debug = TRUE - $cunit : TREE unit # Symtab <GLOBAL>
	where	At level 1/6 in facto
	up	At level 2/6 in facto
	display n	n = 3
	down	At level 1/6 in facto
	print n	n = 2
	delete facto @2
	list	facto @2 : OFF
		facto + : ON
		Other breakpoints are ON
	cont	BREAK in script facto at @enter
	delete facto *
	list	facto @2 : OFF
		facto * : OFF
		facto + : ON
		Other breakpoints are ON
	cont	BREAK in script facto at @exit
	delete .
	list	facto * : OFF
		Other breakpoints are ON
	cont	BREAK in script main at @3
	dump	# Symtab main
		- n = 120 - a = 2 - res = 9999 # Symtab <COMMON> - $cstat = FALSE - $cforlib : TYPE forlib - $verbose = FALSE - $cfile : TYPE flb-file - $version = 1.01 - $csel = FALSE - $debug = TRUE - $cunit : TREE unit # Symtab <GLOBAL>
	cont	Script is terminated