Difference between revisions of "Debugging with GT.M"

Revision as of 22:47, 13 July 2005

Simple 'IDE' with GT.M

This is a simple debugger created with GT.M debugging commands:

It will currently show the source code, with the current line highlighted, as it steps through the code.

Here are the modules TMGIDE.m TMGTERM.m TMGTPSTP.m

To invoke:

do ^TMGIDE

K. Toppenberg

GT.M Debugging commands

This information is from the GT.M Programmer's Manual. I'll just summarize a few points.

• Dumping Information (actually just writes it out) when an error occurs.
• ZSHOW argument
  • ZSHOW "*" dumps all info known
  • ZSHOW "S" dumps the current stack
  • ZSHOW "B" dumps the current breakpoints established with ZBREAK command (below)

• $ECODE

   This is a list of past errors, separated by commas. 
   Subsequent errors are added to the end of the list.
   Example:
     GTM>w $ECODE
     ,M6,Z150373850, 
   Errors beginning with: "M" are standard errors
                          "U" are user errors
                          "Z" are GT.M errors

• $ZSTATUS

   This is detail about the most recent error.
   Example:
     GTM>w $ZSTATUS
     150373850,SubName+3^MyFunct,%GTM-E-UNDEF, Undefined local variable: Jxack

• $ZMESSAGE(x)

   This will give a text message for a given error number.
   Example: To get details about the error number, 150373850, given above...
     GTM>w $ZMESSAGE(150373850)
     %GTM-E-UNDEF, Undefined local variable: !AD

• ZPRINT x (e.g. ZPRINT SubName+3^MyFunct)

   This will display the line that cause the program exception.
   The 'x' may be obtained from $ZSTATUS, or from $ZPOS (see below)

• $ZPOSITION (OR $ZPOS)

   Shows the current position of the current line of execution 
  (or the last line exececuted in case of an error)
  From the manual: $ZPOSITION is a read-only GT.M special variable that provides another tool for locating and displaying the current line. It contains the current entry reference as a character string in the format label+offset^routine, where the label is the closest preceding label. The current entry reference appears at the top of the M invocation stack, that can also be displayed with a ZSHOW “S” command.
 Example:
 GTM>W $ZPOS
 name+2^dmex
 This example writes the current line position.

• ZWRITE

   Shows the entire variable table, displaying all defined variables.

• ZBREAK address:CodeToExecute

   Toggles a break point at address.  If CodeToExecute is null, then a 
   default value of break is used (dropping one back to the command line.)
   If CodeToExecute does not contain break, zbreak (or is not null) then control
   will not be dropped to the command line GTM>

   I believe that GT.M maintains only ONE breakpoint.
   
   e.g. GTM>ZBREAK Label+1^MyFunct:"set x=1" 

• ZSTEP x

   Will execute the program one line at a time.  I think this would be typically
   used after a ZBREAK drops command back to GT.M> prompt.
     ZSTEP INTO -- start execution at current execution point, and stops at
                   next line (even if that line is in a subroutine).
     ZSTEP [OVER] -- start execution at current exec. point, and stop at the 
                   next line at the same level on the invocation stack.
     ZSTEP OUTOF -- ??

• ZCONTINUE

   Continue execution from break point.

• $STACK AND $ZLEVEL

   $STACK starts at 0 and each DO inc's the value, each QUIT dec's it
   $ZLEVEL is $STACK+1

.. More later