$STACK VS $ESTACK QUESTION

[Kevin Toppenberg]

I am trying to figure out how to use $STACK vs $ESTACK.

I know that there is a FUNCTION $STACK(), which is different from the VARIABLE $STACK, which holds the size of the stack array. 

I have been working on my TMGIDE debugger, trying to improve the stack display. 

In my debugger, I am stepping through this test code:

...
 +23 NEW i,JDX,k
 +24 for i=1:1:10 do  write "+"
 +25 .for JDX=1:1:10 do  write "^"
 +26 ..WRITE !,JDX,!
 +27 ..for k=1:1:10 do  write "%"
 +28 ...write "*"
>+29 ...write "^"
 +30 ...write "%"

when on line 29, I ask for display of stack.   I use this code to display the stack.

  NEW STACKSZ SET STACKSZ=$STACK
  write !,"$STACK:",!
  for IDX=0:1:STACKSZ do
  . NEW ENTRY SET ENTRY=$STACK(IDX)
  . NEW POS SET POS=$STACK(IDX,"PLACE")
  . NEW CODE SET CODE=$STACK(IDX,"MCODE")
  . write IDX,") ",ENTRY," -- ",POS,":  ",CODE,! 
  WRITE !,"$ESTACK=",$ESTACK,!
  DO PRESS2GO^TMGUSRI2

This gives me this output:

$STACK:
0) -dir -- +1^GTM$DMOD:
1) DO -- MENUDONE+6^TMGIDE:    DO PROMPT("AllInOne")
2) DO -- PPT2+39^TMGIDE:    XECUTE tmgDbgLine
3) XECUTE -- @:  do ^TMGTEST
4) DO -- TMGTEST+23^TMGTEST:   for i=1:1:10 do  write "+"
5) DO -- TMGTEST+24^TMGTEST:   .for JDX=1:1:10 do  write "^"
6) DO -- TMGTEST+26^TMGTEST:   ..for k=1:1:10 do  write "%"
7) DO -- TMGTEST+28^TMGTEST:   ...write "^"
8) $$ -- SP2+45^TMGIDE2:    IF tmgRunMode'=2 DO  ;"2=Don't show code
9) DO -- SP2+46^TMGIDE2:    . DO CMDPROMPT ;"display prompt and interact with user
10) DO -- CMDPROMPT+8^TMGIDE2:    FOR  DO  QUIT:tmgDone=1
11) DO -- CMDPROMPT+58^TMGIDE2:    . IF tmgAction["STACK" DO HndlStack^TMGIDE2C(.tmgIDEPos,.tmgViewOffset) QUIT
12) DO -- HndlStack+7^TMGIDE2C:    NEW Stack DO GetStackInfo(.Stack,tmgOrigIDEPos)
13) DO -- GetStackInfo+11^TMGIDE2C:    for IDX=0:1:STACKSZ do

$ESTACK=5
----- Press Key To Continue -----

Notice that the lines in green (1,2 ) are indicative of my entry into my debugger ^TMGIDE.  Line 3 in blue is where I tell the debugger to launch ^TMGTEST and lines 8-12 in white are where my debugger is handling my request for stack display, entered at a command prompt.

Now step-by-step debugging is achieved by using ZBREAK and ZSTEP's so that yottadb will execute just 1 command at a time.  After each line is executed, a function in my code, STEPTRAP^TMGIDE2 is called.  And a that code starts like this:

STEPTRAP(tmgIDEPos,tmgMsg)  ;

...

  NEW $ESTACK  ;"Any entries into $ESTACK will be related to debugger, for filtering $STACK
  NEW tmgdbgTruth SET tmgdbgTruth=$TEST   ;"save initial value of $TEST

Notice that as soon as I start the STEPTRAP, is NEW $ESTACK.   The idea being that any additional items added to stack should not be related to running program, so shouldn't be shown. 

What does value of $ESTACK=5 mean in this context? 

CONCLUSIONS:

The stack level seems to be 8 when STEPTRAP is called (SP2 is in STEPTRAP).  Since I NEW $ESTACK, this is apparently set this to 0 (not 1).  We therefore have the following values as the program progresses

• $STACK        $ESTACK
•    8     --      0
•    9     --      1
•   10     --      2
•   11     --      3
•   12     --      4
•   13     --      5

Therefore, to know how to filter out stack entries that apply to the inner working of TMGIDE, I would use $ESTACK (e.g. 5) - $STACK (e.g. 13) - 1 =  8.  And all stack entries for values 8 and greater should not be shown. 

Furthermore, entries 0,1,2 should also not be shown. 

Thanks for listening.  It helps me type these posts out, and I often can figure it out along the way, "rubber ducky" style.

Kevin

[Sam Habiel]

$ESTACK is used in Error trapping with $ETRAP for you to unwind the stack when you get an error. Look at UNWIND^%ZTER for an example implementation; the XWB broker also has an implementation.

--sam

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[David Wicksell]

Hi Kevin.

 You said, "Now step-by-step debugging is achieved by using ZBREAK and ZSTEP's so that yottadb will execute just 1 command at a time."

I have one small correction for you. A ZSTEP will not execute just one command at a time, rather it will execute one _line_ at a time,

regardless of how many commands are on that line. Good luck.

David Wicksell

Fourth Watch Software LC

[Kevin Toppenberg]

David,

Good correction.  I would love for yottadb to allow command by command stepping, but has Bhaskar once told my, this change would be "non-trivial."  :-)

Kevin