Returning values from a basic extension function

[pjw]

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Code: Select all

        move.w  bv..chrix,a1

Haha, thats pretty definitive, yes!

[daniel_baum]

Hi all,

I finally have a working sbasic extension function It takes an sbasic name as a parameter, and returns the value of the last four bytes of the name table entry for that name, which, in the case of an sbasic extension, is the address of the function itself. It returns them as a hex string. I also wrote the same thing in sbasic, so I could find my own function to debug it (using jmon), and, later on, to confirm the results of the assembly language code.

This is the first time I have ever attempted an sbasic extension, so I am rather chuffed that it works. There's still a bit of debugging to do before I am sure that it won't brick the system

I do have a couple of questions: the function does not work fully until I have done a NEW, or loaded a new basic program. Before this, it only works partially, not finding names toward the end of the name list. Any ideas why this might be?

Also, is it possible to change the cursor colour in QD? On my system (QPC2 in high colour mode) it's light blue, and doesn't stand out very well against the grey background.

Thanks to all for your help in getting me started

D.

[NormanDunbar]

This is the first time I have ever attempted an sbasic extension, so I am rather chuffed that it works. There's still a bit of debugging to do before I am sure that it won't brick the system

It's a good feeling isn't it? Well done.

If you are on pre-JS, I think, extensions don't work after loading the code until NEW is called. From JS one, this is not necessary.


Cheers,
Norm.

[daniel_baum]

This is the first time I have ever attempted an sbasic extension, so I am rather chuffed that it works. There's still a bit of debugging to do before I am sure that it won't brick the system

It's a good feeling isn't it? Well done.

If you are on pre-JS, I think, extensions don't work after loading the code until NEW is called. From JS one, this is not necessary.


Cheers,
Norm.

Hi Norm,

It's SMSQ/E 3.36. The extension works. It just fails to find some names which it finds successfully after the NEW.

D.

[mk79]

Also, is it possible to change the cursor colour in QD? On my system (QPC2 in high colour mode) it's light blue, and doesn't stand out very well against the grey background.

Cursors are sprites on SMSQ/E, they can have any colour, alpha transparency and even animation. Check out marcel-theme and fading-cursor here https://www.kilgus.net/smsqe/gd2-high-colour/. Should also be part of the QPCDemo.win file supplied with QPC I think.

Marcel

[mk79]

It's SMSQ/E 3.36. The extension works. It just fails to find some names which it finds successfully after the NEW.

You test in the main SBasic or some daughter SBasic?

Marcel

[daniel_baum]

Hi Marcel,

In the main Sbasic.

D.

Edit: I think I've found the problem. We'll find out tomorrow...

[daniel_baum]

Hi all,

I finally managed to debug my basic extension... it turns out that there are some name table entries with a name pointer of FFFF, and things went screwy when I tried to follow them into the name list. They are SBasic variables of some kind (maybe unused or invalid or something?) , so obviously when you NEW they disappear and everything works. My loop now identifies and ignores them, and everything at least appears to work now

Debugging this entailed printing out intermediate values - so I print out all of the name list strings until I find the one I am looking for, and if I don't find anything I print out how many iterations the loop has performed from start to finish. It also entailed getting very intimate with JMON, which really gives you the retro debugging experience

Anyway, this was one of the longest and toughest debugging sessions I have ever had, and I program for a living But it does give a certain feeling of accomplishment now that it works...

Thanks to all for your help,

D.

[tofro]

Hi all,
I finally managed to debug my basic extension... it turns out that there are some name table entries with a name pointer of FFFF, and things went screwy when I tried to follow them into the name list. They are SBasic variables of some kind (maybe unused or invalid or something?) , so obviously when you NEW they disappear and everything works. My loop now identifies and ignores them, and everything at least appears to work now

Congrats on getting it to work!

Name table entries with -1 as a name pointer are typically expressions or substrings - these are sortof internal to the interpreter (they do have a value, but no name), and obviously, you shouldn't follow the -1 pointer

Tobias

[janbredenbeek]

I finally managed to debug my basic extension... it turns out that there are some name table entries with a name pointer of FFFF, and things went screwy when I tried to follow them into the name list. They are SBasic variables of some kind (maybe unused or invalid or something?) , so obviously when you NEW they disappear and everything works. My loop now identifies and ignores them, and everything at least appears to work now

You've probably found a temporary name table entry which could be the argument to a procedure or function or saved local variable.
I've written a procedure ntdump which generates a dump of the nametable. You can even give it a string argument to search for specific names (unlike EXTRAS!) and it tells you if it's a variable, procedure or function with 'A' appended if it's a procedure argument and 'L' if it's a local variable.
It's still not perfect and gives different results on SMSQ/E and QDOS/Minerva, but it might be useful anyway...

Code: Select all

700 REMark ntdump_bas NameTable Dump Utility
710 REMark v2.0 20190120 Jan Bredenbeek
720 REMark requires: TK2 extensions AND Minerva OR SMSQ
730 DEFine PROCedure ntdump(n$)
740 LOCal l%,nt,ty%,ty$,dt%,dt$,no%,nl%,nl$,q$
750   q$=PARSTR$(n$,1)
755   wh=20:lc=1:REMark window height and counter
760   REMark loop for all NT entries
770   PRINT 'Type','Value','Pointer',,'Name'
775   argb=PEEK_L(\60\-24):locb=PEEK_L(\60\-20):loct=PEEK_L(\60\-16)
780   FOR nt=0 TO PEEK_L(\\28)-PEEK_L(\\24)-8 STEP 8
790     ty%=PEEK(\24\nt):dt%=PEEK(\24\nt+1):REMark name & data type
791     SELect ON ty%
792       =0:ty$="Unset"
793       =1:ty$="Expr"
794       =2:ty$="Var"
795       =3:ty$="Array"
796       =4:ty$="SBproc"
797       =5:ty$="SBfunc"
798       =6:ty$="REP"
799       =7:ty$="FOR"
800       =8:ty$="MCproc"
801       =9:ty$="MCfunc"
802       =REMAINDER :ty$="? ("&HEX$(ty%,8)&")"
803     END SELect
810     no%=PEEK_W(\24\nt+2):REMark namelist offset
815     IF nt>=argb AND no%>=0 THEN no%=PEEK_W(\24\no%+2)
820     IF nt>=argb AND nt<locb THEN ty$=ty$&"A"
825     IF nt>=locb AND nt<loct THEN ty$=ty$&"L"
830     IF no%>=0 THEN
835       nl%=PEEK(\32\no%):nl$=""
840       FOR l%=1 TO nl%:nl$=nl$&CHR$(PEEK(\32\no%+l%))
845     ELSE
850       nl$="*NO NAME*"
855     END IF
860     SELect ON dt%
861       =0:dt$="n/a"
862       =1:dt$="string"
863       =2:dt$="float"
864       =3:dt$="integer"
865       =REMAINDER :dt$="? ("&HEX$(dt%,8)&")"
867     END SELect
870     IF q$<>"" AND NOT (q$ INSTR nl$) THEN NEXT nt
875     lc=lc+1:IF lc>wh THEN
877       i$=INKEY$(-1):IF i$=="q" OR i$=CHR$(27) THEN EXIT nt
878       lc=1
879     END IF
880     PRINT ty$,dt$,HEX$(PEEK_L(\24\nt+4),32),nl$
890   END FOR nt
900 END DEFine ntdump

Jan