Dan writes:
 
> I'm attempting to modify some legacy code in SPL to catch traps and dump
> relevant debugging information in the case the code crashes. This works fine
...
> Is there a way to do code-related traps from SPL? E.g. I would like to trap
> memory protection traps, etc. Or am I simply asking too much of SPL?
 
Yes, try the undocumented XCODETRAP.  It's been around since MPE IV days.
 
SPL calling sequence:
 
   integer
      old'plabel;
   ...
   Procedure xcodetrap (new'plabel, old'plabel);
            value   new'plabel;
            integer new'plabel, old'plabel;
         option external;
 
   ...
   procedure my'codetrap'handler;
      begin
      ...
      end;
 
   ...
   xcodetrap (@my'codetrap'handler, old'plabel);
 
Unlike control-Y's, I don't remember what parameters (if any) are
passed into the user's trap handler...and therefore don't recall
what odd-ball stack manipulations might be necessary to exit a
user codetrap handler.  (Sorry)
 
Some *old* MPE/V code I just found (thanks to the MAGNET Nugget), shows:
 
   procedure arm'stack'trace(abort);                              <<stack>>
      value abort;  integer abort;
      begin
      integer p=q-2, old;
      genmsgu(4,abort);
      stack'trace(0);
      xcodetrap(0,old);
      p := p - 1;                               <<retry instruction>>
      end;
 
Note: (1) I didn't write the above code; (2) I don't know if it works;
(3) it was probably given to me more than 10 years ago by someone in
HP's compiler lab.
 
The NM xcodetrap is similar, except both parameters are 32-bit integers
AND I'm not sure it works if you've armed any POSIX signals....but it
used to work fine prior to MPE/iX 5.0
 
BTW, XCODETRAP was actually documented by HP for a very short time, in
the first-ever MPE XL Trap Handling manual...then they dropped it,
for unknown reasons.
 
SS