Re: [Oorexx-users] PropertySheet error handling issue

[Mark M. <mie...@gm...>]

Hi Staffan,

On Thu, Feb 21, 2013 at 7:52 AM, Staffan Tylen <sta...@gm...>wrote:

> Mark, I've reached a point where most likely an error in my code brings
> down the whole ooRexx environment,
>

By 'brings down the whole ooRexx environment, do you mean the interpreter
terminates, or do you mean the process crashes?  I'm going to assume you
mean the interpreter terminates.


> but without a single message. I've noticed that while running within a
> PropertySheetPage, if I do something like abc~def and abc is a .NIL object,
> then the environment goes down. I usually see an error message when this
> happens but in this case it's all silent so I can't determine if in fact a
> .NIL object is involved.
>

This sounds like a problem in one of the event handlers.  There should be a
condition message printed out, if there isn't, I'm not sure why.



> I can't even determine what method is executing even with tracing.
>


Turn off tracing.  Put a simple say statement in each of your event
handlers, as the first line.  Something like:

say 'enter onClick()'

That should allow you to track down what method the problem is happening
 in.  If I do that and still have a problem, then I put a leaving statement
right before I return from the event handler:

say 'leaving onClick()'

In addition, you probably have some idea of when the problem cropped up.
 So, I would start with the event handlers that you suspect.


> There seems to be a difference in the ooDialog error handling process when
> a PropertySheet is involved, could that be so?
>

PropertySheetDialog dialogs are unlike all other ooDialog dialogs in that
they are manged by the operating system, not by the ooDialog framework.
 That fact is going to cause differences.

In addition, calling back into the interpreter from the native C / C++ code
in the window message processing loop brings up issues different from other
types of Rexx programs.  In particular, if you have a syntax error in the
Rexx call back method, it can lead to every thing getting hung, and you
have to kill the rexx.exe process through the task monitor to get out of
the hang.

Terminating the underlying dialog and the interpreter when a syntax
condition in an event handler is detected prevents the hangs.  The syntax
message should be printed out.  Many times, the syntax condition in the
event handler may not cause a hang.

But, with a PropertySheetDialog dialog, it is much more likely that things
will hang.  In fact it is almost a certainty.   So, when I started working
on property sheet functionality, I started being more careful about ending
the underlying dialog when a syntax condition in an event handler happens.
 So, this is a little different than with other dialogs where I was not as
careful about checking for syntax conditions.

As I said though, the syntax condition should be printed out.  Since it
isn't, I would say that without the terminating code, you would just see
your program hang with no message, and have to kill rexx.exe through the
task manager.

As always, if you can produce an example that shows the problem I can most
likely figure out what the cause is.  I suspect that may be difficult in
this case.  But, if you can I'll gladly look at it.

--
Mark Miesfeld