Re: Debugging output

[Daniel J Sebald]

On 01/31/2016 06:57 PM, LachlanA wrote:
> Daniel Sebald wrote
> >    From what I remember, the stderr/stdout/signal handling is a delicate
> > thing in the GUI/core setup.  There were several bug/patch reports along
> > the way, but I don't think an acceptable solution ever emerged.
> >
> > ... it might have side effects like cntrl-C not working correct
> > or whatnot.  My guess is you won't find a quick fix, although an
> > in-depth fix might be possible.  But there are multiple platforms to
> > consider, so...
> >
> > Search around the Qt documentation for "qt debugging techniques", or
> > "qDebug", and such.  Maybe that will help.
>
> Thanks, Dan.  That is good background to know.  I'll put it low down on the
> to-do list :)
>
> Regarding qDebug, that only works for printing in the Qt portion of the code
> itself.  If GUI behaviour causes a crash in Octave core code, then
> stderr/cerr is still useful, and Qt doesn't provide a stack trace, AFAICT.

I agree, as I use stderr quite a bit by just placing fprintf() in 
various places and watch what does or doesn't appear before the crash. 
A Qt equivalent might be to call a one-line modal dialog box and simply 
hit "OK" every time the text, then note where the crash occurs.  Clumsy, 
but works.

If debugging something in the core of Octave, then octave-cli and 
fprintf(stderr,) still works.

Dan