Re: error_state elimination

[John W. Eaton]

On 11/23/2015 01:09 PM, John W. Eaton wrote:
> On 11/23/2015 12:59 PM, Rik wrote:
>
> > 1) Finish elimination of error_state variable in C++ code (~80
> > instances left)
> >    Help jwe out in this task.  The remaining instances need more thought
> > than the simple eliminations already done.
>
> I would like to get this job done, but at this point I think nearly
> every remaining case will need a little bit of thought, and in some
> cases some careful review to ensure that the code is still behaving as
> it should.

I think this job is finished in core Octave with this changeset:

  http://hg.savannah.gnu.org/hgweb/octave/rev/200ae1d650b7

As far as I know, the only places that error_state is mentioned now are 
the error.h and error.cc files where it is declared and defined for 
backward compatibility.  Eventually we can tag it as deprecated so that 
GCC can warn about it if it used, then some time later we might be able 
to remove it completely.  There is also some code in the JIT compiler 
that appears to have been intended to deal with error_state, but I don't 
really understand it.  It does use the global error_state variable 
directly in one place.  I have not tried to verify that JIT-compiled 
code does the right thing with the new exception-based errors.

There are many opportunities now for adding better error messages for 
value extractor functions.

There are probably also other places where we could do a better job of 
handling exceptions.

And, of course, we could begin removing error_state from Octave Forge, 
but then those files will be dependent on the development version of 
Octave.  I count around 500 instances of error_state in the Octave Forge 
code now.  Just as in the Octave sources, many will be trivial to remove 
but others will require some thought.  In some cases, behavior will not 
be equivalent when using the current Octave Forge code (that assumes 
error_state works as in all previous versions of Octave) with the 
current version of Octave until something is done to handle exceptions.

jwe