[PD-dev] error handlers

[Mathieu Bouchard]

On Fri, 21 Sep 2007, Ed Kelly wrote:

> I've just been looking through source code from cvs, picking at random, 
> and looking for an example of the void error (char *fmt, ...) from the 
> externals howto. I can't find one anywhere!

A lot of externals use post() instead of error() or pd_error(), but you 
can also find the last two in some externals... actually quite a few. 
Use a text search through all files of all folders inside externals/ and 
you will find a long list of them.

> Am I stating the obvious here? It's just that this means that PD patches 
> made using anything other than internals are almost impossible to debug 
> if they're extremely complex like mine is: there simply isn't a way of 
> finding out where the errors are occurring.

It's already troublesome for those that use error() as Miller's pd won't 
register them with "Find Last Error", and even with pd_error(), you can't 
find the next-to-last error in case the error you want a trace for is also 
triggering other errors immediately after, for example.

> Could PD or desiredata have a step-trace function, like MAX?

What DesireData offers, is:

1. the ability to Find Last Error with plain error(), and thus pd_error() 
is deprecated in DesireData and just redirects to error().

2. you actually can get a full stack trace for the last error, instead of 
just the object that called error(), and you can also get a stack trace 
anywhere as a sequence of list messages if you use the new [tracecall] 
class.

What is still upcoming:

3. getting stack trace for the N last errors

4. picking up error messages using the upcoming [rescue] class.

5. figuring out some way to make error messages translatable to other 
languages (French, German, etc.) and rescuable by a 
translation-independent name.

6. record a trace of all messages sent from a given starting point, until 
it comes back to the original point, with a limit of N messages recorded, 
and some way of visually stepping through that log. I don't know whether 
that's the feature you are asking for. I'm not sure I'll be able to 
actually step through the messages being executed as they are executed. 
Maybe I can figure out a way to do that, but it's tricky.

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| Mathieu Bouchard - tél:+1.514.383.3801, Montréal QC Canada