Re: Should undefined behavior be encouraged in Emacs?

["Andreas Röhler" <andreas.roehler@online.de>]

Am 03.10.2011 09:29, schrieb Stephen J. Turnbull:
> Andreas Röhler writes:
>   >  Am 03.10.2011 05:11, schrieb Stefan Monnier:
>   >  >>  The argument given for undefined behavior is that it simplifies
>   >  >>  maintenance of Emacs internals.
>   >  >
>   >  >  I like to keep some corner of the behavior undefined, when I think
>   >  >  that user code that depends on such details is undesirable (e.g. return
>   >  >  values of primitives which are only called for side-effects).
>
>   >  my bet: undefined behavior sources bugs, makes maintenance difficult.
>   >
>   >  Design at the user level certainly deserves a separate approach. It's up
>   >  to implement convenient error-handling than rather than undefined behavior.
>
> I don't know about convenient error-*handling*, but if Stefan wants to
> prevent people from using the value of primitives called only for
> side-effects, he can always provide "convenient error generation" by
> having such primitives return Qunbound (or whatever it's called in
> Emacs sources: the special uninterned symbol placed in the value slot
> of an uninitialized symbol).
>
> ;-) ** 100
>
>

OK, but when on that side-way, I'm afraid of forms specialising the 
special case, remove  specialising the special case by special condition 
again and so on.

see all the active-region stuff for a basic example at a basic level.

Andreas