[DGD] some questions about interpret.cpp

[Carter Cheng]

Thanks Felix. Yes it has been a while. I haven't been much involved in
mudding for the past 5 years or so.
 I was looking over some old projects and just decided to take a look at
the dgd internals and go over them a bit more carefully to see what I
understood and did not understand. I found the setjmp code in error.cpp but
I might be misunderstanding something still.

On Tue, Dec 29, 2015 at 12:13 AM, Felix A. Croes <felix at dworkin.nl> wrote:

> Carter Cheng <cartercheng at gmail.com> wrote:
>
> >[...]
> > 1) in all the kfun style function calls the program counter in the frame
> > f->pc = pc;  and following the call pc = f->pc. What is the purpose of
> > this? I did a casual grep of the kfun directory and no kfuns seem to
> update
> > this variable in the kfun code.
>
> Kfuns can call i_lvalues(), which does modify the program counter.
>
>
> > 2) both rlimits() and catch() recursively call interpretv1. This would
> > suggest in someways that for certain opcodes the code behaves like a
> > call_other function call. I.e. are returns illegal in catch and rlimit
> > blocks? Since the return in the catch/rlimit block would "return" to the
> > instruction following the rlimit/catch as opposed to the caller of the
> > function.
>
> The RETURN instruction has multiple meanings, either return from
> function or exit from (one level of) rlimits or catch.  How it should
> be interpreted depends on the context, which is never ambiguous.
>
> We previously discussed this on 26 June 2010.  Time flies.
>
>
> > 3) catch also uses the C++ try catch but the error code seems to still
> use
> > setjmp longjmp which only minimally rewinds the stack and thus would
> break
> > C++ classes with custom destructors. Is the intent to use exceptions here
> > to get better behavior?
>
> This surprises me.  Where do you see setjmp/longjmp being used?
>
> Regards,
> Felix Croes
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