Subj : Re: Loading code into runtime; and error reporting issues
To   : netscape.public.mozilla.jseng
From : "Alan Kemp" <alan@alankemp.com>
Date : Wed Feb 04 2004 08:59 pm


"Brendan Eich" <brendan@meer.net> wrote in message
news:40213E33.9080209@meer.net...
> Alan Kemp wrote:

[snip]

> That's correct.  ECMA specifies, based on SpiderMonkey's progenitor, and
> on cloned implementations, circa 1996, that functions are bound only on
> entering an execution context.  Compiling doesn't execute anything.

Ah thanks, things make a lot more sense now :-)

> >Secondly, when an attempt to call an undefined function is made I have an
> >error reporter setup to grab the error and handle it.  However, there
seems
> >to be no way of telling when function name was called from the error
> >reporter?  I would like to provide a more meaningful output than the
default
> >"undefined is not a function".  Is that information available at this
stage?
> >
>
> Sure, you should be getting names.  Sample JS shell session:
>
> js> var f;
> js> f()
> 2: TypeError: f is not a function
> js> function f(){return 42;}
> js> f()
> 42
> js> g()
> 5: ReferenceError: g is not defined
> js>
>
> If you don't see the same results for the same input with your
> embedding, then we'll need to debug the code that calls
> js_DecompileValueGenerator before passing the decompiled reference
> expression to the error reporter.  You might breakpoint there and see
> what you can see.

I traced through the code untill I finally got to
js_DecompileValueGenerator, and the place its getting tripped up is here:

/*
* At this point, pc may or may not be null, i.e., we could be in
* a script activation, or we could be in a native frame that was
* called by another native function. Check pc and script.
*/
if (!pc)
    goto do_fallback;

Where by upon going to do_fallback the string "undefined" is returned which
is then used as the function name.

Upon further investigation I have discovered that its only script functions
that I am calling from my c++ code that get names "undefined" in the error
report.  If I call a funtion that then calls another function (which doesn't
exist) the error report correctly shows the name of the function I tried to
call.

Is this expected behaviour?  Or am I likely doing something wrong elsewhere?

Thanks for the help,

Alan

.