Re: [TCLCORE] TIP #329 [try] updated

[Donal K. F. <don...@ma...>]

Twylite wrote:
>> Side question: if you're working in C code there is no "catch context" 
>> -- you just get a non-zero return value.  I had imagined the bytecode 
>> would be similar? 
>>   
> Never mind.   But there need to be bigger health warnings on 
> tclExecute.c and tclCompile.c.

I don't think they make letters that large except in books by Douglas
Adams...

> Of course this is easier said than done.  Everything calls down to "void 
> Tcl_SetObjErrorCode(Tcl_Interp *interp, Tcl_Obj *errorObjPtr)" which 
> makes for one convenient place to fix the problem, but the function is 
> published in the stubs table and returns (void) ... which makes it 
> tricky to fix.

While I know how to fix such things through stub-table rearrangement
(and I've done such in parts of Tk) they're pretty ugly to do. What we
*can* do is make sure that Tcl code doesn't mess this up through
[error], [return] (and [throw]). I don't think anyone is actually
generating bad error codes anyway; at the C level, the convenient API
produces proper lists.

> One could fix TclProcessReturn() to check valuePtr just before calling 
> Tcl_SetObjErrorCode (context below) ...
[...]
> ... which would at least make this safe at a script level, so that only 
> C code calling Tcl_SetObjErrorCode directly can mess things up.

Things are fairly messy in this area.

Donal.