Re: Re-initializing a list after the control returns to gdb...

[Andrew Cagney <ac131313@redhat.com>]

> [Sorry for answering late, got preempted...]
> 
> 
>> In hindsite, it needs to be converted to an observer model (or a new 
>> observer model introduced and the current gdb-hooks changed to one of 
>> the many observers).
> 
> 
> One model that works extremely well is the signals system implemented in
> glib. I find it very nicely done. It would be nice if we could reuse
> this, but this is a very very complex machinery doing probably way too
> much for what we need in GDB.

Yes.  GDB just needs a single consistent event mechanism.

> I would instead suggest something much more simple, like this:
> 
>    enum notice_kinds
>    {
>      breakpoint_created_notice,
>      breakpoint_deleted_notice,
>      ...
>      invalid_last_notice,   /* Should always be last.  */
>    };

gdb-events.sh used individual wrapper functions rather than trusting an 
enum, a void *, and dodgy casts.  This was to ensure that the external 
iterfaces were all strongly typed (calls checked with -Werror) and all 
nasty casts were burried in the .c file.

It did that right.

It, however, made several mistakes:

- it tried to group all the events together (you've proposed individual 
registration which is much more incremental)

- it didn't implement broadcast (as proposed here)

- `event' in GDB has multiple meanings so the name is confusing.

So, can you get a prototype observer working for just your ada event 
(but keep in mind that other events will be boiler-plated)?

As for the names, just use the terminology found in the patterns book - 
observer.[hc].  observer_update_xxx (or notify_xxx), 
observer_attach_xxx, observer_detach_xxx I think.  If GDB needs more 
than one observer, there's a problem.

(oh, unless you've an immediate need for that data/context parameter, 
i'd leave it out - such a mechanis can be left to the person that 
actually needs)

(shh, doco - but I have a cunning plan - see my recent post about 
revamping gdbarch.sh into doc/gdbarch.texi).

Andrew