[Gambas-devel] Free state memory when enumeration BREAKs

[Benoît Minisini]

Le 28/08/2012 17:25, Tobias Boege a écrit :
> Hi,
>
> for my enumeration state, I allocate a buffer via GB.Alloc(). If it happens
> that the enumeration gets aborted by means of BREAK, is there any
> notification mechanism?
>
> And just to be sure I well understood: GB.ListEnum(), GB.NextEnum() and
> GB.GetEnum() are used together to modify all other currently active
> enumerations in case the common enumeration object is modified?
>
> Regards,
> Tobi
>

At the moment, there is no support for allocation associated with an 
enumeration.

During the _next method, GB.GetEnum() returns a pointer to an array of 
four pointers (or four intptr_t, or anything you want that fit). You 
have to use that to store your enumeration state, and nothing more.

At the start of the enumeration, the contents of these four pointers is 
zero.

An enumerator must handle destruction of other objects. But, for 
performance reasons, it cannot ensure that it won't forget any object if 
something change in the enumerated objects.

After an object has been removed from the enumerated object, you can use
GB.ListEnum(), GB.NextEnum() and GB.GetEnum() to browse all current 
enumerations, and modify their state to take the removal into account. 
But this can be a tricky job. Look at gbx_c_collection.c for an example.

At the moment:

- Array enumeration ignores object removal.

- Collection enumeration handles object removal, by checking the state 
of each enumeration. If an enumeration points at the object removal, it 
is moved forward automatically.

So, as you see, the rule for container classes is: removing an object 
during an enumeration has an undefined behaviour, except that the 
interpreter won't crash!

Regards,

-- 
Benoît Minisini