🚀 go-pugleaf

Remy Lebeau (TeamB) wrote:

> > In what context Windows calls my callback function?
> 
> In whatever context called the API function that then called the
> callback.

I wondered about that and hence I delayed answering (then got dragged
off onto a minor problem at work).

Technically the only thing ensuring that a callback is called from
within the thread that passed it is the design of the API and the OS.
There's nothing to stop a callback pointer being passed between
threads. It's therefore more generic to say that a callback is called
in the context of whatever thread is doing the calling.

Of course it would be horrible programming design to pass a callback
between threads but the following scenario is possible:

Thread A passes a callback to a library module.
The library module stores the callback globally.
Thread B while inside the library calls the callback.
...

At this point if the callback is not threadsafe it can cause problems.
-- 
Andrue Cope [TeamB]
[Bicester, Uk]
http://info.borland.com/newsgroups/guide.html