Re: [AD] 4.3 error handling

["Robert Ohannessian" <ROhannessian@xxxxxxxxxx>]

So, C "exceptions" using setjmp don't really work like C++ exceptions,
have lots of gotchas, don't interoperate and (to make them work
correctly) complicate the user code much more than just checking for
return values.

Why is this thread still alive?

If you want Allegro to throw exceptions, write your own C++ wrapper that
checks for errors and throws.

There is no value in adding fake exceptions to Allegro as long as
Allegro still needs to function from C.


> -----Original Message-----
> From: alleg-developers-bounces@xxxxxxxxxx [mailto:alleg-
> developers-bounces@xxxxxxxxxx] On Behalf Of Chris
> Sent: Thursday, June 08, 2006 2:58 AM
> To: alleg-developers@xxxxxxxxxx
> Subject: Re: [AD] 4.3 error handling
> 
> On Wednesday 07 June 2006 23:52, Peter Wang wrote:
> > They are completely independent in my example, e.g. API1 = graphics
> > library, API2 = network library.  The _user_ is using both
libraries,
> > but neither library knows or cares about the other.
> 
> As they shouldn't. A graphics library wouldn't call network functions,
and
> vice versa. I don't see what the problem is. The graphics library
would
> jump
> to its catch on error, and the network lib would jump to its catch on
> error
> (just like using C++, the libs would/should throw an object of a type
> specific to their libraries). You just need to make sure that
regardless
> of
> whichever one it jumps to, it cleans up all relevant code.
> 
> eg:
> 
> try1 {
>    api1a();
>    try2 {
>       api2();
>    }
>    catch2 {
>       api1_throw();
>    }
>    api1b();
> }
> catch1 {
>    cleanup1();
>    cleanup2();
> }
> 
> Or alternatively, disable API2's throwing and check its return value
> manually
> (something you can't do with C++ exceptions). Whichever you want.
> 
> > If you really must, expose a setjmp/longjmp
> > interface.  But do NOT try to make it look like a try-catch system
> > because they are only superficially similar.
> 
> The way I see it, 'al_catch' is pretty much 'catch(AL_ERROR err)' in
C++;
> just
> without the implicit variable creation. It wouldn't catch anything
other
> than
> an Allegro error, which can only be thrown with 'al_throw(err);'
(which
> would
> be 'throw (AL_ERROR)err;'). As such, something like
> 
> throw "foo"; /* a non-Allegro throw */
> 
> would never be caught by
> 
> catch(AL_ERROR err) /* al_catch */
> 
> because it's not the same type. Just make it a point to note that
> Allegro's
> exceptions aren't C++ exceptions and can't catch them, and vice versa.
> 
> But, as I said, I'll concede that trying to make it look like C++
> try/catch
> *may* be a bit too much. A less transparent method would be acceptable
(as
> long as it's not /too/ opaque :P). But the basic idea is a good one,
IMO,
> and
> should be considered.
> 
> 
> --
> https://lists.sourceforge.net/lists/listinfo/alleg-developers
-----------------------------------------------------------------------------------
This email message is for the sole use of the intended recipient(s) and may contain
confidential information.  Any unauthorized review, use, disclosure or distribution
is prohibited.  If you are not the intended recipient, please contact the sender by
reply email and destroy all copies of the original message.
-----------------------------------------------------------------------------------