Exception Handling, Throwing Exception and Try/Catch blocks

[giesbert]

QEventLoop :-))
And throwing exceptions via libraries is not the problem. But perhaps the QApplication eventloop catches them? I didn't look at the QtCode for that up to now.

[goetz]

I catch the exceptions in the methods, where I call the lib's functions. In my special case, there is no event loop that can make things bad.

[Wolf P.]

Gerolf, QEventLoop has no signals and no virtual function, so... In this issue I need to familiarize myself first...
(and: I don't think that you can throw an exception through a binary dynamic link library (with a C API).)

[goetz]

You're right. C does not provide exceptions. You would have to write a C++ wrapper that adds this and that probably makes the API more OO-like (that's what the ImageMagick/GraphicsMagick guys did).

[Wolf P.]

[quote author="Volker" date="1292253297"]I catch the exceptions in the methods, where I call the lib's functions. In my special case, there is no event loop that can make things bad. [/quote] You're right. But If you forget to handle a particular exception your program crashes.
Of course it should be terminated immidiately, but gracefully.

[goetz]

That part of the program is only very small. Basically only one class that uses the lib, and every exception that can be thrown is caught and handled in our case. But I agree, that can be hard to handle all together.

I personally like the concept of exceptions - you can throw them and whoever is responsible catches them and handles the condition. Althoug I never used them in C++ on my own (only in Java), as there are too many pitfalls at the moment.

[giesbert]

Dlls can use exceptions, wolf, if they are C++ dlls. And I don't think, that you create C dlls if you are using Qt, do you? My dlls are normally C++ dlls which export C++ classes. There it could be done, but I don't do it.
And QEventLoop handles asynchronous signals, as QueuedSignals are in fact events :-)

[Wolf P.]

For clarity: I am not in the least interested to write DLLs in C myself. I meant pre-existing DLLs. Try to throw an exception in a Windows callback and you'll see what I was talking about. (Sometimes you have to code against a Windows API.)

I'm sorry that I have expressed this somewhat misleading.

[pip010]

@DenisKormalev said in Exception Handling, Throwing Exception and Try/Catch blocks:

exception-way or errno-way are equal ways. I can't say that one is better than another. They are simply different. Qt chose errno-way at the beginning and uses it now.

NOT THEY ARE NOT!
exception are structured way of both rise the error and handle the error
return codes do not dictate how you handle (the mechansim) , you might even not handle it!, try doing the same with exceptions ;)

[pip010]

@giesbert tier down the application obviously ... exceptions are exceptional ...