[Qt5-feedback] Qt5 and C++ exception

[Thiago Macieira]

Em Wednesday, 29 de June de 2011, às 11:08:52, Stephen Bryant escreveu:
> That's OK, but you need to ensure that non-exception based error
> handling actually exists.
> 
> A number of the template collection methods return void instead of
> reporting failure - such as resize(), push_back() et al.  I'm guessing
> the API was copied from STL, but those explicitly use exceptions.

Those are expected never to fail. Qt doesn't handle OOM gracefully.

The containers have been tested to properly let a std::bad_alloc go through 
though. If new or the type's constructor throws, the container will let the 
exception through.

> Maybe Qt5 could return a bool to denote success/failure?  If one ignores
> the return value, the behaviour would be the same as in Qt4.

Not for OOM situations, except for APIs that are expected to allocate large 
amounts of memory (like QImage and QPixmap).

> The documentation should probably be updated to explicitly say that Qt
> does not catch any exceptions thrown by new.  Actually, the current
> class docs don't seem to say anything about handling failure.

Right, they don't catch. The exception is let through and we try to do some 
cleanup on the catch, then rethrow. But this is implementation behaviour.

We haven't finished getting the containers to be exception-safe, so we don't 
promise it either.

Try not to run out of memory.

-- 
Thiago Macieira - thiago (AT) macieira.info - thiago (AT) kde.org
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