Exception safety with qt

[paul23]

Qt work a lot with raw pointers (why? this isn't the 1990 anymore...). But given that fact I'll have to work myself around this. I notice from the documentation that the layout in those cases often take ownership of the pointer.

However what happens if the container fails & (re)throws an exception - ? ie, consider the following mockup:

std::unique_ptr<QTreeView> tree(new QTreeView());
QLayout layout;
layout.addItem(tree.release());

std::unique_ptr<QTreeView> tree(new QTreeView());
QLayout layout;
layout.addItem(tree.release());

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Now I believe that if an exception occurs during QLayout::addItem() the tree WILL be freed? (layout takes immediate responsibility on the tree when function starts)?

[wysota]

Qt work a lot with raw pointers (why? this isn't the 1990 anymore...)

Hmm... I didn't know there was something wrong with pointers.

std::unique_ptr<QTreeView> tree(new QTreeView());
QLayout layout;
layout.addItem(tree.release());

std::unique_ptr<QTreeView> tree(new QTreeView());
QLayout layout;
layout.addItem(tree.release());

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Now I believe that if an exception occurs during QLayout::addItem() the tree WILL be freed? (layout takes immediate responsibility on the tree when function starts)?

Qt doesn't throw exceptions.

[paul23]

uhm I don't see the noexcept keyword in the functions.. And anything that allocates memory (which a layout WILL do) can throw a std::bad_alloc at the weirdest times.

Manual exception safety is THE reason I choose C++ over C# for developing (I like to keep control in my hand instead of relying on a garbage collector which might or might not act during a time critical operation).

[wysota]

uhm I don't see the noexcept keyword in the functions..

As far as I know noexcept is part of C++11 standard and Qt can be compiled with C++03 compilers.

And anything that allocates memory (which a layout WILL do) can throw a std::bad_alloc at the weirdest times.

Can it? What weirdest times do you have in mind?

Manual exception safety is THE reason I choose C++ over C# for developing (I like to keep control in my hand instead of relying on a garbage collector which might or might not act during a time critical operation).

C++ sucks when it comes to exceptions. C++ compilers suck when it comes to exceptions even more.

[paul23]

any code using operator new() will cause a std::bad_alloc exception (ie when running out of virtual heap memory, or the heap gets corrupted etc etc).

[wysota]

And what's the problem about it? If you want to catch exceptions, you are free to do it in your code.