Question

I see a lot of C++ libraries dealing with dynamic memory allocation this way:

Qimage* _image = new QImage(width, height, QImage::Format_RGB888);
if (!_image)
{ 
    // Failed!
}

I find it interesting that it is possible to check whether an object was succesfully allocated or not with a simple code like if (!_image).

1) I wonder if this is a native feature of the standard new or if this is only possible if you overload operator new with your own implementation.

2) How would I go about implementing operator new in this case, where it receives arguments for the object’s constructor and it returns NULL in case width && height are 0?

Did I get any of this right?

Answer 1

What you see is wrong. new doesn’t return null anymore but throws std::bad_alloc instead

Overloading new has an example. You don’t need to deal with constructor arguments

What you are trying to do is done kindof by make_shared in C++11