C++, "canceling a construction"

Hi /prog/

My is simple, but perhaps not so frequent.

How should I stop a construction of an object (c++)?

Basically I have a class with some data members which must fulfill some requirements. Say we initialize these data members upon construction, if the supplied values were erroneous then I guess I want to stop construction and throw an error. Is this the right idea? How do I "cancel the construction"?

Help much appreciated :)

>>33
I think you've misunderstood my post, though like I said this is kind of arguing semantics. Suppose you had a class containing two 4-byte integers, using 1 byte padding with no virtual table for simplicity, making the object size 8 bytes.

When you declare an instance of this object, 8 bytes will be set aside for this object on the current stack frame, prior to invoking the constructor. A pointer to the beginning of this block of 8 bytes is passed into the constructor as the 'this' parameter.

If an exception is thrown, this block of 8 bytes continues to exist until the stack is unwound in the epilog stub of the calling function.

I feel it's erroneous to state that an object isn't created if an exception is thrown, as this implies there are absolutely zero side-effects if this occurs, when, from the point of view of the generated machine code, this isn't the case.