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 :)

>>40
Quoting the C++ FAQ Lite Section 17:
[17.2] How can I handle a constructor that fails?
Throw an exception. (...)

[17.12] Exception handling seems to make my life more difficult; clearly I'm not the problem, am I??
(...) Here are some "wrong exception-handling mindsets" in no apparent order:
(...)
Confusing logical errors with runtime situations: For example, suppose you have a function f(Foo* p) that must never be called with the NULL pointer. However you discover that somebody somewhere is sometimes passing a NULL pointer anyway. There are two possibilities: either they are passing NULL because they got bad data from an external user (for example, the user forgot to fill in a field and that ultimately resulted in a NULL pointer) or they just plain made a mistake in their own code. In the former case, you should throw an exception since it is a runtime situation (i.e., something you can't detect by a careful code-review; it is not a bug). In the latter case, you should definitely fix the bug in the caller's code. You can still add some code to write a message in the log-file if it ever happens again, and you can even throw an exception if it ever happens again, but you must not merely change the code within f(Foo* p); you must, must, MUST fix the code in the caller(s) of f(Foo* p).