problem in dynamic cast

[Radde]

HI,
Are ther any pitfalls for dynamic cast in type safe downcasting..

[Srini]

> HI,

Are ther any pitfalls for dynamic cast in type safe downcasting..

What exactly do you mean by "pitfalls"?

dynamic_cast is a runtime casting operator. Because the cast is
evaluated at runtime, it is probable that the cast may fail even though
the code compiles. In the case of casting object pointers, the failed
cast will result in a NULL pointer. In the case of casting object
references, the failed cast will result in throwing a bad_cast
exception object. It is very important to note that casting across or
down the class hierarchy using
dynamic_cast is only possible when the base class is a polymorphic
type, that is, the class has at least one virtual method.

Regards,
Srini

[ringofw]

One that caught me last week using code from a third party library that
was not compiled with RTTI turned on ("/GR"). dynamic_cast of a pointer
to such an object (i.e. which should not throw a bad_cast exception, so
it wasn't in a try block) can throw an std::exception with the
following "what".

"Access violation - no RTTI data!"
Proviso: bits of the above may be Microsoft-specific.

[msalters]

ri*****@hotmail.com schreef:

One that caught me last week using code from a third party library that
was not compiled with RTTI turned on ("/GR").

That makes it not C++, and thus off-topic. C++ has RTTI, C doesn't and
there are literally thousands of bastards inbetween without. In
general,
this group doesn't deal with these bastards.

HTH,
Michiel Salters

[Gianni Mariani]

Radde wrote:

HI,
Are ther any pitfalls for dynamic cast in type safe downcasting..

Performance may be an issue and may be dependant on the complexity of
your class definition.

[Stuart MacMartin]

As a general rule, you should not use dynamic_cast in MFC code. Only
use dynamic_cast in MFC code where the code cannot possibly be a
performance bottleneck and even then test your code that it behaves in
a reasonable amount of time. The excessive string compares typically
will grind your application to a halt.

Stuart