User's Guide

Exceptions Thrown by the Standard C++ Library
The following exceptions are thrown by the Standard C++ Library:
• operator new () and operator new [ ] throw a bad_alloc exception when they
cannot obtain a block of storage.
• A dynamic_cast expression throws a bad_cast exception when a cast to a reference type
fails.
• Operator typeid throws a bad_type exception when a pointer to a typeid expression is
zero.
• A bad_exception exception can be thrown when the unexpected handler function is invoked
by unexpected().
NOTE: If no catch clauses are available to catch these exceptions, the default action is program
termination with a call to abort(). (Using the +noeh option does not disable the exceptions
thrown by these library functions.)
type_info Class
type_info is a class in the standard header file <typeinfo>. A reference to an instance of this
class is returned by the typeid operation.
Implementations may differ in the exact details of this class, but in all cases it is a polymorphic
type (has virtual functions) that allows comparisons and a way to access the name of the type.
Usage:
This class is useful for diagnostic information and for implementing services on objects where it is
necessary to know the exact type of the object.
Example:
# include <iostream.h>
# include <typeinfo>
class Base {
virtual void f(); // Must have a virtual
// function to be a
// polymorphic type
// additional class details omitted
};
class Derived : public Base {
// class details omitted
};
void Base::f()
{
// Define function from Base.
}
int main ()
{
Base *p;
// code which does either
// p = new Base; or
// p = new Derived;
if (typeid(*p) == typeid(Base)) // Standard requires
// comparison as part
Exceptions Thrown by the Standard C++ Library 153