C++ In a Nutshell

Handling Exceptions

An exception interrupts the normal flow of control in a program. An exception throws an object from the point where the exception is raised to the point where the exception is handled. In between those points, function calls are aborted, and local scopes are abruptly exited. Local and temporary objects in those scopes are destroyed.

This section discusses exception handling in general and the try statement in particular. For information about other aspects of exception handling, see Chapter 3, which describes the throw expression, and Chapter 5, which describes function try blocks and throw specifications. See also <exception> and <stdexcept> in Chapter 13 for information about the standard exception classes and related functions.

Tip

As the name implies, an exception is used for exceptional circumstances, such as indexing a vector with an index that is out of bounds. The intention in C++ is that try statements should have near zero cost, but throwing and handling an exception can be expensive in terms of performance.

A try statement establishes a local scope plus exception handlers. A try statement begins with the try keyword followed by a compound statement and one or more catch handlers. Each catch handler has an exception type in parentheses followed by a compound statement. The exception type can be a sequence of type specifiers followed by an optional declarator, or it can be an ellipsis:

trycompound-statement
catch(type 
            declarator) compound-statement catch( ...