Handling exceptions

An exception can be handled by a handler.

# Notes

Stack unwinding occurs while control is transferring to a handler. When a handler becomes active, stack unwinding is already completed.

The exception thrown by the throw expression throw 0 does not match a handler of pointer or pointer-to-member type.

Exception objects can never have array or function types, therefore a handler of reference to array or function type is never a match for any exception object.

It is possible to write handlers that can never be executed, for example by placing a handler for a final derived class after a handler for a corresponding unambiguous public base class:

Many implementations overly extend the resolution of CWG issue 388 to handlers of reference to non-const pointer types:

# Example

#include <iostream>
#include <vector>
 
int main()
{
    try
    {
        std::cout << "Throwing an integer exception...\n";
        throw 42;
    }
    catch (int i)
    {
        std::cout << " the integer exception was caught, with value: " << i << '\n';
    }
 
    try
    {
        std::cout << "Creating a vector of size 5... \n";
        std::vector<int> v(5);
        std::cout << "Accessing the 11th element of the vector...\n";
        std::cout << v.at(10); // vector::at() throws std::out_of_range
    }
    catch (const std::exception& e) // caught by reference to base
    {
        std::cout << " a standard exception was caught, with message: '"
                  << e.what() << "'\n";
    }
}

# Defect reports

# See also

• try block
• Throwing exceptions
• Exception handling