Customizing termination behavior for uncaught exceptions in C++

In this article, you will learn about the customizing behavior for uncaught exceptions in C++ with its examples.

C++ exception handling is based on three keywords: try, catch, and throw.

try: A try block contains code that may throw an exception.

Throw: When an error situation arises, the throw keyword is used to throw an exception explicitly.

catch: Catch blocks are used to construct exception handlers that collect and handle specified sorts of exceptions.

When an exception occurs within a try block, control is passed to the first corresponding catch block that resolves that specific type of exception. If no suitable catch block is found, the program will halt suddenly, which is normally undesirable.

When an exception occurs in C++, it is handled according to the behavior described by the try-catch block. However, it is common for an exception to be raised but not caught because the exception handling subsystems fail to identify a matching catch block for that specific exception. In that example, the following sequence of events occurs:

The exception handling subsystem calls the unexpected() This method is provided by the standard C++ library, which describes what happens when an uncaught exception occurs. After that, unexpected calls are terminated() by default.
The terminate function specifies the actions to be taken when the process is terminated. By default, this is called abort().
The procedure has been terminated.

The terminate() and unexpected() method simply execute other procedures to handle an error. As previously mentioned, terminate calls abort() and unexpected calls terminate(). When a special exception handling error occurs, both functions stop the program's execution. However, you may adjust the manner in which termination happens.

The set_terminate(terminate_handler newhandler) method, provided in the header <exception>, is used to alter the termination handler.

Example:

The following program shows how to configure a custom terminating handler:

Filename: Exception. cpp

//A C++ program to create a new termination mechanism for uncaught exceptions.
#include <exception> 
#include <iostream> 
using namespace std; 

// for custom function
void myhandler() 
{ 
	cout << "Inside the termination handler\n"; 
	abort(); 
} 

int main() 
{ 
	//The new termination handler is set
	set_terminate(myhandler); 
	try { 
		cout << "Inside of the try block\n"; 
		throw 100; 
	} 
	catch (char ex) // if an exception occurs
	{ 
		cout << "Inside of the catch block\n"; 
	} 
	return 0; 
} 

Output:

Inside of the try block
Inside the termination handler
Aborted

Explanation:

The myhandler() is a custom function that is used to handle the termination. This function outputs a message indicating that the end of the handler has been activated. The program is terminated by using the abort()
In main() method,
- Use std::set_terminate() method to set the custom terminating handler myhandler(). It indicates that if an uncaught exception arises, myhandler () will be called to handle it.
- The catch function is looking for errors of type char. However, the thrown exception is of type int (value 100). As a result, this catch block will not capture the thrown exceptions.

The set_terminate() method ensures that myhandler() is executed when the program detects an uncaught exception. This handler produces a message and uses abort() to end the application.

Advantages of Customizing termination behavior for an uncaught exception in C++

Controlled Termination: Customized termination handlers enable you to execute controlled termination rather than allowing the application to end abruptly when an unresolved exception occurs. It may include logging, resource cleaning, or telling the user to shut down before the program ends.
Error Reporting: It enables customized error reporting. You can report extensive information regarding the exception, such as stack traces, variable values, or other relevant context, which might help with troubleshooting.
Graceful Exit: When a program encounters exceptional conditions that can be recovered or need special actions (such as preserving data, disconnecting connections, etc.), a custom termination handler allows these activities to be performed before exit.
Application-Specific Handling: The requirements for managing uncaught exceptions may differ throughout applications. Custom termination handlers enable you to define particular actions based on the application's characteristics or the kind of exception received.
Enhanced User Experience: For programs that include a user interface, a customized termination handling can provide an improved user interface by showing understandable error messages or suggesting how to proceed after an unexpected error.
Debugging Assistance: By modifying termination behavior, developers may include extra debugging tools or procedures that trigger when an uncaught exception occurs, assisting in recognizing and resolution of problems or unexpected behaviors.