What is Error Handling?

error handling

Written by Ayesha

Error handling is the process of identifying errors and taking proper actions to ensure that any error relating to the code or execution is handled in a way that the program can continue to process uninterrupted. Error handling constitutes a major portion of any program’s code, dedicated to handling exceptions and error conditions. 

Error Handling

Catching and handling certain errors in various steps of software development is essential to ensure you don’t have to revise the whole code after writing or damage the user experience if the program does not function as intended or crashes without any warning. A major part of writing codes for developing applications is writing logic to handle possible errors that may arise during the software development and execution cycles.

An error exists if;  the code does not perform as it is intended to, the code damages the user (such as damage to the hardware, data, or progress), and if a code-facing error does not inform the user that an error has resulted.

Consequences of Bad Error Handling

When writing a program, it is best to understand that not all logic will work out as expected. A program often may not follow the normal path of execution either because of an error in the main execution path resulting in the program’s misbehavior or an error related to the logic used in the code. Not handling these errors by terminating the program after informing the user or completing the execution by passing it to another section of the code can result in misbehaving, crashing or corrupting user data.

Such a situation can lead to the termination of the program’s normal operations, and if those operations are critical such as a medical x-ray machine result display, driving automated cars, or guiding airplanes and ships, any deviation from the normal working of the program can be disastrous. 

What Good Error Handling Does

As error handling can be critical in defining a user’s experience with the program, good error handling can boost a program’s functionality and reviews. If you anticipate the possibility of errors occurring during the execution of your program, then it is best to take proper measures to handle them.

The first step of error handling is informing the user that an error has occurred. The program should let the user know about the error and possible steps that they can take to avoid it or possible reasons that might have resulted in that error without getting into technicalities.

After the user has been informed, the next step is to help the programmer debug the issue by providing information on how it resulted. It is mostly done through an email sent to the developer or a log file creation with event logs pertaining to the error. Such messages give developers all the information they need to find out the cause of the issue.

Types of Errors

Understanding the different types of errors is necessary and can help in finding various ways to handle them. Following are the types of errors:

Logical errors

A logical error is related to erroneous behavior resulting in an unexpected or wrong output. These are not recognized until the program is executed and does not produce the intended behavior.

Syntax (Compile-time) Errors

A syntax error is an error related to the coding language itself. These errors are also called compile-time errors because they are caught by the compiler and must be removed before the program can be executed. Syntax errors pertain to the clarity and usability of code, wrong placement of one letter character creates critical problems and makes the code incomprehensible to the compiler.

Runtime errors

Runtime error refers to an error that takes place during a program’s execution, as compared to the compilation errors that are identified during compilation. These may be bugs in the program or unsolved issues relating to the program, such as insufficient memory allocation.

Ways to Catch Errors 

Before handling an error, it must be identified. Three events can be used to catch and throw errors these are: 

Error Intermediate Event

These events can be connected to any activity from which an error is expected and then connected to the error handling measure. Such a process is called an error boundary event, in which if an error is found in an activity attached to the error intermediate event, the process flows along the sequence line to error handling measures associated with the event, and then normal processing of the program continues.

Error Event Subprocess

These events are not a part of the normal program sequence but are only used when the error start event associated with them is triggered in the main program. You can use error event subprocesses to handle errors in your process by defining a readable process and defining the error start event of the error event subprocess in the normal process of the program.

Error End Event

Error end events specify an error code and map to an error type, which is thrown from the process to the error-catching event that focuses on measures against these errors. Linking these processes and events can make the program sort so that errors can be captured and proper measures can be taken.

Ways to Handle Errors

After an error has been identified, proper measures are taken to handle the error depending on whether it can be resolved, the process can resume functioning, or if the program needs to be terminated. 

Returning error codes

Runtime error refers to an error that occurs during a program’s execution, compared to the compilation errors identified during compilation. These numerics signify the severity of the failure, information about the responsible subsystem, and an error code. In Windows, a 32-bit value based on the HRESULT data type is used for returning error codes. In Python, this error handling is displayed as a tuple using boost::tuple, or in C++, it is “std::tuple”:

boost::tuple FindName();

boost::tuple result ¼ FindName(); 

if (result.get<0>() ¼¼ OKAY) { std::cout << "Name: " << result.get<1>() << std::endl; }

Throwing exceptions

Throwing exceptions allows the error handling code to be separated from the normal functional flow, making the code easier to understand and edit. These are not limited to returning error codes to every error encountered and can handle multiple errors in a sequence. Errors can also be thrown to a later part of the process instead of handling them as they are encountered. In C++, exceptions can be accessible via a “what()” statement.

Aborting the program

Finally, if an error is too extreme to be safely handled or thrown, the program must be aborted. Many libraries have statements designed for this purpose, such as “abort()” or “exit()”.

Errors and Exceptions

In much smaller programs, error handling is incorporated into the program to ensure that no fatal errors are caused. But when concerned with larger projects, this process can be very time-consuming. For them, error handling gets converted into exception handling, in which instead of jumping to an error state after encountering an issue, the program jumps to an exception state which contains a predefined result or output which is displayed to the user or performed by the program.

Importance of Exception Handling in Programming your Software

Exceptions and error handling go hand in hand, working to improve the user experience and functionality of the program. If a program is unexpectedly terminated, freezes, or delivers an incorrect output, it can reduce the program’s dependability. 

Managing Errors and Exceptions

Managing errors and exceptions properly can result in a clean and easily editable code, improving its maintainability. Errors result from an abnormal or anomalous response from the program’s execution flow, and exceptions are used to streamline these events.

Mishandling or overflowing of exceptions can lead to even more errors and harm to the code by making it brittle, but properly managing exceptions has become a crucial element of modern programming. 

In Ruby, a general pattern of handling exceptions is as follows:

begin

  do_something_that_might_not_work!

rescue SpecificError => e

  do_some_specific_error_clean_up

  retry if some_condition_met?

ensure

  this_will_always_be_executed

end

 

Controlling exceptions rather than handling them immediately is a good practice. A good exception syntax with the use of “ if/else” conditions is given as:

try {

    line = console.readLine();

    if (line.length() == 0) {

        throw new EmptyLineException("The line read from console was empty!");

    }

    console.printLine("Hello %s!" % line);

}

catch (EmptyLineException e) {

    console.printLine("Hello!");

}

catch (Exception e) {

    console.printLine("Error: " + e.message());

}

else {

    console.printLine("The program ran successfully.");

}

finally {

    console.printLine("The program is now terminating.");

}

Best Practices to Utilize Exceptions

Following are some recommended practices to make sure that the exceptions implemented in your program are manageable and keep the code maintainable:

  • Use exceptions where solving the error makes the code complex and unmanageable.
  • Create a small separate code after analyzing the type of exception.
  • Create specific exceptions where possible and avoid using all general exceptions as they can complicate the process of error finding.
  • Create your own application-specific hierarchy of exceptions.
  • If creating a hierarchy is not possible, many languages have built-in exceptions.
  • Never rescue all exceptions simultaneously in the same general handler.
  • Handle the exceptions which are necessary, and expose the ones that are not.

Conclusion

Catching and managing errors is key to ensure you don’t have to revise your whole code if the program doesn’t work as it was meant to. Here, we’ve discussed how you can go about identifiying erros and exceptions before mitigating them to ensure a seamless user experience. There are many consequences to bad error handling, so it’s important to understand what good error handling does. I.e., understand what the different errors are and what you can do about them. If you would like further guidance on securing your software, take a look at our other articles on secure software development.

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