Handling software errors

And, if error codes are so bad and I don't need to be sold on the vices of error codes , is there another alternative? What is the current or soon to be state of the art for error handling that meets the requirements of best practices as outlined above, but doesn't rely on calling code checking the return value of error codes?

This is not always the case: for example, take a look at Objective-C with the Foundation framework. There the NSError is the preferred way to handle errors, despite the existence of what a Java developer would call true exceptions: try, catch, throw, NSException class, etc.

However it is true that many interfaces leak their abstractions with the exceptions thrown. In general I believe the best advice about error handling is this:.

I think if one sticks to that rule of thumb, the amount of "leakage" from abstractions can be very limited and contained. On whether exceptions thrown by a method should be part of its declaration, I believe they should: they are part of the contract defined by this interface: This method does A, or fails with B or C.

In Java, you normally do so by declaring the exceptions you expect to encounter and adding them to the throws part of the declaration of the method. On the other hand, if one of the parsing algorithms failed, there's no reason to pass that exception above unhandled.

It all boils down to one thing: Good interface design. If you design your interface well enough, no amount of exceptions should haunt you. Otherwise, it's not just exceptions that would bother you. One last thing: Some languages, Eiffel for example, have other mechanisms for error handling and simply do not include throwing capabilities.

There, an 'exception' of sort is automatically raised when a postcondition for a routine is not satisfied. I would just like to note that exceptions and error codes aren't the only way to deal with errors and alternate code paths.

Out of the top of the mind, you can have an approach like the one taken by Haskell, where errors can be signaled via abstract data types with multiple constructors think discriminated enums, or null pointers, but typesafe and with the possibility of adding syntatic sugar or helper functions to make the code flow look good.

It works like a nullable pointer, but the do notation guarantees that the whole thing evaluates to null if any of a, b, or c fail.

Another possibility is passing an error handler object as an extra argument to every function you call. This error handler has a method for each possible "exception" that can be signaled by the function you pass it to, and can be used by that function to treat the exceptions where they occur, without necessarily having to rewind the stack via exceptions.

Common LISP does this, and makes it feasible by having syntatic support implicit arguments and having the built-in functions follow this protocol.

One way to deal with this problem is to have the interface specify exactly which exceptions can be thrown under what circumstances and declare that implementations must map their internal exception model to this specification, by catching, converting and re-throwing exceptions if necessary. If you want a "prefect" interface, that's the way to go. In practice, it's usually sufficient to specify exceptions that are logically part of the interface and which a client may want to catch and do something about.

At least the exception can still contain information that helps diagnosing the problem. In fact, with error codes, pretty much the same thing ends up happening, just in a more implicit fashion, and with far more likelihood of information getting lost and the app ending up in an inconsistent state. Lots of good stuff here, I'd just like to add that we should all be wary of code which uses exceptions as part of normal control flow.

Sometimes people get into that trap where anything which isn't the usual case becomes an exception. I've even seen an exception used as a loop termination condition. Exceptions mean "something I can't handle here happened, need to go out to someone else to figure out what to do.

Another degenerate case of exception usage I've seen is people whose first response is "throw an exception. In big applications this becomes problematic when an uncaught exception bubbles up from the nether-regions and blows up the program. I'm not anti-exceptions, but they seem like singletons of a few years ago: used far too frequently and inappropriately. They're perfect for the intended use, but that case is not as broad as some think. Exception specifications are in the same bucket as return and argument types- they are part of the interface.

If you can't conform to that specification, then don't implement the interface. If you never throw, then that's fine. There's nothing leaky about specifying exceptions in an interface. Error codes are beyond bad. They're terrible.

You have to manually remember to check and propagate them, every time, for every call. This violates DRY, for a start, and massively blows up your error-handling code. This repetition is a far bigger problem than any faced by exceptions. You can never silently ignore an exception, but people can and do silently ignore return codes- definitely a bad thing. Error codes are normally associated with a single message, when exception type remains, but a message may vary.

Exception has a stack trace, when error code doesn't. I don't use error codes to debug broken system. This might be specific to JAVA, but when I declare my interfaces I do not specify what exceptions might be thrown by an implementation of that interface, it just doesn't make sense. This is entirely up to you. You may try and catch a very specific type of exception and then catch a more general Exception.

Why not let exception propagate up the stack and then handle it? Alternatively you can look at aspect programming where exception handling becomes a "pluggable" aspect.

I don't understand why is it a problem for you. Yes, you may have one implementation that never fails or throws exceptions and you may have a different implementation that constantly fails and throws exception. If that's the case, then don't specify any exceptions on the interface and your problem is solved.

Would it change anything if instead of exception your implementation returned a result object? You can then interrogate that object. Well Exception handling can have their own interface implementation. Steps involved in the Error Handling testing: Following are the steps involved in the error handling testing: Test Environment Set Up: Test environment is set according to the software testing technique so that the testing process can run smoothly.

This step includes planning for the testing. System which is going to be tested is made sure have less significant data as there might be crash problem in the system during testing.

Skip to content. Change Language. Related Articles. Table of Contents. Improve Article. Periphery Clock Networks. Clock Network Sources. Dedicated Clock Input Pins 4. Internal Logic 4. DPA Outputs 4. PLL Clock Outputs. Clock Control Block. PLL Usage 4. PLL Architecture 4.

PLL Control Signals 4. Clock Feedback Modes 4. Clock Multiplication and Division 4. Programmable Phase Shift 4. Programmable Duty Cycle 4. PLL Cascading 4. Reference Clock Sources 4. Clock Switchover 4. PLL Control Signals. Reset 4. Clock Switchover. Automatic Switchover 4. Automatic Switchover with Manual Override 4. Manual Clock Switchover 4. Verifying Pin Migration Compatibility.

Open-Drain Output 5. Bus-Hold Circuitry 5. Weak Pull-up Resistor. Programmable Current Strength 5. Programmable Output Slew Rate Control 5. Programmable IOE Delay 5. Programmable Open-Drain Output 5.

Programmable Pre-Emphasis 5. Programmable Differential Output Voltage. Dynamic OCT 5. DPA Block 5. Synchronizer 5. Data Realignment Block Bit Slip 5. Non-DPA Mode 5. DPA Mode 5. Soft-CDR Mode. Clocking Differential Transmitters 5. Clocking Differential Receivers 5. Guideline: Pin Placement for Differential Channels 5. Clocking Differential Receivers. Source-Synchronous Timing Budget. Differential Data Orientation 5. Transmitter Channel-to-Channel Skew 5. Hard Memory Controller 6.

Delay-Locked Loop 6. Sequencer 6. Clock Tree 6. Hard Memory Controller. Hard Memory Controller Features 6. Main Control Path 6. Data Buffer Controller. DQS Logic Block. Enhanced Configuration and Configuration via Protocol 7. Configuration Schemes 7. Configuration Details 7. Design Security 7. Configuration Schemes. Active Serial Configuration 7. Passive Serial Configuration 7. Fast Passive Parallel Configuration 7. JTAG Configuration. These applications can anticipate errors, thereby helping in recovering without actual termination of application.

Error-handling techniques for development errors include rigorous proofreading. Error-handling techniques for logic errors or bugs is usually by meticulous application debugging or troubleshooting. Error-handling applications can resolve runtime errors or have their impact minimized by adopting reasonable countermeasures depending on the environment. Most hardware applications include an error-handling mechanism which allows them to recover gracefully from unexpected errors.

As errors could be fatal, error handling is one of the crucial areas for application designers and developers, regardless of the application developed or programming languages used. In worst-case scenarios, the error handling mechanisms force the application to log the user off and shut down the system. By: Brad Rudisail Contributor. By: Kaushik Pal Contributor.