Defensive programming techniques john woods, icon clinical research, dublin, ireland jennie mcguirk, icon clinical research, dublin, ireland abstract often when running programs in sas. Exceptions are a defensive programming technique, theyre not something to be avoided. For example, if a small amount of data is expected as input, but the program accepts any amount, it provides a way for the cracker. One programmer pilots the keyboard while the other. Since i have been a speaker and a teacher, i have always stressed the importance of practicing proper objectoriented programming oop. The good tool that built specifically for that purpose is fody. The idea can be viewed as reducing or eliminating the prospect of murphys law having effect. Defensive programming, avoiding the big mistakes david franklin, litchfield, nh abstract typically, when you build a small garden shed you should first do some planning, then do construction, and finally. Im a principal consultant at coding helmet and an independent trainer and coach. Defensive programming is a practice where you anticipate failures in your code, then add supporting code to detect, isolate, and in some cases, recover from the anticipated failure.
Another common source of error is the programmer assuming something about a programming language. Parameter checking another important defensive programming technique is parameter checking a method or function should always check its input parameters to ensure that they are valid two ways to check parameter values assert if statement that throws exception if parameter is invalid which should you use, asserts or exceptions. Hi everyone, my name is zoran horvat, and welcome to my course, advanced defensive programming techniques. Extensive testing is also important for this process, as is the creation of software that can be audited and checked easily. In defensive programming, we want to make sure our functions have clear requirements, as. Defensive programming is a technique where you assume the worst from all input. It can assist us by targeting defects in the source where they most commonly occur. Defensive coding techniques the curious programmer. Defensive programming mcgill school of computer science. Defensive programming means anticipating and avoiding problems before they occur.
Our previous lessons have introduced the basic tools of programming. Given the length of rock your code defensive programming it is a good fit for a couple of lunch breaks, one or two commute units or a dedicated friday afternoon learning session. Defensive programming practices are often used where high availability, safety, or security is needed defensive programming is an approach to improve software and source code, in terms of. Writing perfect software may be an elusive goal for developers, but a few defensive techniques, routinely applied, can go a long way toward improving the quality of your code. Some surprises we will show that computer programs can behave in unexpected ways. The xp approach is to take the best software practices to the extreme. Instructor defensive programming is a way of programming, where the application should behave in a consistent and predictable manner, even in the case of unexpected conditions. Defensive programming techniques software engineering. Defensive programming often relies on a somewhat paradoxical combination of eliminating unnecessary code while ensuring sufficient amounts are generated to handle all possible user actions. The goal of defensive database programming, the goal of this book, is to help you to produce resilient tsql code that robustly and gracefully handles cases of unintended use, and is resilient to common changes to the database environment. Defensive programming is the practice of anticipating things that will likely go wrong and coding to handle such scenarios as opposed to easily throwing exceptions.
Defensive programming is a approach which tries to ensure a known behavio. What they havent done is show us how to tell whether a program is getting the right answer, and how to tell if its still getting the right answer as we make changes to it. Github aljazsimdefensiveprogrammingframeworkfornet. In simpler terms, it prevents malicious use of the code. This technique is designed to ensure code correctness and reduce the.
In addition, the developer preemptively creates code that anticipates not only potential problems but also specification changes. Defensive programming language speci c defenses design with testing in mind conclusions foundations of defensive programming build systems source control management out of bounds errors regression testing foundation of defensive programming build system. The main thing is to clearly define the contracts primary contract, ordinary failure handling, contract violation handling which defaults to ub of the function. Defensive programming how to finish your project before. Defensive programming stands for the use of guard statements and assertions in your code base actually, the definition of defensive programming is inconsistent across different sources, but ill stick to this one. If youve experienced this, you have probably been the victim of a particular form of defensive programming which i would like to call paranoid programming. Defensive programming is a practice where developers anticipate failures in their code, then add supporting code to detect, isolate, and in some cases, recover from the anticipated failure. Defensive programming lecture in bulgarian this video is unavailable. The whole book in several electronic formats pdf doc docx. It also does not mention the problems with defensive programming which is that it tends to hide the presence of bugs.
Although the complexity of typical production software guarantees that testers will always have a job, we hope you still yearn to produce defectfree software. Hence the xp practice of pair programming, where all code is written by two developers sharing a single workstation. You cant predict your users actions so defend against everything. Defensive programming practices are often used where high availability, safety, or security is needed. These ebooks are available in pdf, epub, and mobi for kindle formats, ready for you to download at. The basic idea behind this approach is to create a program that is able to run properly even through unforeseen processes or when unexpected entries are made by users. Defensive programming is about making a system that protects against any possible circumstances, even difficult customers doing unexpected actions, thats why you validate and verify data every chance you get. Unfortunately, many beginners do not pay enough attention to it. Defensive programming techniques are used especially when a piece of software could be misused mischievously or inadvertently to catastrophic effect.
Defensive programming is a mindset to write your code in such a way that it is hard to use it not in the original intention of the code. Defensive programming defensive programming is about protecting against certain kinds of errors. Range of similar vulnerabilities exploited over time cert injection attacks ex 12. Learn defensive programming techniques pluralsight. The things you have mentioned in the article and many other ideas of defensive programming must be developed and explained in a clear and brief form as you did it. Rock your code defensive programming for microsoft. Summary if you see duplicated preconditions, consider extracting them into a separate type.
First, write the simplest code that could possibly work with a small set of data. The write stuff techniques for writing selfdocumenting code 4. I find the use of the word overly in the overly defensive programming examples problematic. In this course, you will explore the fundamentals of defensive programming including inspections, testing, input validation, error handling, planning, methods. This is a good definition, but a better or maybe simpler definition might just be developing a system that behaves in a predictable manner despite unexpected conditions or inputs.
For example, in oop, you dont want to return a non. Lets look at alexs three rule of defensive programming. Defensive programming techniques are used especially when a piece of software. Defensive programming is a common practice in almost all programming languages and serves the same purpose for all of them.
In fact it turns out that your colleagues effort in the name of defensive programming, is actually undoing builtin defensive programming provided by the language. Without security in mind, extensive validation of input is one area that is often overlooked. Code should be written to handle all case scenarios, not just for the. Defensive programming entails many different things, even though they all revolve around handling the unexpected.
Some information might be too obvious to an experienced. Interestingly, this testdriven methodology is most popular among the practitioners of extreme programming xp, which is more widely known for informality than formality. Defensive programming and design by contracts will be a help to create reliable software with good correctness andor robustness. To reduce the number of null checks, consider using the aspectoriented programming approach. Defensive programming means raising errors loudly via assertions usually whenever something is not perfectly within specification even things that seem very unlikely to ever happen. Defensive programming defensive programming secure programming. I think the intent of this blog article is to focus on ways to enforce the contract, but the variants here that always return normally. By giving informative messages as soon as you see a problem coming, you can simplify debugging, educate your users, and avoid long computations that you know will fail. Defensive programming is the idea that the developer makes as few assumptions as absolutely necessary.212 148 1354 1509 110 1044 1226 358 1348 659 1449 418 825 60 488 1590 61 1150 522 1350 843 43 1041 12 160 644 16 1562 1358 378 1383 613 1397 919 186 334 1136 561 565