Code review

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Code review is systematic examination (often as peer review) of computer source code intended to find and fix mistakes overlooked in the initial development phase, improving both the overall quality of software and the developers' skills.

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[edit] Introduction

Code reviews can often find and remove common vulnerabilities such as format string exploits, race conditions, memory leaks and buffer overflows, thereby improving software security. Online software repositories based on Subversion with Trac, Mercurial, GIT or others allow groups of individuals to collaboratively review code. Additionally, specific tools for collaborative code review can facilitate the code review process.

Automated code reviewing software lessens the task of reviewing large chunks of code on the developer by systematically checking source code for known vulnerabilities. Flawfinder and Rough Auditing Tool for Security (RATS) are two well-known examples of code reviewing software.

[edit] Examples

There are many examples of where it is claimed that adopting code reviews improved a software development project. Notable examples include:

These claims can be hard to evaluate because each project was implemented only once; it's not possible to know for sure how the project would have turned if it hadn't adopted code reviews, or if it had instead adopted other quality control measures.

[edit] Types

Code review practices often fall into two main categories: formal code review and lightweight code review.[citation needed]

Formal code review, such as a Fagan inspection, involves a careful and detailed process with multiple participants and multiple phases. Formal code reviews are the older, traditional method of review, in which software developers attend a series of meetings and review code line by line, usually using printed copies of the material. Formal inspections are extremely thorough and have been proven effective at finding defects in the code under review. However, some criticize formal reviews as taking too long to be practical.[citation needed]

Lightweight code review typically requires less overhead than formal code inspections, though it can be equally effective when done properly.[citation needed] Lightweight reviews are often conducted as part of the normal development process:

  • Over-the-shoulder – One developer looks over the author's shoulder as the latter walks through the code.
  • Email pass-around – Source code management system emails code to reviewers automatically after checkin is made.
  • Pair Programming – Two authors develop code together at the same workstation, such as is common in Extreme Programming.
  • Tool-assisted code review – Authors and reviewers use specialized tools designed for peer code review. Programmers often find tool-assisted code review to be less tedious and more efficient than some other methods.[citation needed]

Many teams that eschew traditional, formal code review use one of the above forms of lightweight review as part of their normal development process. A code review case study published in the book, Best Kept Secrets of Peer Code Review, found that lightweight reviews uncovered as many bugs as formal reviews, but were faster and more cost-effective.

[edit] Criticism

Some argue that code review is less important when certain rules or secure coding methodologies are followed from the software's inception. The Extreme Programming (XP) approach includes the practice of pair programming, which can be argued to be code review during development. XP proponents argue that other XP practices, such as refactoring and creating tests before even writing the code, produces code that doesn't need to be reviewed or rewritten as often and thus speeds software development.


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