This coding standard consists of rules and recommendations, collectively referred to as guidelines. Rules are meant to provide normative requirements for code, whereas recommendations are meant to provide guidance that, when followed, should improve the safety, reliability, and security of software systems. However, a violation of a recommendation does not necessarily indicate the presence of a defect in the code.
Rules
Rules must meet the following criteria:
- Violation of the guideline is likely to result in a defect that may adversely affect the safety, reliability, or security of a system, for example, by introducing a security flaw that may result in an exploitable vulnerability.
- The guideline does not rely on source code annotations or assumptions.
- Conformance to the guideline can be determined through automated analysis (either static or dynamic), formal methods, or manual inspection techniques.
Rules are identified by the label rule.
Recommendations
Recommendations are suggestions for improving code quality. Guidelines are defined to be recommendations when all of the following conditions are met:
- Application of a guideline is likely to improve the safety, reliability, or security of software systems.
- One or more of the requirements necessary for a guideline to be considered a rule cannot be met.
The set of recommendations that a particular development effort adopts depends on the requirements of the final software product. Projects with stricter requirements may decide to dedicate more resources to ensuring the safety, reliability, and security of a system and consequently are likely to adopt a broader set of recommendations.
Recommendations are identified by the label recommendation.
Exceptions
Any rule or recommendation may specify a small set of exceptions detailing the circumstances under which the guideline is not necessary to ensure the safety, reliability, or security of software. Exceptions are informative only and are not required to be followed.
Coding practices that specify one or more exceptions are identified by the label exceptions.
Identifiers
Each rule and recommendation is given a unique identifier. These identifiers consist of three parts:
- A three-letter mnemonic representing the section of the standard
- A two-digit numeric value in the range of 00 to 99
- The letter C indicating that this is a C language guideline
The three-letter mnemonic can be used to group similar coding practices and to indicate to which category a coding practice belongs.
The numeric value is used to give each coding practice a unique identifier. Numeric values in the range of 00 to 29 are reserved for recommendations, and values in the range of 30 to 99 are reserved for rules.