This coding standard consists of rules and recommendations, collectively referred to as guidelines. Rules are meant to provide normative requirements for code, whereas recommendations ; 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 and recommendations are collectively referred to as guidelines.
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 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.
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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.
Noncompliant Code Examples and Compliant Solutions
Noncompliant code examples illustrate code that violates the guideline under discussion. It is important to note that these are only examples, and eliminating all occurrences of the example does not necessarily mean that the code being analyzed is now compliant with the guideline.
Noncompliant code examples are typically followed by compliant solutions, which show how the noncompliant code example can be recoded in a secure, compliant manner. Except where noted, noncompliant code examples should contain violations only of the guideline under discussion. Compliant solutions should comply with all of the secure coding rules but may on occasion fail to comply with a 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.