Implement Rule 22-4-1, only assign literal 0 to errno.

[MichaelRFairhurst]

Description

Implement Rule 22-4-1, only assign literal 0 to errno.

Change request type

• Release or process automation (GitHub workflows, internal scripts)
• Internal documentation
• External documentation
• Query files (.ql, .qll, .qls or unit tests)
• External scripts (analysis report or other code shipped as part of a release)

Rules with added or modified queries

• No rules added
• Queries have been added for the following rules:
  • Rule-22-4-1
• Queries have been modified for the following rules:
  • rule number here

Release change checklist

A change note (development_handbook.md#change-notes) is required for any pull request which modifies:

• The structure or layout of the release artifacts.
• The evaluation performance (memory, execution time) of an existing query.
• The results of an existing query in any circumstance.

If you are only adding new rule queries, a change note is not required.

Author: Is a change note required?

• Yes
• No

🚨🚨🚨
Reviewer: Confirm that format of shared queries (not the .qll file, the
.ql file that imports it) is valid by running them within VS Code.

• Confirmed

Reviewer: Confirm that either a change note is not required or the change note is required and has been added.

• Confirmed

Query development review checklist

For PRs that add new queries or modify existing queries, the following checklist should be completed by both the author and reviewer:

Author

• Have all the relevant rule package description files been checked in?
• Have you verified that the metadata properties of each new query is set appropriately?
• Do all the unit tests contain both "COMPLIANT" and "NON_COMPLIANT" cases?
• Are the alert messages properly formatted and consistent with the style guide?
• Have you run the queries on OpenPilot and verified that the performance and results are acceptable?
  As a rule of thumb, predicates specific to the query should take no more than 1 minute, and for simple queries be under 10 seconds. If this is not the case, this should be highlighted and agreed in the code review process.
• Does the query have an appropriate level of in-query comments/documentation?
• Have you considered/identified possible edge cases?
• Does the query not reinvent features in the standard library?
• Can the query be simplified further (not golfed!)

Reviewer

• Have all the relevant rule package description files been checked in?
• Have you verified that the metadata properties of each new query is set appropriately?
• Do all the unit tests contain both "COMPLIANT" and "NON_COMPLIANT" cases?
• Are the alert messages properly formatted and consistent with the style guide?
• Have you run the queries on OpenPilot and verified that the performance and results are acceptable?
  As a rule of thumb, predicates specific to the query should take no more than 1 minute, and for simple queries be under 10 seconds. If this is not the case, this should be highlighted and agreed in the code review process.
• Does the query have an appropriate level of in-query comments/documentation?
• Have you considered/identified possible edge cases?
• Does the query not reinvent features in the standard library?
• Can the query be simplified further (not golfed!)

[Copilot]

Pull request overview

This PR implements MISRA C++ 2023 Rule 22-4-1, which requires that only the literal value zero should be assigned to errno. The rule aims to discourage the use of errno for error handling in C++ projects, as modern C++ provides better alternatives.

Key Changes:

• Added a new CodeQL query to detect invalid assignments to errno (non-zero values, expressions, variables, or compound assignments)
• Created supporting library for errno detection and integrated it with the existing literals framework
• Added comprehensive test cases covering various assignment scenarios including literals, macros, expressions, and casts

Reviewed changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
rules.csv	Added Rule 22-4-1 entry with Preconditions4 package reference
rule_packages/cpp/Preconditions4.json	Rule package metadata for the new errno assignment query
cpp/misra/src/rules/RULE-22-4-1/InvalidAssignmentToErrno.ql	Main query implementation detecting invalid errno assignments
cpp/common/src/codingstandards/cpp/standardlibrary/Errno.qll	Library for identifying errno variable accesses
cpp/common/src/codingstandards/cpp/exclusions/cpp/Preconditions4.qll	Query metadata and exclusion support for the rule package
cpp/common/src/codingstandards/cpp/exclusions/cpp/RuleMetadata.qll	Integration of Preconditions4 package into metadata system
cpp/misra/test/rules/RULE-22-4-1/test.cpp	Comprehensive test cases for compliant and non-compliant errno usage
cpp/misra/test/rules/RULE-22-4-1/InvalidAssignmentToErrno.qlref	Test query reference
cpp/misra/test/rules/RULE-22-4-1/InvalidAssignmentToErrno.expected	Expected test results
cpp/common/test/includes/standard-library/errno.h	Added standard error macro definitions for testing
cpp/common/test/includes/standard-library/string	Added empty() method to basic_string for test completeness

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[mbaluda]

Suggested minor improvement to the error message

[mbaluda]

LGTM!