CodeQL documentation

No trivial switch statements

ID: cpp/trivial-switch
Kind: problem
Severity: recommendation
Precision: high
Tags:
   - maintainability
   - readability
   - external/jsf
Query suites:
   - cpp-security-and-quality.qls

Click to see the query in the CodeQL repository

The following forms of switch statement are considered trivial:

  1. No cases at all.
  2. Just a default case.
  3. Just one non-default case.
  4. A default case and one non-default case.

Recommendation

Either the switch statement should be replaced with a simpler control flow structure, or it should be extended to handle more cases. Each trivial form has a different replacement:

  1. If there are no cases, the switch statement can be removed.
  2. If there is just one default case, the switch keyword, the default keyword, and the subsequent colon can all be removed.
  3. If there is just one non-default case, the switch statement can be turned into an if statement.
  4. If there is one default case and one non-default case, the switch statement can be turned into an if/else statement.

Example

int f() {
	int val = 0;
	switch(val) { //wrong, use an if instead
	case 0:
		//...
	default:
		//...
	}

	switch(val) { //correct, has 2 cases and a default
	case 0:
		//...
	case 1:
		//...
	default:
		//...
	}
}

References

  • AV Rule 196, Joint Strike Fighter Air Vehicle C++ Coding Standards. Lockheed Martin Corporation, 2005.