CodeQL documentation

Declaration hides variable

ID: cpp/declaration-hides-variable
Kind: problem
Severity: recommendation
Precision: high
Tags:
   - maintainability
   - readability
Query suites:
   - cpp-security-and-quality.qls

Click to see the query in the CodeQL repository

This rule finds declarations of local variables that hide a local variable from a surrounding scope. Such declarations create variables with the same name but different scopes. This makes it difficult to know which variable is actually used in an expression.

Recommendation

Consider changing the name of either variable to keep them distinct.

Example

void f() {
	int i = 10;

	for (int i = 0; i < 10; i++) { //the loop counter hides the variable
		 ...
	}

	{
		int i = 12; //this variable hides the variable in the outer block
		...
	}
}

References

  • B. Stroustrup. The C++ Programming Language Special Edition p 82. Addison Wesley. 2000.