duplicateExpressionTernary

Message: Same expression in both branches of ternary operator

Category: Logic

Severity: Style

Language: C/C++

Description

This checker detects when syntactically identical expressions appear in both the true and false branches of a ternary operator (condition ? true_expr : false_expr).

The warning is triggered when:

• The second and third operands of a ternary operator are syntactically identical expressions
• This includes cases where variables are referenced through aliases that resolve to the same expression

Motivation

The same expression indicates that there might be some logic error or copy-paste mistake.

Examples

Problematic code

// Same expression in both branches
int result = condition ? x : x;  // Warning: duplicateExpressionTernary

// Same variable referenced through alias
const int c = a;
int result = condition ? a : c;  // Warning: duplicateExpressionTernary

Fixed code

// Different expressions in branches
int result = condition ? x : y;  // OK

How to fix

1. Check for copy-paste errors: Verify that both branches are supposed to have the same expression
2. Use different expressions: If the branches should differ, update one of them
3. Simplify the code: If both branches are intentionally the same, remove the ternary operator entirely

Before:

int getValue(bool flag) {
    return flag ? computeValue() : computeValue();  // Same computation in both branches
}

After:

int getValue(bool flag) {
    return computeValue();  // Simplified - condition doesn't matter
}

Or if the branches should differ:

int getValue(bool flag) {
    return flag ? computeValue() : computeAlternativeValue();  // Different computations
}