java:S1751 Inconsistent behavior between empty condition and explicit true

SonarQube Server / Community Build
1

Product: SonarQube Community Build 26.5.0.122743
sonar-java version: sonar-java 8.29 (build 43460)
sonar-java SE version: sonar-java-symbolic-execution 8.16.4 (build 1912)
Java source level: 21 (javac 21, source/target 21)

Rule

S1751 - Loops with at most one iteration should be refactored

Description

There is an inconsistency in how rule java:S1751 handles for loops that execute at most once.

When a for loop has an explicit true condition and contains an unconditional break, the rule correctly raises an issue. However, when the condition is omitted for (;;) (which is semantically identical to for (;true;)), the rule fails to detect that the loop will also execute at most once (False Negative).

Both patterns represent a loop that runs at most one iteration and should be handled consistently.

Reproducer

public class LoopIterationInconsistency {

  // Case A: S1751 fired (Correct)
  void loopWithExplicitTrue() {
    for (; true; ) {
      break;
    }
  }

  // Case B: NO finding (False Negative)
  void loopWithEmptyCondition() {
    for (; ; ) {
      break;
    }
  }
}

Expected behavior

Both loopWithExplicitTrue and loopWithEmptyCondition should trigger a java:S1751 warning because both loops are guaranteed to terminate during the very first iteration due to the unconditional break statement.

Actual behavior

  • loopWithExplicitTrue triggers java:S1751 as expected.
  • loopWithEmptyCondition does not trigger any issue. The static analysis engine seems to treat for (;;) as a special syntax placeholder for infinite loops and consequently misses the S1751 violation within its body.