pow10-rule-02-bounded-loops

name	pow10-rule-02-bounded-loops
description	NASA Power of 10 Rule 2 — Every loop must have a statically determinable upper bound. Severity: blocker.

Rule 2 — Bounded Loops

Severity: blocker

Statement

Every loop must carry an explicit, statically verifiable upper bound on its iteration count. The bound should be a compile-time constant where possible. When the bound depends on runtime input, assert it against a fixed maximum.

Rationale

Bounded loops make termination trivial to prove and worst-case execution time analyzable — required for Rate Monotonic Analysis in real-time systems. Unbounded loops are the most common source of runaway behavior in embedded code.

Universal violation patterns

• while (condition) with no enclosing iteration cap
• for (;;) loops outside an annotated main event loop
• Recursive descent with no depth limit (also violates Rule 1)
• Stream / sequence chains without take(N) cap

Universal remediation pattern

Wrap any potentially-unbounded loop with an explicit counter capped by a compile-time constant. Combine with cancellation context (timeout, channel close, signal) so the loop exits cleanly when work is done.

Per-language guidance

• C: references/c.md
• Go: references/go.md
• Python: references/python.md
• Java: references/java.md
• Kotlin: references/kotlin.md

When violation is justified

main() event loops sometimes must be infinite. Tag them:

// pow10: allow rule=2 until=2099-01-01 owner=fsw-team reason="main event loop, intentional"

Citations

• Holzmann 2006 — Rule 2