pow10-rule-01-control-flow

Rule 1 — Restrict Control Flow to Simple Constructs

Severity: blocker

Statement

Use only straight-line execution, conditionals, and bounded iteration. Forbid goto, setjmp/longjmp, and recursion (direct or indirect, including mutual recursion across translation units).

Rationale

Simple control flow is verifiable by inspection and by static analysis. goto and non-local jumps make reachability undecidable. Recursion makes call graphs unbounded, which defeats stack-depth analysis, coverage, and bounded model checking.

Universal violation patterns

• A function that calls itself, directly or indirectly
• Any goto, longjmp, setjmp
• Cleanup chains implemented via non-local jumps
• Tail-call-optimized recursion (still reads as recursion to a reviewer)

Universal remediation pattern

Replace recursion with explicit iteration over a bounded data structure (work stack, deque, counter). The cap also satisfies Rule 2.

Per-language guidance

Load the file matching the language under review:

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

When violation is justified

State machines requiring genuine non-local exit (e.g., async-safe signal handlers). Isolate to one well-marked module and tag with a waiver:

// pow10: allow rule=1 until=YYYY-MM-DD owner=<handle> reason="..."

Citations

• Holzmann 2006 — Rule 1
• JPL Institutional Coding Standard — Rule 3 (no recursion), Rule 11 (no goto)