Types and Traits

Guideline: Avoid Implicit Integer Wrapping gui_xztNdXA2oFNB

status: draft tags: numerics category: required fls: fls_cokwseo3nnr decidability: decidable scope: module release: 1.85.0;1.85.1 child needs: rat_kYiIiW8R2qD1, non_compl_ex_PO5TyFsRTlWv, compl_ex_WTe7GoPu5Ez0

Code must not rely on Rust’s implicit integer wrapping behavior that may occur in release builds. Instead, explicitly handle potential overflows using the standard library’s checked, saturating, or wrapping operations. Rationale: rat_kYiIiW8R2qD1 status: draft parent needs: gui_xztNdXA2oFNB In debug builds, Rust performs runtime checks for integer overflow and will panic if detected. However, in release builds (with optimizations enabled), unless the flag overflow-checks is turned on, integer operations silently wrap around on overflow, creating potential for silent failures and security vulnerabilities. Note that overflow-checks only brings the default panic behavior from debug into release builds, avoiding potential silent wrap arounds. Nonetheless, abrupt program termination is usually not suitable and, therefore, turning this flag on must not be used as a substitute of explicit handling. Furthermore, the behavior in release mode is under consideration by the The Rust Language Design Team and in the future overflow checking may be turned on by default in release builds (it is a frequently requested change). Safety-critical software requires consistent and predictable behavior across all build configurations. Explicit handling of potential overflow conditions improves code clarity, maintainability, and reduces the risk of numerical errors in production. Non-Compliant Example: non_compl_ex_PO5TyFsRTlWv status: draft parent needs: gui_xztNdXA2oFNB fn calculate_next_position(current: u32, velocity: u32) -> u32 { // Potential for silent overflow in release builds current + velocity } Compliant Example: compl_ex_WTe7GoPu5Ez0 status: draft parent needs: gui_xztNdXA2oFNB fn calculate_next_position(current: u32, velocity: u32) -> u32 { // Explicitly handle potential overflow with checked addition current.checked_add(velocity).expect("Position calculation overflowed") }