Module os_lib 

Lua os standard library — os.* time/date arithmetic, environment, and process control.

Graduation (Idiomatization Sprint 2, Phase 2 — 2026-06-14)

The deterministic half of this module (the os.date/os.time broken-down time arithmetic) is guarded by crates/lua-stdlib/tests/os_strengthen.rs, pinned against the version-suffixed reference binaries. Net-strengthening came FIRST and caught four real version divergences (our impl had applied the modern 5.3+/5.4+ field- and specifier-validation rules to ALL versions); they were fixed in get_field/os_time/os_date, single-source and version-gated. The version gates are load-bearing — keep them explicit.

The time arithmetic is pure Rust, no unsafe, no libc bridge: [decompose_utc]/[compose_utc] implement Howard Hinnant’s exact proleptic-Gregorian algorithms, and [strftime_one] formats specifiers directly. There is no gmtime_r/mktime/strftime FFI to keep.

Impure surface (host-dependent — not reference-pinnable)

os.getenv/tmpname/remove/rename/execute/exit touch the real environment, filesystem, and process; os.clock/os.time’s absolute value and the locale/timezone specifiers (%z/%Z/%c/%x/%X/%r/%p/%P) depend on the host clock/zone/locale. Those route through GlobalState hooks (or std) for native/sandboxed/WASM hosts; only their arg-handling and error-shape are reference-pinned, never their effects.

Structs

TmFields

Local mirror of C’s struct tm.

Constants

OS_LIB

Mapping from Lua-visible names to the Rust implementations of each os.* function.

Functions

open_os

Opens the os library: creates a new table populated with OS_LIB and leaves it on the stack.

Type Aliases

NativeFn

Signature of a Lua native function (the os.* registration entries).