#localtime #safety #soundness


Rust-locked localtime - a sound localtime implementation

3 releases

0.1.2 Feb 19, 2022
0.1.1 Feb 11, 2022
0.1.0 Feb 11, 2022

#518 in Unix APIs

MITNFA license


C 1.5K SLoC // 0.2% comments Rust 134 SLoC // 0.0% comments

Rust-locked localtime implementation

Crate abandoned

This crate is abandoned because there's a pure Rust implemenation - tz-rs. The code is up for archival purposes only.


Warning: this crate is currently proof-of-concept and it wasn't deeply audited! While I believe this fixes the unsoundness, I may have introduced other bug(s). Use at your own risk or, better, help improve it!

This is a fork of a C localtime_r implementation with minimal changes required to make calling it in parallel to setting env from Rust sound. It does so by calling into Rust code to get the environment variable instead of using raw system getenv.

Obviously, this does not interact with the system implementation of localtime_r. E.g. if you call localtime in this crate it will not affect static variables in the system library. This is considered a feature because system localtime library is a huge dumpster fire and if you use it you can easily get UB - not just from setting env vars. (NetBSD implementation is a bit better though.)

This crate is meant to be a cheaper-to-implement alternative to rewriting whole localtime_r in Rust which people are unwilling to do due to large code size. It only required changing a few lines and writing glue Rust code.


The C code, including my modifications, is released into public domain. The Rust code is released under MITNFA license.