Comment by jkrejcha

strerror, at least on glibc, was only made thread safe back in 2020[1], which is really not that long ago in the grand scheme of things. It was WONTFIXed when it was initially reported back in 2005(!). There have only been 10 glibc releases since then and the 2.32 branch is still actively maintained.

There is probably a wide breadth of software that is actively not using that glibc version.

But yeah, agreed that trying to do localization with the builtin functions are fraught with traps and pitfalls. Part of the problem though is less about localization and more due to the fact that you can have bugs inflicted on you if you're not careful to just overwrite the locale with the C locale (and make sure to do this everywhere you can)

[1]: https://sourceware.org/bugzilla/show_activity.cgi?id=1890 (see specifically the target milestone, the 2023 date seems to be overly pessimistic)