setlocale() fails for anything other than "C" (missing locale-archive?)

[timbertson]

Apologies if this has already been covered or is expected, I've searched through a lot of issues but I'm not familiar enough with how glibc locales are supposed to work to know for sure.

Issue description

setlocale() only supports trivial locales (e.g. C). Calling setlocale() with e.g. LC_ALL=en_AU.UTF-8 fails (returns null). I discovered this because after an upgrade, fish shell no longer thinks my locale supports UTF-8: fish-shell/fish-shell#4935

Steps to reproduce

First, the setup:

$ cat setlocale.c
#include <locale.h>
#include <stdio.h>

int main() {
	char* locale = setlocale(LC_ALL, "");
	printf("locale = %s\n", locale);
}

$ cat setlocale.nix 
with (import <nixpkgs> {});
stdenv.mkDerivation {
	name = "setlocale-0";
	buildCommand = ''
		gcc -o $out ${./setlocale.c}
	'';
}

# build one with system libraries:
$ gcc -o setlocale setlocale.c

# and one with nix:
$ nix-build setlocale.nix 
/nix/store/gc3s42m3j2jhvxqp73xp5bhdqfrckfah-setlocale-0

Now, to run them:

$ env LC_ALL=en_AU.UTF-8 ./setlocale 
locale = en_AU.UTF-8

$ env LC_ALL=en_AU.UTF-8 ./result 
locale = (null)

$ env LC_ALL=C ./result 
locale = C

Doing an strace, I found that the nix version is trying to open two locale files:

$ strace -eopenat -f ./result 2>&1 | grep locale-archive
openat(AT_FDCWD, "/nix/store/27x7pinqdsl9f3rpbm8bsszd9fhwq266-glibc-2.27/lib/locale/locale-archive", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/usr/lib/locale/locale-archive", O_RDONLY|O_CLOEXEC) = 3

I'm guessing that my /usr/lib/locale/locale-archive is an old / incompatible version, since an strace confirms that file is opened by the (successful) ./setlocale

LDD info:

My system libc is 2.26, while nixpkgs is 2.27.

$ ldd setlocale
	linux-vdso.so.1 (0x00007f37f2cc3000)
	libc.so.6 => /lib64/libc.so.6 (0x00007f37f26eb000)
	/lib64/ld-linux-x86-64.so.2 (0x00007f37f2aa1000)

$ ll /lib64/libc.so.6
lrwxrwxrwx. 1 root root 12 Mar  2 23:05 /lib64/libc.so.6 -> libc-2.26.so

$ ldd result
	linux-vdso.so.1 (0x00007fffdf7de000)
	libc.so.6 => /nix/store/27x7pinqdsl9f3rpbm8bsszd9fhwq266-glibc-2.27/lib/libc.so.6 (0x00007f360fdc7000)
	/nix/store/27x7pinqdsl9f3rpbm8bsszd9fhwq266-glibc-2.27/lib/ld-linux-x86-64.so.2 => /lib64/ld-linux-x86-64.so.2 (0x00007f361017b000)

$ ll /nix/store/27x7pinqdsl9f3rpbm8bsszd9fhwq266-glibc-2.27/lib/libc.so.6
lrwxrwxrwx. 1 tim tim 12 Jan  1  1970 /nix/store/27x7pinqdsl9f3rpbm8bsszd9fhwq266-glibc-2.27/lib/libc.so.6 -> libc-2.27.so*

If I explicitly provide nix's libc locale archive, it works:

$ env LOCALE_ARCHIVE=/nix/store/8kw71xqs5bz6s68dylv6y13082zn0023-glibc-locales-2.27/lib/locale/locale-archive LC_ALL=en_AU.UTF-8 ./result 
locale = en_AU.UTF-8

Is it possible for libc to use this file by default? If not, is there anything I can put in my ~/.nixpkgs/config.nix to do this globally (ideally without causing mass rebuilds...)?

Technical details

$ nix-shell -p nix-info --run "nix-info -m"
 - system: `"x86_64-linux"`
 - host os: `Linux 4.15.17-300.fc27.x86_64, Fedora, 27 (Workstation Edition)`
 - multi-user?: `no`
 - sandbox: `no`
 - version: `nix-env (Nix) 2.0`
 - channels(tim): `"nixpkgs-18.09pre137305.d91caac6c3e"`
 - nixpkgs: `/home/tim/.nix-defexpr/channels/nixpkgs`

[xeji]

possibly related: #38991

[timbertson]

thanks - definitely sounds familiar, although that seems to be nixos focussed, while this is an issue with plain nixpkgs (where it's likely systems will be running with an incompatible locale-archive for a long time)

[peti]

This is a duplicate of #38991.