Building with musl in CI and the build farm

The need to do $subject came up in [1]. Moving this to a separate 
discussion on -hackers, because there are more issues to solve than just 
the LD_LIBRARY_PATH problem.

Andres Freund:
> FWIW, except for one small issue, building postgres against musl works on
> debian and the tests pass if I install first.
> 
> 
> The small problem mentioned above is that on debian linux/fs.h isn't available
> when building with musl, which in turn causes src/bin/pg_upgrade/file.c to
> fail to compile.  I assume that's not the case on "fully musl" distro?

Correct, I have not seen this before on Alpine.

Here is my progress setting up a buildfarm animal to run on Alpine Linux 
and the issues I found, so far:

The animal runs in a docker container via GitHub Actions in [2]. Right 
now it's still running with --test, until I get the credentials to 
activate it.

I tried to enable everything (except systemd, because Alpine doesn't 
have it) and run all tests. The LDAP tests are failing right now, but 
that is likely something that I need to fix in the Dockerfile - it's 
failing to start the slapd, IIRC. There are other issues, though - all 
of them have open pull requests in that repo [3].

I also had to skip the recovery check. Andrew mentioned that he had to 
do that, too, when he was still running his animal on Alpine. Not sure 
what this is about, yet.

Building --with-icu fails two tests. One of them (001_initdb) is fixed 
by having the "locale" command in your PATH, which is not the case on 
Alpine by default. I assume this will not break on your debian/musl 
build, Andres - but it will also probably not return any sane values, 
because it will run glibc's locale command.
I haven't looked into that in detail, yet, but I think the other test 
(icu/010_database) fails because it expects that setlocale(LC_COLLATE, 
<illegal_value>) throws an error. I think it doesn't do that on musl, 
because LC_COLLATE is not implemented.
Those failing tests are not "just failing", but probably mean that we 
need to do something about how we deal with locale/setlocale on musl.

The last failure is about building --with-nls. This fails with something 
like:

ld: src/port/strerror.c:72:(.text+0x2d8): undefined reference to 
`libintl_gettext'

Of course, gettext-dev is installed, libintl.so is available in /usr/lib 
and it also contains the symbol. So not sure what's happening here.

Andres, did you build --with-icu and/or --with-nls on debian/musl? Did 
you run the recovery tests?

Best,

Wolfgang

[1]: 
https://postgr.es/m/fddd1cd6-dc16-40a2-9eb5-d7fef2101488%40technowledgy.de
[2]: 
https://github.com/technowledgy/postgresql-buildfarm-alpine/actions/workflows/run.yaml
[3]: https://github.com/technowledgy/postgresql-buildfarm-alpine/pulls