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From: Pyry Kontio <pyry.kontio@drasa.eu>
Date: Mon, 17 Feb 2020 13:35:25 +0900
Message-ID: 
 <CACS8yHKjrFOoTKKFOOted4d+16oN438DE0ydtp9y5QrxvcGp2w@mail.gmail.com>
Subject: Problems with statically linking libpq of Postgres 12.0 + musl
To: pgsql-interfaces@lists.postgresql.org
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Hi, I maintain a Docker image for easily building static Rust binaries,
with some commonly used libraries pre-built for static linking.
The image is being used to build, for example, a statically linked
Rust wrapper for libpq. The image uses the Musl C standard library.

I recently tried to upgrade to Postgres 12.0, but I'm encountering
some linking issues I didn't use to have with 11.7.
I've been able to reproduce these issues by linking libpq with
a simple C program.

A short script demonstrating the difference between 12.0 and 11.7
can be found here:

https://pastebin.com/ZLR5zQzY

The script uses a Docker images built from a Dockerfile here:
https://gitlab.com/rust_musl_docker/image/-/blob/master/BaseDockerfile.template

The gist of the problem seems to be that linking against libpq
works with 11.7 like this:
(All the packages built from source against musl reside under /musl;
note also that we use the musl GCC wrapper to build and link.)

$ musl-gcc -static -o test test.o -L /musl/lib/ -lpq

But fails with a bunch of "undefined references" to symbols defined in
libpgcommon and libpgport, with 12.0. Here's a listing of filtered output
of the linker: https://pastebin.com/XYXkg30B

Adding libpgcommon and libpgport fixes the issue:

$ musl-gcc -static -o test test.o -L /musl/lib/ -lpq -lpgport -lpgcommon

I guess I could just add those libraries, and call it a day, but there's a bunch
of things that bother me:

1) What changed between 11.7 and 12.0? Is this change intentional or not?
2) The documentation about building libpq
( https://www.postgresql.org/docs/10/libpq-build.html
doesn't say anything about libpgport and libpgcommon being dependencies.
Are they or are they not?

I'd appreciate any insight about this issue.

All the best,
Pyry Kontio