add an SONAME for shared libraries

[juhp]

Have you considered adding a proper SONAME to the shared libnix* libraries?
Do any other tools use them?

Otherwise maybe it would be better for Linux distros/packagers of nix to place them in a private lib directory
and use RUNPATH to find them (I guess that is already there).

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[Ericson2314]

https://mesonbuild.com/Reference-manual_functions.html#both_libraries_version and https://mesonbuild.com/Reference-manual_functions.html#both_libraries_soversion it looks like one of these needs to be set in all our libraries, and then Meson should do the right thing.

Thanks for noticing! Can you make a PR for this?

[Mic92]

Here is how:

diff --git src/libutil-c/meson.build src/libutil-c/meson.build
index 8131c517c..08d3e2881 100644
--- src/libutil-c/meson.build
+++ src/libutil-c/meson.build
@@ -58,6 +58,7 @@ this_library = library(
   link_args : linker_export_flags,
   prelink : true, # For C++ static initializers
   install : true,
+  version : meson.project_version(),
 )
 
 install_headers(headers, preserve_path : true)

However not sure how helpful the result is:

nix-util-env % readelf -a ./build/src/libutil-c/libnixutilc.so | grep SONAME
 0x000000000000000e (SONAME)             Library soname: [libnixutilc.so.2]

This will be 2 for quiet a while...

[Mic92]

We have a in the nix ecosystem a couple of other tools using the libraries and we also have pkg-config files, but there versions are usually not needed because on every build change of nix, all other tools get rebuild in any case.

[juhp]

I think the soversion does not need to equal the major version, eg it can be 0 for now.
Just that Linux distros like to have versioned .so files, because they split them into a runtime subpackage.

[Mic92]

Done in #13966