[systemd-devel] Standalone libsystemd

[Lennart Poettering]

On Do, 21.03.19 20:19, Ryan Gonzalez (rymg19 at gmail.com) wrote:

> Hello!
>
> I've come to really love using the sd-bus and sd-event APIs for lightweight
> D-Bus access and event loops, and I'm sure I'm not the only one. The amount
> of bindings to other languages for stuff like sd-bus. However, this
> unfortunately doesn't work in a Flatpak environment, and building the
> entirety of systemd for some libsystemd stuff just...isn't that
> great.

Why not? What's the problem? I mean, sure you waste a bit of CPU time,
but if you build a minimal build and just throw away everything you
are not interested in, what's the problem with that?

> My idea was to add a Meson config option that would just build the systemd
> libraries, e.g. -Donly-public-libraries.
>
> That being said, I know that not all the libraries would be buildable this
> way. At minimum, udev requires the library version to match the host:
> https://lists.freedesktop.org/archives/systemd-devel/2014-October/024539.html

While there hasn't been a compat breakage in this for a while we
generally do not guarantee api stability between libudev and udev's
database, so yes, you are are not supposed to mix&match libudev with
arbitrary host udev versions.

> So I guess this comes down to:
>
> - Would libsystemd work standalone? What features *wouldn't* work? (I'm
> guessing the device and journal APIs.)

Depends. sd-bus and sd-event should be fine. sd-device sd-login otoh
probably not so much.

> - Would a flag like this be considered for addition to the build scripts?

Hmm, people request something like this all the time, but I am a bit
conservative on these things, I really don#t want to drown our build
system in too many options that all conflict with each other...

In particular I am not convinced at all that suddenly introducing
negative options (i.e. options that do not disable/enable a specific
component, but disable/enable all but some) is really a great idea, in
particuar, because such logic of "everything else but me" creates all
kinds of conflicts if you combine them with similar options. (i mean,
what is that even supposed to mean then?)

Lennart

--
Lennart Poettering, Berlin