[libcamera-devel] versioning

[Javier Martinez Canillas]

Hello folks,

On 8/15/22 21:17, Christian Rauch via libcamera-devel wrote:
> 
> 
> Am 15.08.22 um 13:59 schrieb Eric Curtin:
>> On Mon, 15 Aug 2022 at 06:29, Laurent Pinchart via libcamera-devel
>> <libcamera-devel at lists.libcamera.org> wrote:
>>>
>>> Hi Christian,
>>>
>>> On Sun, Aug 14, 2022 at 11:44:05PM +0200, Christian Rauch via libcamera-devel wrote:
>>>> Hi Laurent,
>>>>
>>>> I think the SONAME is not the primary reason for tagging/versioning.
>>>> Having API versions is mainly used to check compatibility for other
>>>> projects. That means that the version information has to be encoded in
>>>> some project file, e.g. *.pc files. Using a SONAME is really just useful
>>>> if you want to have multiple versions of a library installed or if you
>>>> want to make sure that you only link a specific version.
>>>
>>> Bumping the SONAME is a requirement from distributions when a new
>>> version breaks ABI compatibility, so I think this is very important. It
>>> will also help avoiding users facing bugs due to incompatibilities
>>> between the version an application was compiled against and the version
>>> installed on the system.
>>

Agreed.

>> This is very important. I also am not the biggest fan of automating
>> the version number bumping against a git mechanism. I have worked on
>> projects like this and although it is convenient it is not ideal for
>> package maintainers amongst other use cases like building against a
>> tarball, etc. Fedora/EPEL are one such example where you upload the
>> sources, you are not connected to the real origin repo directly at
>> all.
>

Also agreed with this. I wonder how much value it would add to bump this
automatically, specially since the plan is to add proper ABI checking to
only bump the major version when there is backward incompatible changes.

As Kieran said, libabigail is quite popular for this and there are other
tools, some of these mentioned in this Fedora wiki page [0].

But I don't think these two should be coupled, for example it can be done
manually this time knowing that some backward incompatible changes were
made since it was versioned as 0.0.0 and the next time do it once the ABI
checker determined that needs to be bumped again.
 
> The SONAME is important, but I still think that the versioning of the
> source is even more important. Without checking for the right version,
> you may encounter compilation failures. If you distribute the *.so files
> with your project (e.g. in a snap, flatpak or other "container"), or
> build everything from source, then the SONAME does not matter so much,
> but you will still need a versioned source.
>>
>> So I would propose manual bumps when required and not tie specifically
>> to the version control system.
>
> This is certainly also an option and I do not have a strong opinion on this.
>

That would be my option too as mentioned, but don't have a strong opinion
either. I personally like how the libvirt project does. Since they have a
stable API/ABI, they never changed the major version which is still after
years set to 0.

One of the core developers has written an excellent good blog post [1] that
explains how they do versioning, but it also provides context and describes
the different meanings of a project version (software, package, SONAME, etc).

For Fedora, we don't have strict requirements of the SONAME versioning. As
long as it follows some convention so we can give heads-up to other package
maintainers when there is a SONAME bump. So that the package can be updated
and built in tandem with the other packages that depend on a given package.

Until there are official libcamera tarball releases, we will continue using
git snapshots in the SRPM (e.g: [2]) and follow the packaging guidelines in
Fedora for this [3].

[0]: https://fedoraproject.org/wiki/How_to_check_for_ABI_changes_in_a_package
[1]: https://www.berrange.com/posts/2011/01/13/versioning-in-the-libvirt-library/
[2]: https://src.fedoraproject.org/rpms/libcamera/blob/f37/f/libcamera.spec#_6
[3]: https://docs.fedoraproject.org/en-US/packaging-guidelines/Versioning/#_snapshots

-- 
Best regards,

Javier Martinez Canillas
Core Platforms
Red Hat