Library sonames

[Benson Muite]

The packaging guidelines indicate that shared libraries should have
sonames, and if not provided by upstream, packager should use a low
number soname such as 0.x.y to enable easy bumping of the soname should
upstream later add one.  This assumes semantic versioning.  If upstream
does not use semantic versioning, is it reasonable to use whatever
versioning scheme they use? One alternative is libtool versioning[1,2].
What to do if the versioning scheme is unclear? In particular is
versioning such as:
libSDL-1.2.so.0 -> libSDL-1.2.so.1.2.68
libserf-1.so.0 -> libserf-1.so.1.3.9
libutempter.so.0 -> libutempter.so.1.2.1
reasonable
or should these all be
libSDL-1.2.so.1 -> libSDL-1.2.so.1.2.68
libserf-1.so.1 -> libserf-1.so.1.3.9
libutempter.so.1 -> libutempter.so.1.2.1

These issues have arisen when reviewing [3]

1) https://autotools.info/libtool/version.html
2)
https://www.gnu.org/software/libtool/manual/html_node/Libtool-versioning.htm...
3) https://bugzilla.redhat.com/show_bug.cgi?id=2241062

[Petr Pisar]

V Thu, Nov 09, 2023 at 04:38:25PM +0300, Benson Muite napsal(a):
> The packaging guidelines indicate that shared libraries should have
> sonames, and if not provided by upstream, packager should use a low
> number soname such as 0.x.y to enable easy bumping of the soname should
> upstream later add one.  This assumes semantic versioning.  If upstream
> does not use semantic versioning, is it reasonable to use whatever
> versioning scheme they use? One alternative is libtool versioning[1,2].
> What to do if the versioning scheme is unclear? In particular is
> versioning such as:
> libSDL-1.2.so.0 -> libSDL-1.2.so.1.2.68
> libserf-1.so.0 -> libserf-1.so.1.3.9
> libutempter.so.0 -> libutempter.so.1.2.1
> reasonable
> or should these all be
> libSDL-1.2.so.1 -> libSDL-1.2.so.1.2.68
> libserf-1.so.1 -> libserf-1.so.1.3.9
> libutempter.so.1 -> libutempter.so.1.2.1

As far as I know the 3-component version schema as used by libtool is
irrelevant for glibc dynamic linker, hence for Fedora. The reason is that what
matters for Fedora are only two files:

libSDL.so       -- used at build time
libSDL-1.2.so.0 -- used at run time

Whether these files are regular files or symlinks and where the symlinks point
does not matter.

What matters is that a soname stored inside the first one (scanelf --soname
/usr/lib64/libSDL.so) matches the later file name.

So for Fedora it's only a matter of aesthetics.

-- Petr