What drives RPM Provides for shared libraries?

[Panu Matilainen]

On Tue, 21 Dec 2010, Tom Lane wrote:

> I'm fooling around with trying to update mysql from 5.1.x to 5.5.x.
> One of the things that's happened in that transition is that they've
> dropped the separate "libmysqlclient_r.so" library --- presumably
> everything in regular "libmysqlclient.so" is now thread-safe.
> Upstream's idea of maintaining ABI compatibility is to provide
> symlinks, libmysqlclient_r.so.16.0.0 -> libmysqlclient.so.16.0.0
> etc.  I find that that only sort of works --- RPM fails to generate
> the --provides entries that it used to.  So for example I have
> this with the old RPMs:
>
> $ rpm -qp mysql-libs-5.1.52-1.fc13.x86_64.rpm --provides
> config(mysql-libs) = 5.1.52-1.fc13
> libmysqlclient.so.16()(64bit)
> libmysqlclient.so.16(libmysqlclient_16)(64bit)
> libmysqlclient_r.so.16()(64bit)
> libmysqlclient_r.so.16(libmysqlclient_16)(64bit)
> mysql-libs = 5.1.52-1.fc13
> mysql-libs(x86-64) = 5.1.52-1.fc13
>
> but the closest I've been able to get with the new ones is
>
> $ rpm -qp mysql-libs-5.5.8-1.fc13.x86_64.rpm --provides
> config(mysql-libs) = 5.5.8-1.fc13
> libmysqlclient.so.16()(64bit)
> libmysqlclient.so.16(libmysqlclient_16)(64bit)
> mysql-libs = 5.5.8-1.fc13
> mysql-libs(x86-64) = 5.5.8-1.fc13
>
> I thought for a bit that RPM was ignoring symlinks for this purpose, but
> even copying instead of symlinking the library didn't get me a second
> set of provides items.  What drives those decisions?

The file must be recognized as being ELF by libmagic for the ELF soname 
dependencies to be generated, so yes the upstream symlink approach wont 
work. The other part of the puzzle is that rpm reads the ELF soname, and 
if it doesn't exist, basename of the file is used as a provide (to match 
the linker behavior). As the mysql libraries apparently do have a soname, 
the basename wont be used even if you copy/link to another name.

One possibility is to keep the upstream created symlinks and add the 
necessary provides manually in the spec.

 	- Panu -