Why versioned library names?

[Siddhesh Poyarekar]

On 23/11/18 5:32 PM, Florian Weimer wrote:
> Why does the default “make install” command install the library files
> with versions in their names and relies on symbolic links to provide the
> official names?
> 
> Is this so that a previous version of glibc can be restored by using
> sln?  If this is the only reason, is it worth keeping this feature?

That has been my understanding as well; I'm not old enough to 
definitively claim that it is.

As for removing this feature, on the contrary I feel like it's not 
sufficient and that we need to strengthen this to make recoveries from 
botched updates more solid, similar to the kernel.  Right now a botched 
glibc update means that you have to go looking for your rescue disc to 
recover.  An ideal set up would be:

1. Versioned (e.g. ld-2.25-200.fc29.so) glibc libraries

2. glibc symlinks set using sln at every boot by the kernel based on a 
configuration file.  A glibc update then only updates that configuration 
file and a subsequent reboot picks up the correct glibc.  This solves 
the race conditions that occur with updates of different library files.

3. A kernel boot option glibcver=2.25-200.fc29 to override the 
configuration file.

Siddhesh

PS: I won't call the config file a systemwide tunable file, but you 
could call it that if you want ;)