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On Dec 8, 2003, at 11:08 AM, John Franklin wrote:

> Hmm... wouldn't want to take a minor number without the decision 
> coming from the library developer.  Can ELF handle a third version 
> number as a build number?  That is, libother.0.1.0 is linked against 
> libc.12, and libother.0.1.1 is linked against libc.13.

ELF doesn't actually *have* shared library version numbers.  Library 
versions are completely a naming scheme in ELF.

Let's take our current scheme as an example.

We generate libraries with names like:

	lib<name>.so.<major>.<minor>

ld(1) looks for libraries with names like:

	lib<name>.so

Encoded in the library is something called an "soname".  By 
*convention*, this is a name of the form:

	lib<name>.so.<major>

This "soname" is what is recorded in the dependency information.  So, 
let's consider:

	* A library named libfoo.so.1.1
	* The "soname" of the library is libfoo.so.1
	* The link-time name that ld(1) looks for is libfoo.so

In this case, the program gets a dependency recorded for a library 
named "libfoo.so.1", and so the run-time dynamic linker will look for a 
file named "libfoo.so.1".  This is why you see symbolic links on 
systems that use ELF shared libraries:

   0 lrwxr-xr-x  1 root  wheel      15 Sep 23 08:06 libkrb5.so@ -> 
libkrb5.so.18.4
   0 lrwxr-xr-x  1 root  wheel      15 Sep 23 08:06 libkrb5.so.18@ -> 
libkrb5.so.18.4
268 -r--r--r--  1 root  wheel  272935 Sep 23 08:06 libkrb5.so.18.4

         -- Jason R. Thorpe <thorpej@wasabisystems.com>


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