Re: linker-script.m4?

[Simon Josefsson]

Bruno Haible <address@hidden> writes:

> Simon Josefsson wrote:
>> The version script file is documented in the LD manual, but a short
>> example would be:
>> 
>> SHISHI_0.0 {
>>   global:
>>     shishi*;
>> 
>>   local:
>>     *;
>> };
>
> Could you please explain what the entire thing is about? Is it about
> hiding some symbols from "nm libshishi.so", for which gcc offers a solution
> at source code level (see [1] and gnulib's m4/visibility.m4)?

No, that's not the primary motivation, but it is a useful side-effect.
If it didn't have that side-effect, hiding the symbols would need to be
done in some other way.

> Or is it about allowing multiple versions of the same symbol to exist
> in the same shared library, something which is supported only by glibc
> and Solaris [2]?

Yes, that is one reason.

> I'm asking because linker scripts only work with GNU ld (I guess).

Yes, I think so.

Further, shared library versioning can be useful when maintaining
packages in GNU/Linux distributions, and it seems people in Debian
prefers that shared libraries always use versioning.  See for example:

http://article.gmane.org/gmane.comp.gnu.gss.general/139

Of course a good reference where this is discussed is:

http://people.redhat.com/drepper/dsohowto.pdf

/Simon