Re: Symbol versioning for secondary libraries is not effective

[Florian Weimer <fweimer at redhat dot com>]

On 01/26/2018 01:46 PM, Joseph Myers wrote:
> On Fri, 26 Jan 2018, Florian Weimer wrote:
>
> > in mind for future changes.  It is also a mild argument in favor of moving
> > symbols into libc.so.6, I think.
>
> Suppose you make the libc.so linker script reference some or all of the
> other libraries inside AS_NEEDED.  Do that result in them being
> automatically linked into shared libraries that use symbols from them, or
> does it only work for executables?

This will not work for libpthread because some libraries really prefer 
to link against the libc.so.6 definitions, at least for the time being, 
where the libc and libpthread implementations offer different trade-offs.

For libm and libld, this approach appears to work.  The AS_NEEDED 
directive is even overriden by an explicit -lm or -ldl on the command, 
which is good.  It looks like this is something to consider for the next 
release.

> Referencing libraries inside AS_NEEDED is arguably friendlier to users
> anyway - e.g. those not familiar with Unix conventions may not expect to
> need to use -lm.

Yes, a missing -lm seems to be a common obstacle.

Thanks,
Florian