[libvirt] [RFC] libvirt-admin: Mark symbols as local

[Guido Günther]

On Wed, Aug 12, 2015 at 11:15:58AM +0100, Daniel P. Berrange wrote:
> On Tue, Aug 11, 2015 at 09:24:59PM +0200, Guido Günther wrote:
> > Otherwise we're leaking some 30+ symbols like
> > 
> >    virAdmConnectClass
> >    virAdmConnectNew
> >    virConnectClass
> >    virConnectCloseCallbackDataClass
> >    virDomainClass
> >    ...
> > 
> > I marked the one symbol needed by the deamon as
> > LIBVIRT_ADMIN_PRIVATE_<VERSION> for now.
> 
> How are you identifying those as leaked ?

I tripped on this by dpkg-gensymbols[1] which uses objdump.

    objdump -w --dynamic-syms src/.libs/libvirt-admin.so | grep " g "

The g meaning global visibility. A similar result can be achieved with
"nm -D".

> IIRC, exports are those symbols marked with 'T' in the nm
> output:
> 
> [man nm]
>        ·   The symbol type.  At least the following types are used;
>            others are, as well, depending on the object file format.
>            If lowercase, the symbol is usually local; if uppercase,
>            the symbol is global (external).  There are however a few
>            lowercase symbols that are shown for special global
>            symbols ("u", "v" and "w").
> 
>            "T"
>            "t" The symbol is in the text (code) section.
> [/man]
> 
> # nm -a .libs/libvirt-admin.so | grep ' T '
> 0000000000001c80 T virAdmConnectClose
> 00000000000017d0 T virAdmConnectOpen
> 0000000000001d30 T virAdmConnectRef
> 
> # nm -a .libs/libvirt-admin.so | grep virAdmConnectNew
> 00000000000037c0 t virAdmConnectNew
> 
> So, IIUC, that lowercase 't' means the symol is local, and
> exported.

I'm seeing

    0000000000003f00 T virAdmConnectNew

so this is consistent with the above but different from what you're
seeing. This binutils 2.25 in case this matters. I think having a

  local:
     *;

Is a good think to have in any case.

Cheers,
 -- Guido