[SCM] Samba Shared Repository - branch master updated - release-4-0-0alpha8-154-g826ee30

[Andrew Bartlett]

On Thu, 2009-07-02 at 10:22 -0400, simo wrote:
> On Thu, 2009-07-02 at 22:58 +1000, tridge at samba.org wrote:
> > Hi Simo,
> > 
> >  > You can't have the 2 libraries installed at the same time.
> > 
> > huh?
> 
> I meant, you can't do it without risks, of course you can physically
> drop in a file.
> 
> >  > If, through dependencies, both get loaded in the same process space, and
> >  > both use the same symbol names, you are doomed.
> > 
> > err .. the loader is supposed to sort that out and use one. Metze has
> > explained that it can screw up (though I don't fully understand how),
> > and has proposed a patch that catches it if it happens. I certainly
> > don't mind putting in that patch as a extra precaution.
> 
> This is how it can happen:
> App A links talloc.so.1 and libsmbclient
> New libsmbclient links talloc.so.2
> 
> At load time glibc loads talloc.so.1 into app A, then it loads
> libsmbclient, which loads talloc.so.2
> Now, most symbols are resolved by talloc.so.1 so glibc does not replace
> them. A few new symbols though are not available so it loads them.
> Simple and devastating.

Isn't this what symbol versions are meant to prevent?

> No, the soname bumps is meant to make your app fail to even start with a
> linker error if you don't have the right version.
> The fact you can install 2 in parallel is just a consequence, sometimes
> useful, sometimes dangerous. In the talloc case I think it is just
> dangerous.

Only dangerous without symbol versions, right?

Andrew Bartlett

-- 
Andrew Bartlett
http://samba.org/~abartlet/
Authentication Developer, Samba Team           http://samba.org

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