Re: [Xen-devel] dynamic libraries

[Adam Heath <doogie@xxxxxxxxxxxxx>]

On Wed, 23 Feb 2005, Keir Fraser wrote:

>
> On 23 Feb 2005, at 21:28, Andrei Petrov wrote:
>
> > While looking at tools build I noticed that same object files are used
> > to build both
> > static and dynamic libraries (libxc, libxutil). It's normally required
> > to compile in
> > PIC form for dynamic ones. At first I thought that no applcations use
> > those libraries,
> > but no, they are used by all of them. Surprisingly it doens't cause
> > any problems (at
> > least nobody's complaining, ld.so even).
> >
> > Well, anyway it doesn't look correct for me, I'd like to come up with
> > a patch
> > but it'll take some time, so I wouldn't mind if some Makefile savvy
> > beat me on it.
> > Short term solution would be always set -fPIC.
>
> Well, we have the functionality in the build system already; it just
> isn't the default.
> Where is it stated that dynamic libraries must be compiled -fPIC? They
> contain
> relocation info and so can be relocated wherever needed at run time.
> Potentially
> less efficient (library relocated to different addresses cannot have
> its text pages
> shared across processes) but I don't see why it is *disallowed*.
>
> If there's a suitably convincing explanation/reason then I will change
> the default setting. :-)

Well, it just doesn't work at all on amd64, as well as other arches.  It just
happens to work on i386, so most people never notice it.


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