Re: ocaml compiled binaries and rpath
On Thu, Apr 17, 2003 at 02:22:22PM +0200, Sven Luther wrote:
[...]
> > Is this symlink (dll -> lib) a hack or is it the Right Thing?
>
> It is a hack, i think.
>
> Basically, the ocaml runtime system will dynamically link files named
> dllxxx.so. This was a name scheme chosen with upstream, and we cannot
> really change it.
>
> What Claudio does is that he need to link one of these dllxxx.so
> libraries into other dllxxx.so libraries,
Maybe OCaml gurus have an opinion about this issue?
> but since gcc expect libraries to be called libxxx.so,
Not fully true, here is a test case:
$ gcc -shared -fPIC -c -o libxxx.so xxx.c
$ gcc -c main.c
$ gcc -o withlib -L. -lxxx main.o
$ gcc -o withdll libxxx.so main.o
$ cmp withdll withlib
$
They are strictly identical. In the last case, libxxx.so is not
considered as a library (which is why you are not wrong ;)), but
as a shared object. And you can then rename it to dllxxx.so.
$ gcc -o withdll dllxxx.so main.o
Unfortunately ocamlopt does not accept input files with a .so extension,
maybe it can be patched to accept them as gcc does?
> he uses this symlink hack. And since it is exactly for that that he
> needs the rpath, it may well be a good idea that he moves the symlink
> to /usr/lib.
An alternative is not to link against the other lib, and let developers
add all the needed libraries when linking. It is not necessarily a bad
thing, you then ensure that there are no linking against conflicting
libraries (as with libpng).
> A clean way would be to move the common stuff in a true library, which
> has a versioned so name, and place this library into /usr/lib, as should
> be, and then have wrapper libraries for it.
>
> The problem is that we plan to have multiple installable versions of
> ocaml. ocaml 3.06 installs in /usr/lib/ocaml/3.06/stublibs while ocaml
> 3.07 would install in /usr/lib/ocaml/3.07/stublibs. If we have the same
> library package for both systems, the either the symlink in /usr/lib,
> the common library in /usr/lib or the path in /etc/ld.so.conf would be
> conflicting.
I guess that ocamlrun will be replaced by ocamlrun-3.06, which will
use its own ld.conf to find the right stublibs directory. An analogy
with ocamlopt is that the linker should be told to look into
/usr/lib/ocaml/x.xx/stublibs and adds an rpath section into the
generated binary if stublibs are needed. Just a dumb idea, I have
no idea whether this is doable or right.
> The real solution for this would be to create a separate package for the
> common part, which is not nice, and probably overkill for a common
> source code of 50 lines or so.
OTOH Remi shows that this was the only problematic example.
Denis
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