From: skaller <skaller@users.sourceforge.net>
To: Xavier Leroy <Xavier.Leroy@inria.fr>
Cc: caml-list@inria.fr
Subject: Re: [Caml-list] PIC
Date: Tue, 27 Dec 2005 23:23:01 +1100 [thread overview]
Message-ID: <1135686181.10470.38.camel@rosella> (raw)
In-Reply-To: <43B1116C.5060407@inria.fr>
On Tue, 2005-12-27 at 11:03 +0100, Xavier Leroy wrote:
> > I notice Ocaml 3.09 has -fPIC option. Thanks! This is a step
> > towards dynamic loading in native code.
Thanks for your summary!
> Encapsulation of compiled OCaml code as a shared library that can be
> called from C is possible, on x86 at least.
[]
> This is a very good approach to use OCaml code from other languages
> (e.g. Java) or as plug-ins (e.g. in Apache).
Indeed! If I understand correctly, this requires redistribution
of "LGPL with Linking Exception" parts of Ocaml only?
> The reason it works particularly well for x86 is that dynamic loaders
> for x86 (both under Unix/Linux and Windows) can relocate arbitrary
> code, not necessarily PIC code. This is unfortunately not the case
> for all target architectures.
> In particular, dynamic loaders for
> x86_64 (AMD64) are much less forgiving.
I suspect you're being polite .. 'broken' seems to the
correct term ;( The same techniques should work for the
x86_64 as the x86 .. just making sure 64 bit values are
supported (by the loader and ELF formats) should be enough.
> The -fPIC option to ocamlopt
> you mention was added to the AMD64 code generator in an attempt to
> generate "more position-independent" code. However, it does not quite
> work yet. A difficulty is the paucity of documentation on what,
> exactly, the Linux AMD64 dynamic loader can relocate.
I see. Ok, thanks for that info. Having looked into this
myself .. I'm not surprised .. Sigh. Is the ia64 any better?
> Dynamic loading of OCaml code from OCaml code raises many other
> issues.
Type safety, version compatibility, etc being a few.
But one can work around this problem, perhaps messily and
riskily, if the codes can be loaded and connected together
with C glue.
> It is currently supported for bytecode only, and will not be
> available for native code in the forseeable future. I have already
> discussed this on this list earlier.
Yes, thanks. I hope I covered the combinations reasonably
well, so your responses are fairly clear summary of the
situation, which is what I was looking for: thanks!
--
John Skaller <skaller at users dot sf dot net>
Felix, successor to C++: http://felix.sf.net
next prev parent reply other threads:[~2005-12-27 12:23 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-12-25 2:07 PIC skaller
2005-12-27 10:03 ` [Caml-list] PIC Xavier Leroy
2005-12-27 12:23 ` skaller [this message]
2005-12-28 9:14 ` Sven Luther
2005-12-31 21:31 ` David Fox
2006-01-01 10:49 ` Ker Lutyn
2006-01-03 23:27 ` Nathaniel Gray
2006-01-04 2:38 ` skaller
2006-01-04 4:54 ` Nathaniel Gray
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