FFI nuisance

FFI nuisance

[Aidan Gauland]

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Hi,

I'm trying to use SDL through Guile's dynamic FFI.  There's a slight
nuisance with the procedure `dynamic-link': the name of the so file on
my system (Debian squeeze) is `libSDL-1.2.so.0', so because of the
`.0' at the end, (dynamic-link "libSDL-1.2") fails to find the file,
even if I give it the full path name (dynamic-link
"/usr/lib/libSDL-1.2.so.0").

I can work around this by making a symlink `libSDL-1.2.so' to
`libSDL-1.2.so.0'.  I really think that it should be possible to load
a so file that doesn't end in .so without having to touch the
filesystem.  Is there a way to do this, or should I submit a feature
request?

Regards,
Aidan Gauland

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Re: FFI nuisance

[Ludovic Courtès]

Hi,

Aidan Gauland <aidalgol@no8wireless.co.nz> writes:

> I'm trying to use SDL through Guile's dynamic FFI.  There's a slight
> nuisance with the procedure `dynamic-link': the name of the so file on
> my system (Debian squeeze) is `libSDL-1.2.so.0'

Isn’t it a packaging bug?  There should be a
‘libSDL-1.2.so’ -> ‘libSDL-1.2.so.0’ symlink.

Thanks,
Ludo’.

Re: FFI nuisance

[Andreas Rottmann]

ludo@gnu.org (Ludovic Courtès) writes:

> Hi,
>
> Aidan Gauland <aidalgol@no8wireless.co.nz> writes:
>
>> I'm trying to use SDL through Guile's dynamic FFI.  There's a slight
>> nuisance with the procedure `dynamic-link': the name of the so file on
>> my system (Debian squeeze) is `libSDL-1.2.so.0'
>
> Isn’t it a packaging bug?  There should be a
> ‘libSDL-1.2.so’ -> ‘libSDL-1.2.so.0’ symlink.
>
Only in the -dev package, which should not be required for running Guile
programs that excercise the FFI.  It is also good practice to use the
entire SONAME of the library in the Guile program, as to avoid random
breakage when the ABI changes (which does imply a SONAME bump on
sanely-maintained libraries).

Regards, Rotty
-- 
Andreas Rottmann -- <http://rotty.yi.org/>

Re: FFI nuisance

[Ludovic Courtès]

Hi,

Andreas Rottmann <a.rottmann@gmx.at> writes:

> ludo@gnu.org (Ludovic Courtès) writes:
>>
>> Aidan Gauland <aidalgol@no8wireless.co.nz> writes:
>>
>>> I'm trying to use SDL through Guile's dynamic FFI.  There's a slight
>>> nuisance with the procedure `dynamic-link': the name of the so file on
>>> my system (Debian squeeze) is `libSDL-1.2.so.0'
>>
>> Isn’t it a packaging bug?  There should be a
>> ‘libSDL-1.2.so’ -> ‘libSDL-1.2.so.0’ symlink.
>>
> Only in the -dev package, which should not be required for running Guile
> programs that excercise the FFI.  It is also good practice to use the
> entire SONAME of the library in the Guile program, as to avoid random
> breakage when the ABI changes (which does imply a SONAME bump on
> sanely-maintained libraries).

Unfortunately, I think this cannot be done portably, because the mapping
of a library’s set of supported interfaces to the SONAME and file name
is system-dependent, at least when using Libtool.

Thanks,
Ludo’.

Re: FFI nuisance

[Aidan Gauland]

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On Wed, Mar 02, 2011 at 03:49:22PM +0100, Andreas Rottmann wrote:
> ludo@gnu.org (Ludovic Courtès) writes:
> 
> > Hi,
> >
> > Aidan Gauland <aidalgol@no8wireless.co.nz> writes:
> >
> >> I'm trying to use SDL through Guile's dynamic FFI.  There's a slight
> >> nuisance with the procedure `dynamic-link': the name of the so file on
> >> my system (Debian squeeze) is `libSDL-1.2.so.0'
> >
> > Isn’t it a packaging bug?  There should be a
> > ‘libSDL-1.2.so’ -> ‘libSDL-1.2.so.0’ symlink.
> >
> Only in the -dev package, which should not be required for running Guile
> programs that excercise the FFI.  It is also good practice to use the
> entire SONAME of the library in the Guile program, as to avoid random
> breakage when the ABI changes (which does imply a SONAME bump on
> sanely-maintained libraries).

When I try to use the entire soname of the library, I get an error.
(`libSDL-1.2.so.0' is actually a link to the regular file
`libSDL-1.2.so.0.11.3'.)  What am I doing wrong?

Example session:
GNU Guile 2.0.0
Copyright (C) 1995-2011 Free Software Foundation, Inc.

Guile comes with ABSOLUTELY NO WARRANTY; for details type `,show w'.
This program is free software, and you are welcome to redistribute it
under certain conditions; type `,show c' for details.

Enter `,help' for help.
scheme@(guile-user)> (define sdl (dynamic-link "libSDL-1.2.so.0.11.3"))
ERROR: In procedure dynamic-link:
ERROR: In procedure dynamic-link: file: "libSDL-1.2.so.0.11.3", message: "file not found"

Entering a new prompt.  Type `,bt' for a backtrace or `,q' to continue.
scheme@(guile-user) [1]> ,bt
In current input:
      1:0  1 (#<procedure a34a0d0 at <current input>:1:0 ()>)
In unknown file:
           0 (dynamic-link "libSDL-1.2.so.0.11.3")
scheme@(guile-user) [1]> ,q
scheme@(guile-user)> ,q

By the way, there is a symlink libSDL.so -> libSDL-1.2.so.11.3, so
there is no packaging bug.  Now I'm trying to figure out how to do as
Andreas says and use the entire soname of the library.

--Aidan

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Re: FFI nuisance

[Andreas Rottmann]

Aidan Gauland <aidalgol@no8wireless.co.nz> writes:

> On Wed, Mar 02, 2011 at 03:49:22PM +0100, Andreas Rottmann wrote:
>> ludo@gnu.org (Ludovic Courtès) writes:
>> 
>> > Hi,
>> >
>> > Aidan Gauland <aidalgol@no8wireless.co.nz> writes:
>> >
>> >> I'm trying to use SDL through Guile's dynamic FFI.  There's a slight
>> >> nuisance with the procedure `dynamic-link': the name of the so file on
>> >> my system (Debian squeeze) is `libSDL-1.2.so.0'
>> >
>> > Isn’t it a packaging bug?  There should be a
>> > ‘libSDL-1.2.so’ -> ‘libSDL-1.2.so.0’ symlink.
>> >
>> Only in the -dev package, which should not be required for running Guile
>> programs that excercise the FFI.  It is also good practice to use the
>> entire SONAME of the library in the Guile program, as to avoid random
>> breakage when the ABI changes (which does imply a SONAME bump on
>> sanely-maintained libraries).
>
> When I try to use the entire soname of the library, I get an error.
> (`libSDL-1.2.so.0' is actually a link to the regular file
> `libSDL-1.2.so.0.11.3'.)  What am I doing wrong?
>
You are doing nothing wrong, that seems to be a limitation of Guile.  I
just wrote a mail regarding that to guile-devel, unfortunatly it doesn't
show up in the mail archive yet; check
<http://lists.gnu.org/archive/html/guile-devel/2011-03/threads.html> in
a few hours -- it should be there then.

Regards, Rotty
-- 
Andreas Rottmann -- <http://rotty.yi.org/>

Re: FFI nuisance

[Andy Wingo]

On Wed 02 Mar 2011 19:43, Aidan Gauland <aidalgol@no8wireless.co.nz> writes:

> When I try to use the entire soname of the library, I get an error.
> (`libSDL-1.2.so.0' is actually a link to the regular file
> `libSDL-1.2.so.0.11.3'.)  What am I doing wrong?

Nothing.  It is an ltdl bug.  I just sent a mail to their list:

  http://thread.gmane.org/gmane.lisp.guile.bugs/5387

Thanks for the report,

Andy
-- 
http://wingolog.org/