FFI on OS X?

FFI on OS X?

[Michael Ellis]

Trying to follow the examples in section 6.20.6 in the manual  I get
the following.

scheme@(guile-user)> (define libm (dynamic-link "/usr/lib/libm.dylib"))
ERROR: In procedure dynamic-link: file: "/usr/lib/libm.dylib",
message: "file not found"

The same library can be loaded and its functions are available with
python ctypes, e.g.

>>> libm=CDLL("/usr/lib/libm.dylib")
>>> libm
<CDLL '/usr/lib/libm.dylib', handle 7fff5fc43d68 at 1004dfc50>
>>> libm.j0
<_FuncPtr object at 0x100599d50>

What am I doing wrong?

Thanks,
Mike

Re: FFI on OS X?

[Hans Aberg]

On 2 Mar 2011, at 21:07, Michael Ellis wrote:

> Trying to follow the examples in section 6.20.6 in the manual  I get
> the following.
> 
> scheme@(guile-user)> (define libm (dynamic-link "/usr/lib/libm.dylib"))
> ERROR: In procedure dynamic-link: file: "/usr/lib/libm.dylib",
> message: "file not found"
...
> What am I doing wrong?

Guile, or what it uses to load libraries, assumes that a dynamic library ends in something else than ".dylib". Make a soft link ('ln -s') ending in ".so", and load this instead, and it will work.

  Hans

Re: FFI on OS X?

[Andy Wingo]

On Wed 02 Mar 2011 21:07, Michael Ellis <michael.f.ellis@gmail.com> writes:

> scheme@(guile-user)> (define libm (dynamic-link "/usr/lib/libm.dylib"))
> ERROR: In procedure dynamic-link: file: "/usr/lib/libm.dylib",
> message: "file not found"

What if you leave off the suffix?

    scheme@(guile-user)> (use-modules (system foreign))
    scheme@(guile-user)> (dynamic-link "libm")
    $1 = #<dynamic-object "libm">

Guile uses libltdl, which does this sort of thing.

Andy
-- 
http://wingolog.org/

Re: FFI on OS X?

[Hans Aberg]

On 2 Mar 2011, at 22:22, Andy Wingo wrote:

> What if you leave off the suffix?
> 
>    scheme@(guile-user)> (use-modules (system foreign))
>    scheme@(guile-user)> (dynamic-link "libm")
>    $1 = #<dynamic-object "libm">

That does not work for me.
  scheme@(guile-user)> (dynamic-link "libm")
  ERROR: In procedure dynamic-link:
  ERROR: In procedure dynamic-link: file: "libm", message: "file not found"

> Guile uses libltdl, which does this sort of thing.

Yes, that is the problem, I think. I saw it on the Bessel-function example in the manual, and reported it before.

Re: FFI on OS X?

[Andy Wingo]

On Wed 02 Mar 2011 23:15, Hans Aberg <haberg-1@telia.com> writes:

>   scheme@(guile-user)> (dynamic-link "libm")
>   ERROR: In procedure dynamic-link:
>   ERROR: In procedure dynamic-link: file: "libm", message: "file not found"

Why does this fail?  Can you strace it?  What version of libltdl do you
have?

Andy
-- 
http://wingolog.org/

Re: FFI on OS X?

[Hans Aberg]

On 3 Mar 2011, at 10:25, Andy Wingo wrote:

> On Wed 02 Mar 2011 23:15, Hans Aberg <haberg-1@telia.com> writes:
> 
>>  scheme@(guile-user)> (dynamic-link "libm")
>>  ERROR: In procedure dynamic-link:
>>  ERROR: In procedure dynamic-link: file: "libm", message: "file not found"
> 
> Why does this fail?  Can you strace it?  

If you tell me how. :-)

However, it works, also full path, with or without file name extension, as long as the name of the library actually opened ends in .so. If it ends in .dylib, it says it is not found.

> What version of libltdl do you
> have?

libltdl.7 from libtool-2.4.

Re: FFI on OS X?

[Andreas Rottmann]

Hans Aberg <haberg-1@telia.com> writes:

> On 3 Mar 2011, at 10:25, Andy Wingo wrote:
>
>> On Wed 02 Mar 2011 23:15, Hans Aberg <haberg-1@telia.com> writes:
>> 
>>>  scheme@(guile-user)> (dynamic-link "libm")
>>>  ERROR: In procedure dynamic-link:
>>>  ERROR: In procedure dynamic-link: file: "libm", message: "file not found"
>> 
>> Why does this fail?  Can you strace it?  
>
> If you tell me how. :-)
>
Apparently, on OS X, "dtruss" does fulfill the role of "strace":
<http://humberto.digi.com.br/blog/2008/02/25/strace-on-mac-os-x-leopard/>.

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

Re: FFI on OS X?

[Michael Ellis]

On Thu, Mar 3, 2011 at 9:36 AM, Andreas Rottmann <a.rottmann@gmx.at> wrote:
> Hans Aberg <haberg-1@telia.com> writes:

>>> Why does this fail? �Can you strace it?
>>
>> If you tell me how. :-)
>>
> Apparently, on OS X, "dtruss" does fulfill the role of "strace":
> <http://humberto.digi.com.br/blog/2008/02/25/strace-on-mac-os-x-leopard/>.

Thanks for the tip about dtruss.  Very useful to know about.

For the record, here's some dtruss output  created when I try to
dynamic-link a library that doesn't have a .so softlink, ie
(dynamic-link "libf77lapack").  As you can see it's trying
'open_nocancel', 'access', and 'stat64' looking for .la and .so in all
all the right places before giving up.


89795/0x1bfacf:  open_nocancel("/usr/local/lib/libf77lapack.la\0",
0x0, 0x1B6)		 = -1 Err#2
89795/0x1bfacf:  open_nocancel("/usr/local/lib/libf77lapack.la\0",
0x0, 0x1B6)		 = -1 Err#2
89795/0x1bfacf:  open_nocancel("/lib/libf77lapack.la\0", 0x0, 0x1B6)		
= -1 Err#2
89795/0x1bfacf:  open_nocancel("/usr/lib/libf77lapack.la\0", 0x0,
0x1B6)		 = -1 Err#2
89795/0x1bfacf:  open_nocancel("libf77lapack.la\0", 0x0, 0x1B6)		 = -1 Err#2
89795/0x1bfacf:  access("/usr/local/lib/libf77lapack.so\0", 0x4,
0x10060A800)		 = -1 Err#2
89795/0x1bfacf:  access("/usr/local/lib/libf77lapack.so\0", 0x4,
0x10060A800)		 = -1 Err#2
89795/0x1bfacf:  access("/lib/libf77lapack.so\0", 0x4, 0x10060A800)		 = -1 Err#2
89795/0x1bfacf:  access("/usr/lib/libf77lapack.so\0", 0x4,
0x10060A800)		 = -1 Err#2
89795/0x1bfacf:  stat64("libf77lapack.so\0", 0x7FFF5FBFE630,
0x7FFF5FBFEC70)		 = -1 Err#2
89795/0x1bfacf:  stat64("/Users/mellis/lib/libf77lapack.so\0",
0x7FFF5FBFEA10, 0x7FFF5FBFEC70)		 = -1 Err#2
89795/0x1bfacf:  stat64("/usr/local/lib/libf77lapack.so\0",
0x7FFF5FBFEA10, 0x7FFF5FBFEC70)		 = -1 Err#2
89795/0x1bfacf:  stat64("/usr/lib/libf77lapack.so\0", 0x7FFF5FBFEA20,
0x7FFF5FBFEC70)		 = -1 Err#2
89795/0x1bfacf:  sigprocmask(0x1, 0x0, 0x7FFF5FBFEEC0)		 = 0x0 0
89795/0x1bfacf:  sigaltstack(0x0, 0x7FFF5FBFEEB0, 0x0)		 = 0 0
89795/0x1bfacf:  write(0x1, "ERROR: In procedure dynamic-link:\nERROR:
In procedure dynamic-link: file: \"libf77lapack\", message: \"file not
found\"\n\0", 0x74)		 = 116 0

If I try to specify the .dylib extension, dtruss shows that it fails
because the standard extensions are being appended, e.g.

open_nocancel("/usr/local/lib/libf77lapack.dylib.la\0", 0x0, 0x1B6)

Is this something that can be fixed within Guile?

Cheers,
Mike

Re: FFI on OS X?

[Andy Wingo]

On Thu 03 Mar 2011 17:53, Michael Ellis <michael.f.ellis@gmail.com> writes:

> On Thu, Mar 3, 2011 at 9:36 AM, Andreas Rottmann <a.rottmann@gmx.at> wrote:
>> Hans Aberg <haberg-1@telia.com> writes:
>
>>>> Why does this fail? �Can you strace it?
>>>
>>> If you tell me how. :-)
>>>
>> Apparently, on OS X, "dtruss" does fulfill the role of "strace":
>> <http://humberto.digi.com.br/blog/2008/02/25/strace-on-mac-os-x-leopard/>.
>
> For the record, here's some dtruss output  created when I try to
> dynamic-link a library that doesn't have a .so softlink, ie
> (dynamic-link "libf77lapack")

Aaahh yes I remember now.  It should have been looking for .dylib but
only wanted .so links, right?  I think this is a libltdl bug.

    http://thread.gmane.org/gmane.lisp.guile.bugs/4483

There were a number of issues there, but I think the point about .dylib
getting added to the default suffix list on OS X got lost.

Andy
-- 
http://wingolog.org/