Re: Mac OS X .dylib not working

[Hans Aberg <haberg@math.su.se>]

On 2 Feb 2010, at 15:20, Ken Raeburn wrote:

>>>> On Mac OS X (trying it on 10.5.8 PPC G4), guile-1.8.7 cannot open
>>>> dynamic library files with name extensions .dylib, but only if they
>>>> are renamed using .so instead. On the Bug-Guile list they say it
>>>> just calls libltdl, in the libtool package. I have installed latest
>>>> of both, but the problem persists:
>>>
>>> libtool should produce modules named *.so on Darwin if you pass the
>>> -module flag at link time.  Typically, -avoid-version is used for
>>> modules as well.
>>
>> But dlopen() on Mac OS X can only open files in the native format,  
>> which isn't ELF, and they are typically named with the .dylib file  
>> name extension. If it finds a .so file on ELF format, all it does  
>> is reporting it cannot be opened.
>
> ".so" doesn't mean ELF format, and on some systems including Mac OS  
> X, "dynamically linked shared library" (e.g., a ".dylib" file) is  
> not the same as "dynamically loadable object".  Did you not see my  
> earlier email to you and the bug-guile list?

The fact is that currently Guile, which relies on libtool, cannot  
open .dylib files, though it works perfectly if they are renamed .so.  
As for what filenames to use, dlopen() does not care - it is something  
imposed by libtool. Also, all new native DLLs (see below) on Mac OS X  
are named .dylib.

I have only seen .bundle that are directories, also are called  
"plugins". 'man dlopen' says:
   dlopen -- load and link a dynamic library or bundle
but does not specify what happens if one tries to open a bundle  
directory. Looking at an Internet Plug-In, I can do:
   file '/Library/Internet Plug-Ins/DRM Plugin.bundle/Contents/MacOS/ 
DRM Plugin'
/Library/Internet Plug-Ins/DRM Plugin.bundle/Contents/MacOS/DRM  
Plugin: header for PowerPC PEF executable

(PEF is the old format used on Mac OS 9 PPC.)

So if one opens this file directly, it has no filename extension at all.

So I suggested on the Bug-Guile list having an opening sequence, say  
trying: the full name, .dylib, and .so. If you think of .so as a  
general POSIX standard not tied to ELF, that is of course OK.

   Hans