Yes, there is a /usr/lib/libdl.so (symlink to 
/opt/gcc.3.3/lib/libdl.so.3.5).  That would be a good way to detect it since 
the header file is in a stranger location /opt/gcc.3.3/include/dlfcn.h. 
There is also the return value of
echo "" | gcc -include dlfcn.h -E -

//Jesse Off

----- Original Message ----- 
From: "Johnny C. Lam" <jlam@netbsd.org>
To: <gnats-bugs@netbsd.org>
Cc: <pkg-manager@netbsd.org>; <pkgsrc-bugs@netbsd.org>
Sent: Thursday, January 20, 2005 5:46 PM
Subject: Re: pkg/29029: bootstrap should USE_BUILTIN.dl=yes in mk.conf for 
Interix


> On Fri, Jan 21, 2005 at 12:32:00AM +0000, joff@embeddedARM.com wrote:
>> Machine: i386
>> >Description:
>> Several packages fail to build with a message
>> "Package X requires dlopen()".  Interix does have dlopen(), just not
>> in a header file /usr/include/dlopen.h.
>> >How-To-Repeat:
>> Try building perl on Interix
>> >Fix:
>> Add a line "USE_BUILTIN.dl=yes" to the example mk.conf during pkgsrc
>> bootstrap or extend detection of builtin dlopen() to a method more
>> resilent than simply checking for the presence of a /usr/include/dlfcn.h
>
> I would rather that we enhance dlopen.builtin.mk to properly detect
> dlopen() on Interix.  In which header are the dl*() functions declared?
> Is there a libdl on Interix?
>
> Cheers,
>
> -- Johnny Lam <jlam@NetBSD.org>
>
>