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From: Raymond Wiker <Raymond.Wiker@fast.no>
To: freebsd-hackers@freebsd.org
Subject: dlopen() and friends from a statically-linked binary?
Date: Thu, 20 Jul 2000 18:33:58 +0200 (CEST)
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	[ Re-sent, as it seemed to get lost on my first try. ]

	Is it possible, at all, to use dlopen etc from a
statically-linked executable? My experiments with FreeBSD-4.0 (see
below) indicate that it's not possible.

	The reason that I'd like this to work is that SBCL (a Common
Lisp implementation, see http://sbcl.sourceforge.net) needs the
addresses of certain library symbols (e.g, errno) when building the
initial lisp image. This seems to require static linking. On the other
hand, SBCL is severely handicapped if it cannot subsequently use
dlopen() to load foreign code into the running lisp system.


raw : ~ $ cat dltest.c
#include <dlfcn.h>
#include <stdio.h>

main()
{
  void *handle;
  void *sym;
  handle = dlopen(0, RTLD_LAZY);
  if (handle == 0)
    {
      fprintf(stderr, "dlopen returned 0: %s\n", dlerror());
    }
  else 
    {
      fprintf(stderr, "Handle: %p, main: %p\n", handle, dlsym(handle, "main"));
    }
  fprintf(stderr, "Handle: %p, main: %p\n", 0, dlsym(0, "main"));
  return 0;
}

raw : ~ $ gcc -static dltest.c -o dltest
raw : ~ $ ./dltest
dlopen returned 0: Service unavailable
Handle: 0x0, main: 0x0

raw : ~ $ gcc dltest.c -o dltest
raw : ~ $ ./dltest
Handle: 0x2805e000, main: 0x0
Handle: 0x0, main: 0x0

[ Note: this seems wrong; according to the manpage for dlsym, the
second call should give the same output as the first. ]

-- 
Raymond Wiker


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