ltdl and inter-library dependencies

[Albert Chin-A-Young]

I have two libraries, libpng.so and libz.so, both compiled with
libtool. The libpng library is installed into /opt/libpng/lib and the
zlib library is installed into /opt/zlib/lib. The platform is
Solaris/SPARC and the version of libtool is from the multi-lang branch.

  $ cd /opt/libpng/lib
  $ ls
  libpng.a         libpng.so        libpng.so.1.0.0
  libpng.la        libpng.so.1
  $ ldd libpng.so
  libz.so.2 =>     (file not found)
  libm.so.1 =>     /usr/lib/libm.so.1
  libc.so.1 =>     /usr/lib/libc.so.1
  libdl.so.1 =>    /usr/lib/libdl.so.1
  /usr/platform/SUNW,Ultra-2/lib/libc_psr.so.1
  $ grep dependency /opt/libpng/lib/libpng.la
  dependency_libs=' -L/opt/zlib/lib /opt/zlib/lib/libz.la -lm'
  $ dump -Lv libpng.so | grep RPATH
  [no output]

  $ cd /opt/zlib/lib
  $ ls
  libz.a         libz.la        libz.so        libz.so.2 libz.so.2.0.0

So, I have the zlib library in /opt/zlib/lib as a dependency on
libpng.so. Is ltdl suppose to allow me to load libpng.so by
automatically loading the zlib.so dependency? I created the following
test program:

#include <stdio.h>
#include <dlfcn.h>
#include "ltdl.h"

int
main (void) {
  void *a, *b;
  lt_dlhandle c = NULL;

  lt_dlinit ();
  c = lt_dlopen ("/opt/libpng/lib/libpng.la");
  if (!c) {
    printf ("%s\n", lt_dlerror ());
  }
}

Running this gives:
  $ ./a.out
  ld.so.1: ./a.out: fatal: libz.so.2: open failed: No such file or directory

Looking at the truss output:
  $ truss ./a.out | grep open
  open("/opt/libpng/lib/libpng.la", O_RDONLY) = 3
  open("/usr/lib/libm", O_RDONLY)                 Err#2 ENOENT
  open("/opt/zlib/lib/libm", O_RDONLY)   Err#2 ENOENT
  open("/lib/libm", O_RDONLY)                     Err#2 ENOENT
  open("/usr/lib/libm", O_RDONLY)                 Err#2 ENOENT
  open("libm.la", O_RDONLY)                       Err#2 ENOENT
  open("/opt/zlib/lib/libm.la", O_RDONLY) Err#2 ENOENT
  open("/lib/libm.la", O_RDONLY)                  Err#2 ENOENT
  open("/usr/lib/libm.la", O_RDONLY)              Err#2 ENOENT
  open("/usr/lib/libm.so", O_RDONLY)              = 3
  open("/opt/zlib/lib/libz.la", O_RDONLY) = 3
  open("/usr/lib/libz.a", O_RDONLY)               Err#2 ENOENT
  open("/opt/zlib/lib/libz.so", O_RDONLY) = 3
  open("/usr/lib/libpng.a", O_RDONLY)             Err#2 ENOENT
  open("/opt/libpng/lib/libpng.so", O_RDONLY) = 3
  open("/usr/lib/libz.so.2", O_RDONLY)            Err#2 ENOENT
  open("/opt/libpng/lib/libpng.so", O_RDONLY) = 3
  open("/usr/lib/libz.so.2", O_RDONLY)            Err#2 ENOENT

-- 
albert chin (address@hidden)