libgomp and dlopen?

[Peter Weilbacher <newsspam@xxxxxxxxxxxxxx>]

[Originally posted in de.comp.os.unix.programming but didn't receive an
answer, so trying again here where I hope it is more on topic.]

I wanted to make some tests using the OpenMP support in the gcc 4.2.0
20060708 snapshot. So I installed it in parallel to the system GCC
("gcc version 3.4.4 20050721 (Red Hat 3.4.4-2)") into /usr/local and set
PATH and LD_LIBRARY_PATH accordingly.

The program that I want to carry the tests out with is actually a plugin
(muse_masterbias.so). The problem is that the program that loads the
plugin using dlopen (actually lt_dlopen but I tried normal dlopen and
that doesn't help), cannot load the plugin any more. Even though ldd
shows that all dependencies are resolved:

  $ ldd /tmp/museptest/lib/muse/plugins/muse-0.00.04/muse_masterbias.so
  libmuse.so.0 => /tmp/museptest/lib/libmuse.so.0 (0x0000002a9565d000)
  libm.so.6 => /lib64/tls/libm.so.6 (0x0000002a95764000)
  libnsl.so.1 => /lib64/libnsl.so.1 (0x0000002a958ea000)
  libc.so.6 => /lib64/tls/libc.so.6 (0x0000002a95a02000)
  libgomp.so.1 => /usr/local/lib64/libgomp.so.1 (0x0000002a95c35000)
  libcpldfs.so.1 => /usr/local/lib/libcpldfs.so.1 (0x0000002a95d3c000)
  libcplui.so.1 => /usr/local/lib/libcplui.so.1 (0x0000002a95e41000)
  libcpldrs.so.1 => /usr/local/lib/libcpldrs.so.1 (0x0000002a95f50000)
  libcplcore.so.1 => /usr/local/lib/libcplcore.so.1 (0x0000002a9605f000)
  /lib64/ld-linux-x86-64.so.2 (0x000000552aaaa000)
  librt.so.1 => /lib64/tls/librt.so.1 (0x0000002a961e0000)
  libpthread.so.0 => /lib64/tls/libpthread.so.0 (0x0000002a962fa000)
  libqfits.so => /usr/local/lib/libqfits.so (0x0000002a9640f000)
  libcext.so.0 => /usr/local/lib/libcext.so.0 (0x0000002a99c4a000)

The Problem is probably with loading libgomp.so, even though again all
dependencies are resolved.

  $ ldd /usr/local/lib64/libgomp.so.1
  librt.so.1 => /lib64/tls/librt.so.1 (0x0000002a9565f000)
  libpthread.so.0 => /lib64/tls/libpthread.so.0 (0x0000002a95779000)
  libc.so.6 => /lib64/tls/libc.so.6 (0x0000002a9588e000)
  /lib64/ld-linux-x86-64.so.2 (0x000000552aaaa000)

If I try to load the libs by hand (with lt_dlopen) I get this output:

lt_dlopen=libgomp.so.1
Could not open libgomp.so.1:
  /usr/local/lib64/libgomp.so.1: shared object cannot be dlopen()ed
lt_dlopen=librt.so.1
lt_dlopen=libpthread.so.0
lt_dlopen=libc.so.6
lt_dlopen=/lib64/ld-linux-x86-64.so.2
lt_dlopen=/tmp/museptest/lib/muse/plugins/muse-0.00.04/muse_masterbias.so
Could not open
/tmp/museptest/lib/muse/plugins/muse-0.00.04/muse_masterbias.so:
  libgomp.so.1: shared object cannot be dlopen()ed

(The lt_dlopen output is just a printf, the error messages after the
colon are from lt_dlerror().) I also rebuilt the calling program using
the same gcc 4.2 alpha.

Can someone enlighten me why libgomp cannot be loaded dynamically or
give me a hint what I am doing wrong or how I can debug this further?

TIA,
   Peter.