environment:
  SuSE 2.6.13-15-default
  gcc (GCC) 4.0.2 20050901 (prerelease) (SUSE Linux)

When compiling a software package that uses NPTL I get the
following Linker error:
/lib/librt.so.1: undefined reference to `__librt_enable_asynccancel@GLIBC_PRIVATE'
/lib/librt.so.1: undefined reference to `__librt_multiple_threads@GLIBC_PRIVATE'
/lib/librt.so.1: undefined reference to `__librt_disable_asynccancel@GLIBC_PRIVATE'

Symbols in /lib/librt-2.3.5.so:
00008a00 b __libc_missing_posix_timers
         U __libc_pwrite@@GLIBC_PRIVATE
         U __librt_disable_asynccancel@@GLIBC_PRIVATE
         U __librt_enable_asynccancel@@GLIBC_PRIVATE
         U __librt_multiple_threads@@GLIBC_PRIVATE

Sybols in /lib/libc-2.3.5.so:
000cbbe0 t __libc_disable_asynccancel
000cbbe0 T __librt_disable_asynccancel
000cbb70 t __libc_enable_asynccancel
000cbb70 T __librt_enable_asynccancel
0011e968 b __libc_multiple_threads
0011e968 B __librt_multiple_threads

Could be caused by http://sources.redhat.com/ml/libc-hacker/2004-05/msg00006.html