the right way to link pthread into shared libraries?

[Mikhail Teterin]

Hello!

I was always under the impression, that using ${PTHREAD_LIBS} on
compiler's command line would produce a library, which is properly
linked with the correct threading implementation.

Unfortunately, that does not seem to be the case:

/bin/sh /opt/bin/libtool --tag=CXX --mode=link c++ -pipe -O2 -fno-strict-aliasing -pipe -march=opteron -D_THREAD_SAFE    -o libIlmThread.la -rpath /opt/lib -version-info 4:0:0 -no-undefined IlmThreadPool.lo IlmThread.lo IlmThreadSemaphore.lo IlmThreadMutex.lo IlmThreadPosix.lo IlmThreadSemaphorePosix.lo IlmThreadSemaphorePosixCompat.lo IlmThreadMutexPosix.lo ../Iex/libIex.la -pthread 
c++ -shared -nostdlib /usr/lib/crti.o /usr/lib/crtbeginS.o  .libs/IlmThreadPool.o .libs/IlmThread.o .libs/IlmThreadSemaphore.o .libs/IlmThreadMutex.o .libs/IlmThreadPosix.o .libs/IlmThreadSemaphorePosix.o .libs/IlmThreadSemaphorePosixCompat.o .libs/IlmThreadMutexPosix.o  -Wl,--rpath -Wl,/var/ports/graphics/OpenEXR/work/openexr-1.4.0/Iex/.libs -Wl,--rpath -Wl,/opt/lib ../Iex/.libs/libIex.so -pthread -L/usr/lib -lstdc++ -lm -lgcc_pic /usr/lib/crtendS.o /usr/lib/crtn.o  -march=opteron -pthread -pthread -pthread -Wl,-soname -Wl,libIlmThread.so.4 -o .libs/libIlmThread.so.4
(cd .libs && rm -f libIlmThread.so && ln -s libIlmThread.so.4 libIlmThread.so)
(cd .libs && rm -f libIlmThread.so && ln -s libIlmThread.so.4 libIlmThread.so)
ar cru .libs/libIlmThread.a  IlmThreadPool.o IlmThread.o IlmThreadSemaphore.o IlmThreadMutex.o IlmThreadPosix.o IlmThreadSemaphorePosix.o IlmThreadSemaphorePosixCompat.o IlmThreadMutexPosix.o
ranlib .libs/libIlmThread.a
creating libIlmThread.la
(cd .libs && rm -f libIlmThread.la && ln -s ../libIlmThread.la libIlmThread.la)
mi at aldan:work/openexr-1.4.0/IlmThread (1403) ldd .libs/libIlmThread.so.4
.libs/libIlmThread.so.4:
        libIex.so.4 => /var/ports/graphics/OpenEXR/work/openexr-1.4.0/Iex/.libs/libIex.so.4 (0x800943000)
        libstdc++.so.5 => /usr/lib/libstdc++.so.5 (0x800a59000)
        libm.so.4 => /lib/libm.so.4 (0x800c50000)

Although `-pthread' can be seen several times on the command line,
the resulting executable is NOT linked with libpthread.so and the
pthread_* functions called from the library are left undefined...

Please, advise. Thanks!

 -mi