it looks like protobuf is not properly built, because there are pthread_* symbols references in its .so, but there's no NEEDED entry for libpthread. At least when trying to configure protobuf-c, linking fails, and when trying to link a stupid program (e.g. int main(void) { return 0;) against libprotobuf, one has to use -lpthread -lprotobuf, -lprotobuf being insufficient. I *think* protobuf is at fault here, but I'd like some input before reporting the bug there.
The libprotobuf.so.4.0.0 should be linked against libpthread.so due to -pthread flag. Maybe bug of libtool or rest of the toolchain.
It looks like long standing bug in the libtool [1]: #468555 libtool: linking with g++ uses -nostdlib and does not add -lpthread or -lgcc In [2]: **************************** The docs say: No startup files and only the libraries you specify will be passed to the linker. So this is not a GCC bug as it says only the libraries you specify will be passed to the linker, and -pthread is not you specifing a library. **************************** Petr [1] http://bugs.debian.org//cgi-bin/bugreport.cgi?bug=468555 [2] http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25460