Hi, I seem to have a problem when trying to link C++ code that refers to the boost regex library, when this is done so that it is compiled on a 64 bit Linux system, but for a 32 bit target. I get the following error: libboost_regex.so: undefined reference to `__sync_fetch_and_add_4' collect2: ld returned 1 exit status I wonder what needs to be done to fix this. steps to reproduce: - compile boost for 32 bit, by: ./bjam architecture=x86 address-model=32 --prefix=/path/to/boost install - try to compile & link a very simple sample code (see the end of the mail) g++ -m32 -L//path/to/boost/lib -I/path/to/boost/include -lboost_regex -o hello hello.cxx /path/to/boost/lib/libboost_regex.so: undefined reference to `__sync_fetch_and_add_4' collect2: ld returned 1 exit status when compiling the same code for 64 bit, it compiles fine. seeing this thread: http://lists.boost.org/Archives/boost/2008/04/135586.php I also tried the following: g++ -m32 -DBOOST_SP_USE_PTHREADS -L//path/to/boost/lib -I/path/to/boost/include -lboost_regex -o hello hello.cxx g++ -m32 -DBOOST_SP_DISABLE_THREADS -L//path/to/boost/lib -I/path/to/boost/include -lboost_regex -o hello hello.cxx but I got the same results :( any help would be appreciated. Akos details: platfrom: Ubuntu 10.10 64 bit compiler: g++ 4.4.4 boost: 1.45.0 the sample code I used is very minimalistic: #include <boost/regex.hpp> int main(void) { boost::regex LF("\\\\n"), CR("\\\\r"), TAB("\\\\t"); return 0; }