Hi, According to the boost web site, this mailing list is the preferred way to report bugs, so I subscribed and send you this: I believe the example /boost/libs/serialization/example/portable_binary_oarchive.hpp doesn't work correctly. On my platform, Mac OS X, the endian conversion is performed. For a small negative number (say -42l), the endian conversion results in a big negative number (-687865857). The size, however, is computed _before_ the endian conversion, so it is 1 (one) in this case, which is not high enough to hold the converted long. I guess the solution is to do the endian conversion first, then the size computation. That seems to work for me. Based on the 1_33_1 sources, my version of save_impl is now: void save_impl(long l){ // we choose to use litle endian #ifdef BOOST_BIG_ENDIAN char * first = static_cast<char *>(static_cast<void *>(& l)); char * last = first + sizeof(l) - 1; for(;first < last;++first, --last) { char x = *last; *last = *first; *first = x; } #endif long ll = l; char size = 0; do{ ll >>= 8; ++size; }while(ll != -1 && ll != 0); os.put(size); save_binary(& l, size); } I hope this helps in improving the example. Regards, Stefan van den Oord