Hi, The simple test program a.cpp below has no problem to compile on linux g++, but failed on AIX xlC compiler. Does any one know if the problem is related to the xlC compiler or the ptr_list.hpp file ? Thanks, Gary 4:43pm 19 Ggfu@sds:~/tmp> xlC_r -I/home_dir/Ggfu/BOOST/boost_1_36_0 -c a.cpp "/home_dir/Ggfu/BOOST/boost_1_36_0/boost/ptr_container/ptr_list.hpp", line 44.9: 1540-0400 (S) "boost::ptr_list::release" has a conflicting declaration. "/home_dir/Ggfu/BOOST/boost_1_36_0/boost/ptr_container/ptr_list.hpp", line 44.9: 1540-0425 (I) "release" is defined on line 44 of "/home_dir/Ggfu/BOOST/boost_1_36_0/boost/ptr_container/ptr_list.hpp". ----------------- a.cpp #include <boost/ptr_container/ptr_list.hpp> boost::ptr_list< std::string > y; int main() { return 0; }