I am difficulty determining the location of the segfault in the following code: boost::uint32_t reserve_length = 0; std::ifstream file_handle_ref ( name.c_str(), std::ios::binary | std::ios::in ); if ( ! file_handle_ref.is_open() ) // Expecting result of is_open() to be true { std::cerr << "Error opening " << name << std::endl; std::cerr << " " << strerror(errno) << std::endl; std::cerr << boost::format("Exception throw in %s at line %d") % __FILE__ % __LINE__ << std::endl; throw errors::IO_Exception (errors::IO_Exception::FATAL_IO_ERROR); } file_handle_ref.seekg( 0, std::ios::end ); reserve_length = file_handle_ref.tellg(); std::cout << "Reserve length = " << reserve_length << std::endl; <SEGFAULT> std::cout << boost::format ("reserve_length (method 1) = %d") % reserve_length << std::endl; </SEGFAULT> ==452== Invalid read of size 4 ==452== at 0x480228C3: std::ostreambuf_iterator<char, std::char_traits<char> > std::num_put<char, std::ostreambuf_iterator<char, std::char_traits<char> > >::_M_insert_int<unsigned long>(std::ostreambuf_iterator<char, std::char_traits<char> >, std::ios_base&, char, unsigned long) const (in /usr/lib/libstdc++.so.6.0.8) ==452== by 0x48022BAF: std::num_put<char, std::ostreambuf_iterator<char, std::char_traits<char> > >::do_put(std::ostreambuf_iterator<char, std::char_traits<char> >, std::ios_base&, char, unsigned long) const (in /usr/lib/libstdc++.so.6.0.8) ==452== by 0x4802B63C: std::ostream::operator<<(unsigned) (in /usr/lib/libstdc++.so.6.0.8) ==452== by 0x4197E59: void boost::io::detail::put_last<char, std::char_traits<char>, unsigned>(std::basic_ostream<char, std::char_traits<char> >&, unsigned&) (feed_args.hpp:113) ==452== by 0x4197F85: void boost::io::detail::put<char, std::char_traits<char>, std::allocator<char>, unsigned&>(unsigned&, boost::io::detail::format_item<char, std::char_traits<char>, std::allocator<char> > const&, boost::basic_format<char, std::char_traits<char>, std::allocator<char> >::string_type&, std::char_traits<char>::internal_streambuf_t&, std::locale*) (feed_args.hpp:150) ==452== by 0x4198724: void boost::io::detail::distribute<char, std::char_traits<char>, std::allocator<char>, unsigned&>(boost::basic_format<char, std::char_traits<char>, std::allocator<char> >&, unsigned&) (feed_args.hpp:241) ==452== by 0x4198783: boost::basic_format<char, std::char_traits<char>, std::allocator<char> >& boost::io::detail::feed<char, std::char_traits<char>, std::allocator<char>, unsigned&>(boost::basic_format<char, std::char_traits<char>, std::allocator<char> >&, unsigned&) (feed_args.hpp:251) ==452== by 0x4198849: boost::basic_format<char, std::char_traits<char>, std::allocator<char> >& boost::basic_format<char, std::char_traits<char>, std::allocator<char> >::operator%<unsigned>(unsigned&) (format_class.hpp:68) ==452== by 0x41940EE: libreverse::data_container::Memory_Map::Memory_Map(std::string, unsigned) (Memory_Map.cpp:87) ==452== by 0x41D2D85: libreverse::io::File::read_Image() (File.cpp:119) ==452== by 0x41D30F1: libreverse::io::File::init() (File.cpp:151) ==452== by 0x8089A2B: libreverse::wpef_module::PE_File<32>::init() (PE_File_T.cpp:48) ==452== Address 0x30 is not stack'd, malloc'd or (recently) free'd ==452== I made a driver program for this line. The driver works fine. #include <boost/cstdint.hpp> #include <boost/format.hpp> #include <iostream> #include <fstream> int main (int, char**) { boost::uint32_t reserve_length = 0; std::ifstream input_ref ( "kernel32.dll", std::ios::binary | std::ios::in ); input_ref.seekg ( 0, std::ios::end ); reserve_length = input_ref.tellg(); std::cout << boost::format("Something done %d") % reserve_length << std::endl; } So I cannot provide you an easy example. I am sorry about this. I hope I am asking an intelligent question. Stephen