Hi, I have to build a program with g++ and fpack-struct option turned on. 1) version gcc 3.4.2 20041017 (Red Hat 3.4.2-6.fc3) 2) testh.cpp #include <ext/hash_map> using namespace __gnu_cxx; int main (int argc, char* argv[]) { hash_map<int, int> inttale; return 0; } 3)The command line to build : # g++ testh.cpp -fpack-struct In file included from /usr/lib/gcc/i386-redhat-linux/3.4.2/../../../../include/c++/3.4.2/ios:49, from /usr/lib/gcc/i386-redhat-linux/3.4.2/../../../../include/c++/3.4.2/ostream:4 5, from /usr/lib/gcc/i386-redhat-linux/3.4.2/../../../../include/c++/3.4.2/iterator: 71, from /usr/lib/gcc/i386-redhat-linux/3.4.2/../../../../include/c++/3.4.2/ext/hasht able.h:69, from /usr/lib/gcc/i386-redhat-linux/3.4.2/../../../../include/c++/3.4.2/ext/hash_ map:65, from testh.cpp:1: /usr/lib/gcc/i386-redhat-linux/3.4.2/../../../../include/c++/3.4.2/bits/ios_ base.h: In member function `std::_Ios_Fmtflags std::ios_base::setf(std::_Ios_Fmtflags)': /usr/lib/gcc/i386-redhat-linux/3.4.2/../../../../include/c++/3.4.2/bits/ios_ base.h:536: error: cannot bind packed field `((std::ios_base*)this)->std::ios_base::_M_flags' to `std::_Ios_Fmtflags&' (... to make it short :-) ) 4) I know that I can apply a specific attribute to the structures that have to be packed. May be a #pragma pack could also do the trick. BUT: the program I have to build is made of hundred of source files and has always been built with the pack-struct option. Thus it's a very hard task to modify the sources and I would realy prefer a nicer way to do it :-). So, I am just looking for a good advice... Thanks for your help !!