Hi everybody, I modified the code to automatically generate IDs of registration groups. The registration now is as simple as: #include BOOST_TYPEOF_INCREMENT_REGISTRATION_GROUP() BOOST_TYPEOF_REGISTER_TYPE(...); BOOST_TYPEOF_REGISTER_TEMPLATE(...); ... I also added some tests that should cause the ODR violation (see odr.hpp, odr1.cpp, odr2.cpp). VC7.1 is fine with them, however I can't make GCC 3.3 to compile this, and it stops much before the ODR could be diagnosed. Looks like this compiler totally can't handle the case when I try to use typeof (native or not) inside a template. When I force the typeof emulation, I am getting: "sorry, unimplemented: `method_call_expr' not supported by dump_expr" on every attempt to use my encoding/decoding stuff inside a template. From searching the web it looks like this is some kind of known bug related to improper handeling of sizeof(). Since sizeof() is the central part of all this, I don't really know how to work it around... This would probably be OK, since GCC has the native typeof support. However, when I use the native support, I run into a different problem that can be illustrated by the following code: template<class T, class U> typeof(T() + U()) sum(const T& t, const U& u) { return t + u; } main() { sum(5, 3.14); // this is line 9 return 0; } The compile of this code fails with following message: a.cpp:9: internal compiler error: in write_type, at cp/mangle.c:1555 GCC appears to be fine when the native typeof is used inside _class_ templates, though. I would really appreciate if anybody shed some light on any of these problems... The code is in the Spirit CVS and at: http://groups.yahoo.com/group/boost/files/typeof.zip Again, eveything is working fine in VC7.1. If anybody could try any other compiler (to build main.cpp, odr1.cpp, and odr2.cpp together), I would really appreciate this. Thanks, Arkadiy