When preprocessing the code #define $jack int test; $jack using any preprocessor using the wave library, in this case the samples/lexed_tokens/lexed_tokens preprocessor , gives the following error: PP_DEFINE (#369) at test.C ( 1/ 1): >#define< SPACE (#393) at test.C ( 1/ 8): > < lexed_tokens: /home/saebjornsen1/projects/boost/boost/wave/token_ids.hpp:497: boost::wave::util::flex_string<char, std::char_traits<char>, std::allocator<char>, boost::wave::util::CowString<boost::wave::util::AllocatorStringStorage<char, std::allocator<char> >, char*> > boost::wave::get_token_name(boost::wave::token_id): Assertion `id < T_LAST_TOKEN-T_FIRST_TOKEN' failed. Aborted using the preprocesor cpp (from the gcc team) I get (as cpp test.C): # 1 "test.C" # 1 "<built-in>" # 1 "<command line>" # 1 "test.C" int test; I believe the problem lies in that the lexer does not recognize the '$' as a valid character within the name of macro definition. Thanks Andreas Saebjoernsen