Here my stripped version still crashes with segfault: ----<snio>---- #include <boost/spirit.hpp> #include <iostream> using namespace boost::spirit; struct Configurable { const char* name; // name of the configurable module const rule<>& parser; // parser for config items, normally // a couple of OR-connected terms. }; rule<> __ = ch_p(' '); // separator char. was a bit more complex // in the original code std::string conn, port, ident_name, ident_pw; /* // the original parser crashes with segfault: const Configurable cfg = { "Hardtest", +( *__ | ("connect" >> __ >> str_p[assign_a(conn)] >> ':' >> int_p[assign_a(port)]) | ("identity" >> __ >> str_p[assign_a(ident_name)] >> __ >> str_p[assign_a(ident_pw)] ) | "hard" ) }; */ // a simplicistic parser that still crashes: const Configurable cfg = { "Hardtest", +( __ ) }; int main(int argc, char** argv) { // original config string: // "connect foo.bar:123 identity root fF2.oby!sy" or the like. parse("hard ", cfg.parser); // <--- CRASHES! // this works: // parse("hard ", +(__) ); }; ----<snap>---- The stack trace of GNU gdb is: Program received signal SIGSEGV, Segmentation fault. 0x000000000040184e in boost::spirit::impl::rule_base<boost::spirit::rule<boost::spirit::nil_t, boost::spirit::nil_t, boost::spirit::nil_t>, boost::spirit::rule<boost::spirit::nil_t, boost::spirit::nil_t, boost::spirit::nil_t> const&, boost::spirit::nil_t, boost::spirit::nil_t, boost::spirit::nil_t>::parse_main<boost::spirit::scanner<char const*, boost::spirit::scanner_policies<boost::spirit::iteration_policy, boost::spirit::match_policy, boost::spirit::action_policy> > > (this=0x7fff29fcea10, scan=@0x7fff29fcea00) at /usr/include/boost/spirit/core/non_terminal/impl/rule.ipp:189 189 hit = rule_base_access::get(*derived_this) (gdb) bt #0 0x000000000040184e in boost::spirit::impl::rule_base<boost::spirit::rule<boost::spirit::nil_t, boost::spirit::nil_t, boost::spirit::nil_t>, boost::spirit::rule<boost::spirit::nil_t, boost::spirit::nil_t, boost::spirit::nil_t> const&, boost::spirit::nil_t, boost::spirit::nil_t, boost::spirit::nil_t>::parse_main<boost::spirit::scanner<char const*, boost::spirit::scanner_policies<boost::spirit::iteration_policy, boost::spirit::match_policy, boost::spirit::action_policy> > > (this=0x7fff29fcea10, scan=@0x7fff29fcea00) at /usr/include/boost/spirit/core/non_terminal/impl/rule.ipp:189 #1 0x00000000004018f7 in boost::spirit::impl::rule_base<boost::spirit::rule<boost::spirit::nil_t, boost::spirit::nil_t, boost::spirit::nil_t>, boost::spirit::rule<boost::spirit::nil_t, boost::spirit::nil_t, boost::spirit::nil_t> const&, boost::spirit::nil_t, boost::spirit::nil_t, boost::spirit::nil_t>::parse<boost::spirit::scanner<char const*, boost::spirit::scanner_policies<boost::spirit::iteration_policy, boost::spirit::match_policy, boost::spirit::action_policy> > > (this=0x7fff29fcea10, scan=@0x7fff29fcea00) at /usr/include/boost/spirit/core/non_terminal/impl/rule.ipp:171 #2 0x000000000040197b in boost::spirit::parse<char const*, boost::spirit::rule<boost::spirit::nil_t, boost::spirit::nil_t, boost::spirit::nil_t> > (first_=@0x7fff29fcea58, last=@0x7fff29fcea68, p=@0x7fff29fcea10) at /usr/include/boost/spirit/core/impl/parser.ipp:28 #3 0x0000000000401a34 in boost::spirit::parse<char, boost::spirit::rule<boost::spirit::nil_t, boost::spirit::nil_t, boost::spirit::nil_t> > (str=0x402420 "hard ", p=@0x7fff29fcea10) at /usr/include/boost/spirit/core/impl/parser.ipp:45 #4 0x0000000000400973 in main (argc=1, argv=0x7fff29fceb88) at cfgTest.cc:38 I am using boost 1.35 (yes, it is quite old. Is this a bug in boost that is fixed in newer versions? I didn't found something related in the changelogs) on Linux x86_64, gcc 4.3.2 (Debian "Lenny"). Perhaps somebody knows an answer except "use spirit 2!" :-) Lars R.