if cp_demangled_name_to_comp with demangled_name 
"std::deque<boost::function<void()>, std::allocator<boost::function<void()> > >"
then a 'syntax error' error message is generated.

how to reproduce:
install python pretty-printers as described here: 
http://sourceware.org/gdb/wiki/STLSupport

test-program:
#include <deque>
#include <boost/function.hpp>

int main() {
        std::deque<boost::function<void()> > dek;
        return dek.size();
}

debug program and try to 'print dek'

suggested solution:

adding "function" to the alternatives of the
template_arg production in cp-name-parser.y should fix this problem