I'm running configure against 0.9.2 (--with-gui=no --with-qrencode=no --with-miniupnpc=no) and I got this rare warning (this is the first time I saw this). It's probably something wrong with my OS, but I thought to share this anyway because it hopefully can be relatively easily checked.
CXX rpcserver.o
In file included from rpcprotocol.h:20:0,
from rpcserver.h:10,
from rpcserver.cpp:6:
json/json_spirit_writer_template.h: In function 'String_type json_spirit::add_esc_chars(const String_type&) [with String_type = std::basic_string<char>]':
json/json_spirit_writer_template.h:169:13: instantiated from 'void json_spirit::Generator<Value_type, Ostream_type>::output(const String_type&) [with Value_type = json_spirit::Value_impl<json_spirit::Config_vector<std::basic_string<char> > >, Ostream_type = std::basic_ostringstream<char>, json_spirit::Generator<Value_type, Ostream_type>::String_type = std::basic_string<char>]'
json/json_spirit_writer_template.h:125:34: instantiated from 'void json_spirit::Generator<Value_type, Ostream_type>::output(const Value_type&) [with Value_type = json_spirit::Value_impl<json_spirit::Config_vector<std::basic_string<char> > >, Ostream_type = std::basic_ostringstream<char>]'
json/json_spirit_writer_template.h:114:13: instantiated from 'json_spirit::Generator<Value_type, Ostream_type>::Generator(const Value_type&, Ostream_type&, bool) [with Value_type = json_spirit::Value_impl<json_spirit::Config_vector<std::basic_string<char> > >, Ostream_type = std::basic_ostringstream<char>]'
json/json_spirit_writer_template.h:233:9: instantiated from 'void json_spirit::write_stream(const Value_type&, Ostream_type&, bool) [with Value_type = json_spirit::Value_impl<json_spirit::Config_vector<std::basic_string<char> > >, Ostream_type = std::basic_ostringstream<char>]'
json/json_spirit_writer_template.h:243:9: instantiated from 'typename Value_type::String_type json_spirit::write_string(const Value_type&, bool) [with Value_type = json_spirit::Value_impl<json_spirit::Config_vector<std::basic_string<char> > >, typename Value_type::String_type = std::basic_string<char>]'
rpcserver.cpp:750:42: instantiated from here
json/json_spirit_writer_template.h:79:63: warning: comparison is always true due to limited range of data type [-Wtype-limits]