Some of the boost::format constructors do not initialize the object locals in the order of declaration, leading to annoying warnings from g++: $ cat test.cc #include <boost/format.hpp> std::string ntos(int n, std::locale & l) { return (boost::format("%d", l) % n).str(); } $ g++ -c -Wall test.cc /usr/include/boost/format/format_class.hpp: In constructor 'boost::basic_format<Ch, Tr, Alloc>::basic_format(const Ch*, const std::locale&) [with Ch = char, Tr = std::char_traits<char>, Alloc = std::allocator<char>]': test.cc:5: instantiated from here /usr/include/boost/format/format_class.hpp:137: warning: 'boost::basic_format<char, std::char_traits<char>, std::allocator<char> >::loc_' will be initialized after /usr/include/boost/format/format_class.hpp:135: warning: 'unsigned char boost::basic_format<char, std::char_traits<char>, std::allocator<char>

::exceptions_'/usr/include/boost/format/format_implementation.hpp:38: warning: when initialized here

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