PDAL_DLL inline std::string::size_type
    extractSpaces(const std::string& s, std::string::size_type p)
    //    { return extract(s, p, (int(*)(int))std::isspace); }
        { return extract(s, p, [](int i){return i == ' ';}); }

When I compile this on gcc 7.4 I get:

/home/acbell/pdalinstall/include/pdal/util/Utils.hpp:475:5: warning: mangled name for ‘std::__cxx11::basic_string<char>::size_type pdal::Utils::extract(const string&, std::__cxx11::basic_string<char>::size_type, PREDICATE) [with PREDICATE = int (*)(int) throw ()]’ will change in C++17 because the exception specification is part of a function type [-Wnoexcept-type]

with the first version of the extract, but not the second.  This seems strange.  Why would the compiler think that the pointer to the function I'm providing throws?