utils: make HexMap constexpr

include/opendht/infohash.h

@@ -356,7 +356,7 @@ private:
     static constexpr const char* hex_digits = "0123456789abcdef";
 };
 
-OPENDHT_PUBLIC extern const HexMap hex_map;
+OPENDHT_PUBLIC constexpr HexMap hex_map = {};
 
 inline std::string
 toHex(const uint8_t* data, size_t size) {

src/utils.cpp

@@ -39,8 +39,6 @@ const char* version() {
     return PACKAGE_VERSION;
 }
 
-const HexMap hex_map = {};
-
 static constexpr std::array<uint8_t, 12> MAPPED_IPV4_PREFIX {{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0xff, 0xff}};
 
 std::pair<std::string, std::string>