diff --git a/base/string_utils.hpp b/base/string_utils.hpp
index 8fc2228b40..1ebec6dc13 100644
--- a/base/string_utils.hpp
+++ b/base/string_utils.hpp
@@ -1,6 +1,7 @@
 #pragma once
 
 #include "base/buffer_vector.hpp"
+#include "base/macros.hpp"
 #include "base/stl_add.hpp"
 
 #include <algorithm>
@@ -337,28 +338,29 @@ bool IsInArray(T(&arr)[N], TT const & t)
 
 /// @name From string to numeric.
 //@{
-bool to_int(char const * s, int & i, int base = 10);
-bool to_uint(char const * s, unsigned int & i, int base = 10);
-bool to_uint64(char const * s, uint64_t & i);
-bool to_int64(char const * s, int64_t & i);
-bool to_float(char const * s, float & f);
-bool to_double(char const * s, double & d);
+WARN_UNUSED_RESULT bool to_int(char const * s, int & i, int base = 10);
+WARN_UNUSED_RESULT bool to_uint(char const * s, unsigned int & i, int base = 10);
+WARN_UNUSED_RESULT bool to_uint64(char const * s, uint64_t & i);
+WARN_UNUSED_RESULT bool to_int64(char const * s, int64_t & i);
+WARN_UNUSED_RESULT bool to_float(char const * s, float & f);
+WARN_UNUSED_RESULT bool to_double(char const * s, double & d);
 
-inline bool is_number(std::string const & s)
+WARN_UNUSED_RESULT inline bool is_number(std::string const & s)
 {
   int64_t dummy;
   return to_int64(s.c_str(), dummy);
 }
 
-inline bool to_int(std::string const & s, int & i, int base = 10) { return to_int(s.c_str(), i, base); }
-inline bool to_uint(std::string const & s, unsigned int & i, int base = 10)
+WARN_UNUSED_RESULT inline bool to_int(std::string const & s, int & i, int base = 10) { return to_int(s.c_str(), i, base); }
+WARN_UNUSED_RESULT inline bool to_uint(std::string const & s, unsigned int & i, int base = 10)
 {
   return to_uint(s.c_str(), i, base);
 }
-inline bool to_uint64(std::string const & s, uint64_t & i) { return to_uint64(s.c_str(), i); }
-inline bool to_int64(std::string const & s, int64_t & i) { return to_int64(s.c_str(), i); }
-inline bool to_float(std::string const & s, float & f) { return to_float(s.c_str(), f); }
-inline bool to_double(std::string const & s, double & d) { return to_double(s.c_str(), d); }
+
+WARN_UNUSED_RESULT inline bool to_uint64(std::string const & s, uint64_t & i) { return to_uint64(s.c_str(), i); }
+WARN_UNUSED_RESULT inline bool to_int64(std::string const & s, int64_t & i) { return to_int64(s.c_str(), i); }
+WARN_UNUSED_RESULT inline bool to_float(std::string const & s, float & f) { return to_float(s.c_str(), f); }
+WARN_UNUSED_RESULT inline bool to_double(std::string const & s, double & d) { return to_double(s.c_str(), d); }
 //@}
 
 /// @name From numeric to string.