3 files changed, 18 insertions, 8 deletions
diff --git a/src/libutil/args.hh b/src/libutil/args.hh
index 62b9516d8..823d843aa 100644
--- a/src/libutil/args.hh
+++ b/src/libutil/args.hh
@@ -87,7 +87,9 @@ protected:
         template<class I>
         Handler(I * dest)
             : fun([=](std::vector<std::string> ss) {
-                if (!string2Int(ss[0], *dest))
+                if (auto n = string2Int<I>(ss[0]))
+                    *dest = *n;
+                else
                     throw UsageError("'%s' is not an integer", ss[0]);
               })
             , arity(1)
diff --git a/src/libutil/config.cc b/src/libutil/config.cc
index 7af3e7883..7467e5ac0 100644
--- a/src/libutil/config.cc
+++ b/src/libutil/config.cc
@@ -230,7 +230,9 @@ template<typename T>
 void BaseSetting<T>::set(const std::string & str, bool append)
 {
     static_assert(std::is_integral<T>::value, "Integer required.");
-    if (!string2Int(str, value))
+    if (auto n = string2Int<T>(str))
+        value = *n;
+    else
         throw UsageError("setting '%s' has invalid value '%s'", name, str);
 }
 
diff --git a/src/libutil/util.hh b/src/libutil/util.hh
index 0f82bed78..7a4d5fe92 100644
--- a/src/libutil/util.hh
+++ b/src/libutil/util.hh
@@ -397,21 +397,27 @@ bool statusOk(int status);
 
 
 /* Parse a string into an integer. */
-template<class N> bool string2Int(const string & s, N & n)
+template<class N>
+std::optional<N> string2Int(const std::string & s)
 {
-    if (string(s, 0, 1) == "-" && !std::numeric_limits<N>::is_signed)
-        return false;
+    if (s.substr(0, 1) == "-" && !std::numeric_limits<N>::is_signed)
+        return {};
     std::istringstream str(s);
+    N n;
     str >> n;
-    return str && str.get() == EOF;
+    if (str && str.get() == EOF) return n;
+    return {};
 }
 
 /* Parse a string into a float. */
-template<class N> bool string2Float(const string & s, N & n)
+template<class N>
+std::optional<N> string2Float(const string & s)
 {
     std::istringstream str(s);
+    N n;
     str >> n;
-    return str && str.get() == EOF;
+    if (str && str.get() == EOF) return n;
+    return {};
 }