Upstream: https://savannah.gnu.org/bugs/download.php?file_id=31132
--- ddd/strclass.h
+++ ddd/strclass.h
@@ -810,10 +810,10 @@ public:
     friend int split(const string& x, string *res, int maxn, 
 		     const regex& sep);
 
-    friend string common_prefix(const string& x, const string& y, 
-				int startpos = 0);
-    friend string common_suffix(const string& x, const string& y, 
-				int startpos = -1);
+    inline string common_prefix(const string& x, const string& y);
+    friend string common_prefix(const string& x, const string& y, int startpos);
+    inline string common_suffix(const string& x, const string& y);
+    friend string common_suffix(const string& x, const string& y, int startpos);
     friend string replicate(char c, int n);
     friend string replicate(const string& y, int n);
     friend string join(const string *src, int n, const string& sep);
@@ -863,9 +863,10 @@ public:
     friend inline std::ostream& operator<<(std::ostream& s, const subString& x);
     friend std::istream& operator>>(std::istream& s, string& x);
 
-    friend int readline(std::istream& s, string& x, 
-			char terminator = '\n',
-			int discard_terminator = 1);
+    inline int readline(std::istream& s, string& x);
+    inline int readline(std::istream& s, string& x, char terminator);
+    friend int readline(std::istream& s, string& x, char terminator,
+			int discard_terminator);
 
     // Status
     unsigned int length() const;
@@ -1456,6 +1457,16 @@ inline string operator + (char x, const subString& y)
     string r; cat(x, y, r); return r;
 }
 
+inline string common_prefix(const string& x, const string& y)
+{
+    return common_prefix(x, y, 0);
+}
+
+inline string common_suffix(const string& x, const string& y)
+{
+    return common_suffix(x, y, -1);
+}
+
 inline string reverse(const string& x) 
 {
     string r; r.rep = string_Sreverse(x.rep, r.rep); return r;
@@ -1476,6 +1487,16 @@ inline string capitalize(const string& x)
     string r; r.rep = string_Scapitalize(x.rep, r.rep); return r;
 }
 
+inline int readline(std::istream& s, string& x)
+{
+    return readline(s, x, '\n', 1);
+}
+
+inline int readline(std::istream& s, string& x, char terminator)
+{
+    return readline(s, x, terminator, 1);
+}
+
 // prepend
 
 inline string& string::prepend(const string& y)