diff -ruN -x '*.am' ddd-3.3.12/ddd/strclass.h my/ddd/strclass.h
--- ddd-3.3.12/ddd/strclass.h	2009-02-11 18:25:06.000000000 +0100
+++ my/ddd/strclass.h	2019-11-22 22:00:49.000267420 +0100
@@ -543,7 +543,6 @@
     bool OK() const; 
 };
 
-
 class string
 {
     friend class subString;
@@ -811,9 +810,9 @@
 		     const regex& sep);
 
     friend string common_prefix(const string& x, const string& y, 
-				int startpos = 0);
+				int startpos);
     friend string common_suffix(const string& x, const string& y, 
-				int startpos = -1);
+				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);
@@ -864,8 +863,8 @@
     friend std::istream& operator>>(std::istream& s, string& x);
 
     friend int readline(std::istream& s, string& x, 
-			char terminator = '\n',
-			int discard_terminator = 1);
+			char terminator,
+			int discard_terminator);
 
     // Status
     unsigned int length() const;
@@ -882,6 +881,58 @@
     bool OK() const;
 };
 
+inline void cat(const string&, const string&, string&);
+inline void cat(const string&, const subString&, string&);
+inline void cat(const string&, const constSubString&, string&);
+inline void cat(const string&, const char*, string&);
+inline void cat(const string&, char*, string&);
+inline void cat(const string&, char, string&);
+
+inline void cat(const subString&, const string&, string&);
+inline void cat(const subString&, const subString&, string&);
+inline void cat(const subString&, const char*, string&);
+inline void cat(const subString&, char*, string&);
+inline void cat(const subString&, char, string&);
+
+inline void cat(const char*, const string&, string&);
+inline void cat(const char*, const subString&, string&);
+inline void cat(const char*, const char*, string&);
+inline void cat(const char*, char*, string&);
+inline void cat(const char*, char, string&);
+
+inline void cat(char*, const string&, string&);
+inline void cat(char*, const subString&, string&);
+inline void cat(char*, const char*, string&);
+inline void cat(char*, char*, string&);
+inline void cat(char*, char, string&);
+
+inline void cat(char, const string&, string&);
+inline void cat(char, const subString&, string&);
+inline void cat(char, const char*, string&);
+inline void cat(char, char*, string&);
+inline void cat(char, char, string&);
+
+int split(const string& x, string *res, int maxn, 
+		     const string& sep);
+int split(const string& x, string *res, int maxn, 
+		     const regex& sep);
+
+string common_prefix(const string& x, const string& y, 
+				int startpos = 0);
+string common_suffix(const string& x, const string& y, 
+				int startpos = -1);
+string replicate(char c, int n);
+string replicate(const string& y, int n);
+string join(const string *src, int n, const string& sep);
+
+inline std::ostream& operator<<(std::ostream& s, const string& x);
+inline std::ostream& operator<<(std::ostream& s, const subString& x);
+std::istream& operator>>(std::istream& s, string& x);
+
+int readline(std::istream& s, string& x, 
+			char terminator = '\n',
+			int discard_terminator = 1);
+
 // Inject names manually to accomodate argument-dependent name lookup (ADL)
 // (aka Koenig lookup). The rule is that friend declarations are visible
 // when found through ADL because an argument of the call happens to be