Add support for C++11 using declarations for inheriting constructors

Closes #2641

CHANGES.current

@@ -7,6 +7,10 @@ the issue number to the end of the URL: https://github.com/swig/swig/issues/
 Version 4.2.0 (in progress)
 ===========================
 
+2023-07-04: wsfulton
+            #2641 Add support for C++11 using declarations for inheriting
+            constructors.
+
 2023-06-30: wsfulton
             #2640 Fix syntax error parsing an expression which calls a function
             with no parameters within additional brackets.

Doc/Manual/CPlusPlus11.html

@@ -73,8 +73,7 @@
 
 
 <p>This chapter gives you a brief overview about the SWIG
-implementation of the C++11 standard. This part of SWIG is still a work in
+implementation of the C++11 standard.
-progress. 
 </p>
 <p>SWIG supports the new C++ syntax changes with some minor limitations
 in some areas such as decltype expressions and variadic templates. Wrappers for the
@@ -863,12 +862,9 @@ where peer constructors can be called. SWIG handles this without any issue.
 
 <p>
 The second improvement is constructor inheritance via a <tt>using</tt> declaration.
-This is parsed correctly, but the additional constructors are not currently added to the derived proxy class in the target language.
+The extra constructors provided by the <tt>using</tt> declaration will add the appropriate constructors into the target language proxy derived classes.
-An example is shown below:
+In the example below a wrapper for the <tt>DerivedClass(int)</tt> constructor is added to <tt>DerivedClass</tt>:
-<!--
+
-The extra constructors provided by the <tt>using</tt> syntax will add the appropriate constructors into the target language proxy derived classes.
-In the example below a wrapper for the <tt>DerivedClass(int)</tt> is added to <tt>DerivedClass</tt>:
--->
 </p>
 
 <div class="code"><pre>
@@ -883,6 +879,10 @@ class DerivedClass: public BaseClass {
 };
 </pre></div>
 
+<p>
+<b>Compatibility note:</b> SWIG-4.2.0 was the first version to generate wrappers for constructors inherited via <tt>using</tt> declarations.
+</p>
+
 <p>
 The final part is member initialization at the site of the declaration.
 This kind of initialization is handled by SWIG.

Doc/Manual/SWIGPlus.html

@@ -5347,6 +5347,11 @@ you wrap this code in Python, the module works just like you would expect:
 </pre>
 </div>
 
+<p>
+The C++11 standard supports using declarations for inheriting constructors and this is covered in
+<a href="CPlusPlus11_object_construction_improvement">Object construction improvement</a>.
+</p>
+
 <p>
 C++ <tt>using</tt> declarations can also be used to change access when applicable.
 For example, protected methods in a base class can be made public in a derived class:

Examples/test-suite/common.mk

@@ -637,6 +637,7 @@ CPP11_TEST_CASES += \
 	cpp11_uniform_initialization \
 	cpp11_unrestricted_unions \
 	cpp11_userdefined_literals \
+	cpp11_using_constructor \
 	cpp11_using_typedef_struct \
 	cpp11_variadic_function_templates \
 	cpp11_variadic_templates \

Examples/test-suite/cpp11_inheriting_constructors.i

@@ -10,6 +10,7 @@ private:
   int _val;
 public:
   BaseClass(int iValue) { _val = iValue; }
+  int retrieveValue() { return _val; }
 };
 
 // Constructor inheritance via using declaration

Examples/test-suite/java/cpp11_inheriting_constructors_runme.java

@@ -0,0 +1,27 @@
+import cpp11_inheriting_constructors.*;
+
+public class cpp11_inheriting_constructors_runme {
+
+  static {
+    try {
+	System.loadLibrary("cpp11_inheriting_constructors");
+    } catch (UnsatisfiedLinkError e) {
+      System.err.println("Native code library failed to load. See the chapter on Dynamic Linking Problems in the SWIG Java documentation for help.\n" + e);
+      System.exit(1);
+    }
+  }
+
+  public static void main(String argv[]) {
+    // Constructor inheritance via using declaration
+    DerivedClass d = new DerivedClass(10);
+    if (d.retrieveValue() != 10)
+        throw new RuntimeException("retrieveValue() failed");
+
+    // Member initialization at the site of the declaration
+    SomeClass s = new SomeClass();
+    if (s.getValue() != 5)
+        throw new RuntimeException("s.value failed");
+  }
+}
+
+

Examples/test-suite/java/cpp11_using_constructor_runme.java

@@ -0,0 +1,27 @@
+
+import cpp11_using_constructor.*;
+
+public class cpp11_using_constructor_runme {
+
+  static {
+    try {
+	System.loadLibrary("cpp11_using_constructor");
+    } catch (UnsatisfiedLinkError e) {
+      System.err.println("Native code library failed to load. See the chapter on Dynamic Linking Problems in the SWIG Java documentation for help.\n" + e);
+      System.exit(1);
+    }
+  }
+
+  public static void main(String argv[]) {
+    // Public base constructors
+    new PublicDerived1(0, "hi").meth();
+    new PublicDerived2().meth();
+    new PublicDerived2(0, "hi").meth();
+    new PublicDerived3().meth();
+    new PublicDerived3(0, "hi").meth();
+    new PublicDerived4().meth();
+
+    // Protected base constructors
+    // Cannot test these as the constructors are protected
+  }
+}

Examples/test-suite/python/cpp11_inheriting_constructors_runme.py

@@ -0,0 +1,11 @@
+from cpp11_inheriting_constructors import *
+
+# Constructor inheritance via using declaration
+d = DerivedClass(10)
+if d.retrieveValue() != 10:
+    raise RuntimeError("retrieveValue() failed");
+
+# Member initialization at the site of the declaration
+s = SomeClass()
+if s.value != 5:
+    raise RuntimeError("s.value failed");

Examples/test-suite/python/cpp11_using_constructor_runme.py

@@ -0,0 +1,13 @@
+from cpp11_using_constructor import *
+
+
+# Public base constructors
+a = PublicDerived1(0, "hi").meth()
+a = PublicDerived2().meth()
+a = PublicDerived2(0, "hi").meth()
+a = PublicDerived3().meth()
+a = PublicDerived3(0, "hi").meth()
+a = PublicDerived4().meth()
+
+# Protected base constructors
+# Cannot test these as the constructors are protected

Source/CParse/parser.y

@@ -497,9 +497,12 @@ static void add_symbols(Node *n) {
 	  }
 	}
       } else {
-	  Setattr(n,"access", "public");
+	Setattr(n, "access", "public");
       }
+    } else if (extendmode && !inclass) {
+      Setattr(n, "access", "public");
     }
+
     if (Getattr(n,"sym:name")) {
       n = nextSibling(n);
       continue;

Source/Modules/allocate.cxx

@@ -755,11 +755,13 @@ Allocate():
 
     Node *c = 0;
     for (c = firstChild(n); c; c = nextSibling(c)) {
-      if (Strcmp(nodeType(c), "cdecl") == 0) {
+      if (Equal(nodeType(c), "cdecl")) {
 	process_exceptions(c);
 
 	if (inclass)
 	  class_member_is_defined_in_bases(c, inclass);
+      } else if (Equal(nodeType(c), "constructor")) {
+	constructorDeclaration(c);
       }
     }
 
@@ -868,21 +870,22 @@ Allocate():
     if (!inclass)
       return SWIG_OK;
     Parm *parms = Getattr(n, "parms");
+    AccessMode access_mode = accessModeFromString(Getattr(n, "access"));
 
     process_exceptions(n);
     if (!extendmode) {
       if (!ParmList_numrequired(parms)) {
 	/* Class does define a default constructor */
 	/* However, we had better see where it is defined */
-	if (cplus_mode == PUBLIC) {
+	if (access_mode == PUBLIC) {
 	  Setattr(inclass, "allocate:default_constructor", "1");
-	} else if (cplus_mode == PROTECTED) {
+	} else if (access_mode == PROTECTED) {
 	  Setattr(inclass, "allocate:default_base_constructor", "1");
 	}
       }
       /* Class defines some kind of constructor. May or may not be public */
       Setattr(inclass, "allocate:has_constructor", "1");
-      if (cplus_mode == PUBLIC) {
+      if (access_mode == PUBLIC) {
 	Setattr(inclass, "allocate:public_constructor", "1");
       }
     } else {
@@ -931,9 +934,9 @@ Allocate():
       if (copy_constructor) {
 	Setattr(n, "copy_constructor", "1");
 	Setattr(inclass, "allocate:has_copy_constructor", "1");
-	if (cplus_mode == PUBLIC) {
+	if (access_mode == PUBLIC) {
 	  Setattr(inclass, "allocate:copy_constructor", "1");
-	} else if (cplus_mode == PROTECTED) {
+	} else if (access_mode == PROTECTED) {
 	  Setattr(inclass, "allocate:copy_base_constructor", "1");
 	}
       }

Source/Modules/lang.cxx

@@ -221,94 +221,138 @@ int Dispatcher::emit_children(Node *n) {
 int Dispatcher::defaultHandler(Node *) {
   return SWIG_OK;
 }
+
 int Dispatcher::extendDirective(Node *n) {
   return defaultHandler(n);
 }
+
 int Dispatcher::applyDirective(Node *n) {
   return defaultHandler(n);
 }
+
 int Dispatcher::clearDirective(Node *n) {
   return defaultHandler(n);
 }
+
 int Dispatcher::constantDirective(Node *n) {
   return defaultHandler(n);
 }
+
 int Dispatcher::fragmentDirective(Node *n) {
   return defaultHandler(n);
 }
+
 int Dispatcher::importDirective(Node *n) {
   return defaultHandler(n);
 }
+
 int Dispatcher::includeDirective(Node *n) {
   return defaultHandler(n);
 }
+
 int Dispatcher::insertDirective(Node *n) {
   return defaultHandler(n);
 }
+
 int Dispatcher::moduleDirective(Node *n) {
   return defaultHandler(n);
 }
+
 int Dispatcher::nativeDirective(Node *n) {
   return defaultHandler(n);
 }
+
 int Dispatcher::pragmaDirective(Node *n) {
   return defaultHandler(n);
 }
+
 int Dispatcher::typemapDirective(Node *n) {
   return defaultHandler(n);
 }
+
 int Dispatcher::typemapitemDirective(Node *n) {
   return defaultHandler(n);
 }
+
 int Dispatcher::typemapcopyDirective(Node *n) {
   return defaultHandler(n);
 }
+
 int Dispatcher::typesDirective(Node *n) {
   return defaultHandler(n);
 }
+
 int Dispatcher::cDeclaration(Node *n) {
   return defaultHandler(n);
 }
+
 int Dispatcher::externDeclaration(Node *n) {
   return defaultHandler(n);
 }
+
 int Dispatcher::enumDeclaration(Node *n) {
   return defaultHandler(n);
 }
+
 int Dispatcher::enumvalueDeclaration(Node *n) {
   return defaultHandler(n);
 }
+
 int Dispatcher::enumforwardDeclaration(Node *n) {
   return defaultHandler(n);
 }
+
 int Dispatcher::classDeclaration(Node *n) {
   return defaultHandler(n);
 }
+
 int Dispatcher::templateDeclaration(Node *n) {
   return defaultHandler(n);
 }
+
 int Dispatcher::lambdaDeclaration(Node *n) {
   return defaultHandler(n);
 }
+
 int Dispatcher::classforwardDeclaration(Node *n) {
   return defaultHandler(n);
 }
+
 int Dispatcher::constructorDeclaration(Node *n) {
   return defaultHandler(n);
 }
+
 int Dispatcher::destructorDeclaration(Node *n) {
   return defaultHandler(n);
 }
+
 int Dispatcher::accessDeclaration(Node *n) {
   return defaultHandler(n);
 }
+
 int Dispatcher::usingDeclaration(Node *n) {
   return defaultHandler(n);
 }
+
 int Dispatcher::namespaceDeclaration(Node *n) {
   return defaultHandler(n);
 }
 
+Dispatcher::AccessMode Dispatcher::accessModeFromString(String *access) {
+  Dispatcher::AccessMode mode = PUBLIC;
+  if (Cmp(access, "public") == 0) {
+    mode = PUBLIC;
+  } else if (Cmp(access, "private") == 0) {
+    mode = PRIVATE;
+  } else if (Cmp(access, "protected") == 0) {
+    mode = PROTECTED;
+  } else {
+    assert(0);
+  }
+  return mode;
+}
+
+
 /* Allocators */
 Language::Language():
 none_comparison(NewString("$arg != 0")),
@@ -2675,7 +2719,7 @@ int Language::constructorDeclaration(Node *n) {
     Setattr(CurrentClass, "sym:cleanconstructor", "1");
   }
 
-  if ((cplus_mode != PUBLIC)) {
+  if (!is_public(n)) {
     /* check only for director classes */
     if (!Swig_directorclass(CurrentClass) || !need_nonpublic_ctor(n))
       return SWIG_NOWRAP;

Source/Modules/swigmod.h

@@ -98,6 +98,7 @@ public:
 
 protected:
   AccessMode cplus_mode;
+  AccessMode accessModeFromString(String *access);
 };
 
 /* ----------------------------------------------------------------------------

Source/Modules/typepass.cxx

@@ -1012,7 +1012,7 @@ class TypePass:private Dispatcher {
 	/* Only a single symbol is being used.  There are only a few symbols that
 	   we actually care about.  These are typedef, class declarations, and enum */
 	String *ntype = nodeType(ns);
-	if (Strcmp(ntype, "cdecl") == 0) {
+	if (Equal(ntype, "cdecl") || Equal(ntype, "constructor")) {
 	  if (checkAttribute(ns, "storage", "typedef")) {
 	    /* A typedef declaration */
 	    String *uname = Getattr(n, "uname");
@@ -1040,7 +1040,7 @@ class TypePass:private Dispatcher {
 	      }
 
 	      while (c) {
-		if (Strcmp(nodeType(c), "cdecl") == 0) {
+		if (Strcmp(nodeType(c), ntype) == 0) {
 		  if (!(Swig_storage_isstatic(c)
 			|| checkAttribute(c, "storage", "typedef")
 			|| Strstr(Getattr(c, "storage"), "friend")
@@ -1074,8 +1074,6 @@ class TypePass:private Dispatcher {
 		      Node *nn = copyNode(c);
 		      Setfile(nn, Getfile(n));
 		      Setline(nn, Getline(n));
-		      Delattr(nn, "access");	// access might be different from the method in the base class
-		      Setattr(nn, "access", Getattr(n, "access"));
 		      if (!Getattr(nn, "sym:name"))
 			Setattr(nn, "sym:name", symname);
 		      Symtab *st = Getattr(n, "sym:symtab");
@@ -1083,7 +1081,19 @@ class TypePass:private Dispatcher {
 		      Setattr(nn, "sym:symtab", st);
 		      // The real parent is the "using" declaration node, but subsequent code generally handles
 		      // and expects a class member to point to the parent class node
-		      Setattr(nn, "parentNode", parentNode(n));
+		      Node *parent = parentNode(n);
+		      Setattr(nn, "parentNode", parent);
+
+		      if (Equal(ntype, "constructor")) {
+			Setattr(nn, "name", Getattr(parent, "name"));
+			Setattr(nn, "sym:name", Getattr(parent, "sym:name"));
+			// Note that the added constructor's access is the same as that of
+			// the base class' constructor not of the using declaration
+		      } else {
+			// Access might be different from the method in the base class
+			Delattr(nn, "access");
+			Setattr(nn, "access", Getattr(n, "access"));
+		      }
 
 		      if (!GetFlag(nn, "feature:ignore")) {
 			ParmList *parms = CopyParmList(Getattr(c, "parms"));