Python -builtin fix wrapping constructors with varargs

Fix compilation error when using -builtin and wrapping varargs in constructors

Closes #1942

CHANGES.current

@@ -7,6 +7,10 @@ the issue number to the end of the URL: https://github.com/swig/swig/issues/
 Version 4.1.0 (in progress)
 ===========================
 
+2021-03-23: wsfulton
+            #1942 [Python] Fix compilation error in wrappers when using -builtin
+            and wrapping varargs in constructors.
+
 2021-03-22: goto40
             #1977 Fix handling of template template parameters.
 

Examples/test-suite/kwargs_feature.i

@@ -126,3 +126,21 @@ struct Extending2 {};
 struct ExtendingOptArgs1 {};
 struct ExtendingOptArgs2 {};
 %}
+
+// Varargs
+%warnfilter(SWIGWARN_LANG_VARARGS_KEYWORD) VarargConstructor::VarargConstructor; // Can't wrap varargs with keyword arguments enabled
+%warnfilter(SWIGWARN_LANG_VARARGS_KEYWORD) VarargConstructor::vararg_method; // Can't wrap varargs with keyword arguments enabled
+%inline %{
+struct VarargConstructor {
+  char *str;
+  VarargConstructor(const char *fmt, ...) {
+    str = new char[strlen(fmt) + 1];
+    strcpy(str, fmt);
+  }
+  void vararg_method(const char *fmt, ...) {
+    delete [] str;
+    str = new char[strlen(fmt) + 1];
+    strcpy(str, fmt);
+  }
+};
+%}

Examples/test-suite/python/kwargs_feature_runme.py

@@ -122,3 +122,18 @@ try:
     raise RuntimeError("missed exception")
 except TypeError as e:
     pass
+
+# Varargs
+f = VarargConstructor(fmt="Ciao")
+f.vararg_method(fmt="Bonjour")
+try:
+    f = VarargConstructor(nonexistent="Ciao")
+    raise RuntimeError("missed exception")
+except TypeError as e:
+    pass
+
+try:
+    f.vararg_method(nonexistent="Bonjour")
+    raise RuntimeError("missed exception")
+except TypeError as e:
+    pass

Examples/test-suite/python/varargs_runme.py

@@ -3,6 +3,10 @@ import varargs
 if varargs.test("Hello") != "Hello":
     raise RuntimeError("Failed")
 
+vc = varargs.VarargConstructor("Hey there")
+if vc.str != "Hey there":
+    raise RuntimeError("Failed")
+
 f = varargs.Foo("Greetings")
 if f.str != "Greetings":
     raise RuntimeError("Failed")

Examples/test-suite/varargs.i

@@ -1,17 +1,31 @@
-// Tests SWIG's *default* handling of varargs (function varargs, not preprocessor varargs).
+// Tests SWIG's handling of varargs (function varargs, not preprocessor varargs).
 // The default behavior is to simply ignore the varargs.
 %module varargs
 
+// Default handling of varargs
+
+%inline %{
+char *test(const char *fmt, ...) {
+  return (char *) fmt;
+}
+
+struct VarargConstructor {
+  char *str;
+  VarargConstructor(const char *fmt, ...) {
+    str = new char[strlen(fmt) + 1];
+    strcpy(str, fmt);
+  }
+};
+%}
+
+// %varargs support
+
 %varargs(int mode = 0) test_def;
 %varargs(int mode = 0) Foo::Foo;
 %varargs(int mode = 0) Foo::statictest(const char*fmt, ...);
 %varargs(2, int mode = 0) test_plenty(const char*fmt, ...);
 
 %inline %{
-char *test(const char *fmt, ...) {
-  return (char *) fmt;
-}
-
 const char *test_def(const char *fmt, ...) {
   return fmt;
 }
@@ -40,5 +54,4 @@ public:
 const char *test_plenty(const char *fmt, ...) {
   return fmt;
 }
-
 %}

Source/Modules/python.cxx

@@ -2753,7 +2753,7 @@ public:
       if (!varargs) {
 	Printv(f->def, linkage, wrap_return, wname, "(PyObject *", self_param, ", PyObject *args", builtin_kwargs, ") {", NIL);
       } else {
-	Printv(f->def, linkage, wrap_return, wname, "__varargs__", "(PyObject *", self_param, ", PyObject *args, PyObject *varargs) {", NIL);
+	Printv(f->def, linkage, wrap_return, wname, "__varargs__", "(PyObject *", self_param, ", PyObject *args, PyObject *varargs", builtin_kwargs, ") {", NIL);
       }
       if (allow_kwargs) {
 	Swig_warning(WARN_LANG_OVERLOAD_KEYWORD, input_file, line_number, "Can't use keyword arguments with overloaded functions (%s).\n", Swig_name_decl(n));
@@ -3253,10 +3253,10 @@ public:
 	Printf(f->code, "  Py_XINCREF(swig_obj[i + %d]);\n", num_fixed_arguments);
 	Printf(f->code, "}\n");
       } else {
-	Printf(f->code, "newargs = PyTuple_GetSlice(args,0,%d);\n", num_fixed_arguments);
-	Printf(f->code, "varargs = PyTuple_GetSlice(args,%d,PyTuple_Size(args));\n", num_fixed_arguments);
+	Printf(f->code, "newargs = PyTuple_GetSlice(args, 0, %d);\n", num_fixed_arguments);
+	Printf(f->code, "varargs = PyTuple_GetSlice(args, %d, PyTuple_Size(args));\n", num_fixed_arguments);
       }
-      Printf(f->code, "resultobj = %s__varargs__(%s,newargs,varargs);\n", wname, builtin ? "self" : "NULL");
+      Printf(f->code, "resultobj = %s__varargs__(%s, newargs, varargs%s);\n", wname, builtin ? "self" : "NULL", strlen(builtin_kwargs) == 0 ? "" : ", kwargs");
       Append(f->code, "Py_XDECREF(newargs);\n");
       Append(f->code, "Py_XDECREF(varargs);\n");
       Append(f->code, "return resultobj;\n");