swig -go: treat non-const references as pointers

Also clean up the handling of int* and int& to convert between the C
type int and the Go type int, which are often different sizes.

Fixes #2210

Examples/test-suite/go/go_director_inout_runme.go

@@ -14,6 +14,26 @@ func (p *GoMyClass) Adjust(m map[string]interface{}) wrap.GoRetStruct {
 	return wrap.GoRetStruct{s}
 }
 
+func (p *GoMyClass) S1(s string) {
+	if s != "S1" {
+		panic(s)
+	}
+}
+
+func (p *GoMyClass) S2(s *string) {
+	if *s != "S2" {
+		panic(s)
+	}
+	*s = "R2"
+}
+
+func (p *GoMyClass) S3(s *string) {
+	if *s != "S3" {
+		panic(s)
+	}
+	*s = "R3"
+}
+
 func main() {
 	a := wrap.NewDirectorMyClass(&GoMyClass{})
 	m := map[string]interface{}{
@@ -24,6 +44,18 @@ func main() {
 		panic(s)
 	}
 
+	a.S1("S1")
+	str := "S2"
+	a.S2(&str)
+	if str != "R2" {
+		panic(str)
+	}
+	str = "S3"
+	a.S3(&str)
+	if str != "R3" {
+		panic(str)
+	}
+
 	a = wrap.NewDirectorMyClass(nil)
 	s = a.Adjust(m)
 	if s.Str != `{"first":"second"}` {

Examples/test-suite/go_director_inout.i

@@ -2,6 +2,8 @@
 
 %module(directors="1") go_director_inout
 
+%include <std_string.i>
+
 %{
 #include <string>
 %}
@@ -108,6 +110,25 @@ type GoRetStruct struct {
   $1.str.assign($input.p, $input.n);
 %}
 
+%typemap(directorin) std::string & (_gostring_ temp) {
+    $input = &temp;
+    temp.p = (char *) $1.data();
+    temp.n = $1.size();
+}
+%typemap(directorargout) std::string & {
+    _gostring_ *tmp = $input;
+    $1.assign(tmp->p, tmp->p + tmp->n);
+}
+
+%typemap(directorin) std::string * (_gostring_ temp) {
+    $input = &temp;
+    $input->p = (char *) $1->data();
+    $input->n = $1->size();
+}
+%typemap(directorargout) std::string * {
+    $1->assign($input->p, $input->p + $input->n);
+}
+
 %feature("director") MyClass;
 
 %inline
@@ -121,6 +142,10 @@ class MyClass {
     r.str = s.str;
     return r;
   }
+
+  virtual void S1(std::string s) = 0;
+  virtual void S2(std::string& s) = 0;
+  virtual void S3(std::string* s) = 0;
 };
 
 %}