Ruby opaque pointer handling regression fix

This bug was introduced in swig-3.0.8 in #146252 adding shared_ptr
support. An ObjectPreviouslyDeleted error was incorrectly thrown
when the pointer was used as a parameter after being set to zero
via a call to 'DATA_PTR(self) = 0'.

It isn't clear to me which approach is better in this corner case,
so I've gone for backwards compatibility and restored the old behaviour.

Closes #602

Examples/test-suite/ruby/Makefile.in

@@ -30,7 +30,8 @@ CPP_TEST_CASES = \
 #	stl_new
 
 C_TEST_CASES += \
-	li_cstring
+	li_cstring \
+	ruby_manual_proxy \
 
 include $(srcdir)/../common.mk
 

Examples/test-suite/ruby/ruby_manual_proxy_runme.rb

@@ -0,0 +1,49 @@
+#!/usr/bin/env ruby
+#
+# The Subversion bindings use this manually written proxy class approach
+# to the Ruby bindings. Note that in C the struct svn_fs_t is an
+# opaque pointer and the Ruby FileSystem proxy class is hand written around it.
+# This testcase tests this and the C close function and subsequent error
+# handling.
+
+require 'swig_assert'
+require 'ruby_manual_proxy'
+
+module Svn
+  module Fs
+    module_function
+    def create(path)
+      f = Ruby_manual_proxy::svn_fs_create(path)
+      return f
+    end
+
+    FileSystem = SWIG::TYPE_p_svn_fs_t
+    class FileSystem
+      class << self
+        def create(*args)
+          Fs.create(*args)
+        end
+      end
+      def path
+        Ruby_manual_proxy::svn_fs_path(self)
+      end
+    end
+  end
+end
+
+f = Svn::Fs::FileSystem.create("/tmp/myfile")
+path = f.path
+f.close
+begin
+  # regression in swig-3.0.8 meant ObjectPreviouslyDeleted error was thrown instead
+  path = f.path
+  raise RuntimeError.new("IOError (1) not thrown")
+rescue IOError
+end
+
+file = nil
+begin
+  path = Ruby_manual_proxy::svn_fs_path(file)
+  raise RuntimeError.new("IOError (2) not thrown")
+rescue IOError
+end

Examples/test-suite/ruby_manual_proxy.i

@@ -0,0 +1,66 @@
+%module ruby_manual_proxy
+
+
+%typemap(in, numinputs=0) SWIGTYPE ** ($*1_ltype temp) "$1 = &temp;";
+
+%typemap(argout) SWIGTYPE **OUTPARAM {
+  $result = SWIG_Ruby_AppendOutput($result, SWIG_NewPointerObj(*$1, $*1_descriptor, 0));
+}
+
+%apply SWIGTYPE **OUTPARAM {
+  svn_fs_t **
+};
+
+%typemap(check) svn_fs_t * {
+  if (!$1) {
+    svn_swig_rb_raise_svn_fs_already_close();
+  }
+}
+
+%{
+typedef struct svn_fs_t {
+  char path[256];
+} svn_fs_t;
+
+void svn_fs_create(svn_fs_t **fs_p, const char *path) {
+  svn_fs_t *fs = (svn_fs_t *)malloc(sizeof(svn_fs_t));
+  strncpy(fs->path, path, 256);
+  *fs_p = fs;
+}
+const char *svn_fs_path(svn_fs_t *fs) {
+  return fs->path;
+}
+%}
+
+typedef struct svn_fs_t svn_fs_t;
+void svn_fs_create(svn_fs_t **fs_p, const char *path);
+const char *svn_fs_path(svn_fs_t *fs);
+
+%{
+static void svn_swig_rb_raise_svn_fs_already_close(void) {
+  rb_raise(rb_eIOError, "already closed");
+}
+
+static VALUE svn_fs_swig_rb_close(VALUE self) {
+  if (!DATA_PTR(self)) {
+    svn_swig_rb_raise_svn_fs_already_close();
+  }
+
+  DATA_PTR(self) = NULL;
+
+  return Qnil;
+}
+
+static VALUE svn_fs_swig_rb_closed(VALUE self) {
+  return DATA_PTR(self) ? Qfalse : Qtrue;
+}
+%}
+
+%insert("init") %{
+  {
+    VALUE cSvnfs;
+    cSvnfs = rb_const_get(_mSWIG, rb_intern("TYPE_p_svn_fs_t"));
+    rb_define_method(cSvnfs, "close",
+                     VALUEFUNC(svn_fs_swig_rb_close), 0);
+  }
+%}