gpoll: introduce new ghandle type

We've long discussed having a ghandle type corresponding to HANDLE on windows
and an int (fd) elsewhere.  Let's add that now.

We continue to maintain the 'fd' field as being an integer on Windows in order
to avoid warnings about implicit casts in existing software.  'ghandleint' was
introduced for that purpose.

docs/reference/glib/glib-sections.txt

@@ -544,6 +544,10 @@ g_child_watch_add
 g_child_watch_add_full
 
 <SUBSECTION>
+ghandle
+ghandleint
+%G_HANDLE_NULL
+g_handle_is_valid
 GPollFD
 g_poll
 G_POLLFD_FORMAT

glib/docs.c

@@ -2370,5 +2370,43 @@
  * Since: 2.6
  */
  
+/* ghandle {{{1 */
+/**
+ * ghandle:
+ *
+ * Corresponds to a HANDLE on Windows and a file descriptor elsewhere.
+ *
+ * Since: 2.44
+ */
+
+/**
+ * ghandleint:
+ *
+ * An integer with the same size as #ghandle.  Used in #GPollFD as the
+ * 'fd' field.
+ *
+ * Since: 2.44
+ */
+
+/**
+ * G_HANDLE_INVALID:
+ *
+ * A value used to denote an invalid handle.  Can always be safely
+ * compared to #ghandle.
+ *
+ * See also g_handle_is_valid().
+ *
+ * Since: 2.44
+ */
+
+/**
+ * g_handle_is_valid:
+ * @handle: a #ghandle
+ *
+ * Checks if a #ghandle is valid (ie: not equal to G_HANDLE_NULL).
+ *
+ * Since: 2.44
+ */
+
  /* Epilogue {{{1 */
 /* vim: set foldmethod=marker: */

glib/gpoll.h

@@ -74,6 +74,24 @@ typedef gint    (*GPollFunc)    (GPollFD *ufds,
                                  guint    nfsd,
                                  gint     timeout_);
 
+#ifdef G_OS_WIN32
+typedef gintptr ghandleint;
+typedef gpointer ghandle;
+#define G_HANDLE_NULL (NULL)
+#else
+typedef gint ghandleint;
+typedef gint ghandle;
+#define G_HANDLE_NULL (-1)
+#endif
+
+G_STATIC_ASSERT(sizeof (ghandle) == sizeof (ghandleint));
+
+static inline gboolean
+g_handle_is_valid (ghandle handle)
+{
+  return handle != G_HANDLE_NULL;
+}
+
 /**
  * GPollFD:
  * @fd: the file descriptor to poll (or a HANDLE on Win32)
@@ -89,13 +107,7 @@ typedef gint    (*GPollFunc)    (GPollFD *ufds,
  */
 struct _GPollFD
 {
-#if defined (G_OS_WIN32) && GLIB_SIZEOF_VOID_P == 8
-#ifndef __GTK_DOC_IGNORE__
-  gint64	fd;
-#endif
-#else
-  gint		fd;
-#endif
+  ghandleint    fd;
   gushort 	events;
   gushort 	revents;
 };