Allow passing unset GValues to g_value_unset()

This makes it more useful as an autocleanup func.

Also, add a minimal test of g_value_init/g_value_reset/g_value_unset.

https://bugzilla.gnome.org/show_bug.cgi?id=755766

gobject/tests/value.c

@@ -0,0 +1,95 @@
+#define GLIB_VERSION_MIN_REQUIRED       GLIB_VERSION_2_30
+#include <glib-object.h>
+
+static void
+test_value_basic (void)
+{
+  GValue value = G_VALUE_INIT;
+
+  g_assert_false (G_IS_VALUE (&value));
+  g_assert_false (G_VALUE_HOLDS_INT (&value));
+  g_value_unset (&value);
+  g_assert_false (G_IS_VALUE (&value));
+  g_assert_false (G_VALUE_HOLDS_INT (&value));
+
+  g_value_init (&value, G_TYPE_INT);
+  g_assert_true (G_IS_VALUE (&value));
+  g_assert_true (G_VALUE_HOLDS_INT (&value));
+  g_assert_false (G_VALUE_HOLDS_UINT (&value));
+  g_assert_cmpint (g_value_get_int (&value), ==, 0);
+
+  g_value_set_int (&value, 10);
+  g_assert_cmpint (g_value_get_int (&value), ==, 10);
+
+  g_value_reset (&value);
+  g_assert_true (G_IS_VALUE (&value));
+  g_assert_true (G_VALUE_HOLDS_INT (&value));
+  g_assert_cmpint (g_value_get_int (&value), ==, 0);
+
+  g_value_unset (&value);
+  g_assert_false (G_IS_VALUE (&value));
+  g_assert_false (G_VALUE_HOLDS_INT (&value));
+}
+
+static gint
+cmpint (gconstpointer a, gconstpointer b)
+{
+  const GValue *aa = a;
+  const GValue *bb = b;
+
+  return g_value_get_int (aa) - g_value_get_int (bb);
+}
+
+static void
+test_valuearray_basic (void)
+{
+  GValueArray *a;
+  GValueArray *a2;
+  GValue v = G_VALUE_INIT;
+  GValue *p;
+  gint i;
+
+  a = g_value_array_new (20);
+
+  g_value_init (&v, G_TYPE_INT);
+  for (i = 0; i < 100; i++)
+    {
+      g_value_set_int (&v, i);
+      g_value_array_append (a, &v);
+    }
+
+  g_assert_cmpint (a->n_values, ==, 100);
+  p = g_value_array_get_nth (a, 5);
+  g_assert_cmpint (g_value_get_int (p), ==, 5);
+
+  for (i = 20; i < 100; i+= 5)
+    g_value_array_remove (a, 100 - i);
+
+  for (i = 100; i < 150; i++)
+    {
+      g_value_set_int (&v, i);
+      g_value_array_prepend (a, &v);
+    }
+
+  g_value_array_sort (a, cmpint);
+  for (i = 0; i < a->n_values - 1; i++)
+    g_assert_cmpint (g_value_get_int (&a->values[i]), <=, g_value_get_int (&a->values[i+1]));
+
+  a2 = g_value_array_copy (a);
+  for (i = 0; i < a->n_values; i++)
+    g_assert_cmpint (g_value_get_int (&a->values[i]), ==, g_value_get_int (&a2->values[i]));
+
+  g_value_array_free (a);
+  g_value_array_free (a2);
+}
+
+int
+main (int argc, char *argv[])
+{
+  g_test_init (&argc, &argv, NULL);
+
+  g_test_add_func ("/value/basic", test_value_basic);
+  g_test_add_func ("/value/array/basic", test_valuearray_basic);
+
+  return g_test_run ();
+}