shared: add nm_clear_g_free()

libnm-core/tests/test-general.c

@@ -2527,7 +2527,7 @@ test_setting_compare_wireless_cloned_mac_address (void)
 	g_assert_cmpstr ("stable-bia", ==, nm_setting_wireless_get_cloned_mac_address ((NMSettingWireless *) new));
 	g_object_get (new, NM_SETTING_WIRELESS_CLONED_MAC_ADDRESS, &str1, NULL);
 	g_assert_cmpstr ("stable-bia", ==, str1);
-	g_clear_pointer (&str1, g_free);
+	nm_clear_g_free (&str1);
 
 	success = nm_setting_compare (old, new, NM_SETTING_COMPARE_FLAG_EXACT);
 	g_assert (!success);

shared/nm-utils/nm-macros-internal.h

@@ -373,6 +373,27 @@ nm_g_object_unref (gpointer obj)
 		g_object_unref (obj);
 }
 
+/* basically, replaces
+ *   g_clear_pointer (&location, g_free)
+ * with
+ *   nm_clear_g_free (&location)
+ *
+ * Another advantage is that by using a macro and typeof(), it is more
+ * typesafe and gives you for example a compiler warning when pp is a const
+ * pointer or points to a const-pointer.
+ */
+#define nm_clear_g_free(pp) \
+	({  \
+		typeof (*(pp)) *_pp = (pp); \
+		typeof (**_pp) *_p = *_pp; \
+		\
+		if (_p) { \
+			*_pp = NULL; \
+			g_free (_p); \
+		} \
+		!!_p; \
+	})
+
 static inline gboolean
 nm_clear_g_source (guint *id)
 {