shared: don't validate type-string in G_VARIANT_TYPE() cast macro in production code

shared/nm-default.h

@@ -174,6 +174,35 @@
 #endif
 #endif
 
+#if NM_MORE_ASSERTS == 0
+#ifndef G_DISABLE_CAST_CHECKS
+/* Unless compiling with G_DISABLE_CAST_CHECKS, glib performs type checking
+ * during G_VARIANT_TYPE() via g_variant_type_checked_(). This is not necesary
+ * because commonly this cast is needed during something like
+ *
+ *   g_variant_builder_init (&props, G_VARIANT_TYPE ("a{sv}"));
+ *
+ * Note that in if the variant type would be invalid, the check still
+ * wouldn't make the buggy code magically work. Instead of passing a
+ * bogus type string (bad), it would pass %NULL to g_variant_builder_init()
+ * (also bad).
+ *
+ * Also, a function like g_variant_builder_init() already validates
+ * the input type via something like
+ *
+ *   g_return_if_fail (g_variant_type_is_container (type));
+ *
+ * So, by having G_VARIANT_TYPE() also validate the type, we validate
+ * twice, whereas the first validation is rather pointless because it
+ * doesn't prevent the function to be called with invalid arguments.
+ *
+ * Just patch G_VARIANT_TYPE() to perform no check.
+ */
+#undef G_VARIANT_TYPE
+#define G_VARIANT_TYPE(type_string) ((const GVariantType *) (type_string))
+#endif
+#endif
+
 #include <stdlib.h>
 
 /*****************************************************************************/