static value Val_opt (void *ptr, Val_ptr_t Val_ptr);
/*static value option_default (value option, value deflt);*/
static void _raise_virterror (const char *fn) Noreturn;
-static void not_supported (const char *fn) Noreturn;
static value Val_virterror (virErrorPtr err);
/* Use this around synchronous libvirt API calls to release the OCaml