-SRD_PRIV int py_attr_as_str(PyObject *py_obj, const char *attr, char **outstr);
-SRD_PRIV int py_dictitem_as_str(PyObject *py_obj, const char *key, char **outstr);
-SRD_PRIV int py_str_as_str(PyObject *py_str, char **outstr);
-SRD_PRIV int py_strlist_to_char(PyObject *py_strlist, char ***outstr);
-SRD_PRIV struct srd_decoder_inst *srd_inst_find_by_obj(GSList *stack,
- PyObject *obj);
+SRD_PRIV int py_attr_as_str(const PyObject *py_obj, const char *attr,
+ char **outstr);
+SRD_PRIV int py_dictitem_as_str(const PyObject *py_obj, const char *key,
+ char **outstr);
+SRD_PRIV int py_str_as_str(const PyObject *py_str, char **outstr);
+SRD_PRIV int py_strlist_to_char(const PyObject *py_strlist, char ***outstr);
+SRD_PRIV struct srd_decoder_inst *srd_inst_find_by_obj(const GSList *stack,
+ const PyObject *obj);