+/*
+ * Match and parse a config key of the form:
+ *
+ * section.(subsection.)?key
+ *
+ * (i.e., what gets handed to a config_fn_t). The caller provides the section;
+ * we return -1 if it does not match, 0 otherwise. The subsection and key
+ * out-parameters are filled by the function (and subsection is NULL if it is
+ * missing).
+ */
+extern int parse_config_key(const char *var,
+ const char *section,
+ const char **subsection, int *subsection_len,
+ const char **key);
+