- * If invo_name isn't NULL or empty, it precedes the output seperated by ": ".
- * If what isn't NULL, errno as a string is appended.
- * A non-empty what separates fmt from errno, surrounded by " " and ": ".
- * BUG: No space separator before errno if what is "".
- * If tail isn't NULL or empty then ", " and tail are appended
- * before the finishing "\n".
- * In summary: "invo_name: fmt what: errno, tail\n". */
+ * If invo_name isn't NULL or empty then "invo_name: " precedes fmt.
+ * If what isn't NULL or empty then " what" is appended.
+ * If what isn't NULL then ": errno" is appended.
+ * If tail isn't NULL or empty then ", tail" is appended.
+ * A "\n" finishes the output to stderr.
+ * In summary: "[invo_name: ]fmt[[ what]: errno][, tail]\n". */