* Arguments: @gfreduce *r@ = structure to fill in
* @mp *x@ = an integer
*
- * Returns: Zero for success, nonzero on error.
+ * Returns: Zero if successful; nonzero on failure. The current
+ * algorithm always succeeds when given positive @x@. Earlier
+ * versions used to fail on particular kinds of integers, but
+ * this is guaranteed not to happen any more.
*
* Use: Initializes a context structure for reduction.
*/