X509_cmp.pod: Point out that the X509_NAME_cmp() arguments may be NULL
@@ -29,7 +29,8 @@ I<a> and I<b>. The comparison is based on the B<memcmp> result of the hash
values of two B<X509> objects and the canonical (DER) encoding values.
The X509_NAME_cmp() function compares two B<X509_NAME> objects indicated by
-parameters I<a> and I<b>. The comparison is based on the B<memcmp> result of the
+parameters I<a> and I<b>, any of which may be NULL.
+The comparison is based on the B<memcmp> result of the
canonical (DER) encoding values of the two objects using L<i2d_X509_NAME(3)>.
This procedure adheres to the matching rules for Distinguished Names (DN)
given in RFC 4517 section 4.2.15 and RFC 5280 section 7.1.
