PR comments; document obscure code implications

crypto/fipsmodule/ec/ec.c

@@ -490,8 +490,9 @@ int EC_GROUP_cmp(const EC_GROUP *a, const EC_GROUP *b, BN_CTX *ignored) {
 
   // |a| and |b| are both custom curves. We compare the entire curve structure
   // if both |a| and |b| are complete. If either are incomplete (due to legacy
-  // OpenSSL mistakes, custom curve construction is sadly done in two parts), we
-  // only compare the parts that are available.
+  // OpenSSL mistakes, custom curve construction is sadly done in two parts
+  // |EC_GROUP_new_curve_GFp| -> |EC_GROUP_set_generator|), we only compare
+  // the parts that are available.
   if (a->has_order && b->has_order) {
     return a->meth != b->meth || BN_cmp(&a->order.N, &b->order.N) != 0 ||
            BN_cmp(&a->field.N, &b->field.N) != 0 ||

crypto/fipsmodule/ec/internal.h

@@ -635,7 +635,11 @@ struct ec_group_st {
   // comment is a human-readable string describing the curve.
   const char *comment;
 
-  int curve_name;  // optional NID for named curve
+  // curve_name is the optional NID for named curves. |oid| and |oid_len| are
+  // populated with values corresponding to the named curve's NID.
+  // |NID_undef| is used to imply that the curve is a custom explicit curve and
+  // the oid values are empty if so.
+  int curve_name;
   uint8_t oid[9];
   uint8_t oid_len;