Don't include NID_undef in short/long name tables

NID_undef actually has names, but OBJ_sn2nid and OBJ_ln2nid's calling
convention cannot distinguish finding NID_undef from finding nothing.
Thus we may as well save 4 bytes by omitting this.

Change-Id: I6102e67141a2f5524aacf0ea84e6a2b2d2add534
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/63529
Commit-Queue: David Benjamin <davidben@google.com>
Reviewed-by: Bob Beck <bbe@google.com>

crypto/obj/obj_dat.h

@@ -8980,7 +8980,6 @@ static const uint16_t kNIDsInShortNameOrder[] = {
     16 /* ST */,
     143 /* SXNetID */,
     458 /* UID */,
-    0 /* UNDEF */,
     948 /* X25519 */,
     964 /* X25519Kyber768Draft00 */,
     961 /* X448 */,
@@ -10670,7 +10669,6 @@ static const uint16_t kNIDsInLongNameOrder[] = {
     106 /* title */,
     682 /* tpBasis */,
     436 /* ucl */,
-    0 /* undefined */,
     888 /* uniqueMember */,
     55 /* unstructuredAddress */,
     49 /* unstructuredName */,

crypto/obj/obj_test.cc

@@ -56,6 +56,9 @@ TEST(ObjTest, TestBasic) {
   };
   CBS_init(&cbs, kUnknownDER, sizeof(kUnknownDER));
   ASSERT_EQ(NID_undef, OBJ_cbs2nid(&cbs));
+
+  EXPECT_EQ(NID_undef, OBJ_sn2nid("UNDEF"));
+  EXPECT_EQ(NID_undef, OBJ_ln2nid("undefined"));
 }
 
 TEST(ObjTest, TestSignatureAlgorithms) {

crypto/obj/objects.go

@@ -640,8 +640,12 @@ func writeData(path string, objs *objects) error {
 
 	fmt.Fprintf(&b, "\nstatic const uint16_t kNIDsInShortNameOrder[] = {\n")
 	for _, nid := range nids {
+		// Including NID_undef in the table does not do anything. Whether OBJ_sn2nid
+		// finds the object or not, it will return NID_undef.
+		if nid != 0 {
 			fmt.Fprintf(&b, "%d /* %s */,\n", nid, objs.byNID[nid].shortName)
 		}
+	}
 	fmt.Fprintf(&b, "};\n")
 
 	// Emit a list of NIDs sorted by long name.
@@ -656,8 +660,12 @@ func writeData(path string, objs *objects) error {
 
 	fmt.Fprintf(&b, "\nstatic const uint16_t kNIDsInLongNameOrder[] = {\n")
 	for _, nid := range nids {
+		// Including NID_undef in the table does not do anything. Whether OBJ_ln2nid
+		// finds the object or not, it will return NID_undef.
+		if nid != 0 {
 			fmt.Fprintf(&b, "%d /* %s */,\n", nid, objs.byNID[nid].longName)
 		}
+	}
 	fmt.Fprintf(&b, "};\n")
 
 	// Emit a list of NIDs sorted by OID.