vclock: fix big lsn handling

Fixes commit 8031071e ("Lightweight vclock_create and vclock_copy").

Closes #4033

src/box/vclock.h

@@ -165,7 +165,7 @@ vclock_get(const struct vclock *vclock, uint32_t replica_id)
 	 */
 	replica_id &= VCLOCK_MAX - 1;
 	/* Evaluate a bitmask to avoid branching. */
-	int64_t mask = 0 - ((vclock->map >> replica_id) & 0x1);
+	int64_t mask = 0ULL - ((vclock->map >> replica_id) & 0x1);
 	return mask & vclock->lsn[replica_id];
 }
 

test/xlog-py/big_lsn.result

+box.info.lsn
+---
+- 0
+...
+box.space._schema:delete('dummy')
+---
+...
+box.info.lsn
+---
+- 123456789123
+...
+box.space._schema:delete('dummy')
+---
+...
+box.snapshot()
+---
+- ok
+...
+box.info.lsn
+---
+- 123456789124
+...
+box.space._schema:delete('dummy')
+---
+...
+box.snapshot()
+---
+- ok
+...

test/xlog-py/big_lsn.test.py

+import os
+
+#
+# Check that Tarantool handles huge LSNs well (gh-4033).
+#
+
+# Fill an empty directory.
+server.stop()
+server.deploy()
+server.admin("box.info.lsn")
+server.admin("box.space._schema:delete('dummy')")
+server.stop()
+
+# Bump the instance vclock by tweaking the last xlog.
+old_lsn = 1
+new_lsn = 123456789123
+wal_dir = os.path.join(server.vardir, server.name)
+old_wal = os.path.join(wal_dir, "%020d.xlog" % old_lsn)
+new_wal = os.path.join(wal_dir, "%020d.xlog" % new_lsn)
+with open(old_wal, "r+") as f:
+    s = f.read()
+    s = s.replace("VClock: {1: %d}" % old_lsn,
+                  "VClock: {1: %d}" % new_lsn)
+    f.seek(0)
+    f.write(s)
+os.rename(old_wal, new_wal)
+
+# Recover and make a snapshot.
+server.start()
+server.admin("box.info.lsn")
+server.admin("box.space._schema:delete('dummy')")
+server.admin("box.snapshot()")
+server.stop()
+
+# Try one more time.
+server.start()
+server.admin("box.info.lsn")
+server.admin("box.space._schema:delete('dummy')")
+server.admin("box.snapshot()")