From 241017bc1fa07a3faf7c6543ecc41905630bf03f Mon Sep 17 00:00:00 2001
From: Alexey Milovidov <milovidov@yandex-team.ru>
Date: Fri, 7 Aug 2020 02:52:18 +0300
Subject: [PATCH] Fix error in parseDateTimeBestEffort

---
 src/Common/BitHelpers.h                                        | 2 ++
 src/IO/parseDateTimeBestEffort.cpp                             | 1 +
 .../01432_parse_date_time_best_effort_timestamp.reference      | 3 +++
 .../01432_parse_date_time_best_effort_timestamp.sql            | 3 +++
 4 files changed, 9 insertions(+)
 create mode 100644 tests/queries/0_stateless/01432_parse_date_time_best_effort_timestamp.reference
 create mode 100644 tests/queries/0_stateless/01432_parse_date_time_best_effort_timestamp.sql

diff --git a/src/Common/BitHelpers.h b/src/Common/BitHelpers.h
index 639a0c026ff..699e379b8d3 100644
--- a/src/Common/BitHelpers.h
+++ b/src/Common/BitHelpers.h
@@ -1,6 +1,7 @@
 #pragma once
 
 #include <cstddef>
+#include <cassert>
 #include <type_traits>
 #include <common/defines.h>
 
@@ -11,6 +12,7 @@
   */
 inline unsigned int bitScanReverse(unsigned int x)
 {
+    assert(x != 0);
     return sizeof(unsigned int) * 8 - 1 - __builtin_clz(x);
 }
 
diff --git a/src/IO/parseDateTimeBestEffort.cpp b/src/IO/parseDateTimeBestEffort.cpp
index c350bd1ddc1..d84ac76b164 100644
--- a/src/IO/parseDateTimeBestEffort.cpp
+++ b/src/IO/parseDateTimeBestEffort.cpp
@@ -104,6 +104,7 @@ ReturnType parseDateTimeBestEffortImpl(
             return false;
     };
 
+    res = 0;
     UInt16 year = 0;
     UInt8 month = 0;
     UInt8 day_of_month = 0;
diff --git a/tests/queries/0_stateless/01432_parse_date_time_best_effort_timestamp.reference b/tests/queries/0_stateless/01432_parse_date_time_best_effort_timestamp.reference
new file mode 100644
index 00000000000..36cee487d54
--- /dev/null
+++ b/tests/queries/0_stateless/01432_parse_date_time_best_effort_timestamp.reference
@@ -0,0 +1,3 @@
+2020-08-07 01:29:00
+1973-03-03 12:46:40
+2020-08-07 00:00:00
diff --git a/tests/queries/0_stateless/01432_parse_date_time_best_effort_timestamp.sql b/tests/queries/0_stateless/01432_parse_date_time_best_effort_timestamp.sql
new file mode 100644
index 00000000000..071fefe0403
--- /dev/null
+++ b/tests/queries/0_stateless/01432_parse_date_time_best_effort_timestamp.sql
@@ -0,0 +1,3 @@
+SELECT parseDateTimeBestEffort('1596752940', 'Europe/Moscow');
+SELECT parseDateTimeBestEffort('100000000', 'Europe/Moscow');
+SELECT parseDateTimeBestEffort('20200807', 'Europe/Moscow');