MDEV-19166 Assertion `!is_zero_datetime()' failed in Timestamp_or_zero_datetime::tv

mysql-test/main/type_temporal_innodb.result

@@ -172,3 +172,16 @@ CREATE TABLE tbl SELECT * FROM t1 WHERE t1.c1 = (SELECT c2 FROM t2 WHERE pk = 6)
 ERROR 22007: Truncated incorrect datetime value: '0000-00-00 00:00:00'
 DROP TABLE t1,t2;
 SET sql_mode=DEFAULT;
+#
+# MDEV-19166 Assertion `!is_zero_datetime()' failed in Timestamp_or_zero_datetime::tv
+#
+CREATE TABLE t1 (f TIMESTAMP DEFAULT 0) ENGINE=InnoDB;
+INSERT INTO t1 VALUES ('2024-02-29');
+SELECT * FROM t1 WHERE SUBSTR(1 FROM BIT_LENGTH(f) FOR DEFAULT(f));
+f
+Warnings:
+Warning	1292	Truncated incorrect INTEGER value: ''
+DROP TABLE t1;
+#
+# End of 10.4 tests
+#

mysql-test/main/type_temporal_innodb.test

@@ -81,3 +81,18 @@ CREATE TABLE tbl SELECT * FROM t1 WHERE t1.c1 = (SELECT c2 FROM t2 WHERE pk = 6)
 # ^^^ there is no column c2 in table t2
 DROP TABLE t1,t2;
 SET sql_mode=DEFAULT;
+
+
+--echo #
+--echo # MDEV-19166 Assertion `!is_zero_datetime()' failed in Timestamp_or_zero_datetime::tv
+--echo #
+
+CREATE TABLE t1 (f TIMESTAMP DEFAULT 0) ENGINE=InnoDB;
+INSERT INTO t1 VALUES ('2024-02-29');
+SELECT * FROM t1 WHERE SUBSTR(1 FROM BIT_LENGTH(f) FOR DEFAULT(f));
+DROP TABLE t1;
+
+
+--echo #
+--echo # End of 10.4 tests
+--echo #

sql/item.cc

@@ -9909,7 +9909,7 @@ Datetime Item_cache_timestamp::to_datetime(THD *thd)
     null_value= true;
     return Datetime();
   }
-  return Datetime(thd, Timestamp_or_zero_datetime(m_native).tv());
+  return m_native.to_datetime(thd);
 }
 
 

sql/item_timefunc.cc

@@ -1220,7 +1220,7 @@ bool Item_func_unix_timestamp::get_timestamp_value(my_time_t *seconds,
   Timestamp_or_zero_datetime_native_null native(current_thd, args[0], true);
   if ((null_value= native.is_null() || native.is_zero_datetime()))
     return true;
-  Timestamp_or_zero_datetime tm(native);
+  Timestamp tm(native);
   *seconds= tm.tv().tv_sec;
   *second_part= tm.tv().tv_usec;
   return false;

sql/sql_type.h

@@ -2377,6 +2377,10 @@ class Timestamp: protected Timeval
   }
   bool to_TIME(THD *thd, MYSQL_TIME *ltime, date_mode_t fuzzydate) const;
   bool to_native(Native *to, uint decimals) const;
+  Datetime to_datetime(THD *thd) const
+  {
+    return Datetime(thd, *this);
+  }
   long fraction_remainder(uint dec) const
   {
     return my_time_fraction_remainder(tv_usec, dec);
@@ -2417,7 +2421,7 @@ class Timestamp: protected Timeval
   - real TIMESTAMP (seconds and microseconds since epoch), or
   - zero datetime '0000-00-00 00:00:00.000000'
 */
-class Timestamp_or_zero_datetime: public Timestamp
+class Timestamp_or_zero_datetime: protected Timestamp
 {
   bool m_is_zero_datetime;
 public:
@@ -2434,14 +2438,11 @@ class Timestamp_or_zero_datetime: public Timestamp
   Timestamp_or_zero_datetime(THD *thd, const MYSQL_TIME *ltime, uint *err_code);
   Datetime to_datetime(THD *thd) const
   {
-    return Datetime(thd, *this);
+    if (is_zero_datetime())
+      return Datetime();
+    return Timestamp::to_datetime(thd);
   }
   bool is_zero_datetime() const { return m_is_zero_datetime; }
-  const struct timeval &tv() const
-  {
-    DBUG_ASSERT(!is_zero_datetime());
-    return Timestamp::tv();
-  }
   void trunc(uint decimals)
   {
     if (!is_zero_datetime())
@@ -2487,7 +2488,7 @@ class Timestamp_or_zero_datetime_native:
   {
     return is_zero_datetime() ?
            Datetime() :
-           Datetime(thd, Timestamp_or_zero_datetime(*this).tv());
+           Datetime(thd, Timestamp(*this).tv());
   }
   bool is_zero_datetime() const
   {