Initialize binlog event scalar members

libs/mysql/binlog/event/binlog_event.cpp

@@ -194,10 +194,10 @@ bool Log_event_footer::event_checksum_test(unsigned char *event_buf,
       flags = le16toh(flags);
       if (flags & LOG_EVENT_BINLOG_IN_USE_F)
         event_buf[FLAGS_OFFSET] &= ~LOG_EVENT_BINLOG_IN_USE_F;
-        /*
-           The only algorithm currently is CRC32. Zero indicates
-           the binlog file is checksum-free *except* the FD-event.
-        */
+      /*
+         The only algorithm currently is CRC32. Zero indicates
+         the binlog file is checksum-free *except* the FD-event.
+      */
 #ifndef NDEBUG
       BAPI_ASSERT(fd_alg == BINLOG_CHECKSUM_ALG_CRC32 || fd_alg == 0);
 #endif
@@ -232,7 +232,12 @@ bool Log_event_footer::event_checksum_test(unsigned char *event_buf,
 }
 
 Log_event_header::Log_event_header(Event_reader &reader)
-    : data_written(0), log_pos(0), m_is_valid(false) {
+    : type_code(ENUM_END_EVENT),
+      unmasked_server_id(0),
+      data_written(0),
+      log_pos(0),
+      flags(0),
+      m_is_valid(false) {
   BAPI_ENTER("Log_event_header::Log_event_header(Event_reader &)");
 
   /*

libs/mysql/binlog/event/binlog_event.h

@@ -724,7 +724,12 @@ class Log_event_header {
   typedef unsigned char Byte;
 
   explicit Log_event_header(Log_event_type type_code_arg = ENUM_END_EVENT)
-      : type_code(type_code_arg), data_written(0), log_pos(0), flags(0) {
+      : type_code(type_code_arg),
+        unmasked_server_id(0),
+        data_written(0),
+        log_pos(0),
+        flags(0),
+        m_is_valid(true) {
     when.tv_sec = 0;
     when.tv_usec = 0;
   }

libs/mysql/binlog/event/rows_event.cpp

@@ -407,8 +407,12 @@ Table_map_event::Optional_metadata_fields::Optional_metadata_fields(
 
 Rows_event::Rows_event(const char *buf, const Format_description_event *fde)
     : Binary_log_event(&buf, fde),
+      m_type(ENUM_END_EVENT),
       m_table_id(0),
+      m_flags(0),
       m_width(0),
+      n_bits_len(0),
+      var_header_len(0),
       columns_before_image(0),
       columns_after_image(0),
       row(0) {

libs/mysql/binlog/event/rows_event.h

@@ -919,8 +919,12 @@ class Rows_event : public Binary_log_event {
   */
   explicit Rows_event(Log_event_type type_arg)
       : Binary_log_event(type_arg),
+        m_type(type_arg),
         m_table_id(0),
+        m_flags(0),
         m_width(0),
+        n_bits_len(0),
+        var_header_len(0),
         columns_before_image(0),
         columns_after_image(0),
         row(0) {}

unittest/gunit/binlogevents/CMakeLists.txt

@@ -32,6 +32,7 @@ INCLUDE_DIRECTORIES(SYSTEM ${GMOCK_INCLUDE_DIRS})
 
 # Add tests
 SET(TESTS
+  event_initialization
   gno_intervals
   grow_calculator
   gtids

unittest/gunit/binlogevents/event_initialization-t.cc

@@ -0,0 +1,62 @@
+/* Copyright (c) 2026, Oracle and/or its affiliates.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License, version 2.0,
+   as published by the Free Software Foundation.
+
+   This program is designed to work with certain software (including
+   but not limited to OpenSSL) that is licensed under separate terms,
+   as designated in a particular file or component or in included license
+   documentation.  The authors of MySQL hereby grant you an additional
+   permission to link the program and your derivative works with the
+   separately licensed software that they have either included with the
+   program or referenced in the documentation.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License, version 2.0, for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA */
+
+#include <array>
+
+#include <gtest/gtest.h>
+
+#include "mysql/binlog/event/binlog_event.h"
+#include "mysql/binlog/event/control_events.h"
+#include "mysql/binlog/event/rows_event.h"
+
+namespace mysql::binlog::event::unittests {
+
+TEST(EventInitializationTest, LogEventHeaderDefaults) {
+  Log_event_header header;
+
+  EXPECT_EQ(0, header.when.tv_sec);
+  EXPECT_EQ(0, header.when.tv_usec);
+  EXPECT_EQ(ENUM_END_EVENT, header.type_code);
+  EXPECT_EQ(0U, header.unmasked_server_id);
+  EXPECT_EQ(0U, header.data_written);
+  EXPECT_EQ(0U, header.log_pos);
+  EXPECT_EQ(0U, header.flags);
+  EXPECT_TRUE(header.get_is_valid());
+}
+
+TEST(EventInitializationTest, MalformedRowsEventHasDeterministicState) {
+  const Format_description_event fde(BINLOG_VERSION, "8.0.0");
+  std::array<char, LOG_EVENT_MINIMAL_HEADER_LEN> buffer{};
+  buffer[EVENT_TYPE_OFFSET] = static_cast<char>(WRITE_ROWS_EVENT);
+  buffer[EVENT_LEN_OFFSET] = static_cast<char>(buffer.size());
+
+  Rows_event event(buffer.data(), &fde);
+
+  EXPECT_FALSE(event.header()->get_is_valid());
+  EXPECT_EQ(0U, event.get_table_id());
+  EXPECT_EQ(0U, event.get_flags());
+  EXPECT_EQ(0U, event.get_width());
+  EXPECT_EQ(0U, event.get_null_bits_len());
+}
+
+}  // namespace mysql::binlog::event::unittests