MDEV-20923:UBSAN: member access within address … which does not point to an object of type 'xid_count_per_binlog'

Problem:
-------
Accessing a member within 'xid_count_per_binlog' structure results in
following error when 'UBSAN' is enabled.

member access within address 0xXXX which does not point to an object of type
'xid_count_per_binlog'

Analysis:
---------
The problem appears to be that no constructor for 'xid_count_per_binlog' is
being called, and thus the vtable will not be initialized.

Fix:
---
Defined a parameterized constructor for 'xid_count_per_binlog' class.

1 files changed, 12 insertions, 1 deletions

diff --git a/sql/log.h b/sql/log.h
index b4c9b24a3a9..277e5c6f69c 100644
--- a/sql/log.h
+++ b/sql/log.h
@@ -587,7 +587,18 @@ public:
     long xid_count;
     /* For linking in requests to the binlog background thread. */
     xid_count_per_binlog *next_in_queue;
-    xid_count_per_binlog();   /* Give link error if constructor used. */
+    xid_count_per_binlog(char *log_file_name, uint log_file_name_len)
+      :binlog_id(0), xid_count(0)
+    {
+      binlog_name_len= log_file_name_len;
+      binlog_name= (char *) my_malloc(binlog_name_len, MYF(MY_ZEROFILL));
+      if (binlog_name)
+        memcpy(binlog_name, log_file_name, binlog_name_len);
+    }
+    ~xid_count_per_binlog()
+    {
+      my_free(binlog_name);
+    }
   };
   I_List<xid_count_per_binlog> binlog_xid_count_list;
   mysql_mutex_t LOCK_binlog_background_thread;