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.

Author: sujatha-s

sql/log.cc

@@ -3216,7 +3216,7 @@ void MYSQL_BIN_LOG::cleanup()
       DBUG_ASSERT(!binlog_xid_count_list.head());
       WSREP_XID_LIST_ENTRY("MYSQL_BIN_LOG::cleanup(): Removing xid_list_entry "
                            "for %s (%lu)", b);
-      my_free(b);
+      delete b;
     }
 
     mysql_mutex_destroy(&LOCK_log);
@@ -3580,17 +3580,9 @@ bool MYSQL_BIN_LOG::open(const char *log_name,
         */
         uint off= dirname_length(log_file_name);
         uint len= strlen(log_file_name) - off;
-        char *entry_mem, *name_mem;
-        if (!(new_xid_list_entry = (xid_count_per_binlog *)
-              my_multi_malloc(MYF(MY_WME),
-                              &entry_mem, sizeof(xid_count_per_binlog),
-                              &name_mem, len,
-                              NULL)))
+        new_xid_list_entry= new xid_count_per_binlog(log_file_name+off, (int)len);
+        if (!new_xid_list_entry)
           goto err;
-        memcpy(name_mem, log_file_name+off, len);
-        new_xid_list_entry->binlog_name= name_mem;
-        new_xid_list_entry->binlog_name_len= len;
-        new_xid_list_entry->xid_count= 0;
 
         /*
           Find the name for the Initial binlog checkpoint.
@@ -3607,7 +3599,10 @@ bool MYSQL_BIN_LOG::open(const char *log_name,
         mysql_mutex_unlock(&LOCK_xid_list);
         if (!b)
           b= new_xid_list_entry;
-        strmake(buf, b->binlog_name, b->binlog_name_len);
+        if (b->binlog_name)
+          strmake(buf, b->binlog_name, b->binlog_name_len);
+        else
+          goto err;
         Binlog_checkpoint_log_event ev(buf, len);
         DBUG_EXECUTE_IF("crash_before_write_checkpoint_event",
                         flush_io_cache(&log_file);
@@ -3711,7 +3706,7 @@ bool MYSQL_BIN_LOG::open(const char *log_name,
     {
       WSREP_XID_LIST_ENTRY("MYSQL_BIN_LOG::open(): Removing xid_list_entry for "
                            "%s (%lu)", b);
-      my_free(binlog_xid_count_list.get());
+      delete binlog_xid_count_list.get();
     }
     mysql_cond_broadcast(&COND_xid_list);
     WSREP_XID_LIST_ENTRY("MYSQL_BIN_LOG::open(): Adding new xid_list_entry for "
@@ -3758,7 +3753,7 @@ Turning logging off for the whole duration of the MySQL server process. \
 To turn it on again: fix the cause, \
 shutdown the MySQL server and restart it.", name, errno);
   if (new_xid_list_entry)
-    my_free(new_xid_list_entry);
+    delete new_xid_list_entry;
   if (file >= 0)
     mysql_file_close(file, MYF(0));
   close(LOG_CLOSE_INDEX);
@@ -4252,7 +4247,7 @@ bool MYSQL_BIN_LOG::reset_logs(THD *thd, bool create_new_log,
       DBUG_ASSERT(b->xid_count == 0);
       WSREP_XID_LIST_ENTRY("MYSQL_BIN_LOG::reset_logs(): Removing "
                            "xid_list_entry for %s (%lu)", b);
-      my_free(binlog_xid_count_list.get());
+      delete binlog_xid_count_list.get();
     }
     mysql_cond_broadcast(&COND_xid_list);
     reset_master_pending--;
@@ -9736,7 +9731,7 @@ TC_LOG_BINLOG::mark_xid_done(ulong binlog_id, bool write_checkpoint)
       break;
     WSREP_XID_LIST_ENTRY("TC_LOG_BINLOG::mark_xid_done(): Removing "
                          "xid_list_entry for %s (%lu)", b);
-    my_free(binlog_xid_count_list.get());
+    delete binlog_xid_count_list.get();
   }
 
   mysql_mutex_unlock(&LOCK_xid_list);

sql/log.h

@@ -587,7 +587,18 @@ class MYSQL_BIN_LOG: public TC_LOG, private MYSQL_LOG
     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;