Bug #33931 assertion at write_ignored_events_info_to_relay_log if init_slave_thread() fails

and
bug#33932  assertion at handle_slave_sql if init_slave_thread() fails

the asserts were caused by 
  bug33931: having thd deleted at time of executing err: code plus
            a missed initialization;
  bug33932: initialization of slave_is_running member was missed;

fixed with relocating mi members initialization and removing delete thd
It is safe to do as deletion happens later explicitly in the caller of
init_slave_thread().

Todo: at merging the test is better to be moved into suite/bugs for 5.x (when x>0).


sql/slave.cc:
  adding the bugs simulating code;
  relocating some assignments to satisfy the asserts;
mysql-test/r/rpl_bug33931.result:
  the new result file
mysql-test/t/rpl_bug33931-slave.opt:
  option to spark the simulation code
mysql-test/t/rpl_bug33931.test:
  tests check that slave does not crash as before.
  Slave threads must be in NO running state in the end.

mysql-test/r/rpl_bug33931.result

+reset master;
+stop slave;
+reset slave;
+start slave;
+show slave status;
+Slave_IO_State	#
+Master_Host	127.0.0.1
+Master_User	root
+Master_Port	MASTER_PORT
+Connect_Retry	1
+Master_Log_File	
+Read_Master_Log_Pos	4
+Relay_Log_File	#
+Relay_Log_Pos	#
+Relay_Master_Log_File	
+Slave_IO_Running	No
+Slave_SQL_Running	No
+Replicate_Do_DB	
+Replicate_Ignore_DB	
+Replicate_Do_Table	
+Replicate_Ignore_Table	
+Replicate_Wild_Do_Table	
+Replicate_Wild_Ignore_Table	
+Last_Errno	0
+Last_Error	
+Skip_Counter	0
+Exec_Master_Log_Pos	0
+Relay_Log_Space	#
+Until_Condition	None
+Until_Log_File	
+Until_Log_Pos	0
+Master_SSL_Allowed	No
+Master_SSL_CA_File	
+Master_SSL_CA_Path	
+Master_SSL_Cert	
+Master_SSL_Cipher	
+Master_SSL_Key	
+Seconds_Behind_Master	#

mysql-test/t/rpl_bug33931-slave.opt

+--loose-debug=d,simulate_io_slave_error_on_init,simulate_sql_slave_error_on_init

mysql-test/t/rpl_bug33931.test

+# Test for 
+# Bug #33931  	assertion at write_ignored_events_info_to_relay_log if init_slave_thread() fails
+# Bug #33932  	assertion at handle_slave_sql if init_slave_thread() fails
+
+source include/have_debug.inc;
+source include/have_log_bin.inc;
+
+connect (master,127.0.0.1,root,,test,$MASTER_MYPORT,);
+connect (slave,127.0.0.1,root,,test,$SLAVE_MYPORT,);
+
+
+connection master;
+reset master;
+
+connection slave;
+--disable_warnings
+stop slave;
+--enable_warnings
+reset slave;
+start slave;
+
+connection master;
+save_master_pos;
+connection slave;
+
+#
+# slave is going to stop because of emulated failures
+# but there won't be any crashes nor asserts hit.
+#
+source include/wait_for_slave_to_stop.inc;
+
+--replace_result $MASTER_MYPORT MASTER_PORT                                     
+--replace_column 1 # 8 # 9 # 23 # 33 #                                          
+query_vertical show slave status;
+
+# no clean-up is needed
+

sql/slave.cc

@@ -2895,6 +2895,9 @@ void set_slave_thread_default_charset(THD* thd, RELAY_LOG_INFO *rli)
 static int init_slave_thread(THD* thd, SLAVE_THD_TYPE thd_type)
 {
   DBUG_ENTER("init_slave_thread");
+#if !defined(DBUG_OFF)
+  int simulate_error= 0;
+#endif
   thd->system_thread = (thd_type == SLAVE_THD_SQL) ?
     SYSTEM_THREAD_SLAVE_SQL : SYSTEM_THREAD_SLAVE_IO; 
   thd->security_ctx->skip_grants();
@@ -2914,10 +2917,17 @@ static int init_slave_thread(THD* thd, SLAVE_THD_TYPE thd_type)
   thd->thread_id = thread_id++;
   pthread_mutex_unlock(&LOCK_thread_count);
 
+  DBUG_EXECUTE_IF("simulate_io_slave_error_on_init",
+                  simulate_error|= (1 << SLAVE_THD_IO););
+  DBUG_EXECUTE_IF("simulate_sql_slave_error_on_init",
+                  simulate_error|= (1 << SLAVE_THD_SQL););
+#if !defined(DBUG_OFF)
+  if (init_thr_lock() || thd->store_globals() || simulate_error & (1<< thd_type))
+#else
   if (init_thr_lock() || thd->store_globals())
+#endif
   {
     thd->cleanup();
-    delete thd;
     DBUG_RETURN(-1);
   }
 
@@ -3515,6 +3525,7 @@ slave_begin:
 
   thd= new THD; // note that contructor of THD uses DBUG_ !
   THD_CHECK_SENTRY(thd);
+  mi->io_thd = thd;
 
   pthread_detach_this_thread();
   thd->thread_stack= (char*) &thd; // remember where our stack is
@@ -3525,7 +3536,6 @@ slave_begin:
     sql_print_error("Failed during slave I/O thread initialization");
     goto err;
   }
-  mi->io_thd = thd;
   pthread_mutex_lock(&LOCK_thread_count);
   threads.append(thd);
   pthread_mutex_unlock(&LOCK_thread_count);
@@ -3865,9 +3875,11 @@ slave_begin:
 
   thd = new THD; // note that contructor of THD uses DBUG_ !
   thd->thread_stack = (char*)&thd; // remember where our stack is
+  rli->sql_thd= thd;
   
   /* Inform waiting threads that slave has started */
   rli->slave_run_id++;
+  rli->slave_running = 1;
 
   pthread_detach_this_thread();
   if (init_slave_thread(thd, SLAVE_THD_SQL))
@@ -3882,7 +3894,6 @@ slave_begin:
     goto err;
   }
   thd->init_for_queries();
-  rli->sql_thd= thd;
   thd->temporary_tables = rli->save_temporary_tables; // restore temp tables
   pthread_mutex_lock(&LOCK_thread_count);
   threads.append(thd);
@@ -3895,7 +3906,6 @@ slave_begin:
     start receiving data so we realize we are not caught up and
     Seconds_Behind_Master grows. No big deal.
   */
-  rli->slave_running = 1;
   rli->abort_slave = 0;
   pthread_mutex_unlock(&rli->run_lock);
   pthread_cond_broadcast(&rli->start_cond);