LP #1582761: memory leak in mysqlbinlog

**Reported in Launchpad by Laurynas Biveinis last update 23-05-2016 09:08:57

This is a copy of https://bugs.mysql.com/bug.php?id=78223:

rpl.rpl_row_mysqlbinlog 'row' [ fail ]
...
=================================================================
==3018==ERROR: LeakSanitizer: detected memory leaks

Direct leak of 88 byte(s) in 1 object(s) allocated from:
#0 0x7f573942c54a in malloc (/usr/lib/x86_64-linux-gnu/libasan.so.2+0x9854a)
#1 0x4b63a8 in my_malloc /home/laurynas/mysql-server/mysys/my_malloc.c:38
#2 0x426229 in Log_event::operator new(unsigned long) /home/laurynas/mysql-server/sql/log_event.h:1071
#3 0x426229 in Log_event::read_log_event(char const*, unsigned int, char const*, Format_description_log_event const) /home/laurynas/mysql-server/sql/log_event.cc:1300
#4 0x42d855 in dump_remote_log_entries /home/laurynas/mysql-server/client/mysqlbinlog.cc:1844
#5 0x42d855 in dump_log_entries /home/laurynas/mysql-server/client/mysqlbinlog.cc:1685
#6 0x42e8aa in main /home/laurynas/mysql-server/client/mysqlbinlog.cc:2354
#7 0x7f573853f82f in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x2082f)

Indirect leak of 18 byte(s) in 1 object(s) allocated from:
#0 0x7f573942c54a in malloc (/usr/lib/x86_64-linux-gnu/libasan.so.2+0x9854a)
#1 0x4b63a8 in my_malloc /home/laurynas/mysql-server/mysys/my_malloc.c:38
#2 0x4b6aa8 in my_strndup /home/laurynas/mysql-server/mysys/my_malloc.c:161
#3 0x41dd7e in Rotate_log_event::Rotate_log_event(char const*, unsigned int, Format_description_log_event const*) /home/laurynas/mysql-server/sql/log_event.cc:5299
#4 0x426240 in Log_event::read_log_event(char const*, unsigned int, char const*, Format_description_log_event const) /home/laurynas/mysql-server/sql/log_event.cc:1300
#5 0x42d855 in dump_remote_log_entries /home/laurynas/mysql-server/client/mysqlbinlog.cc:1844
#6 0x42d855 in dump_log_entries /home/laurynas/mysql-server/client/mysqlbinlog.cc:1685
#7 0x42e8aa in main /home/laurynas/mysql-server/client/mysqlbinlog.cc:2354
#8 0x7f573853f82f in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x2082f)

Fixed in 5.7 by

commit 6772eb52d666bfc11b52b1c99e27bd7d96874f01
Author: Andrei Elkin <andrei.elkin@oracle.com>
Date: Fri Dec 11 17:14:06 2015 +0200

Bug#21697461 MEMORY LEAK IN MYSQLBINLOG

*Problem description*

At running mtr with a recently introduced --valgrind-clients
instances of not deallocated memory were revealed along the following
execution path:

Rotate_log_event::Rotate_log_event() -> ...
inary_log::Rotate_event::Rotate_event() ->
bapi_strndup() -> ... my_raw_malloc

The reason is turned down to be missed 'delete' for fake
(as defined by ev->when == 0) Rotate event
in case binlog is read from a running server (remote dumping).

*Fixed*

with calling the delete operator in proper places where
the fake Rotate event becomes out of interest at once after its reading,
that is its handling skips process_event().

That's done with care to clear the event's temp_buf.