MWL#180: Fix bug where setting @@global.binlog_checksum did not actually change the value.

mysql-test/suite/rpl/r/rpl_checksum.result

@@ -27,13 +27,22 @@ show binary logs;
 Log_name	File_size
 master-bin.000001	#
 set @@global.binlog_checksum = NONE;
+select @@global.binlog_checksum;
+@@global.binlog_checksum
+NONE
 *** must be rotations seen ***
 show binary logs;
 Log_name	File_size
 master-bin.000001	#
 master-bin.000002	#
 set @@global.binlog_checksum = default;
+select @@global.binlog_checksum;
+@@global.binlog_checksum
+NONE
 set @@global.binlog_checksum = CRC32;
+select @@global.binlog_checksum;
+@@global.binlog_checksum
+CRC32
 set @@global.binlog_checksum = CRC32;
 set @@global.master_verify_checksum = 0;
 set @@global.master_verify_checksum = default;

mysql-test/suite/rpl/t/rpl_checksum.test

@@ -40,13 +40,16 @@ connection master;
 
 source include/show_binary_logs.inc;
 set @@global.binlog_checksum = NONE;
+select @@global.binlog_checksum;
 --echo  *** must be rotations seen ***
 source include/show_binary_logs.inc;
 
 set @@global.binlog_checksum = default;
+select @@global.binlog_checksum;
 
 # testing lack of side-effects in non-effective update of binlog_checksum:
 set @@global.binlog_checksum = CRC32;
+select @@global.binlog_checksum;
 set @@global.binlog_checksum = CRC32; 
 
 set @@global.master_verify_checksum = 0;

sql/log.cc

@@ -6994,7 +6994,7 @@ static void
 binlog_checksum_update(MYSQL_THD thd, struct st_mysql_sys_var *var,
                        void *var_ptr, const void *save)
 {
-  ulong value=  *((ulong *)var_ptr);
+  ulong value=  *((ulong *)save);
 
   pthread_mutex_lock(mysql_bin_log.get_log_lock());
   if(mysql_bin_log.is_open())