SET @old_debug = @@GLOBAL.debug;
set debug= 'T';
select @@debug;
@@debug
T
set debug= '+P';
select @@debug;
@@debug
P:T
set debug= '-P';
select @@debug;
@@debug
T
#
# Bug #52629: memory leak from sys_var_thd_dbug in 
#  binlog.binlog_write_error
#
SET GLOBAL debug='d,injecting_fault_writing';
SELECT @@global.debug;
@@global.debug
d,injecting_fault_writing
SET GLOBAL debug='';
SELECT @@global.debug;
@@global.debug

SET GLOBAL debug=@old_debug;
#
# Bug #56709: Memory leaks at running the 5.1 test suite
# 
SET @old_local_debug = @@debug;
SET @@debug='d,foo';
SELECT @@debug;
@@debug
d,foo
SET @@debug='';
SELECT @@debug;
@@debug

SET @@debug = @old_local_debug;
End of 5.1 tests