[#MDEV-21361] +d,-d may break consistent state of DEBUG

There're few issues around using +d,-d with the intent to increment and restore the former
state of DEBUG_DBUG variable.
In particular when +d, keyword adds the very first keyword and by thus activates the state
for the specified keyword the following -d,keyword does remove the keyword but leaves the active state for everything, including pollution of the server error log.

ommit 0b9400d1f54f4ae9b84decf53352850171880f1e

Author: Thayumanavar <thayumanavar.x.sachithanantha@oracle.com>

Date:   Thu May 2 16:22:57 2013 +0530

    BUG#11765644: DEBUG 'D' LIST SHOULD STAY EMPTY AFTER SET

                  DEBUG="+D,<SYMBOL>"

    PROBLEM AND FIX:

    When the debug 'd' flag has been set to empty, then all

    DBUG_ macros are enabled. But if one then sets debug="

    +d,foo" then only foo, all others are turned off. The

    expected/intended behaviour should be to add debug for

    'symbol' in addition to whatever was enabled before.

    The fix adds keyword to the stack of active keyword list

    if debug was not enabled for all symbols. Also turn debug

    off if the last keyword is removed from the stack of

    keywords. NOTE: This shall require a change in the docs

    to reflect the changed behaviour in this bug

[MDEV-21361] +d,-d may break consistent state of DEBUG_DBUG Created: 2019-12-19 Updated: 2022-09-23
Status:	Open
Project:	MariaDB Server
Component/s:	None
Affects Version/s:	None
Fix Version/s:	10.2

[MDEV-21361] +d,-d may break consistent state of DEBUG_DBUG Created: 2019-12-19 Updated: 2022-09-23