The macro my_offsetof() performs pointer arithmetics that may be
undefined behavior. As reported in MDEV-26272, it may cause
clang -fsanitize=undefined to generate invalid memory references.

struct PFS_events_statements: Convert to std::is_standard_layout
by encapsulating the standard-layout struct PFS_events instead of
deriving from it, so that the standard macro offsetof() can be used.

PFS_events_statements::copy(): Renamed from copy_events_statements().
A cast to void* is now needed in memcpy() to avoid GCC -Wclass-memaccess
"writing to an object ... leaves 64 bytes unchanged".

There's no need for Debian to set config items to their
default. Left commented user, datadir and tmpdir as
these may want to be changed. lc-messages and skip-external-locks
are so infrequently set even listing them looks overly verbose.

socket left uncommented in [client-server] as various client
implementations may have different defaults compiled in.

MDEV-23805 simplified the treatment of empty tables during ALTER TABLE,
which could prevent the scenarios that were previously reported and
fixed as MDEV-16131 and MDEV-24730.

With the MDEV-23805 fix, the statement
SET DEBUG_SYNC = 'now WAIT_FOR copied';
could occasionally time out, depending on timing.
Apparently, there was a race condition where purge could resume
(and empty the table) before ALTER TABLE got the chance to execute.
We must prevent the purge of history from running before
ALTER TABLE has started executing.

fil_space_decrypt(): change signature to return status via dberr_t only.
Also replace impossible condition with an assertion and prove it via
test cases.

  This bug affected queries with two or more references to a CTE referring
another CTE if the definition of the latter contained an invocation of
a stored function that used a base table. The bug could lead to a bogus
error message or to an assertion failure.
  For any non-first reference to CTE cte1 With_element::clone_parsed_spec()
is called that parses the specification of cte1 to construct the unit
structure for this usage of cte1. If cte1 refers to another CTE cte2
outside of the specification of cte1 then With_element::clone_parsed_spec()
has to be called for cte2 as well. This call is made by the function
LEX::resolve_references_to_cte() within the invocation of the function
With_element::clone_parsed_spec() for cte1.
  When the specification of a CTE is parsed all table references encountered
in it must be added to the global list of table references for the query.
As the specification for the non-first usage of a CTE is parsed at a
recursive call of the parser the function With_element::clone_parsed_spec()
invoked at this recursive call should takes care of appending the list of
table references encountered in the specification of this CTE cte1 to the
list of table references created for the query. And it should do it after
the call of LEX::resolve_references_to_cte() that resolves references to
CTEs defined outside of the specification of cte1 because this call may
invoke the parser again for specifications of other CTEs and  the table
references from their specifications must ultimately appear in the global
list of table references of the query.
  The code of With_element::clone_parsed_spec() misplaced the call of
LEX::resolve_references_to_cte(). As a result LEX::query_tables_last used
for the query that was supposed to point to the field 'next_global' of the
last element in the global list of table references actually pointed to
'next_global' of the previous element.
  The above inconsistency certainly caused serious problems when table
references used in the stored functions invoked in cloned specifications
of CTEs were added to the global list of table references.

In commit 7ae21b18 (MDEV-12353)
the recovery of ROW_FORMAT=COMPRESSED tables was changed.
Changes would be logged in a physical format for the compressed
page image, so that the page need not be decompressed or compressed
during recovery.

page_zip_write_rec(): Log any update of the delete-mark flag in the
ROW_FORMAT=COMPRESSED page.

page_zip_dir_insert(): Copy the delete-mark flag. A delete-marked
record may be inserted by btr_cur_pessimistic_update() via
btr_cur_insert_if_possible(), page_cur_tuple_insert(),
page_cur_insert_rec_zip(). In the observed scenario, it was
an ROLLBACK. Presumably, the test case involved repeated DELETE
and INSERT of the same key, or updating a key back and forth.
This change alone might make the adjustment in page_zip_write_rec()
redundant, but we play it safe because we failed to create a
minimal test case for this scenario.

Rows_log_event::do_apply_event(): Correct the mistake that was made in
the merge 5f8561a6.

In Galera, the query cache will be invalidated near the end
of the function.

buf_flush_check_neighbors(): Relax a debug assertion that
could fail for the very last page(s) of a ROW_FORMAT=COMPRESSED tables          using a 1024-byte or 2048-byte page size.

This assertion started to fail after
commit d09426f9 (MDEV-26537)
modified the .ibd file extension to occur in steps of 4096 bytes.

reapply patch 96b472c0
It was not merged correctly into 10.5+

- In ha_innobase::prepare_inplace_alter_table(), InnoDB should
check whether the table is empty. If the table is empty then
server should avoid downgrading the MDL after prepare phase.
It is more like instant alter, does change only in dicationary
and metadata.

- Changed few debug test case to make non-empty DDL table

Upon investigation, decided this to be a compiler bug
(happens with new compiler, on code that did not change for the last 15 years)

Fixed by de-optimizing single function remove_key(), using MSVC pragma

Upon investigation, decided this to be a compiler bug
(happens with new compiler, on code that did not change for the last 15 years)

Fixed by de-optimizing single function remove_key(), using MSVC pragma

MDEV-26991: CURRENT_TEST: main.mysql_binary_zero_insert 'grep' is not recognized as an internal or external command, operable program or batch file.

Removed grep from mysqldump command stream and instead,
extend the search_file pattern to search for rows containing
binary zeros instead of any occurance of '00' in the input

If it is not enabled, build wsrep as static "stub" library from wsrep_dummy.cc
´

Allow static plugins to export symbols (on Unix)
wsrep_info relies on wsrep defined symbols (e.g  LOCK_wsrep_config_state)
exported from mysqld

Means, plugin will not be available in embedded, even if compiled-in

This reverts commit 1a3570de.

This reverts commit e45f7f48.

- Add unit test.

Code cleanup: Remove Json_writer::is_on_fmt_helper_call. We already
maintain this state in fmt_helper.

If it is not enabled, build wsrep as static "stub" library from wsrep_dummy.cc
´

Allow static plugins to export symbols (on Unix)
wsrep_info relies on wsrep defined symbols (e.g  LOCK_wsrep_config_state)
exported from mysqld

in test main.range_vs_index_merge one path requires named JSON object:
assert.c:0(.annobin_assert.c_end)[0x7fe9d2270a76]
sql/my_json_writer.cc:43(Json_writer::on_start_object())[0x555e284f048a]
sql/my_json_writer.cc:59(Json_writer::start_object())[0x555e284ee6e8]
sql/my_json_writer.h:377(Json_writer_object::Json_writer_object(THD*))[0x555e281dce11]
sql/opt_range.cc:5137(get_best_disjunct_quick(PARAM*, SEL_IMERGE*, double))[0x555e287c576b]
sql/opt_range.cc:5492(merge_same_index_scans(PARAM*, SEL_IMERGE*, TRP_INDEX_MERGE*, double))[0x555e287c6cf6]
sql/opt_range.cc:5287(get_best_disjunct_quick(PARAM*, SEL_IMERGE*, double))[0x555e287c607a]
sql/opt_range.cc:3000(SQL_SELECT::test_quick_select

another one requires unnamed JSON:
mariadbd: /home/name/server/sql/my_json_writer.cc:379: bool Single_line_formatting_helper::on_add_member(const char*, size_t): Assertion `state== INACTIVE || state ==
assert.c:0(.annobin_assert.c_end)[0x7f33d8df8a76]
sql/my_json_writer.cc:380(Single_line_formatting_helper::on_add_member(char const*, unsigned long))[0x558362f6a717]
sql/my_json_writer.cc:150(Json_writer::add_member(char const*, unsigned long))[0x558362f69a91]
sql/my_json_writer.cc:146(Json_writer::add_member(char const*))[0x558362f69a5f]
sql/my_json_writer.h:383(Json_writer_object::Json_writer_object(THD*, char const*))[0x558362ceccaa]
sql/opt_range.cc:5139(get_best_disjunct_quick(PARAM*, SEL_IMERGE*, double))[0x5583632407d0]
sql/opt_range.cc:3000(SQL_SELECT::test_quick_select