Thanks to Varun Gupta for suggesting this. This seems to
make main.innodb_ext_key,off more stable.

Invoking memcpy() on a NULL pointer is undefined behaviour
(even if the length is 0) and gives the compiler permission to
assume that the pointer is nonnull. Recent versions of GCC
(starting with version 8) are more aggressively optimizing away
checks for NULL pointers. This undefined behaviour would cause
a SIGSEGV in the test main.func_encrypt on an optimized debug build
on GCC 10.2.0.

This regression was introduced in
commit afc9d00c.
This is a partial backport of
commit 199863d7 from 10.4.

 MDEV-24033: SIGSEGV in __memcmp_avx2_movbe from queue_insert | SIGSEGV in __memcmp_avx2_movbe from native_compare

The issue here was the system variable max_sort_length was being applied
to decimals and it was truncating the value for decimals to the number
of bytes set by max_sort_length.
This was leading to a buffer overflow as the values were written
to the buffer without truncation and then we moved the offset to
the number of bytes(set by max_sort_length), that are needed for comparison.

The fix is to not apply max_sort_length for fixed size types like INT,
DECIMALS and only apply max_sort_length for CHAR, VARCHARS, TEXT and
BLOBS.

Also, revert the work-around for the test that was attempted in
commit 85613a32.

This issue was caught by MemorySanitizer as well as on the
Microsoft Windows debug builds, thanks to /MD being used
starting with 10.4.

The code fix will also be applied to 10.2 because the regression
was introduced in commit afc9d00c.

Test itself is not deterministic.

Disable galera_var_replicate_myisam until fixed on 10.4

Use 9 byte (min length packet)

This bug was already fixed in a previous commit.
Added test case from the MDEV to prove it's fixed.

The crash happens because a double free in the case CREATE TABLE fails
because there is a conflicting tables on disk.

Fixed by ensuring that the double free can't happen.

On my system, OpenSuse, I got a compilation error that some arguments
to getgrouplist() where not initialized

For some reason, in the test main,innodb_ext_key,off
we frequently get unexpected EXPLAIN output, in particular
on Microsoft Windows debug builders. Let us comment out that
EXPLAIN statement for now.

The problem was that opt_sum_query() was, as part of MIN/MAX optimization,
doing read operations on constant tables that where already closed

Fixed by ensuring we don't try to read from tables that are closed.

Additional case for PS protocol: UPDATE is converted to multi-update
in mysql_multi_update_prepare().

and restore the test modified in the same commit
(the non-replication related deadlock will be reported separately)

Implement a different fix for
"MDEV-19232: Floating point precision / value comparison problem"

Instead of truncating decimal values after every division,
truncate them for comparison purposes.

This reverts commit 62d73df6 but keeps the test.

followup for 3e807d25 and eae10a87

In case of direct execution(stmtid=-1, mariadb_stmt_execute_direct in C
API) application is in control of how many parameters client sends to
the server. In case this number is not equal to actual query parameters
number, the server may start to interprete packet data incorrectly, e.g.
starting from the size of null bitmap. And that could cause it to crash
at some point. The commit introduces some additional COM_STMT_EXECUTE
packet sanity checks:
- checking that "types sent" byte is set, and the value is equal to 1.
  if it's not direct execution, then that value is 0 or 1.
- checking that parameter type value is a valid type, and parameter
  flags value is 0 or only "unsigned" bit is set
- added more checks that read does not go beyond the end of the packet

mariabackup deallocated uninitialized
write_filt_ctxt.u.wf_incremental_ctxt in xtrabackup_copy_datafile() when
some table should be skipped due to parsed DDL redo log record.

An assertion inadvertently contained an assignment and an implicit
comparison to zero. The intention was to test equality.

Tighten access control - deny FILE_CREATE_PIPE_INSTANCE permission to
everyone except current user (the one that runs mysqld)

Old SDK is missing #define SECURITY_MAX_SID_STRING_CHARACTERS

Remove unnecessary condition and add necessary include
for non debug Galera library.

A wsrep transaction was started for EXECUTE IMMEDIATE, which
caused assertion failure when the executed statement was
CREATE TABLE which should be executed in TOI mode.

As a fix, don't start wsrep transaction for EXECUTE IMMEDIATE
to let the wsrep state logic to be handled from inside stored
procedure codepath.
Reviewed-by: Jan Lindström <jan.lindstrom@mariadb.com>