MDEV-26110: Do not rely on alignment on static allocation

It is implementation-defined whether alignment requirements
that are larger than std::max_align_t (typically 8 or 16 bytes)
will be honored by the compiler and linker.

It turns out that on IBM AIX, both alignas() and MY_ALIGNED()
only guarantees alignment up to 16 bytes.

For some data structures, specifying alignment to the CPU
cache line size (typically 64 or 128 bytes) is a mere performance
optimization, and we do not really care whether the requested
alignment is guaranteed.

But, for the correct operation of direct I/O, we do require that
the buffers be aligned at a block size boundary.

field_ref_zero: Define as a pointer, not an array.
For innochecksum, we can make this point to unaligned memory;
for anything else, we will allocate an aligned buffer from the heap.
This buffer will be used for overwriting freed data pages when
innodb_immediate_scrub_data_uncompressed=ON. And exactly that code
hit an assertion failure on AIX, in the test innodb.innodb_scrub.

log_sys.checkpoint_buf: Define as a pointer to aligned memory
that is allocated from heap.

log_t::file::write_header_durable(): Reuse log_sys.checkpoint_buf
instead of trying to allocate an aligned buffer from the stack.

1 files changed, 1 insertions, 1 deletions

diff --git a/storage/innobase/row/row0ins.cc b/storage/innobase/row/row0ins.cc
index 4b1926c0ec0..96cc3aa413e 100644
--- a/storage/innobase/row/row0ins.cc
+++ b/storage/innobase/row/row0ins.cc
@@ -3424,7 +3424,7 @@ row_ins_index_entry_set_vals(
 				field->len = UNIV_SQL_NULL;
 				field->type.prtype = DATA_BINARY_TYPE;
 			} else {
-				ut_ad(col->len <= sizeof field_ref_zero);
+				ut_ad(col->len <= UNIV_PAGE_SIZE_MAX);
 				ut_ad(ind_field->fixed_len <= col->len);
 				dfield_set_data(field, field_ref_zero,
 						ind_field->fixed_len);