MDEV-24958 Server crashes in my_strtod ... with DEFAULT(blob)

Fixes also:
MDEV-24942 Server crashes in _ma_rec_pack... with DEFAULT() on BLOB

This was caused by two different bugs, both related to that the default
value for the blob was not calculated before it was used:
- There where now Item_default_value::..result() wrappers, which is
  needed as item in HAVING uses these.  This causes crashes when
  using a reference to a DEFAULT(blob_field) in HAVING. It also
  caused wrong results when used with other fields with default value
  expressions that are not constants.
- create_tmp_field() did not take into account that blob fields with
  default expressions are not yet initialized. Fixed by treating
  Item_default_value(blob) like a normal item expression.

1 files changed, 20 insertions, 0 deletions

diff --git a/mysql-test/main/having.test b/mysql-test/main/having.test
index 179af14559f..8b0cc244f51 100644
--- a/mysql-test/main/having.test
+++ b/mysql-test/main/having.test
@@ -890,3 +890,23 @@ SELECT t, next_seq_value() r FROM t1 FORCE INDEX(t)
 DROP TABLE t1;
 DROP FUNCTION next_seq_value;
 DROP TABLE series;
+
+--echo #
+--echo # MDEV-24958 Server crashes in my_strtod /
+--echo # Value_source::Converter_strntod::Converter_strntod with DEFAULT(blob)
+--echo #
+--echo # MDEV-24942 Server crashes in _ma_rec_pack / _ma_write_blob_record with
+--echo # DEFAULT() on BLOB
+--echo #
+
+CREATE TABLE t1 (id INT, f MEDIUMTEXT NOT NULL DEFAULT 'A');
+INSERT INTO t1 VALUES (1,'foo'),(2,'bar');
+SELECT f FROM t1 GROUP BY id ORDER BY DEFAULT(f);
+SELECT DEFAULT(f) AS h FROM t1 HAVING h > 5;
+SELECT DEFAULT(f) AS h FROM t1 HAVING h >= 0;
+SELECT DEFAULT(f) AS h FROM t1 HAVING h >= 'A';
+
+alter table t1 add column b int default (rand()+1+3);
+--replace_column 1 #
+select default(b) AS h FROM t1 HAVING h > "2";
+drop table t1;