MDEV-32249 strings/ctype-ucs2.c:2336: my_vsnprintf_utf32: Assertion `(n % 4)...

MDEV-32249 strings/ctype-ucs2.c:2336: my_vsnprintf_utf32: Assertion `(n % 4) == 0' failed in my_vsnprintf_utf32 on INSERT

The crash inside my_vsnprintf_utf32() happened correctly,
because the caller methods:
  Field_string::sql_rpl_type()
  Field_varstring::sql_rpl_type()
mis-used the charset library and sent pure ASCII data to the
virtual function snprintf() of a utf32 CHARSET_INFO.

It was wrong to use Field::charset() in sql_rpl_type().
We're printing the metadata (the data type) here, not the column data.
The string contraining the data type of a CHAR/VARCHAR column
is a pure ASCII string.

Fixing to use res->charset() to print, like all virtual implementations
of sql_type() do.

Review was done by Andrei Elkin.
Thanks to Andrei for proposing MTR test improvents.

mysql-test/suite/rpl/r/rpl_row_utf32.result

@@ -19,6 +19,64 @@ connection master;
 INSERT INTO t1(c1) VALUES ('insert into t1');
 DROP TABLE t1;
 connection slave;
+#
+# MDEV-32249 strings/ctype-ucs2.c:2336: my_vsnprintf_utf32: Assertion `(n
+#
+#
+# Testing with VARCHAR
+#
+connection slave;
+include/stop_slave.inc
+SET GLOBAL SLAVE_TYPE_CONVERSIONS= '';
+include/start_slave.inc
+connection master;
+CREATE TABLE t1 (a INT);
+connection slave;
+ALTER TABLE t1 MODIFY a VARCHAR(1) CHARACTER SET utf32;
+connection master;
+INSERT INTO t1 VALUES (1);
+connection slave;
+include/wait_for_slave_sql_error.inc [errno=1677]
+SHOW CREATE TABLE t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `a` varchar(1) CHARACTER SET utf32 COLLATE utf32_general_ci DEFAULT NULL
+) ENGINE=MyISAM DEFAULT CHARSET=latin1 COLLATE=latin1_swedish_ci
+SELECT * FROM t1 ORDER BY a;
+a
+SET GLOBAL SQL_SLAVE_SKIP_COUNTER = 1;
+START SLAVE;
+connection master;
+DROP TABLE t1;
+connection slave;
+#
+# Testing with CHAR
+#
+connection slave;
+include/stop_slave.inc
+SET GLOBAL SLAVE_TYPE_CONVERSIONS= '';
+include/start_slave.inc
+connection master;
+CREATE TABLE t1 (a INT);
+connection slave;
+ALTER TABLE t1 MODIFY a CHAR(1) CHARACTER SET utf32;
+connection master;
+INSERT INTO t1 VALUES (1);
+connection slave;
+include/wait_for_slave_sql_error.inc [errno=1677]
+SHOW CREATE TABLE t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `a` char(1) CHARACTER SET utf32 COLLATE utf32_general_ci DEFAULT NULL
+) ENGINE=MyISAM DEFAULT CHARSET=latin1 COLLATE=latin1_swedish_ci
+SELECT * FROM t1 ORDER BY a;
+a
+SET GLOBAL SQL_SLAVE_SKIP_COUNTER = 1;
+START SLAVE;
+connection master;
+DROP TABLE t1;
+connection slave;
+connection slave;
 SET GLOBAL SLAVE_TYPE_CONVERSIONS= @saved_slave_type_conversions;
 include/stop_slave.inc
 include/start_slave.inc

mysql-test/suite/rpl/t/rpl_row_utf32.test

@@ -34,10 +34,78 @@ DROP TABLE t1;
 
 --sync_slave_with_master
 
+--echo #
+--echo # MDEV-32249 strings/ctype-ucs2.c:2336: my_vsnprintf_utf32: Assertion `(n
+--echo #
+
+--echo #
+--echo # Testing with VARCHAR
+--echo #
+
+-- connection slave
+-- source include/stop_slave.inc
+SET GLOBAL SLAVE_TYPE_CONVERSIONS= '';
+-- source include/start_slave.inc
+
+--connection master
+CREATE TABLE t1 (a INT);
+
+--sync_slave_with_master
+ALTER TABLE t1 MODIFY a VARCHAR(1) CHARACTER SET utf32;
+
+--connection master
+INSERT INTO t1 VALUES (1);
+
+--connection slave
+# ER_SLAVE_CONVERSION_FAILED
+--let $slave_sql_errno= 1677
+--source include/wait_for_slave_sql_error.inc
+SHOW CREATE TABLE t1;
+SELECT * FROM t1 ORDER BY a;
+SET GLOBAL SQL_SLAVE_SKIP_COUNTER = 1;
+START SLAVE;
+
+--connection master
+DROP TABLE t1;
+--sync_slave_with_master
+
+--echo #
+--echo # Testing with CHAR
+--echo #
+
+-- connection slave
+-- source include/stop_slave.inc
+SET GLOBAL SLAVE_TYPE_CONVERSIONS= '';
+-- source include/start_slave.inc
+
+--connection master
+CREATE TABLE t1 (a INT);
+
+--sync_slave_with_master
+ALTER TABLE t1 MODIFY a CHAR(1) CHARACTER SET utf32;
+
+--connection master
+INSERT INTO t1 VALUES (1);
+
+--connection slave
+# ER_SLAVE_CONVERSION_FAILED
+--let $slave_sql_errno= 1677
+--source include/wait_for_slave_sql_error.inc
+SHOW CREATE TABLE t1;
+SELECT * FROM t1 ORDER BY a;
+SET GLOBAL SQL_SLAVE_SKIP_COUNTER = 1;
+START SLAVE;
+
+--connection master
+DROP TABLE t1;
+--sync_slave_with_master
+
+
 # assertion: the slave woul hit an/several assertions:
 #            before and during slave conversion procedure
 #            Now that is fixed, it wont.
 
+-- connection slave
 SET GLOBAL SLAVE_TYPE_CONVERSIONS= @saved_slave_type_conversions;
 -- source include/stop_slave.inc
 -- source include/start_slave.inc

sql/field.cc

@@ -7487,9 +7487,10 @@ void Field_string::sql_type(String &res) const
 */
 void Field_string::sql_rpl_type(String *res) const
 {
-  CHARSET_INFO *cs=charset();
   if (Field_string::has_charset())
   {
+    CHARSET_INFO *cs= res->charset();
+    DBUG_ASSERT(cs->mbminlen == 1);
     size_t length= cs->cset->snprintf(cs, (char*) res->ptr(),
                                       res->alloced_length(),
                                       "char(%u octets) character set %s",
@@ -7978,9 +7979,10 @@ void Field_varstring::sql_type(String &res) const
 */
 void Field_varstring::sql_rpl_type(String *res) const
 {
-  CHARSET_INFO *cs=charset();
   if (Field_varstring::has_charset())
   {
+    CHARSET_INFO *cs= res->charset();
+    DBUG_ASSERT(cs->mbminlen == 1);
     size_t length= cs->cset->snprintf(cs, (char*) res->ptr(),
                                       res->alloced_length(),
                                       "varchar(%u octets) character set %s",