MDEV-19252 Problem with DBUG_ASSERT_AS_PRINTF and marked_for_write()

Problem was that DBUG_FIX_WRITE_SET was not enabled when using
DBUG_ASSERT_AS_PRINTF

mysql-test/main/unique.result

+CREATE TABLE t2 (n BLOB, UNIQUE(n));
+INSERT INTO t2 VALUES (1);
+DELETE FROM t2 WHERE n = 1;
+DROP TABLE t2;

mysql-test/main/unique.test

+--source include/have_innodb.inc
+
+#
+# MDEV-19252 Warning about assertion failure marked_for_write_or_computed()
+# printed by release build with DBUG_ASSERT_AS_PRINTF, but no failure on debug
+# build
+#
+
+CREATE TABLE t2 (n BLOB, UNIQUE(n));
+INSERT INTO t2 VALUES (1);
+DELETE FROM t2 WHERE n = 1;
+DROP TABLE t2;

sql/field.cc

@@ -67,14 +67,19 @@ inline bool Field::marked_for_read() const
           ptr < table->record[0] + table->s->reclength)));
 }
 
+/*
+  The name of this function is a bit missleading as in 10.4 we don't
+  have to test anymore if the field is computed. Instead we mark
+  changed fields with DBUG_FIX_WRITE_SET() in table.cc
+*/
 
 inline bool Field::marked_for_write_or_computed() const
 {
-  return is_stat_field || !table ||
-         (!table->write_set ||
-          bitmap_is_set(table->write_set, field_index) ||
-          (!(ptr >= table->record[0] &&
-          ptr < table->record[0] + table->s->reclength)));
+  return (is_stat_field || !table ||
+          (!table->write_set ||
+           bitmap_is_set(table->write_set, field_index) ||
+           (!(ptr >= table->record[0] &&
+              ptr < table->record[0] + table->s->reclength))));
 }
 
 

sql/table.cc

@@ -8080,10 +8080,10 @@ class Turn_errors_to_warnings_handler : public Internal_error_handler
 
 
 /*
-  to satisfy ASSERT_COLUMN_MARKED_FOR_WRITE Field's assert we temporarily
+  to satisfy marked_for_write_or_computed() Field's assert we temporarily
   mark field for write before storing the generated value in it
 */
-#ifndef DBUG_OFF
+#ifdef DBUG_ASSERT_EXISTS
 #define DBUG_FIX_WRITE_SET(f) bool _write_set_fixed= !bitmap_fast_test_and_set(write_set, (f)->field_index)
 #define DBUG_RESTORE_WRITE_SET(f) if (_write_set_fixed) bitmap_clear_bit(write_set, (f)->field_index)
 #else