Bug#28388217 - SERVER CAN FAIL WHILE REPLICATING CONDITIONAL COMMENTS

Cause: In case of version based condtional comments, if the condition evaluates to false, it is converted to a regular comment for replication by replacing "!" by " ". Nested comment in a conditional comment is replicated as is. Nested comments are supported only in case of conditional comments and when a the comment on slave is no more a conditional comment, the statement execution fails on the slave. Fix: Convert the nested comment, start from "/*" to "(*" and comment end from "*/" to "*)" for replication. Change-Id: I1a8e385a267b2370529eade094f0258fa96886c0

Author: Maheedhar PV

sql/sql_lex.cc

@@ -1,5 +1,5 @@
-/* Copyright (c) 2000, 2014, Oracle and/or its affiliates.
- Copyright (c) 2009, 2018, MariaDB Corporation
+/* Copyright (c) 2000, 2019, Oracle and/or its affiliates.
+ Copyright (c) 2009, 2020, MariaDB Corporation
 
  This program is free software; you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
@@ -940,17 +940,27 @@ static inline uint int_token(const char *str,uint length)
 */
 bool consume_comment(Lex_input_stream *lip, int remaining_recursions_permitted)
 {
+ // only one level of nested comments are allowed
+ DBUG_ASSERT(remaining_recursions_permitted == 0 ||
+ remaining_recursions_permitted == 1);
  reg1 uchar c;
  while (! lip->eof())
  {
  c= lip->yyGet();
 
- if (remaining_recursions_permitted > 0)
+ if (remaining_recursions_permitted == 1)
  {
  if ((c == '/') && (lip->yyPeek() == '*'))
  {
+ lip->yyUnput('('); // Replace nested "/*..." with "(*..."
+ lip->yySkip(); // and skip "("
+
  lip->yySkip(); /* Eat asterisk */
- consume_comment(lip, remaining_recursions_permitted-1);
+ if (consume_comment(lip, 0))
+ return true;
+
+ lip->yyUnput(')'); // Replace "...*/" with "...*)"
+ lip->yySkip(); // and skip ")"
  continue;
  }
  }