MDEV-26186 280 Bytes lost in mysys/array.c, mysys/hash.c, sql/sp.cc,...

MDEV-26186 280 Bytes lost in mysys/array.c, mysys/hash.c, sql/sp.cc, sql/sp.cc, sql/item_create.cc, sql/item_create.cc, sql/sql_yacc.yy:10748 when using oracle sql_mode

There was a memory leak under these conditions:
- YYABORT was called in the end-of-rule action of a rule containing expr_lex
- This expr_lex was not bound to any sp_lex_keeper

Bison did not call %destructor <expr_lex> in this case, because its stack
already contained a reduced upper-level rule.

Fixing rules starting with RETURN, CONTINUE, EXIT keywords:

Turning end-of-rule actions with YYABORT into mid-rule actions
by adding an empty trailing { } block. This prevents the upper level
rule from being reduced without calling %destructor <expr_lex>.

In other rules expr_lex is used not immediately before the last
end-of-rule { } block, so they don't need changes.

mysql-test/suite/compat/oracle/r/sp-memory-leak.result

+#
+# Start of 10.5 tests
+#
+#
+# MDEV-26186 280 Bytes lost in mysys/array.c, mysys/hash.c, sql/sp.cc, sql/sp.cc, sql/item_create.cc, sql/item_create.cc, sql/sql_yacc.yy:10748 when using oracle sql_mode
+#
+SET sql_mode= 'oracle';
+BEGIN CONTINUE WHEN f0();
+ERROR 42000: CONTINUE with no matching label: 
+SET sql_mode= 'oracle';
+BEGIN CONTINUE label WHEN f0();
+ERROR 42000: CONTINUE with no matching label: label
+SET sql_mode= 'oracle';
+BEGIN EXIT WHEN f0();
+ERROR 42000: EXIT with no matching label: 
+SET sql_mode= 'oracle';
+BEGIN EXIT label WHEN f0();
+ERROR 42000: EXIT with no matching label: label
+SET sql_mode= 'oracle';
+WHILE f(8)<1 DO SELECT 1;;
+ERROR 42000: You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near 'DO SELECT 1' at line 1
+SET sql_mode= 'oracle';
+BEGIN DECLARE CONTINUE HANDLER FOR SQLEXCEPTION RETURN f0();
+ERROR 42000: RETURN is only allowed in a FUNCTION
+#
+# End of 10.5 tests
+#

mysql-test/suite/compat/oracle/t/sp-memory-leak.test

+--echo #
+--echo # Start of 10.5 tests
+--echo #
+
+--echo #
+--echo # MDEV-26186 280 Bytes lost in mysys/array.c, mysys/hash.c, sql/sp.cc, sql/sp.cc, sql/item_create.cc, sql/item_create.cc, sql/sql_yacc.yy:10748 when using oracle sql_mode
+--echo #
+
+SET sql_mode= 'oracle';
+--error ER_SP_LILABEL_MISMATCH
+BEGIN CONTINUE WHEN f0();
+
+SET sql_mode= 'oracle';
+--error ER_SP_LILABEL_MISMATCH
+BEGIN CONTINUE label WHEN f0();
+
+SET sql_mode= 'oracle';
+--error ER_SP_LILABEL_MISMATCH
+BEGIN EXIT WHEN f0();
+
+SET sql_mode= 'oracle';
+--error ER_SP_LILABEL_MISMATCH
+BEGIN EXIT label WHEN f0();
+
+SET sql_mode= 'oracle';
+--error ER_PARSE_ERROR
+--query WHILE f(8)<1 DO SELECT 1;
+
+SET sql_mode= 'oracle';
+--error ER_SP_BADRETURN
+BEGIN DECLARE CONTINUE HANDLER FOR SQLEXCEPTION RETURN f0();
+
+--echo #
+--echo # End of 10.5 tests
+--echo #

sql/sql_yacc.yy

@@ -1526,6 +1526,43 @@ bool my_yyoverflow(short **a, YYSTYPE **b, size_t *yystacksize);
     delete $$;
 } <expr_lex>
 
+
+/*
+
+// COMMENT_FOR_DESCTRUCTOR:
+//
+// %destructor is only invoked if the rule parsing fails in the middle.
+// If we call YYABORT from the last code block %destructor is not called,
+// because Bison's stack already contains the reduced upper level rule.
+// If we need to invoke the %destructor after the YYABORT in the last code
+// block, we have to add another dummy empty end-of-rule action {} at the end.
+
+// So to have a %destructor work properly with YYABORT,
+// make sure to turn a grammar like this:
+
+rule:
+        KEYWORD expr_lex
+        {
+          if (condition) // End-of-rule action
+            YYABORT;
+        }
+        ;
+
+// into:
+
+rule:
+        KEYWORD expr_lex
+        {
+          if (condition) // This is now a mid-rule action
+            YYABORT;
+        }
+        {
+          // A dummy empty end-of-rule action.
+        }
+        ;
+*/
+
+
 %type <assignment_lex>
         assignment_source_lex
         assignment_source_expr
@@ -3731,6 +3768,7 @@ sp_proc_stmt_return:
                                                           $2->get_item(), $2)))
               MYSQL_YYABORT;
           }
+          { /* See the comment 'COMMENT_FOR_DESCTRUCTOR' near %destructor */ }
         | RETURN_ORACLE_SYM
           {
             LEX *lex= Lex;
@@ -3757,11 +3795,13 @@ sp_proc_stmt_exit_oracle:
             if (unlikely($3->sp_exit_statement(thd, $3->get_item())))
               MYSQL_YYABORT;
           }
+          { /* See the comment 'COMMENT_FOR_DESCTRUCTOR' near %destructor */ }
         | EXIT_ORACLE_SYM label_ident WHEN_SYM expr_lex
           {
             if (unlikely($4->sp_exit_statement(thd, &$2, $4->get_item())))
               MYSQL_YYABORT;
           }
+          { /* See the comment 'COMMENT_FOR_DESCTRUCTOR' near %destructor */ }
         ;
 
 sp_proc_stmt_continue_oracle:
@@ -3780,11 +3820,13 @@ sp_proc_stmt_continue_oracle:
             if (unlikely($3->sp_continue_when_statement(thd)))
               MYSQL_YYABORT;
           }
+          { /* See the comment 'COMMENT_FOR_DESCTRUCTOR' near %destructor */ }
         | CONTINUE_ORACLE_SYM label_ident WHEN_SYM expr_lex
           {
             if (unlikely($4->sp_continue_when_statement(thd, &$2)))
               MYSQL_YYABORT;
           }
+          { /* See the comment 'COMMENT_FOR_DESCTRUCTOR' near %destructor */ }
         ;