0d3720c12a
The parser works as follows:
The rule expr_lex returns a pointer to a newly created sp_expr_lex
instance which is not linked to any MariaDB structures yet - it is
pointed only from a Bison stack variable. The sp_expr_lex instance
gets linked to other structures (such as sp_instr_jump_if_not) later,
after scanning some following grammar.
Problem before the fix:
If a parse error happened immediately after expr_lex (before it got linked),
the created sp_expr_lex value got lost causing a memory leak.
Fix:
- Using Bison's "destructor" directive to free the results of expr_lex
on parse/oom errors.
- Moving the call for LEX::cleanup_lex_after_parse_error() from
MYSQL_YYABORT and yyerror inside parse_sql().
This is needed because Bison calls destructors after yyerror(),
while it's important to delete the sp_expr_lex instance before
LEX::cleanup_lex_after_parse_error().
The latter frees the memory root containing the sp_expr_lex instance.
After this change the code block are executed in the following order:
- yyerror() -- now only raises the error to DA (no cleanup done any more)
- %destructor { delete $$; } <expr_lex> -- destructs the sp_expr_lex instance
- LEX::cleanup_lex_after_parse_error() -- frees the memory root containing
the sp_expr_lex instance
- Removing the "delete sublex" related code from restore_lex():
- restore_lex() is called in most cases on success, when delete is not needed.
- There is one place when restore_lex() is called on error:
In sp_create_assignment_instr(). But in this case LEX::sp_lex_in_use
is true anyway.
The patch adds a new DBUG_ASSERT(lex->sp_lex_in_use) to guard this.
Code status:
ci.appveyor.com
MariaDB: The open source relational database
MariaDB was designed as a drop-in replacement of MySQL(R) with more features, new storage engines, fewer bugs, and better performance.
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https://mariadb.com/kb/en/mariadb-vs-mysql-features/
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https://mariadb.com/kb/en/new-and-old-releases/
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