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Before this fix, the parser would accept illegal code in SQL exceptions handlers, that later causes the runtime to crash when executing the code, due to memory violations in the exception handler stack. The root cause of the problem is instructions within an exception handler that jumps to code located outside of the handler. This is illegal according to the SQL 2003 standard, since labels located outside the handler are not supposed to be visible (they are "out of scope"), so any instruction that jumps to these labels, like ITERATE or LEAVE, should not parse. The section of the standard that is relevant for this is : SQL:2003 SQL/PSM (ISO/IEC 9075-4:2003) section 13.1 <compound statement>, syntax rule 4 <quote> The scope of the <beginning label> is CS excluding every <SQL schema statement> contained in CS and excluding every <local handler declaration list> contained in CS. <beginning label> shall not be equivalent to any other <beginning label>s within that scope. </quote> With this fix, the C++ class sp_pcontext, which represent the "parsing context" tree (a.k.a symbol table) of a stored procedure, has been changed as follows: - constructors have been cleaned up, so that only building a root node for the tree is public; building nodes inside a tree is not public. - a new member, m_label_scope, indicates if a given syntactic context belongs to a DECLARE HANDLER block, - label resolution, in the method find_label(), has been changed to implement the restriction of scope regarding labels used in a compound statement. The actions in the parser, when parsing the body of a SQL exception handler, have been changed as follows: - the implementation of an exception handler (DECLARE HANDLER) now creates explicitly a new sp_pcontext, to isolate the code inside the handler from the containing compound statement context. - registering exception handlers as a result occurs in the parent context, see the rule sp_hcond_element - the code in sp_hcond_list has been cleaned up, to avoid code duplication In addition, the flags IN_SIMPLE_CASE and IN_HANDLER, declared in sp_head.h have been removed, since they are unused and broken by design (as seen with Bug 19194 (Right recursion in parser for CASE causes excessive stack usage, limitation), representing a stack in a single flag is not possible. Tests in sp-error have been added to show that illegal constructs are now rejected. Tests in sp have been added for code coverage, to show that ITERATE or LEAVE statements are legal when jumping to a label in scope, inside the body of an exception handler.
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