Backport from mysql-trunk of:

------------------------------------------------------------
revno: 3258
committer: Jon Olav Hauglid <jon.hauglid@oracle.com>
branch nick: mysql-trunk-bug12663165
timestamp: Thu 2011-07-14 10:05:12 +0200
message:
  Bug#12663165 SP DEAD CODE REMOVAL DOESN'T UNDERSTAND CONTINUE HANDLERS
  
  When stored routines are loaded, a simple optimizer tries to locate
  and remove dead code. The problem was that this dead code removal
  did not work correctly with CONTINUE handlers.
  
  If a statement triggers a CONTINUE handler, the following statement
  will be executed after the handler statement has completed. This
  means that the following statement is not dead code even if the
  previous statement unconditionally alters control flow. This fact
  was lost on the dead code removal routine, which ended up with
  removing instructions that could have been executed. This could
  then lead to assertions, crashes and generally bad behavior when
  the stored routine was executed.
  
  This patch fixes the problem by marking as live code all stored
  routine instructions that are in the same scope as a CONTINUE handler.
  
  Test case added to sp.test.

mysql-test/r/sp.result

@@ -7087,6 +7087,26 @@ COUNT(DISTINCT d)
 2
 DROP FUNCTION f1;
 DROP TABLE t1, t2;
+#
+# Bug#12663165 SP DEAD CODE REMOVAL DOESN'T UNDERSTAND CONTINUE HANDLERS
+#
+DROP FUNCTION IF EXISTS f1;
+CREATE FUNCTION f1() RETURNS INT
+BEGIN
+DECLARE CONTINUE HANDLER FOR SQLEXCEPTION BEGIN END;
+BEGIN
+DECLARE CONTINUE HANDLER FOR SQLEXCEPTION RETURN f1();
+BEGIN
+DECLARE CONTINUE HANDLER FOR SQLEXCEPTION RETURN f1();
+RETURN f1();
+END;
+END;
+RETURN 1;
+END $
+SELECT f1();
+f1()
+1
+DROP FUNCTION f1;
 # ------------------------------------------------------------------
 # -- End of 5.1 tests
 # ------------------------------------------------------------------

mysql-test/t/sp.test

@@ -8397,6 +8397,35 @@ DROP FUNCTION f1;
 DROP TABLE t1, t2;
 
 
+--echo #
+--echo # Bug#12663165 SP DEAD CODE REMOVAL DOESN'T UNDERSTAND CONTINUE HANDLERS
+--echo #
+
+--disable_warnings
+DROP FUNCTION IF EXISTS f1;
+--enable_warnings
+
+delimiter $;
+CREATE FUNCTION f1() RETURNS INT
+BEGIN
+  DECLARE CONTINUE HANDLER FOR SQLEXCEPTION BEGIN END;
+  BEGIN
+    DECLARE CONTINUE HANDLER FOR SQLEXCEPTION RETURN f1();
+    BEGIN
+     DECLARE CONTINUE HANDLER FOR SQLEXCEPTION RETURN f1();
+     RETURN f1();
+    END;
+  END;
+RETURN 1;
+END $ 
+delimiter ;$
+
+# This used to cause an assertion.
+SELECT f1();
+
+DROP FUNCTION f1;
+
+
 --echo # ------------------------------------------------------------------
 --echo # -- End of 5.1 tests
 --echo # ------------------------------------------------------------------

sql/sp_head.cc

@@ -3356,6 +3356,23 @@ sp_instr_hpush_jump::opt_mark(sp_head *sp, List<sp_instr> *leads)
     m_optdest= sp->get_instr(m_dest);
   }
   sp->add_mark_lead(m_dest, leads);
+
+  /*
+    For continue handlers, all instructions in the scope of the handler
+    are possible leads. For example, the instruction after freturn might
+    be executed if the freturn triggers the condition handled by the
+    continue handler.
+
+    m_dest marks the start of the handler scope. It's added as a lead
+    above, so we start on m_dest+1 here.
+    m_opt_hpop is the hpop marking the end of the handler scope.
+  */
+  if (m_type == SP_HANDLER_CONTINUE)
+  {
+    for (uint scope_ip= m_dest+1; scope_ip <= m_opt_hpop; scope_ip++)
+      sp->add_mark_lead(scope_ip, leads);
+  }
+
   return m_ip+1;
 }
 

sql/sp_head.h

@@ -1000,7 +1000,7 @@ class sp_instr_hpush_jump : public sp_instr_jump
 public:
 
   sp_instr_hpush_jump(uint ip, sp_pcontext *ctx, int htype, uint fp)
-    : sp_instr_jump(ip, ctx), m_type(htype), m_frame(fp)
+    : sp_instr_jump(ip, ctx), m_type(htype), m_frame(fp), m_opt_hpop(0)
   {
     m_cond.empty();
   }
@@ -1022,6 +1022,15 @@ public:
     return m_ip;
   }
 
+  virtual void backpatch(uint dest, sp_pcontext *dst_ctx)
+  {
+    DBUG_ASSERT(!m_dest || !m_opt_hpop);
+    if (!m_dest)
+      m_dest= dest;
+    else
+      m_opt_hpop= dest;
+  }
+
   inline void add_condition(struct sp_cond_type *cond)
   {
     m_cond.push_front(cond);
@@ -1031,6 +1040,7 @@ private:
 
   int m_type;			///< Handler type
   uint m_frame;
+  uint m_opt_hpop;              // hpop marking end of handler scope.
   List<struct sp_cond_type> m_cond;
 
 }; // class sp_instr_hpush_jump : public sp_instr_jump

sql/sql_yacc.yy

@@ -2532,9 +2532,15 @@ sp_decl:
             sp_instr_hpush_jump *i=
               new sp_instr_hpush_jump(sp->instructions(), ctx, $2,
 	                              ctx->current_var_count());
-            if (i == NULL ||
-	        sp->add_instr(i) ||
-                sp->push_backpatch(i, ctx->push_label((char *)"", 0)))
+            if (i == NULL || sp->add_instr(i))
+              MYSQL_YYABORT;
+
+            /* For continue handlers, mark end of handler scope. */
+            if ($2 == SP_HANDLER_CONTINUE &&
+                sp->push_backpatch(i, ctx->last_label()))
+              MYSQL_YYABORT;
+
+            if (sp->push_backpatch(i, ctx->push_label(empty_c_string, 0)))
               MYSQL_YYABORT;
           }
           sp_hcond_list sp_proc_stmt