Fixed BUG#14498: Stored procedures: hang if undefined variable and exception

  The problem was to continue at the right place in the code after the
  test expression in a flow control statement fails with an exception
  (internally, the test in sp_instr_jump_if_not), and the exception is
  caught by a continue handler. Execution must then be resumed after the
  the entire flow control statement (END IF, END WHILE, etc).


mysql-test/r/sp.result:
  New test case for BUG#14498.
mysql-test/t/sp.test:
  New test case for BUG#14498.
  (Note that one call is disabled at the moment. Depends on BUG#14643.)
sql/sp_head.cc:
  Added a continuation destination for sp_instr_jump_if_not, for the case when
  an error in the test expression causes a continue handler to catch.
  This includes new members in sp_instr_jump_if_not, adjustment of the optmizer
  (mark and move methods), and separate backpatching code (since we can't use
  the normal one for this).
  
  Also removed the class sp_instr_jump, since it's never used.
  
  ...and added some comments to the optimizer.
sql/sp_head.h:
  Added a continuation destination for sp_instr_jump_if_not, for the case when
  an error in the test expression causes a continue handler to catch.
  This includes new members in sp_instr_jump_if_not, adjustment of the optmizer
  (mark and move methods), and separate backpatching code (since we can't use
  the normal one for this).
  
  Also removed the class sp_instr_jump, since it's never used.
sql/sql_yacc.yy:
  Added backpatching of the continue destination for all conditional statements
  (using sp_instr_jump_if_not).

3 files changed, 138 insertions, 110 deletions

diff --git a/sql/sp_head.cc b/sql/sp_head.cc
index abc66ce0b21..7d3a708a5a8 100644
--- a/sql/sp_head.cc
+++ b/sql/sp_head.cc
@@ -437,13 +437,14 @@ sp_head::operator delete(void *ptr, size_t size)
 
 sp_head::sp_head()
   :Query_arena(&main_mem_root, INITIALIZED_FOR_SP),
-   m_flags(0), m_returns_cs(NULL)
+   m_flags(0), m_returns_cs(NULL), m_cont_level(0)
 {
   extern byte *
     sp_table_key(const byte *ptr, uint *plen, my_bool first);
   DBUG_ENTER("sp_head::sp_head");
 
   m_backpatch.empty();
+  m_cont_backpatch.empty();
   m_lex.empty();
   hash_init(&m_sptabs, system_charset_info, 0, 0, 0, sp_table_key, 0, 0);
   hash_init(&m_sroutines, system_charset_info, 0, 0, 0, sp_sroutine_key, 0, 0);
@@ -1569,6 +1570,39 @@ sp_head::check_backpatch(THD *thd)
 }
 
 void
+sp_head::new_cont_backpatch(sp_instr_jump_if_not *i)
+{
+  m_cont_level+= 1;
+  if (i)
+  {
+    /* Use the cont. destination slot to store the level */
+    i->m_cont_dest= m_cont_level;
+    (void)m_cont_backpatch.push_front(i);
+  }
+}
+
+void
+sp_head::add_cont_backpatch(sp_instr_jump_if_not *i)
+{
+  i->m_cont_dest= m_cont_level;
+  (void)m_cont_backpatch.push_front(i);
+}
+
+void
+sp_head::do_cont_backpatch()
+{
+  uint dest= instructions();
+  uint lev= m_cont_level--;
+  sp_instr_jump_if_not *i;
+
+  while ((i= m_cont_backpatch.head()) && i->m_cont_dest == lev)
+  {
+    i->m_cont_dest= dest;
+    (void)m_cont_backpatch.pop();
+  }
+}
+
+void
 sp_head::set_info(char *definer, uint definerlen,
 		  longlong created, longlong modified,
 		  st_sp_chistics *chistics, ulong sql_mode)
@@ -1782,7 +1816,10 @@ sp_head::show_create_function(THD *thd)
 
 
 /*
-  TODO: what does this do??
+  Do some minimal optimization of the code:
+    1) Mark used instructions
+       1.1) While doing this, shortcut jumps to jump instructions
+    2) Compact the code, removing unused instructions
 */
 
 void sp_head::optimize()
@@ -1805,7 +1842,7 @@ void sp_head::optimize()
     else
     {
       if (src != dst)
-      {
+      {                         // Move the instruction and update prev. jumps
 	sp_instr *ibp;
 	List_iterator_fast<sp_instr> li(bp);
 
@@ -1813,8 +1850,7 @@ void sp_head::optimize()
 	while ((ibp= li++))
 	{
 	  sp_instr_jump *ji= static_cast<sp_instr_jump *>(ibp);
-	  if (ji->m_dest == src)
-	    ji->m_dest= dst;
+          ji->set_destination(src, dst);
 	}
       }
       i->opt_move(dst, &bp);
@@ -2145,65 +2181,6 @@ sp_instr_jump::opt_move(uint dst, List<sp_instr> *bp)
 
 
 /*
-  sp_instr_jump_if class functions
-*/
-
-int
-sp_instr_jump_if::execute(THD *thd, uint *nextp)
-{
-  DBUG_ENTER("sp_instr_jump_if::execute");
-  DBUG_PRINT("info", ("destination: %u", m_dest));
-  DBUG_RETURN(m_lex_keeper.reset_lex_and_exec_core(thd, nextp, TRUE, this));
-}
-
-int
-sp_instr_jump_if::exec_core(THD *thd, uint *nextp)
-{
-  Item *it;
-  int res;
-
-  it= sp_prepare_func_item(thd, &m_expr);
-  if (!it)
-    res= -1;
-  else
-  {
-    res= 0;
-    if (it->val_bool())
-      *nextp = m_dest;
-    else
-      *nextp = m_ip+1;
-  }
-
-  return res;
-}
-
-void
-sp_instr_jump_if::print(String *str)
-{
-  str->reserve(12);
-  str->append("jump_if ");
-  str->qs_append(m_dest);
-  str->append(' ');
-  m_expr->print(str);
-}
-
-uint
-sp_instr_jump_if::opt_mark(sp_head *sp)
-{
-  sp_instr *i;
-
-  marked= 1;
-  if ((i= sp->get_instr(m_dest)))
-  {
-    m_dest= i->opt_shortcut_jump(sp, this);
-    m_optdest= sp->get_instr(m_dest);
-  }
-  sp->opt_mark(m_dest);
-  return m_ip+1;
-}
-
-
-/*
   sp_instr_jump_if_not class functions
 */
 
@@ -2224,7 +2201,10 @@ sp_instr_jump_if_not::exec_core(THD *thd, uint *nextp)
 
   it= sp_prepare_func_item(thd, &m_expr);
   if (! it)
+  {
     res= -1;
+    *nextp = m_cont_dest;
+  }
   else
   {
     res= 0;
@@ -2241,10 +2221,12 @@ sp_instr_jump_if_not::exec_core(THD *thd, uint *nextp)
 void
 sp_instr_jump_if_not::print(String *str)
 {
-  str->reserve(16);
+  str->reserve(24);
   str->append("jump_if_not ");
   str->qs_append(m_dest);
-  str->append(' ');
+  str->append('(');
+  str->qs_append(m_cont_dest);
+  str->append(") ");
   m_expr->print(str);
 }
 
@@ -2261,9 +2243,35 @@ sp_instr_jump_if_not::opt_mark(sp_head *sp)
     m_optdest= sp->get_instr(m_dest);
   }
   sp->opt_mark(m_dest);
+  if ((i= sp->get_instr(m_cont_dest)))
+  {
+    m_cont_dest= i->opt_shortcut_jump(sp, this);
+    m_cont_optdest= sp->get_instr(m_cont_dest);
+  }
+  sp->opt_mark(m_cont_dest);
   return m_ip+1;
 }
 
+void
+sp_instr_jump_if_not::opt_move(uint dst, List<sp_instr> *bp)
+{
+  /*
+    cont. destinations may point backwards after shortcutting jumps
+    during the mark phase. If it's still pointing forwards, only
+    push this for backpatching if sp_instr_jump::opt_move() will not
+    do it (i.e. if the m_dest points backwards).
+   */
+  if (m_cont_dest > m_ip)
+  {                             // Forward
+    if (m_dest < m_ip)
+      bp->push_back(this);
+  }
+  else if (m_cont_optdest)
+    m_cont_dest= m_cont_optdest->m_ip; // Backward
+  /* This will take care of m_dest and m_ip */
+  sp_instr_jump::opt_move(dst, bp);
+}
+
 
 /*
   sp_instr_freturn class functions
diff --git a/sql/sp_head.h b/sql/sp_head.h
index ed0f3987e01..e822ed96c02 100644
--- a/sql/sp_head.h
+++ b/sql/sp_head.h
@@ -38,6 +38,7 @@ sp_get_flags_for_command(LEX *lex);
 
 struct sp_label;
 class sp_instr;
+class sp_instr_jump_if_not;
 struct sp_cond_type;
 struct sp_pvar;
 
@@ -240,6 +241,18 @@ public:
   int
   check_backpatch(THD *thd);
 
+  // Start a new cont. backpatch level. If 'i' is NULL, the level is just incr.
+  void
+  new_cont_backpatch(sp_instr_jump_if_not *i);
+
+  // Add an instruction to the current level
+  void
+  add_cont_backpatch(sp_instr_jump_if_not *i);
+
+  // Backpatch (and pop) the current level to the current position.
+  void
+  do_cont_backpatch();
+
   char *name(uint *lenp = 0) const
   {
     if (lenp)
@@ -310,6 +323,18 @@ private:
   } bp_t;
   List<bp_t> m_backpatch;	// Instructions needing backpatching
   /*
+    We need a special list for backpatching of conditional jump's continue
+    destination (in the case of a continue handler catching an error in
+    the test), since it would otherwise interfere with the normal backpatch
+    mechanism - jump_if_not instructions have two different destination
+    which are to be patched differently.
+    Since these occur in a more restricted way (always the same "level" in
+    the code), we don't need the label.
+   */
+  List<sp_instr_jump_if_not> m_cont_backpatch;
+  uint m_cont_level;            // The current cont. backpatch level
+
+  /*
     Multi-set representing optimized list of tables to be locked by this
     routine. Does not include tables which are used by invoked routines.
 
@@ -622,50 +647,17 @@ public:
       m_dest= dest;
   }
 
-protected:
-
-  sp_instr *m_optdest;		// Used during optimization
-
-}; // class sp_instr_jump : public sp_instr
-
-
-class sp_instr_jump_if : public sp_instr_jump
-{
-  sp_instr_jump_if(const sp_instr_jump_if &); /* Prevent use of these */
-  void operator=(sp_instr_jump_if &);
-
-public:
-
-  sp_instr_jump_if(uint ip, sp_pcontext *ctx, Item *i, LEX *lex)
-    : sp_instr_jump(ip, ctx), m_expr(i), m_lex_keeper(lex, TRUE)
-  {}
-
-  sp_instr_jump_if(uint ip, sp_pcontext *ctx, Item *i, uint dest, LEX *lex)
-    : sp_instr_jump(ip, ctx, dest), m_expr(i), m_lex_keeper(lex, TRUE)
-  {}
-
-  virtual ~sp_instr_jump_if()
-  {}
-
-  virtual int execute(THD *thd, uint *nextp);
-
-  virtual int exec_core(THD *thd, uint *nextp);
-
-  virtual void print(String *str);
-
-  virtual uint opt_mark(sp_head *sp);
-
-  virtual uint opt_shortcut_jump(sp_head *sp, sp_instr *start)
+  virtual void set_destination(uint old_dest, uint new_dest)
   {
-    return m_ip;
+    if (m_dest == old_dest)
+      m_dest= new_dest;
   }
 
-private:
+protected:
 
-  Item *m_expr;			// The condition
-  sp_lex_keeper m_lex_keeper;
+  sp_instr *m_optdest;		// Used during optimization
 
-}; // class sp_instr_jump_if : public sp_instr_jump
+}; // class sp_instr_jump : public sp_instr
 
 
 class sp_instr_jump_if_not : public sp_instr_jump
@@ -675,12 +667,16 @@ class sp_instr_jump_if_not : public sp_instr_jump
 
 public:
 
+  uint m_cont_dest;             // Where continue handlers will go
+
   sp_instr_jump_if_not(uint ip, sp_pcontext *ctx, Item *i, LEX *lex)
-    : sp_instr_jump(ip, ctx), m_expr(i), m_lex_keeper(lex, TRUE)
+    : sp_instr_jump(ip, ctx), m_cont_dest(0), m_expr(i),
+      m_lex_keeper(lex, TRUE), m_cont_optdest(0)
   {}
 
   sp_instr_jump_if_not(uint ip, sp_pcontext *ctx, Item *i, uint dest, LEX *lex)
-    : sp_instr_jump(ip, ctx, dest), m_expr(i), m_lex_keeper(lex, TRUE)
+    : sp_instr_jump(ip, ctx, dest), m_cont_dest(0), m_expr(i),
+      m_lex_keeper(lex, TRUE), m_cont_optdest(0)
   {}
 
   virtual ~sp_instr_jump_if_not()
@@ -699,10 +695,20 @@ public:
     return m_ip;
   }
 
+  virtual void opt_move(uint dst, List<sp_instr> *ibp);
+
+  virtual void set_destination(uint old_dest, uint new_dest)
+  {
+    sp_instr_jump::set_destination(old_dest, new_dest);
+    if (m_cont_dest == old_dest)
+      m_cont_dest= new_dest;
+  }
+
 private:
 
   Item *m_expr;			// The condition
   sp_lex_keeper m_lex_keeper;
+  sp_instr *m_cont_optdest;     // Used during optimization
 
 }; // class sp_instr_jump_if_not : public sp_instr_jump
 
diff --git a/sql/sql_yacc.yy b/sql/sql_yacc.yy
index 109dcd7e86a..a93ac1e7061 100644
--- a/sql/sql_yacc.yy
+++ b/sql/sql_yacc.yy
@@ -2009,14 +2009,21 @@ sp_proc_stmt:
 	    }
 	    sp->restore_lex(YYTHD);
 	  }
-	| IF sp_if END IF {}
+        | IF
+          { Lex->sphead->new_cont_backpatch(NULL); }
+          sp_if END IF
+          { Lex->sphead->do_cont_backpatch(); }
 	| CASE_SYM WHEN_SYM
 	  {
 	    Lex->sphead->m_flags&= ~sp_head::IN_SIMPLE_CASE;
+            Lex->sphead->new_cont_backpatch(NULL);
 	  }
-	  sp_case END CASE_SYM {}
+          sp_case END CASE_SYM { Lex->sphead->do_cont_backpatch(); }
         | CASE_SYM
-          { Lex->sphead->reset_lex(YYTHD); }
+          {
+            Lex->sphead->reset_lex(YYTHD);
+            Lex->sphead->new_cont_backpatch(NULL);
+          }
           expr WHEN_SYM
 	  {
 	    /* We "fake" this by using an anonymous variable which we
@@ -2038,6 +2045,7 @@ sp_proc_stmt:
 	  sp_case END CASE_SYM
 	  {
 	    Lex->spcont->pop_pvar();
+            Lex->sphead->do_cont_backpatch();
 	  }
 	| sp_labeled_control
 	  {}
@@ -2306,6 +2314,7 @@ sp_if:
                                                                $2, lex);
 
 	    sp->push_backpatch(i, ctx->push_label((char *)"", 0));
+            sp->add_cont_backpatch(i);
             sp->add_instr(i);
             sp->restore_lex(YYTHD);
 	  }
@@ -2360,6 +2369,7 @@ sp_case:
               lex->variables_used= 1;
 	    }
 	    sp->push_backpatch(i, ctx->push_label((char *)"", 0));
+            sp->add_cont_backpatch(i);
             sp->add_instr(i);
             sp->restore_lex(YYTHD);
 	  }
@@ -2489,6 +2499,7 @@ sp_unlabeled_control:
 
 	    /* Jumping forward */
 	    sp->push_backpatch(i, lex->spcont->last_label());
+            sp->new_cont_backpatch(i);
             sp->add_instr(i);
             sp->restore_lex(YYTHD);
 	  }
@@ -2500,6 +2511,7 @@ sp_unlabeled_control:
 	    sp_instr_jump *i = new sp_instr_jump(ip, lex->spcont, lab->ip);
 
 	    lex->sphead->add_instr(i);
+            lex->sphead->do_cont_backpatch();
 	  }
         | REPEAT_SYM sp_proc_stmts1 UNTIL_SYM 
           { Lex->sphead->reset_lex(YYTHD); }
@@ -2513,6 +2525,8 @@ sp_unlabeled_control:
                                                                lex);
             lex->sphead->add_instr(i);
             lex->sphead->restore_lex(YYTHD);
+            /* We can shortcut the cont_backpatch here */
+            i->m_cont_dest= ip+1;
 	  }
 	;