Fixed BUG#3294: Stored procedure crash if table dropped before use.

Dropping the table was not the real problem, the problem was with errors
  occuring within error handlers.


mysql-test/r/sp-error.result:
  New test case for BUG#3294.
mysql-test/t/sp-error.test:
  New test case for BUG#3294.
sql/sp_head.cc:
  Use hreturn instruction both for continue and exit handlers (a special case
  of a jump).
sql/sp_head.h:
  Use hreturn instruction both for continue and exit handlers (a special case
  of a jump).
sql/sp_rcontext.cc:
  Keep track on if we're in a handler already, for error handling.
sql/sp_rcontext.h:
  Keep track on if we're in a handler already, for error handling.
sql/sql_yacc.yy:
  Use hreturn instruction both for continue and exit handlers (a special case
  of a jump).

mysql-test/r/sp-error.result

@@ -485,4 +485,13 @@ create procedure bug4344() drop procedure bug4344|
 ERROR HY000: Can't drop a PROCEDURE from within another stored routine
 create procedure bug4344() drop function bug4344|
 ERROR HY000: Can't drop a FUNCTION from within another stored routine
+drop procedure if exists bug3294|
+create procedure bug3294()
+begin
+declare continue handler for sqlexception drop table t5;
+drop table t5;
+end|
+call bug3294()|
+ERROR 42S02: Unknown table 't5'
+drop procedure bug3294|
 drop table t1|

mysql-test/t/sp-error.test

@@ -5,7 +5,7 @@
 # Make sure we don't have any procedures left.
 delete from mysql.proc;
 
-# A test "global" procedures, i.e. not belonging to any database.
+# A test of "global" procedures, i.e. not belonging to any database.
 create function .f1() returns int return 1;
 create procedure .p1() select 1, database();
 create procedure p1() select 2, database();
@@ -650,6 +650,22 @@ create procedure bug4344() drop procedure bug4344|
 --error 1357
 create procedure bug4344() drop function bug4344|
 
+#
+# BUG#3294: Stored procedure crash if table dropped before use
+# (Actually, when an error occurs within an error handler.)
+--disable_warnings
+drop procedure if exists bug3294|
+--enable_warnings
+create procedure bug3294()
+begin
+  declare continue handler for sqlexception drop table t5;
+  drop table t5;
+end|
+
+--error 1051
+call bug3294()|
+drop procedure bug3294|
+
 
 drop table t1|
 

sql/sp_head.cc

@@ -499,6 +499,7 @@ sp_head::execute(THD *thd)
 	ip= hip;
 	ret= 0;
 	ctx->clear_handler();
+	ctx->in_handler= TRUE;
 	continue;
       }
     }
@@ -1586,19 +1587,40 @@ int
 sp_instr_hreturn::execute(THD *thd, uint *nextp)
 {
   DBUG_ENTER("sp_instr_hreturn::execute");
-  thd->spcont->restore_variables(m_frame);
+  if (m_dest)
-  *nextp= thd->spcont->pop_hstack();
+    *nextp= m_dest;
+  else
+  {
+    thd->spcont->restore_variables(m_frame);
+    *nextp= thd->spcont->pop_hstack();
+  }
+  thd->spcont->in_handler= FALSE;
   DBUG_RETURN(0);
 }
 
 void
 sp_instr_hreturn::print(String *str)
 {
-  str->reserve(12);
+  str->reserve(16);
   str->append("hreturn ");
   str->qs_append(m_frame);
+  if (m_dest)
+    str->qs_append(m_dest);
 }
 
+uint
+sp_instr_hreturn::opt_mark(sp_head *sp)
+{
+  if (m_dest)
+    return sp_instr_jump::opt_mark(sp);
+  else
+  {
+    marked= 1;
+    return UINT_MAX;
+  }
+}
+
+
 //
 // sp_instr_cpush
 //

sql/sp_head.h

@@ -677,7 +677,7 @@ private:
 }; // class sp_instr_hpop : public sp_instr
 
 
-class sp_instr_hreturn : public sp_instr
+class sp_instr_hreturn : public sp_instr_jump
 {
   sp_instr_hreturn(const sp_instr_hreturn &);	/* Prevent use of these */
   void operator=(sp_instr_hreturn &);
@@ -685,7 +685,7 @@ class sp_instr_hreturn : public sp_instr
 public:
 
   sp_instr_hreturn(uint ip, sp_pcontext *ctx, uint fp)
-    : sp_instr(ip, ctx), m_frame(fp)
+    : sp_instr_jump(ip, ctx), m_frame(fp)
   {}
 
   virtual ~sp_instr_hreturn()
@@ -695,11 +695,7 @@ public:
 
   virtual void print(String *str);
 
-  virtual uint opt_mark(sp_head *sp)
+  virtual uint opt_mark(sp_head *sp);
-  {
-    marked= 1;
-    return UINT_MAX;
-  }
 
 private:
 

sql/sp_rcontext.cc

@@ -32,6 +32,7 @@ sp_rcontext::sp_rcontext(uint fsize, uint hmax, uint cmax)
   : m_count(0), m_fsize(fsize), m_result(NULL), m_hcount(0), m_hsp(0),
     m_hfound(-1), m_ccount(0)
 {
+  in_handler= FALSE;
   m_frame= (Item **)sql_alloc(fsize * sizeof(Item*));
   m_outs= (int *)sql_alloc(fsize * sizeof(int));
   m_handler= (sp_handler_t *)sql_alloc(hmax * sizeof(sp_handler_t));
@@ -58,6 +59,8 @@ sp_rcontext::set_item_eval(uint idx, Item *i, enum_field_types type)
 int
 sp_rcontext::find_handler(uint sql_errno)
 {
+  if (in_handler)
+    return 0;			// Already executing a handler
   if (m_hfound >= 0)
     return 1;			// Already got one
 

sql/sp_rcontext.h

@@ -46,6 +46,8 @@ class sp_rcontext : public Sql_alloc
 
  public:
 
+  bool in_handler;
+
   sp_rcontext(uint fsize, uint hmax, uint cmax);
 
   ~sp_rcontext()

sql/sql_yacc.yy

@@ -1599,13 +1599,17 @@ sp_decl:
 	    sp_head *sp= lex->sphead;
 	    sp_pcontext *ctx= lex->spcont;
 	    sp_label_t *hlab= lex->spcont->pop_label(); /* After this hdlr */
+	    sp_instr_hreturn *i;
 
 	    if ($2 == SP_HANDLER_CONTINUE)
-	      sp->add_instr(new sp_instr_hreturn(sp->instructions(), ctx,
+	    {
-	                                         ctx->current_pvars()));
+	      i= new sp_instr_hreturn(sp->instructions(), ctx,
+	                              ctx->current_pvars());
+	      sp->add_instr(i);
+	    }
 	    else
 	    {  /* EXIT or UNDO handler, just jump to the end of the block */
-	      sp_instr_jump *i= new sp_instr_jump(sp->instructions(), ctx);
+	      i= new sp_instr_hreturn(sp->instructions(), ctx, 0);
 
 	      sp->add_instr(i);
 	      sp->push_backpatch(i, lex->spcont->last_label()); /* Block end */