From 405bd2af117384e009c3feffe1fd7d9019bf9d2b Mon Sep 17 00:00:00 2001
From: Gleb Shchepa <gshchepa@mysql.com>
Date: Mon, 18 May 2009 09:21:25 +0500
Subject: Bug #44768: SIGFPE crash when selecting rand from a view containing
null
The RAND(N) function where the N is a field of "constant" table
(table of single row) failed with a SIGFPE.
Evaluation of RAND(N) rely on constant status of its argument.
Current server "seeded" random value for each constant argument
only once, in the Item_func_rand::fix_fields method.
Then the server skipped a call to seed_random() in the
Item_func_rand::val_real method for such constant arguments.
However, non-constant state of an argument may be changed
after the call to fix_fields, if an argument is a field of
"constant" table. Thus, pre-initialization of random value
in the fix_fields method is too early.
Initialization of random value by seed_random() has been
removed from Item_func_rand::fix_fields method.
The Item_func_rand::val_real method has been modified to
call seed_random() on the first evaluation of this method
if an argument is a function.
mysql-test/r/func_math.result:
Added test case for bug #44768.
mysql-test/t/func_math.test:
Added test case for bug #44768.
sql/item_func.cc:
Bug #44768: SIGFPE crash when selecting rand from a view containing null
1. Initialization of random value by seed_random() has been
removed from Item_func_rand::fix_fields method.
2. The Item_func_rand::val_real method has been modified to
call seed_random() on the first evaluation of this method
if an argument is a function.
sql/item_func.h:
Bug #44768: SIGFPE crash when selecting rand from a view containing null
1. The Item_func_rand::first_eval has been added to trace
the first evaluation of the val_real method.
2. The Item_func_rand::cleanup method has been added to
cleanup the first_eval flag.
---
sql/item_func.h | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
(limited to 'sql/item_func.h')
diff --git a/sql/item_func.h b/sql/item_func.h
index 147dfcc9d36..e512c94efc1 100644
--- a/sql/item_func.h
+++ b/sql/item_func.h
@@ -696,14 +696,16 @@ public:
class Item_func_rand :public Item_real_func
{
struct rand_struct *rand;
+ bool first_eval; // TRUE if val_real() is called 1st time
public:
- Item_func_rand(Item *a) :Item_real_func(a), rand(0) {}
+ Item_func_rand(Item *a) :Item_real_func(a), rand(0), first_eval(TRUE) {}
Item_func_rand() :Item_real_func() {}
double val_real();
const char *func_name() const { return "rand"; }
bool const_item() const { return 0; }
void update_used_tables();
bool fix_fields(THD *thd, Item **ref);
+ void cleanup() { first_eval= TRUE; Item_real_func::cleanup(); }
private:
void seed_random (Item * val);
};
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