[PATCH 7/9] drivers/rtc: correct error-handling code

[PATCH 7/9] drivers/rtc: correct error-handling code

[Julia Lawall]

From: Julia Lawall <julia@diku.dk>

This code is not executed before ds1307->rtc has been successfully
initialized to the result of calling rtc_device_register.  Thus the test
that ds1307->rtc is not NULL is always true.

A simplified version of the semantic match that finds this problem is as
follows: (http://coccinelle.lip6.fr/)

// <smpl>
@match exists@
expression x, E;
statement S1, S2;
@@

x = rtc_device_register(...)
... when != x = E
(
*  if (x == NULL || ...) S1 else S2
|
*  if (x == NULL && ...) S1 else S2
)
// </smpl>

Signed-off-by: Julia Lawall <julia@diku.dk>

---
 drivers/rtc/rtc-ds1307.c            |    3 +--
 1 files changed, 1 insertions(+), 2 deletions(-)

diff --git a/drivers/rtc/rtc-ds1307.c b/drivers/rtc/rtc-ds1307.c
index 47a93c0..eb99ee4 100644
--- a/drivers/rtc/rtc-ds1307.c
+++ b/drivers/rtc/rtc-ds1307.c
@@ -896,8 +896,7 @@ read_rtc:
 	return 0;
 
 exit_irq:
-	if (ds1307->rtc)
-		rtc_device_unregister(ds1307->rtc);
+	rtc_device_unregister(ds1307->rtc);
 exit_free:
 	kfree(ds1307);
 	return err;

Re: [rtc-linux] [PATCH 7/9] drivers/rtc: correct error-handling code

[Wolfram Sang]

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On Tue, Jul 28, 2009 at 05:55:33PM +0200, Julia Lawall wrote:
> 
> From: Julia Lawall <julia@diku.dk>
> 
> This code is not executed before ds1307->rtc has been successfully
> initialized to the result of calling rtc_device_register.  Thus the test
> that ds1307->rtc is not NULL is always true.
> 
> A simplified version of the semantic match that finds this problem is as
> follows: (http://coccinelle.lip6.fr/)
> 
> // <smpl>
> @match exists@
> expression x, E;
> statement S1, S2;
> @@
> 
> x = rtc_device_register(...)
> ... when != x = E
> (
> *  if (x == NULL || ...) S1 else S2
> |
> *  if (x == NULL && ...) S1 else S2
> )
> // </smpl>
> 
> Signed-off-by: Julia Lawall <julia@diku.dk>

Acked-by: Wolfram Sang <w.sang@pengutronix.de>

-- 
Pengutronix e.K.                           | Wolfram Sang                |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |

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