linux-kernel - Re: [PATCH] tty/serial: Fix uninitialized variable warning

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Date:	Sun, 03 Mar 2013 21:36:53 -0500
From:	Peter Hurley <peter@...leysoftware.com>
To:	Grant Likely <grant.likely@...retlab.ca>
Cc:	linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH] tty/serial: Fix uninitialized variable warning

On Mon, 2013-03-04 at 09:35 +0800, Grant Likely wrote:
> drivers/tty/serial/8250/8250.c: In function 'serial_unlink_irq_chain':
> drivers/tty/serial/8250/8250.c:1676:19: warning: 'i' may be used uninitialized in this function
> 
> There isn't an actual bug here since the function tests the condition
> that would cause i to be uninitialized before dereferencing i. However,
> at least some versions of GCC complain as shown above. (in my case,
> powerpc gcc 2.5.2). Initializing i to NULL makes it clear to GCC and the
> casual code reviewer that i will not be dereferenced to a random
> address.
> 
> Signed-off-by: Grant Likely <grant.likely@...retlab.ca>
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> ---
> Greg, some may argue that this is a tool problem, not a kernel problem,
> but it is useful to me. If anyone objects I'm not going to spend any
> time championing for this patch.
> 
> g.
> 
>  drivers/tty/serial/8250/8250.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/tty/serial/8250/8250.c b/drivers/tty/serial/8250/8250.c
> index 0efc815..cbbedcf 100644
> --- a/drivers/tty/serial/8250/8250.c
> +++ b/drivers/tty/serial/8250/8250.c
> @@ -1673,7 +1673,7 @@ static int serial_link_irq_chain(struct uart_8250_port *up)
>  
>  static void serial_unlink_irq_chain(struct uart_8250_port *up)
>  {
> -	struct irq_info *i;
> +	struct irq_info *i = NULL;

struct irq_info *uninitialized_var(i);

For gcc, the uninitialized_var() #define is in
include/linux/compiler-gcc.h

Regards,
Peter Hurley


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