linux-kernel - Re: [Xen-devel] [PATCH 2/9] xen/pciback: Return proper error code from sscanf.

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Date:	Fri, 30 Sep 2011 08:45:26 +0100
From:	"Jan Beulich" <JBeulich@...e.com>
To:	"Konrad Rzeszutek Wilk" <konrad.wilk@...cle.com>
Cc:	"Dan Carpenter" <error27@...il.com>,
	<xen-devel@...ts.xensource.com>, <linux-kernel@...r.kernel.org>
Subject: Re: [Xen-devel] [PATCH 2/9] xen/pciback: Return proper error
	 code from sscanf.

>>> On 29.09.11 at 21:52, Konrad Rzeszutek Wilk <konrad.wilk@...cle.com> wrote:
> . instead of just hardcoding it to be -EINVAL.
> 
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
> ---
>  drivers/xen/xen-pciback/pci_stub.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/xen/xen-pciback/pci_stub.c 
> b/drivers/xen/xen-pciback/pci_stub.c
> index 32d6891..d985b65 100644
> --- a/drivers/xen/xen-pciback/pci_stub.c
> +++ b/drivers/xen/xen-pciback/pci_stub.c
> @@ -868,7 +868,7 @@ static inline int str_to_slot(const char *buf, int 
> *domain, int *bus,
>  	if (err == 4)
>  		return 0;
>  	else if (err < 0)
> -		return -EINVAL;
> +		return err;
>  
>  	/* try again without domain */
>  	*domain = 0;

This should then also be done for the final return from the function:

	return err < 0 ? err : -EINVAL;

But: Where did you read that {v,}sscanf() would return -E... values in
hypothetical error cases? The C standard says it would return EOF
when reaching the end of the input string before doing the first
conversion; lib/vsprintf.c doesn't do so, and also doesn't say it might
return -E... codes. Bottom line is that I think the code is more correct
the way it is without this change.

Jan

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