linux-kernel - Re: [tpmdd-devel] [PATCH 1/2] tpm/tpm_ppi: Do not compare strcmp(a, b) == -1

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Date:	Wed, 30 Oct 2013 10:45:35 -0600
From:	Jason Gunthorpe <jgunthorpe@...idianresearch.com>
To:	Peter Huewe <peterhuewe@....de>
Cc:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	Rajiv Andrade <mail@...jiv.net>,
	tpmdd-devel@...ts.sourceforge.net,
	Xiaoyan Zhang <xiaoyan.zhang@...el.com>,
	Gang Wei <gang.wei@...el.com>
Subject: Re: [tpmdd-devel] [PATCH 1/2] tpm/tpm_ppi: Do not compare strcmp(a,
 b) == -1

On Wed, Oct 30, 2013 at 01:40:27AM +0100, Peter Huewe wrote:
> strcmp does return the difference between two strings not only -1,0,1
> consequently
>  if (strcmp (a,b) == -1)
> might lead to taking the wrong branch
> 
> -> compare with <= instead.

I've always thought this was the preferred idiom:

cmp(a,b) == 0
cmp(a,b) < 0
cmp(a,b) > 0

As the operator matches what is actually happening in all cases.

'>= -1' doesn't mean a >= b.

Regards,
Jason
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