linux-kernel - Re: [PATCH 4/4] tracing/filters: Fix MATCH_EBD

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Message-ID: <4B258FF2.3070600@cn.fujitsu.com>
Date:	Mon, 14 Dec 2009 09:08:02 +0800
From:	Li Zefan <lizf@...fujitsu.com>
To:	rostedt@...dmis.org
CC:	Ingo Molnar <mingo@...e.hu>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Wenji Huang <wenji.huang@...cle.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/4] tracing/filters: Fix MATCH_EBD_ONLY filter matching

>>  static int regex_match_end(char *str, struct regex *r, int len)
>>  {
>> -	char *ptr = strstr(str, r->pattern);
>> +	int strlen = len - 1;
>>  
>> -	if (ptr && (ptr[r->len] == 0))
>> +	if (strlen >= r->len &&
>> +	    !memcmp(str + strlen - r->len, r->pattern, r->len))
> 
> Please use memcmp() == 0, I've seen too many bugs with !*cmp as well as
> with *cmp, because humans tend to think instinctively when reading this
> that ! is not a match. With "== 0" we think that "==" is a match and
>  "!=" is a miss.
> 

Though I sometimes don't care much about this, I do
think memcmp() == 0 is better.

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