Re: [PATCH 05/12] genirq/debugfs: Replace strncmp with str_has_prefix

[Marc Zyngier <maz@kernel.org>]

On 30/07/2019 11:58, Chuhong Yuan wrote:
> Thomas Gleixner <tglx@linutronix.de> 于2019年7月30日周二 下午5:17写道：
>>
>> On Mon, 29 Jul 2019, Chuhong Yuan wrote:
>>
>>> strncmp(str, const, len) is error-prone.
>>> We had better use newly introduced
>>> str_has_prefix() instead of it.
>>
>> Can you please provide a proper explanation why the below strncmp() is
>> error prone?
>>
> 
> If the size is less than 7, for example, 2, then even if buf is "tr", the
> result will still be true. This is an error.
> strncmp(str, const, len) is error-prone mainly because the len is easy
> to be wrong.
> 
>> Just running a script and copying some boiler plate changelog saying
>> 'strncmp() is error prone' does not cut it.
>>
>>> -     if (!strncmp(buf, "trigger", size)) {
>>> +     if (str_has_prefix(buf, "trigger")) {
>>
>> Especially when the resulting code is not equivalent.
>>
> 
> I think here the semantic is the comparison should only return true
> when buf is "trigger".

Not quite. It will satisfy the condition for 't', 'tr', 'trig',
'trigger', and of course 'triggerthissillyinterruptwhichImdebugging'.

I agree that the semantic is a bit bizarre and maybe not quite expected,
but still... You seem to be changing the semantic without any
justification other than "this is safer".

Thanks,

	M.
-- 
Jazz is not dead, it just smells funny...