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SubjectRe: [PATCH] tty: n_hdlc: Use flexible-array member
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On 1/21/20 09:14, Gustavo A. R. Silva wrote:
>
>
> On 1/21/20 09:00, Mikael Magnusson wrote:
>> Gustavo Silva wrote:
>>> On 1/20/20 23:54, Jiri Slaby wrote:
>>>> On 21. 01. 20, 0:45, Gustavo A. R. Silva wrote:
>>>>> diff --git a/drivers/tty/n_hdlc.c b/drivers/tty/n_hdlc.c
>>>>> index 98361acd3053..b5499ca8757e 100644
>>>>> --- a/drivers/tty/n_hdlc.c
>>>>> +++ b/drivers/tty/n_hdlc.c
>>>>> @@ -115,7 +115,7 @@
>>>>> struct n_hdlc_buf {
>>>>> struct list_head list_item;
>>>>> int count;
>>>>> - char buf[1];
>>>>> + char buf[];
>>>>> };
>>>>>
>>>>> #define N_HDLC_BUF_SIZE (sizeof(struct n_hdlc_buf) + maxframe)
>>>>
>>>> Have you checked, that you don't have to "+ 1" here now?
>>>>
>>>
>>> Yep. That's not necessary.
>>>
>>> _In terms of memory allocation_, zero-length/one-element arrays and flexible-array
>>> members work exactly the same way.
>>
>> This is not true, but maybe it's still not necessary in this particular code, I didn't examine it.
>>
>
> I should have said _in terms of dynamic memory allocation_.
>
> Your example is correct:
>
> "... a one-element array always occupies at least as much space as a single object of the type."[1]
>
> But the above does not affect on the current code.
>

Oh wait! Yeah; I see the issue in #define N_HDLC_BUF_SIZE (sizeof(struct n_hdlc_buf) + maxframe) now...

I need to double check this.

Thanks for the feedback!
--
Gustavo

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