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Re: [review] manual: Clarify strnlen, wcsnlen, strndup null termination behavior


On Okt 30 2019, Florian Weimer wrote:

> * Andreas Schwab:
>
>> On Okt 30 2019, Florian Weimer wrote:
>>
>>> * Andreas Schwab:
>>>
>>>> On Okt 30 2019, Florian Weimer (Code Review) wrote:
>>>>
>>>>> +Note that @var{s} must be an array of at least @var{maxlen} bytes.  It
>>>>> +is undefined to call @code{strnlen} on a shorter array, even if it is
>>>>> +known that the shorter array contains a null terminator.
>>>>
>>>> This is not true.  strnlen _always_ stops before the null byte.
>>>
>>> This is not how it is specified in POSIX.
>>
>> Yes, it is.
>>
>>     The strnlen() function shall return the number of bytes preceding
>>     the first null byte in the array to which s points, if s contains a
>>     null byte within the first maxlen bytes; otherwise, it shall return
>>     maxlen.
>>
>> There is nothing undefined here.  Your interpretation would be
>> completely useless anyway.
>
> It says “array”

Yes, because a null terminator is not required.

> But it does NOT say that reading stops after the first null terminator.

Yes, it does, see above.  Otherwise it doesn't make sense.

Andreas.

-- 
Andreas Schwab, SUSE Labs, schwab@suse.de
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