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From: Andreas Schwab <schwab@suse.de>
To: Florian Weimer <fweimer@redhat.com>
Cc: libc-alpha@sourceware.org
Subject: Re: [review] manual: Clarify strnlen, wcsnlen, strndup null termination behavior
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Date: Wed, 30 Oct 2019 11:00:00 -0000
In-Reply-To: <87a79i33kt.fsf@oldenburg2.str.redhat.com> (Florian Weimer's
	message of "Wed, 30 Oct 2019 11:55:30 +0100")
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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.

Andreas.

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