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From: Keith Thompson <Keith.S.Thompson+u@gmail.com>
Newsgroups: comp.lang.c
Subject: Re: Buffer contents well-defined after fgets() reaches EOF ?
Date: Tue, 11 Feb 2025 13:59:33 -0800
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James Kuyper <jameskuyper@alumni.caltech.edu> writes:
> On 2/10/25 23:54, Lawrence D'Oliveiro wrote:
>> On Mon, 10 Feb 2025 22:33:03 -0500, James Kuyper wrote:
> ...
>>> "The fgets function reads at most one less than the number of characters
>>> specified by n from the stream pointed to by stream into the array
>>> pointed to by s." (7.32.7.2p2)
>>>
>>> If the buffer length is 1, "at most one less than the number ...
>>> specified" is 0. Therefore, fgets() cannot read any characters into the
>>> buffer, no matter what the contents of the input stream are. Again,
>>> since there is no "last byte read into the array", there is no location
>>> where a null byte should be written.
>> 
>> Have you tried it? I have.
>
> I just tried it, using gcc  and found that fgets() does set the first
> byte of the buffer to a null character. Therefore, it doesn't conform to
> the requirements of the standard. That's not particularly surprising -
> calling fgets with useless arguments isn't something that I'd expect to
> be a high priority on their pre-delivery tests.

As you know, gcc doesn't implement fgets().  Were you using GNU libc?

-- 
Keith Thompson (The_Other_Keith) Keith.S.Thompson+u@gmail.com
void Void(void) { Void(); } /* The recursive call of the void */