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From: James Kuyper <jameskuyper@alumni.caltech.edu>
Newsgroups: comp.lang.c
Subject: Re: Buffer contents well-defined after fgets() reaches EOF ?
Date: Tue, 11 Feb 2025 13:07:53 -0500
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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.