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From: Janis Papanagnou <janis_papanagnou+ng@hotmail.com>
Newsgroups: comp.lang.c
Subject: Re: Whaddaya think?
Date: Mon, 17 Jun 2024 09:35:07 +0200
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On 17.06.2024 08:29, Keith Thompson wrote:
> Janis Papanagnou <janis_papanagnou+ng@hotmail.com> writes:
>>[...]
>>
>> Elsethread I suggested to merge the malloc() with the realloc() call.
>> The resulting code would be simpler (and might address that problem).
>>
>>     int chunk = 10;
>>     int bufsize = 1;
>>     char *  anchor = NULL;
>>     while ((anchor = realloc (anchor, bufsize += chunk)) != NULL  &&
>>             fgets (anchor+bufsize-chunk-1, chunk+1, stdin) != NULL)
>>         ;
>>     puts (anchor);
>>
>>
>> Do you see the exposed problem (or any other issues) here, too?
> 
> If stdin is empty, you never store anything in the buffer and
> puts(anchor) has undefined behavior because there might be a terminating
> '\0'.  If the first realloc() fails, anchor is a null pointer and again
> puts(anchor) has undefined behavior.
> 
> If nothing goes wrong, puts() adds an extra newline to the output.

Yes, the purpose of puts() was to show whether the function that I
wanted to check works properly on a long line of data.

> 
> That's all that jumped out at me looking at the code, but did you test
> it with multi-line input?  When I tried it it printed only the first
> line of input (followed by that extra newline).
> 
> I'm still not entirely sure what the code is supposed to do.

I just wanted the realloc-append logic codified and verified. (As
a possible building block to create a function for the purpose of
the original task outlined by the OP.)

Janis