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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: Sun, 16 Feb 2025 01:04:11 -0500
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On 2/15/25 22:29, Janis Papanagnou wrote:
> On 15.02.2025 18:29, Michael S wrote:
>> On Fri, 14 Feb 2025 20:51:38 +0100
>> Janis Papanagnou <janis_papanagnou+ng@hotmail.com> wrote:
>>>
>>> Actually, in the same code, I'm also using the strtok() function
>>
>> strtok() is one of the relatively small set of more problemetic
>> functions in C library that are not thread-safe.
>
> I know that it's not thread-safe. (You can't miss that information
> if you look up the man page to inspect the function interface.)
>
>> If you only care about POSIX target, the I'd reccomend to avoid strtok
>> and to use strtok_r().

If you cannot assume POSIX, but can assume C2011 or later, you might be
able to use strtok_s() instead. You need to add

#ifdef __STDC_LIB_EXT1__
    #define __STDC_WANT_LIB_EXT1__ 1
    // strtok_s() will be declared in <string.h>
#endif
#include <string.h>

> But since I don't use threads - neither here nor did I ever needed
> them generally in my "C" contexts - that's unnecessary. Isn't it?

No. What makes strtok() problematic can come up without any use of
threads. Consider for the moment a bug I had to investigate. A function
that was looping through strtok() calls to parse a string called a
utility function during each pass through the loop. The utility function
also called strtok() in a loop to parse an entirely different string for
a different purpose. Exercise for the student: figure out what the
consequences were.