Re: gettid

From: Jakub Wilk <jwilk@jwilk.net>
To: Jonny Grant <jg@jguk.org>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>, <linux-man@vger.kernel.org>
Subject: Re: gettid
Date: Wed, 17 Jun 2020 12:22:32 +0200	[thread overview]
Message-ID: <20200617102232.7zzi2klj3onh2nur@jwilk.net> (raw)
In-Reply-To: <23ca3363-5a24-9862-4872-811678527b50@jguk.org>

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* Jonny Grant <jg@jguk.org>, 2020-06-16, 12:36:
>SYNOPSIS         top
>   #define _GNU_SOURCE
>   #include <unistd.h>
>   #include <sys/types.h>
>
>   pid_t gettid(void);
>
>I can compile on Ubuntu without #define _GNU_SOURCE and call gettid()
>
>Maybe that line can be removed?

I don't think so. Here's what I get (with GCC 9):

   $ gcc test.c
   test.c: In function ‘main’:
   test.c:6:9: warning: implicit declaration of function ‘gettid’; did you mean ‘getgid’? [-Wimplicit-function-declaration]
       6 |  return gettid();
         |         ^~~~~~
         |         getgid

Prepending "#define _GNU_SOURCE" fixes the above.

-- 
Jakub Wilk

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#include <unistd.h>
#include <sys/types.h>

int main(int argc, char **argv)
{
	return gettid();	
}