Re: [Bug 214871] New: Man(3) system outdated

[Adhemerval Zanella <adhemerval.zanella@linaro.org>]

On 02/11/2021 06:58, Alejandro Colomar (man-pages) via Libc-alpha wrote:
> Hi Adhemerval, Michael,
> 
> On 11/1/21 13:06, zatrazz wrote:
>> Hi Alejandro,
>>
>> Indeed we changed glibc to use posix_spawn on system and popen on  2.29 since
>> to use posix_spawn (which uses clone (CLONE_VFORK | CLONE_VM)).  It plays
>> way better with Linux memory subsystem than fork() + exec() specially when such
>> calls are used with process with large RSS.
> 
> I applied the following patch.  I'll close the bug.
> 
> Thanks,
> 
> Alex

I forgot to add that neither system(), posix_spawn(), nor popen() call
atfork handlers [1].  POSIX recently changed their description to make
it implementation-defined instead of unspecified [2], so I think it
is worth to change that is not really behave as called by fork() (since
it will run atfork handlers).

[1] https://sourceware.org/bugzilla/show_bug.cgi?id=17490
[2] https://www.austingroupbugs.net/view.php?id=1317

> 
> ---
>     system.3: It doesn't call fork anymore
> 
>     Reported-by: Michael Kearney <mikekearney85@hotmail.com>
>     Cc: Adhemerval Zanella <zatrazz@gmail.com>
>     Signed-off-by: Alejandro Colomar <alx.manpages@gmail.com>
> 
> diff --git a/man3/system.3 b/man3/system.3
> index 880fe93c6..bde45ed82 100644
> --- a/man3/system.3
> +++ b/man3/system.3
> @@ -40,9 +40,9 @@ system \- execute a shell command
>  .SH DESCRIPTION
>  The
>  .BR system ()
> -library function uses
> +library function behaves as if it used
>  .BR fork (2)
> -to create a child process that executes the shell command specified in
> +to create a child process that executed the shell command specified in
>  .I command
>  using
>  .BR execl (3)
> 
> 
>