[PATCH v2 5/8] posix: Do not clobber errno by atfork handlers

[Florian Weimer]

* Adhemerval Zanella via Libc-alpha:

> Changes from v1:
> * Move the errno set/restore to parent branch.
> ---
> Checked on x86_64-linux-gnu.
> ---
>  posix/fork.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/posix/fork.c b/posix/fork.c
> index cc1bdc1232..a4fdd44e1e 100644
> --- a/posix/fork.c
> +++ b/posix/fork.c
> @@ -68,7 +68,6 @@ __libc_fork (void)
>      }
>  
>    pid_t pid = _Fork ();
> -
>    if (pid == 0)
>      {
>        fork_system_setup ();
> @@ -99,6 +98,11 @@ __libc_fork (void)
>      }
>    else
>      {
> +      /* If _Fork failed, preserve its errno value.  */
> +      int save_errno;
> +      if (pid < 0)
> +	save_errno = errno;
> +
>        /* Release acquired locks in the multi-threaded case.  */
>        if (multiple_threads)
>  	{
> @@ -111,6 +115,9 @@ __libc_fork (void)
>  
>        /* Run the handlers registered for the parent.  */
>        __run_fork_handlers (atfork_run_parent, multiple_threads);
> +
> +      if (pid < 0)
> +       __set_errno (save_errno);
>      }
>  
>    return pid;

This is okay.  GCC does not warn about the uninitialized save_errno
here; I checked with build-many-glibcs.py.  Apparently the middle-end is
smart enough to detect that the conditions match.

Thanks,
Florian