Re: [PATCH v2] test-skeleton: redirect stderr to stdout

[Mike Frysinger <vapier at gentoo dot org>]

On 17 Jun 2016 12:12, Pedro Alves wrote:
> On 06/17/2016 06:29 AM, Mike Frysinger wrote:
> 
> > +  /* Bind stderr to stdout so that tests don't have to worry about which
> > +     one to use, and whether funcs they use (e.g. assert) will go to the
> > +     wrong place.  */
> > +  fclose (stderr);
> > +  if (dup2 (STDOUT_FILENO, STDERR_FILENO) == -1)
> > +    {
> > +      printf ("binding stderr to stdout failed: %m\n");
> > +      exit (1);
> > +    }
> > +  stderr = fdopen (STDERR_FILENO, "w");
> > +  /* Since stderr always starts out unbuffered, recreate that here.  */
> > +  setbuf (stderr, NULL);
> 
> Why do you need to fclose/fdopen stderr at all?
> Just the "dup2 (STDOUT_FILENO, STDERR_FILENO)" should be enough.

we discussed it here where i asked for docs:
https://sourceware.org/ml/libc-alpha/2016-06/msg00636.html

> Note that that's what
> 
>  http://pubs.opengroup.org/onlinepubs/9699919799/functions/dup.html
> 
> suggests in its example section:
> 
> ~~~~~~~~~~~~~~~~~~~~~
>  Redirecting Error Messages
> 
>  The following example redirects messages from stderr to stdout.
> 
>  #include <unistd.h>
>  ...
>  dup2(1, 2);
>  ...
> ~~~~~~~~~~~~~~~~~~~~~

that only guarantees the fd level.  where do we guarantee the stdio level ?
-mike

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