Use of _REENTRANT and _THREAD_SAFE feature macros

[Andreas Jaeger <aj@arthur.rhein-neckar.de>]

Looking through features.h I noticed that we have _REENTRANT and
_THREAD_SAFE but don't really need them anymore.

<features.h> has:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   _REENTRANT		Select additionally reentrant object.
   _THREAD_SAFE		Same as _REENTRANT, often used by other systems.

#if defined _REENTRANT || defined _THREAD_SAFE
# define __USE_REENTRANT	1
#endif
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

__USE_REENTRANT is used in only two places in the glibc headers:
<unistd.h> uses:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
#ifdef __USE_REENTRANT
/* Return at most NAME_LEN characters of the login name of the user in NAME.
   If it cannot be determined or some other error occurred, return the error
   code.  Otherwise return 0.  */
extern int getlogin_r __P ((char *__name, size_t __name_len));
#endif
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

And <stdio/stdio.h> uses it also:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
#ifdef __USE_REENTRANT
/* This is the reentrant variant of `tmpnam'.  The only difference is
   that it does not allow S to be NULL.  */
extern char *tmpnam_r __P ((char *__s));
#endif
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

>From the description of _REENTRANT in NOTES:
     If you define one of these macros, reentrant versions of several
     functions get declared.
I would have expected a lot of more functions to be defined and not
only getlogin_r[1].  Is this really intented and ok?

Andreas

Footnotes: 
[1]  Most systems don't use <stdio/stdio.h> but <libio/libio.h> which
     defines tmpnam_r with #ifdef __USE_MISC.

-- 
 Andreas Jaeger   aj@arthur.rhein-neckar.de    jaeger@informatik.uni-kl.de
  for pgp-key finger ajaeger@alma.student.uni-kl.de