standards/188173: O_NOFOLLOW visibility not POSIX 2008 conforming

[Bruce Evans]

On Sat, 5 Apr 2014, Jilles Tjoelker wrote:

> On Sat, Apr 05, 2014 at 11:16:07PM +0300, Konstantin Belousov wrote:
>
>> diff --git a/sys/sys/fcntl.h b/sys/sys/fcntl.h
>> index 3461f8b..2691449 100644
>> --- a/sys/sys/fcntl.h
>> +++ b/sys/sys/fcntl.h
>> @@ -96,7 +96,7 @@ typedef	__pid_t		pid_t;
>>  #define	O_FSYNC		0x0080		/* synchronous writes */
>>  #endif
>>  #define	O_SYNC		0x0080		/* POSIX synonym for O_FSYNC */
>> -#if __BSD_VISIBLE
>> +#if __POSIX_VISIBLE >= 200809
>>  #define	O_NOFOLLOW	0x0100		/* don't follow symlinks */
>>  #endif
>>  #define	O_CREAT		0x0200		/* create if nonexistent */
>
> This looks good, but I went ahead and made the other new POSIX.1-2008
> things visible as well and removed redundant __BSD_VISIBLE condition
> parts:

That __BSD_VISIBLE is redundant is a bit confusing.  Perhaps add or
expand a comment about this.

> Index: sys/sys/fcntl.h
> ===================================================================
> --- sys/sys/fcntl.h	(revision 263842)
> +++ sys/sys/fcntl.h	(working copy)
> ...
> @@ -211,7 +211,7 @@ typedef	__pid_t		pid_t;
> #define	F_SETFD		2		/* set file descriptor flags */
> #define	F_GETFL		3		/* get file status flags */
> #define	F_SETFL		4		/* set file status flags */
> -#if __BSD_VISIBLE || __XSI_VISIBLE || __POSIX_VISIBLE >= 200112
> +#if __XSI_VISIBLE || __POSIX_VISIBLE >= 200112
> #define	F_GETOWN	5		/* get SIGIO/SIGURG proc/pgrp */
> #define	F_SETOWN	6		/* set SIGIO/SIGURG proc/pgrp */
> #endif

__XSI_VISIBLE seems to be the only condition that is sometimes needed in
ifdefs together with __POSIX_VISIBLE.

Many or most of the XSI ifdefs are out of date, with lots of XSI stuff
having been moved into POSIX but the ifdefs not being updated.  Fixing
this would probably give many more relatively complicated ifdefs like
the above.

The BSD vs POSIX redundancy is also in:

% capability.h:#if __BSD_VISIBLE || __XSI_VISIBLE || __POSIX_VISIBLE >= 200112
% capability.h:#if __BSD_VISIBLE || __XSI_VISIBLE || __POSIX_VISIBLE >= 200112

Old XSI ifdefs in new FreeBSD code seem to be nonsense.

% signal.h:#if __BSD_VISIBLE || __POSIX_VISIBLE > 0 && __POSIX_VISIBLE <= 200112

Perhaps complicated enough to be correct.

% stat.h:#if __BSD_VISIBLE || __POSIX_VISIBLE >= 200809

The above is from grepping <sys> for VISIBLE and selecting lines with || and
removing lines without BSD_VISIBLE.  Many more lines have XSI || POSIX, but
not in enough files to give much chance that these are complete.

Sampling of errors and complications outside of <sys>:

./dirent.h:#if __BSD_VISIBLE || __XSI_VISIBLE

Seems to be redundant.  I think BSD implies the latest version of XSI.
So this should use just XSI.

./langinfo.h:#if __BSD_VISIBLE || __XSI_VISIBLE <= 500

Need both here since 500 is not the latest XSI.  Assuming 500 is correct.

./netdb.h:#if __BSD_VISIBLE || (__POSIX_VISIBLE && __POSIX_VISIBLE <= 200112)

BSD together with POSIX is necessary when the POSIX test is reversed.

./setjmp.h:#if __BSD_VISIBLE || __XSI_VISIBLE >= 600

Another complicated test.  Symbols are rarely removed, so such tests are rare.

% ./stdio.h:#if __BSD_VISIBLE || __POSIX_VISIBLE >= 200809
% ./stdio.h:#if __BSD_VISIBLE || __POSIX_VISIBLE >= 200112 || __XSI_VISIBLE
% ./stdio.h:#if __BSD_VISIBLE || __POSIX_VISIBLE <= 199506

Note: reversed test.

% ./stdio.h:#if __BSD_VISIBLE || __XSI_VISIBLE > 0 && __XSI_VISIBLE < 600

Note: reversed test.  The previous reversed test may be broken, since
it is missing a check for '> 0'.  Elsewhere, the test for '> 0' is
obfuscated by writing it as a boolean check for != 0 with implicit 0.

% ./stdio.h:#if __BSD_VISIBLE || __POSIX_VISIBLE >= 200809
% ./stdio.h:#endif /* __BSD_VISIBLE || __POSIX_VISIBLE >= 200809 */
% ./string.h:#if __POSIX_VISIBLE >= 200809 || __BSD_VISIBLE
% ./string.h:#if __POSIX_VISIBLE >= 200112 || __XSI_VISIBLE
% ./string.h:#if __POSIX_VISIBLE >= 200809 || __BSD_VISIBLE
% ./string.h:#if __POSIX_VISIBLE >= 200809 || __BSD_VISIBLE
% ./string.h:#if __POSIX_VISIBLE >= 199506 || __XSI_VISIBLE >= 500
% ./string.h:#if __POSIX_VISIBLE >= 200809 || defined(_XLOCALE_H_)

Redundancies are most dense in these 2 popular headers.  The tests
(mainly the redundant parts) are also obfuscated by writing them in
random orders (mostly BSD first in stdio.h and BSD last in string.h).
All of the randomly ordered redundancies in stdio.h and string.h are
new with the 2008 or 2012 versions of POSIX.  One in fcntl.h was old
with the 2001 version of POSIX.

Bruce