all: be less strict about usage if POSIX 2008

sort, tail, and uniq now support traditional usage like 'sort +2'
and 'tail +10' on systems conforming to POSIX 1003.1-2008 and later.
* NEWS: Document this.
* doc/coreutils.texi (Standards conformance, tail invocation)
(sort invocation, uniq invocation, touch invocation):
Document new behavior, or behavior's dependence on POSIX 1003.1-2001.
* src/sort.c (struct keyfield.traditional_used):
Rename from obsolete_used, since implementations are now allowed
to support it.  All uses changed.
(main): Allow traditional usage if _POSIX2_VERSION is 200809.
* src/tail.c (parse_obsolete_option): Distinguish between
traditional usage (which POSIX 2008 and later allows) and obsolete
(which it still does not).
* src/uniq.c (strict_posix2): New function.
(main): Allow traditional usage if _POSIX2_VERSION is 200809.
* tests/misc/tail.pl: Test for new behavior.

3 files changed, 23 insertions, 14 deletions

diff --git a/src/sort.c b/src/sort.c
index 62acb6298..aa52b7569 100644
--- a/src/sort.c
+++ b/src/sort.c
@@ -224,7 +224,7 @@ struct keyfield
   bool month;			/* Flag for comparison by month name. */
   bool reverse;			/* Reverse the sense of comparison. */
   bool version;			/* sort by version number */
-  bool obsolete_used;		/* obsolescent key option format is used. */
+  bool traditional_used;	/* Traditional key option format is used. */
   struct keyfield *next;	/* Next keyfield to try. */
 };
 
@@ -2394,7 +2394,7 @@ key_warnings (struct keyfield const *gkey, bool gkey_only)
 
   for (key = keylist; key; key = key->next, keynum++)
     {
-      if (key->obsolete_used)
+      if (key->traditional_used)
         {
           size_t sword = key->sword;
           size_t eword = key->eword;
@@ -4183,7 +4183,8 @@ main (int argc, char **argv)
   size_t nthreads = 0;
   size_t nfiles = 0;
   bool posixly_correct = (getenv ("POSIXLY_CORRECT") != NULL);
-  bool obsolete_usage = (posix2_version () < 200112);
+  int posix_ver = posix2_version ();
+  bool traditional_usage = ! (200112 <= posix_ver && posix_ver < 200809);
   char **files;
   char *files_from = NULL;
   struct Tokens tok;
@@ -4288,13 +4289,13 @@ main (int argc, char **argv)
     {
       /* Parse an operand as a file after "--" was seen; or if
          pedantic and a file was seen, unless the POSIX version
-         predates 1003.1-2001 and -c was not seen and the operand is
+         is not 1003.1-2001 and -c was not seen and the operand is
          "-o FILE" or "-oFILE".  */
       int oi = -1;
 
       if (c == -1
           || (posixly_correct && nfiles != 0
-              && ! (obsolete_usage
+              && ! (traditional_usage
                     && ! checkonly
                     && optind != argc
                     && argv[optind][0] == '-' && argv[optind][1] == 'o'
@@ -4315,8 +4316,8 @@ main (int argc, char **argv)
             {
               bool minus_pos_usage = (optind != argc && argv[optind][0] == '-'
                                       && ISDIGIT (argv[optind][1]));
-              obsolete_usage |= minus_pos_usage && !posixly_correct;
-              if (obsolete_usage)
+              traditional_usage |= minus_pos_usage && !posixly_correct;
+              if (traditional_usage)
                 {
                   /* Treat +POS1 [-POS2] as a key if possible; but silently
                      treat an operand as a file if it is not a valid +POS1.  */
@@ -4356,7 +4357,7 @@ main (int argc, char **argv)
                             badfieldspec (optarg1,
                                       N_("stray character in field spec"));
                         }
-                      key->obsolete_used = true;
+                      key->traditional_used = true;
                       insertkey (key);
                     }
                 }
diff --git a/src/tail.c b/src/tail.c
index 2a72a93f0..caa54076a 100644
--- a/src/tail.c
+++ b/src/tail.c
@@ -1981,7 +1981,6 @@ parse_obsolete_option (int argc, char * const *argv, uintmax_t *n_units)
   const char *p;
   const char *n_string;
   const char *n_string_end;
-  bool obsolete_usage;
   int default_count = DEFAULT_N_LINES;
   bool t_from_start;
   bool t_count_lines = true;
@@ -1994,7 +1993,9 @@ parse_obsolete_option (int argc, char * const *argv, uintmax_t *n_units)
          || (3 <= argc && argc <= 4 && STREQ (argv[2], "--"))))
     return false;
 
-  obsolete_usage = (posix2_version () < 200112);
+  int posix_ver = posix2_version ();
+  bool obsolete_usage = posix_ver < 200112;
+  bool traditional_usage = obsolete_usage || 200809 <= posix_ver;
   p = argv[1];
 
   switch (*p++)
@@ -2003,8 +2004,8 @@ parse_obsolete_option (int argc, char * const *argv, uintmax_t *n_units)
       return false;
 
     case '+':
-      /* Leading "+" is a file name in the non-obsolete form.  */
-      if (!obsolete_usage)
+      /* Leading "+" is a file name in the standard form.  */
+      if (!traditional_usage)
         return false;
 
       t_from_start = true;
@@ -2014,7 +2015,7 @@ parse_obsolete_option (int argc, char * const *argv, uintmax_t *n_units)
       /* In the non-obsolete form, "-" is standard input and "-c"
          requires an option-argument.  The obsolete multidigit options
          are supported as a GNU extension even when conforming to
-         POSIX 1003.1-2001, so don't complain about them.  */
+         POSIX 1003.1-2001 or later, so don't complain about them.  */
       if (!obsolete_usage && !p[p[0] == 'c'])
         return false;
 
diff --git a/src/uniq.c b/src/uniq.c
index 0e118da9d..896ce938f 100644
--- a/src/uniq.c
+++ b/src/uniq.c
@@ -226,6 +226,13 @@ Also, comparisons honor the rules specified by 'LC_COLLATE'.\n\
   exit (status);
 }
 
+static bool
+strict_posix2 (void)
+{
+  int posix_ver = posix2_version ();
+  return 200112 <= posix_ver && posix_ver < 200809;
+}
+
 /* Convert OPT to size_t, reporting an error using MSGID if OPT is
    invalid.  Silently convert too-large values to SIZE_MAX.  */
 
@@ -533,7 +540,7 @@ main (int argc, char **argv)
           {
             unsigned long int size;
             if (optarg[0] == '+'
-                && posix2_version () < 200112
+                && ! strict_posix2 ()
                 && xstrtoul (optarg, NULL, 10, &size, "") == LONGINT_OK
                 && size <= SIZE_MAX)
               skip_chars = size;