POSIX-conformance patch for obsolete usages of "touch"

[Paul Eggert]

In reviewing today's "tail" patch, I see now that the old POSIX
requires support for the obsolescent Y2k-vulnerable usages of "touch"
only for dates in the range 1969--1999.  Since this obsolescent usage
conflicts with the current POSIX standard (and GNU touch chatters
about this) I installed the following patch to minimize its scope.

2005-11-01  Paul Eggert  <address@hidden>

        * NEWS: "tail -c 2 FILE" and "touch 0101000000" now operate as
        POSIX 1002.1-2001 requires.
        * doc/coreutils.texi (touch invocation): The old usage works only
          for 1969-1999 now.
        * src/touch.c (main): Pass PDS_PRE_2000 to posixtime.
        * tests/touch/obsolescent: Add y2000 test.
        * lib/posixtm.h (PDS_PRE_2000): New macro.
        * lib/posixtm.c (year): Arg is now syntax_bits rather than 
allow_century.
        All usages changed.  Reject dates outside the range 1969-1999 if
        PDS_PRE_2000 is used.

Index: NEWS
===================================================================
RCS file: /fetish/cu/NEWS,v
retrieving revision 1.333
diff -p -u -r1.333 NEWS
--- NEWS        1 Nov 2005 23:04:37 -0000       1.333
+++ NEWS        1 Nov 2005 23:40:12 -0000
@@ -22,9 +22,10 @@ GNU coreutils NEWS                      
 
   tac now works when stdin is a tty, even on non-Linux systems
 
-  "tail -c 2 FILE" now operates as POSIX 1003.1-2001 requires, even
-  when "tail" is conforming to older POSIX standards, as the
-  newly-mandated behavior is upward-compatible with the old.
+  "tail -c 2 FILE" and "touch 0101000000" now operate as POSIX
+  1003.1-2001 requires, even when coreutils is conforming to older
+  POSIX standards, as the newly-required behavior is upward-compatible
+  with the old.
 
 ** Build-related bug fixes
 
Index: doc/coreutils.texi
===================================================================
RCS file: /fetish/cu/doc/coreutils.texi,v
retrieving revision 1.291
diff -p -u -r1.291 coreutils.texi
--- doc/coreutils.texi  1 Nov 2005 23:05:00 -0000       1.291
+++ doc/coreutils.texi  1 Nov 2005 23:40:15 -0000
@@ -8726,7 +8726,8 @@ If no timestamp is given with any of the
 @option{-t} options, and if there are two or more @var{file}s and the
 first @var{file} is of the form @address@hidden@var{YY}]} and this
 would be a valid argument to the @option{-t} option (if the @var{YY}, if
-any, were moved to the front), that argument is interpreted as the time
+any, were moved to the front), and if the represented year
+is in the range 1969--1999, that argument is interpreted as the time
 for the other files instead of as a file name.
 This obsolete behavior can be enabled or disabled with the
 @env{_POSIX2_VERSION} environment variable (@pxref{Standards
Index: lib/posixtm.c
===================================================================
RCS file: /fetish/cu/lib/posixtm.c,v
retrieving revision 1.22
diff -p -u -r1.22 posixtm.c
--- lib/posixtm.c       22 Sep 2005 06:05:39 -0000      1.22
+++ lib/posixtm.c       1 Nov 2005 23:40:15 -0000
@@ -62,8 +62,8 @@ time_t mktime ();
     (PDS_LEADING_YEAR | PDS_CENTURY | PDS_SECONDS)
 
   touch mmddhhmm[YY] FILE... (obsoleted by POSIX 1003.1-2001)
-    8 or 10 digits
-    (PDS_TRAILING_YEAR)
+    8 or 10 digits, YY (if present) must be in the range 69-99
+    (PDS_TRAILING_YEAR | PDS_PRE_2000)
 
   date mmddhhmm[[CC]YY]
     8, 10, or 12 digits
@@ -72,7 +72,7 @@ time_t mktime ();
 */
 
 static int
-year (struct tm *tm, const int *digit_pair, size_t n, int allow_century)
+year (struct tm *tm, const int *digit_pair, size_t n, unsigned int syntax_bits)
 {
   switch (n)
     {
@@ -82,11 +82,15 @@ year (struct tm *tm, const int *digit_pa
         POSIX requires that 00-68 be interpreted as 2000-2068,
         and that 69-99 be interpreted as 1969-1999.  */
       if (digit_pair[0] <= 68)
-       tm->tm_year += 100;
+       {
+         if (syntax_bits & PDS_PRE_2000)
+           return 1;
+         tm->tm_year += 100;
+       }
       break;
 
     case 2:
-      if (!allow_century)
+      if (! (syntax_bits & PDS_CENTURY))
        return 1;
       tm->tm_year = digit_pair[0] * 100 + digit_pair[1] - 1900;
       break;
@@ -148,7 +152,7 @@ posix_time_parse (struct tm *tm, const c
   p = pair;
   if (syntax_bits & PDS_LEADING_YEAR)
     {
-      if (year (tm, p, len - 4, syntax_bits & PDS_CENTURY))
+      if (year (tm, p, len - 4, syntax_bits))
        return 1;
       p += len - 4;
       len = 4;
@@ -164,7 +168,7 @@ posix_time_parse (struct tm *tm, const c
   /* Handle any trailing year.  */
   if (syntax_bits & PDS_TRAILING_YEAR)
     {
-      if (year (tm, p, len, syntax_bits & PDS_CENTURY))
+      if (year (tm, p, len, syntax_bits))
        return 1;
     }
 
Index: lib/posixtm.h
===================================================================
RCS file: /fetish/cu/lib/posixtm.h,v
retrieving revision 1.7
diff -p -u -r1.7 posixtm.h
--- lib/posixtm.h       14 May 2005 07:58:06 -0000      1.7
+++ lib/posixtm.h       1 Nov 2005 23:40:15 -0000
@@ -27,6 +27,7 @@
 # define PDS_TRAILING_YEAR 2
 # define PDS_CENTURY 4
 # define PDS_SECONDS 8
+# define PDS_PRE_2000 16
 
 bool posixtime (time_t *p, const char *s, unsigned int syntax_bits);
 
Index: src/touch.c
===================================================================
RCS file: /fetish/cu/src/touch.c,v
retrieving revision 1.136
diff -p -u -r1.136 touch.c
--- src/touch.c 26 Sep 2005 23:02:14 -0000      1.136
+++ src/touch.c 1 Nov 2005 23:40:15 -0000
@@ -375,7 +375,8 @@ main (int argc, char **argv)
   /* The obsolete `MMDDhhmm[YY]' form is valid IFF there are
      two or more non-option arguments.  */
   if (!date_set && 2 <= argc - optind && posix2_version () < 200112
-      && posixtime (&newtime[0].tv_sec, argv[optind], PDS_TRAILING_YEAR))
+      && posixtime (&newtime[0].tv_sec, argv[optind],
+                   PDS_TRAILING_YEAR | PDS_PRE_2000))
     {
       newtime[0].tv_nsec = 0;
       newtime[1] = newtime[0];
Index: tests/touch/obsolescent
===================================================================
RCS file: /fetish/cu/tests/touch/obsolescent,v
retrieving revision 1.3
diff -p -u -r1.3 obsolescent
--- tests/touch/obsolescent     7 Sep 2004 06:23:09 -0000       1.3
+++ tests/touch/obsolescent     1 Nov 2005 23:40:15 -0000
@@ -36,4 +36,8 @@ for ones in 11111111 1111111111; do
   done
 done
 
+y2000=0101000000
+rm -f $y2000 file || fail=1
+touch $y2000 file && test -f $y2000 && test -f file || fail=1
+
 (exit $fail); exit $fail