When comparing mtimes for the -u and -Z options and the target is

'too old', use pathconfat(_PC_TIMESTAMP_RESOLUTION, AT_SYMLINK_NOFOLLOW)
to get the timestamp resolution to which the _source_ timestamp
should be truncated for a stable comparison.

Problem reported by Walter Alejandro Iglesias (wai(at)roquesor.com)
ok millert@

diff --git a/bin/pax/ar_subs.c b/bin/pax/ar_subs.c
index c542aa6..172d684 100644 (file)
--- a/bin/pax/ar_subs.c
+++ b/bin/pax/ar_subs.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: ar_subs.c,v 1.51 2023/07/10 16:28:33 jeremy Exp $     */
+/*     $OpenBSD: ar_subs.c,v 1.52 2024/05/18 05:21:38 guenther Exp $   */
 /*     $NetBSD: ar_subs.c,v 1.5 1995/03/21 09:07:06 cgd Exp $  */
 
 /*-
@@ -146,23 +146,60 @@ list(void)
 }
 
 static int
-cmp_file_times(int mtime_flag, int ctime_flag, ARCHD *arcn, struct stat *sbp)
+cmp_file_times(int mtime_flag, int ctime_flag, ARCHD *arcn, const char *path)
 {
        struct stat sb;
+       long res;
 
-       if (sbp == NULL) {
-               if (lstat(arcn->name, &sb) != 0)
-                       return (0);
-               sbp = &sb;
-       }
+       if (path == NULL)
+               path = arcn->name;
+       if (lstat(path, &sb) != 0)
+               return (0);
 
-       if (ctime_flag && mtime_flag)
-               return (timespeccmp(&arcn->sb.st_mtim, &sbp->st_mtim, <=) &&
-                       timespeccmp(&arcn->sb.st_ctim, &sbp->st_ctim, <=));
-       else if (ctime_flag)
-               return (timespeccmp(&arcn->sb.st_ctim, &sbp->st_ctim, <=));
-       else
-               return (timespeccmp(&arcn->sb.st_mtim, &sbp->st_mtim, <=));
+       /*
+        * The target (sb) mtime might be rounded down due to the limitations
+        * of the FS it's on.  If it's strictly greater or we don't care about
+        * mtime, then precision doesn't matter, so check those cases first.
+        */
+       if (ctime_flag && mtime_flag) {
+               if (timespeccmp(&arcn->sb.st_mtim, &sb.st_mtim, <=))
+                       return timespeccmp(&arcn->sb.st_ctim, &sb.st_ctim, <=);
+               if (!timespeccmp(&arcn->sb.st_ctim, &sb.st_ctim, <=))
+                       return 0;
+               /* <= ctim, but >= mtim */
+       } else if (ctime_flag)
+               return timespeccmp(&arcn->sb.st_ctim, &sb.st_ctim, <=);
+       else if (timespeccmp(&arcn->sb.st_mtim, &sb.st_mtim, <=))
+               return 1;
+
+       /* 
+        * If we got here then the target arcn > sb for mtime *and* that's
+        * the deciding factor.  Check whether they're equal after rounding
+        * down the arcn mtime to the precision of the target path.
+        */
+       res = pathconfat(AT_FDCWD, path, _PC_TIMESTAMP_RESOLUTION,
+           AT_SYMLINK_NOFOLLOW);
+       if (res == -1)
+               return 0;
+
+       /* nanosecond resolution?  previous comparisons were accurate */
+       if (res == 1)
+               return 0;
+
+       /* common case: second accuracy */
+       if (res == 1000000000)
+               return arcn->sb.st_mtime <= sb.st_mtime;
+
+       if (res < 1000000000) {
+               struct timespec ts = arcn->sb.st_mtim;
+               ts.tv_nsec = (ts.tv_nsec / res) * res;
+               return timespeccmp(&ts, &sb.st_mtim, <=);
+       } else {
+               /* not a POSIX compliant FS */
+               res /= 1000000000;
+               return ((arcn->sb.st_mtime / res) * res) <= sb.st_mtime;
+               return arcn->sb.st_mtime <= ((sb.st_mtime / res) * res);
+       }
 }
 
 /*
@@ -842,14 +879,12 @@ copy(void)
                        /*
                         * if existing file is same age or newer skip
                         */
-                       res = lstat(dirbuf, &sb);
-                       *dest_pt = '\0';
-
-                       if (res == 0) {
+                       if (cmp_file_times(uflag, Dflag, arcn, dirbuf)) {
+                               *dest_pt = '\0';
                                ftree_skipped_newer(arcn);
-                               if (cmp_file_times(uflag, Dflag, arcn, &sb))
-                                       continue;
+                               continue;
                        }
+                       *dest_pt = '\0';
                }
 
                /*