--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,20 @@
+2010-07-14  Paul R. Eggert  <eggert@cs.ucla.edu>
+
+	getcwd: on Solaris, work better if ancestors are inaccessible
+	* lib/getcwd.c (__getcwd): If getcwd returns EINVAL for zero
+	buffer and size, try again with a large buffer.  This works better
+	on Solaris, since its getcwd succeeds even if the path to the root
+	is inaccessible, and this is helpful in common cases such as .zfs
+	hidden directories.  Problem reported by J Chapman Flack in
+	http://lists.gnu.org/archive/html/bug-tar/2010-06/msg00000.html
+	Use system getcwd if it's declared, not merely if it's partly
+	working; use the partly-working test only to avoid needless effort
+	if the system getcwd fails.
+	* m4/getcwd-path-max.m4 (gl_FUNC_GETCWD_PATH_MAX): Omit
+	comment that was already obsolete and is now even more obsolete.
+	* modules/getcwd (Depends-on): Depend on strdup, since __getcwd
+	now might call strdup.
+
 2010-07-13  Paul R. Eggert  <eggert@cs.ucla.edu>
 
 	pthread: Add enough so that coreutils/src/sort.c compiles.

--- a/lib/getcwd.c
+++ b/lib/getcwd.c
@@ -136,13 +136,11 @@
   size_t allocated = size;
   size_t used;
 
-#if HAVE_PARTLY_WORKING_GETCWD
-  /* The system getcwd works, except it sometimes fails when it
-     shouldn't, setting errno to ERANGE, ENAMETOOLONG, or ENOENT.  If
-     AT_FDCWD is not defined, the algorithm below is O(N**2) and this
-     is much slower than the system getcwd (at least on GNU/Linux).
-     So trust the system getcwd's results unless they look
-     suspicious.
+#if HAVE_RAW_DECL_GETCWD
+  /* If AT_FDCWD is not defined, the algorithm below is O(N**2) and
+     this is much slower than the system getcwd (at least on
+     GNU/Linux).  So trust the system getcwd's results unless they
+     look suspicious.
 
      Use the system getcwd even if we have openat support, since the
      system getcwd works even when a parent is unreadable, while the
@@ -150,8 +148,27 @@
 
 # undef getcwd
   dir = getcwd (buf, size);
-  if (dir || (errno != ERANGE && errno != ENAMETOOLONG && errno != ENOENT))
+  if (dir)
     return dir;
+
+  /* Solaris getcwd (NULL, 0) fails with errno == EINVAL, but it has
+     internal magic that lets it work even if an ancestor directory is
+     inaccessible, which is better in many cases.  So in this case try
+     again with a buffer that's almost always big enough.  */
+  if (errno == EINVAL && buf == NULL && size == 0)
+    {
+      char big_buffer[BIG_FILE_NAME_LENGTH + 1];
+      dir = getcwd (big_buffer, sizeof big_buffer);
+      if (dir)
+        return strdup (dir);
+    }
+
+# if HAVE_PARTLY_WORKING_GETCWD
+  /* The system getcwd works, except it sometimes fails when it
+     shouldn't, setting errno to ERANGE, ENAMETOOLONG, or ENOENT.    */
+  if (errno != ERANGE && errno != ENAMETOOLONG && errno != ENOENT)
+    return NULL;
+# endif
 #endif
 
   if (size == 0)

--- a/m4/getcwd-path-max.m4
+++ b/m4/getcwd-path-max.m4
@@ -183,8 +183,6 @@
   no,*)
     AC_DEFINE([HAVE_PARTLY_WORKING_GETCWD], [1],
       [Define to 1 if getcwd works, except it sometimes fails when it shouldn't,
-       setting errno to ERANGE, ENAMETOOLONG, or ENOENT.  If __GETCWD_PREFIX
-       is not defined, it doesn't matter whether HAVE_PARTLY_WORKING_GETCWD
-       is defined.]);;
+       setting errno to ERANGE, ENAMETOOLONG, or ENOENT.]);;
   esac
 ])

--- a/modules/getcwd
+++ b/modules/getcwd
@@ -17,6 +17,7 @@
 stdbool
 unistd
 malloc-posix
+strdup-posix
 
 configure.ac:
 gl_FUNC_GETCWD