--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,18 @@
+2011-08-30  Paul Eggert  <eggert@cs.ucla.edu>
+
+	openat: work around AIX 7.1 fstatat bug
+	Problem reported by Kevin Brott for GNU tar, in the thread containing
+	<http://lists.gnu.org/archive/html/bug-tar/2011-08/msg00015.html>.
+	* lib/fstatat.c (rpl_fstatat): Do not invoke underlying fstatat if
+	FSTATAT_ST_SIZE_ETC_BROKEN.
+	(fstatat) [FSTATAT_ST_SIZE_ETC_BROKEN && HAVE_FSTATAT]: #define to
+	rpl_fstatat.
+	* m4/openat.m4 (gl_FUNC_FSTATAT): New macro, with the fstatat-relevant
+	part of gl_FUNC_OPENAT.  Also, check for the AIX 7.1 bug, and use
+	AC_CHECK_FUNCS_ONCE for fstatat.
+	(gl_FUNC_OPENAT): Use it.  Use AC_CHECK_FUNCS_ONCE for
+	fchmodat, mkdirat, openat and unlinkat.
+
 2011-08-30  Bruno Haible  <bruno@clisp.org>
 
 	Avoid endless recursions if config.h includes some header files.

--- a/lib/fstatat.c
+++ b/lib/fstatat.c
@@ -25,7 +25,7 @@
 #include <fcntl.h>
 #include <string.h>
 
-#if HAVE_FSTATAT
+#if HAVE_FSTATAT && ! FSTATAT_ST_SIZE_ETC_BROKEN
 
 # undef fstatat
 
@@ -65,7 +65,12 @@
   return result;
 }
 
-#else /* !HAVE_FSTATAT */
+#else /* ! (HAVE_FSTATAT && ! FSTATAT_ST_SIZE_ETC_BROKEN) */
+
+# if HAVE_FSTATAT
+#  undef fstatat
+#  define fstatat rpl_fstatat
+# endif
 
 /* On mingw, the gnulib <sys/stat.h> defines `stat' as a function-like
    macro; but using it in AT_FUNC_F2 causes compilation failure
@@ -107,4 +112,4 @@
 # undef AT_FUNC_POST_FILE_PARAM_DECLS
 # undef AT_FUNC_POST_FILE_ARGS
 
-#endif /* !HAVE_FSTATAT */
+#endif /* ! (HAVE_FSTATAT && ! FSTATAT_ST_SIZE_ETC_BROKEN) */

--- a/m4/openat.m4
+++ b/m4/openat.m4
@@ -1,4 +1,4 @@
-# serial 33
+# serial 34
 # See if we need to use our replacement for Solaris' openat et al functions.
 
 dnl Copyright (C) 2004-2011 Free Software Foundation, Inc.
@@ -23,8 +23,7 @@
   GNULIB_UNLINKAT=1
 
   AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])
-  AC_CHECK_FUNCS_ONCE([lchmod])
-  AC_CHECK_FUNCS([fchmodat fstatat mkdirat openat unlinkat])
+  AC_CHECK_FUNCS_ONCE([fchmodat lchmod mkdirat openat unlinkat])
   AC_REQUIRE([gl_FUNC_LSTAT_FOLLOWS_SLASHED_SYMLINK])
   AC_REQUIRE([gl_FUNC_UNLINK])
   case $ac_cv_func_openat+$gl_cv_func_lstat_dereferences_slashed_symlink in
@@ -37,13 +36,11 @@
     # Solaris 9 has *at functions, but uniformly mishandles trailing
     # slash in all of them.
     REPLACE_OPENAT=1
-    REPLACE_FSTATAT=1
     REPLACE_UNLINKAT=1
     ;;
   *)
     HAVE_OPENAT=0
     HAVE_UNLINKAT=0 # No known system with unlinkat but not openat
-    HAVE_FSTATAT=0 # No known system with fstatat but not openat
     gl_PREREQ_OPENAT;;
   esac
   if test $ac_cv_func_fchmodat != yes; then
@@ -53,6 +50,7 @@
     HAVE_MKDIRAT=0
   fi
   gl_FUNC_FCHOWNAT
+  gl_FUNC_FSTATAT
 ])
 
 # gl_FUNC_FCHOWNAT_DEREF_BUG([ACTION-IF-BUGGY[, ACTION-IF-NOT_BUGGY]])
@@ -155,6 +153,65 @@
     [HAVE_FCHOWNAT=0])
 ])
 
+# If we have the fstatat function, and it has the bug (in AIX 7.1)
+# that it does not fill in st_size correctly, use the replacement function.
+AC_DEFUN([gl_FUNC_FSTATAT],
+[
+  AC_REQUIRE([gl_SYS_STAT_H_DEFAULTS])
+  AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])
+  AC_REQUIRE([gl_FUNC_LSTAT_FOLLOWS_SLASHED_SYMLINK])
+  AC_CHECK_FUNCS_ONCE([fstatat openat])
+
+  if test $ac_cv_func_fstatat = no; then
+    HAVE_FSTATAT=0
+  else
+    AC_CACHE_CHECK([whether fstatat fills in st_size etc.],
+      [gl_cv_func_fstatat_st_size_etc],
+      [gl_cv_func_fstatat_st_size_etc=no
+       echo xxx >conftest.file
+       AC_RUN_IFELSE(
+         [AC_LANG_SOURCE(
+            [[
+              #include <fcntl.h>
+              #include <sys/stat.h>
+
+              int
+              main (void)
+              {
+                struct stat a;
+                struct stat b;
+                if (fstatat (AT_FDCWD, "conftest.file", &a,
+                             AT_SYMLINK_NOFOLLOW)
+                    != 0)
+                  return 1;
+                if (lstat ("conftest.file", &b) != 0)
+                  return 2;
+                if (a.st_size != b.st_size) return 3;
+                if (a.st_dev != b.st_dev) return 4;
+                if (a.st_ino != b.st_ino) return 5;
+                if (a.st_mode != b.st_mode) return 6;
+                if (a.st_nlink != b.st_nlink) return 7;
+                if (a.st_uid != b.st_uid) return 8;
+                if (a.st_gid != b.st_gid) return 9;
+                /* Don't check time members, to avoid caching issues.  */
+                return 0;
+              }
+            ]])],
+         [gl_cv_func_fstatat_st_size_etc=yes])])
+
+    case $gl_cv_func_fstatat_st_size_etc+$gl_cv_func_lstat_dereferences_slashed_symlink in
+    yes+yes) ;;
+    *) REPLACE_FSTATAT=1
+       if test $gl_cv_func_fstatat_st_size_etc != yes; then
+         AC_DEFINE([FSTATAT_ST_SIZE_ETC_BROKEN], [1],
+           [Define to 1 if fstatat does not fill in st_size etc.,
+            as in AIX 7.1.])
+       fi
+       ;;
+    esac
+  fi
+])
+
 AC_DEFUN([gl_PREREQ_OPENAT],
 [
   AC_REQUIRE([AC_C_INLINE])