Prepare for radical source tree reorganization. zack/build-layout-experiment

All top-level files and directories are moved into a temporary storage
directory, REORG.TODO, except for files that will certainly still
exist in their current form at top level when we're done (COPYING,
COPYING.LIB, LICENSES, NEWS, README), all old ChangeLog files (which
are moved to the new directory OldChangeLogs, instead), and the
generated file INSTALL (which is just deleted; in the new order, there
will be no generated files checked into version control).

1 files changed, 72 insertions, 0 deletions

diff --git a/REORG.TODO/sysdeps/generic/eloop-threshold.h b/REORG.TODO/sysdeps/generic/eloop-threshold.h
new file mode 100644
index 0000000000..da6be07a50
--- /dev/null
+++ b/REORG.TODO/sysdeps/generic/eloop-threshold.h
@@ -0,0 +1,72 @@
+/* Threshold at which to diagnose ELOOP.  Generic version.
+   Copyright (C) 2012-2017 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#ifndef _ELOOP_THRESHOLD_H
+#define _ELOOP_THRESHOLD_H      1
+
+#include <limits.h>
+#include <sys/param.h>
+
+/* POSIX specifies SYMLOOP_MAX as the "Maximum number of symbolic
+   links that can be reliably traversed in the resolution of a
+   pathname in the absence of a loop."  This makes it a minimum that
+   we should certainly accept.  But it leaves open the possibility
+   that more might sometimes work--just not "reliably".
+
+   For example, Linux implements a complex policy whereby there is a
+   small limit on the number of direct symlink traversals (a symlink
+   to a symlink to a symlink), but larger limit on the total number of
+   symlink traversals overall.  Hence the SYMLOOP_MAX number should be
+   the small one, but the limit library functions enforce on users
+   should be the larger one.
+
+   So, we use the larger of the reported SYMLOOP_MAX (if any) and our
+   own constant MIN_ELOOP_THRESHOLD, below.  This constant should be
+   large enough that it never rules out a file name and directory tree
+   that the underlying system (i.e. calls to 'open' et al) would
+   resolve successfully.  It should be small enough that actual loops
+   are detected without a huge number of iterations.  */
+
+#ifndef MIN_ELOOP_THRESHOLD
+# define MIN_ELOOP_THRESHOLD    40
+#endif
+
+/* Return the maximum number of symlink traversals to permit
+   before diagnosing ELOOP.  */
+static inline unsigned int __attribute__ ((const))
+__eloop_threshold (void)
+{
+#ifdef SYMLOOP_MAX
+  const int symloop_max = SYMLOOP_MAX;
+#else
+  /* The function is marked 'const' even though we use memory and
+     call a function, because sysconf is required to return the
+     same value in every call and so it must always be safe to
+     call __eloop_threshold exactly once and reuse the value.  */
+  static long int sysconf_symloop_max;
+  if (sysconf_symloop_max == 0)
+    sysconf_symloop_max = __sysconf (_SC_SYMLOOP_MAX);
+  const unsigned int symloop_max = (sysconf_symloop_max <= 0
+                                    ? _POSIX_SYMLOOP_MAX
+                                    : sysconf_symloop_max);
+#endif
+
+  return MAX (symloop_max, MIN_ELOOP_THRESHOLD);
+}
+
+#endif  /* eloop-threshold.h */