Remove eloop-threshold.h

On both Linux and Hurd the __eloop_threshold() is always a constant
(40 and 32 respectively), so there is no need to always call
__sysconf (_SC_SYMLOOP_MAX) for Linux case (!SYMLOOP_MAX).  To avoid
a name clash with gnulib, rename the new file min-eloop-threshold.h.

Checked on x86_64-linux-gnu and with a build for x86_64-gnu.
Reviewed-by: DJ Delorie <dj@redhat.com>

1 files changed, 42 insertions, 0 deletions

diff --git a/sysdeps/generic/min-eloop-threshold.h b/sysdeps/generic/min-eloop-threshold.h
new file mode 100644
index 0000000..2ac12ed
--- /dev/null
+++ b/sysdeps/generic/min-eloop-threshold.h
@@ -0,0 +1,42 @@
+/* Minimum threshold at which to diagnose ELOOP.  Generic version.
+   Copyright (C) 2012-2025 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
+   <https://www.gnu.org/licenses/>.  */
+
+#ifndef _MIN_ELOOP_THRESHOLD_H
+#define _MIN_ELOOP_THRESHOLD_H      1
+
+/* 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.
+
+   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.  */
+
+#define MIN_ELOOP_THRESHOLD    40
+
+#endif