| /* Threshold at which to diagnose ELOOP. Generic version. | |
| Copyright (C) 2012-2023 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/>. */ | |
| /* 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. */ | |
| /* Return the maximum number of symlink traversals to permit | |
| before diagnosing ELOOP. */ | |
| static inline unsigned int _GL_ATTRIBUTE_CONST | |
| __eloop_threshold (void) | |
| { | |
| const int symloop_max = SYMLOOP_MAX; | |
| /* 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); | |
| return MAX (symloop_max, MIN_ELOOP_THRESHOLD); | |
| } | |