-#serial 7
-dnl Run a program to determine whether whether link(2) follows symlinks.
+# serial 19
+dnl Run a program to determine whether link(2) follows symlinks.
dnl Set LINK_FOLLOWS_SYMLINKS accordingly.
-# Copyright (C) 1999, 2000, 2001, 2004, 2005 Free Software Foundation, Inc.
+# Copyright (C) 1999-2001, 2004-2006, 2009-2014 Free Software Foundation, Inc.
# This file is free software; the Free Software Foundation
# gives unlimited permission to copy and/or distribute it,
# with or without modifications, as long as this notice is preserved.
-AC_DEFUN([gl_AC_FUNC_LINK_FOLLOWS_SYMLINK],
+dnl This macro can be used to emulate POSIX linkat. If
+dnl LINK_FOLLOWS_SYMLINKS is 0, link matches linkat(,0), and
+dnl linkat(,AT_SYMLINK_FOLLOW) requires a readlink. If it is 1,
+dnl link matches linkat(,AT_SYMLINK_FOLLOW), and there is no way
+dnl to do linkat(,0) on symlinks (on all other file types,
+dnl link() is sufficient). If it is -1, use a Solaris specific
+dnl runtime test. If it is -2, use a generic runtime test.
+AC_DEFUN([gl_FUNC_LINK_FOLLOWS_SYMLINK],
[dnl
- AC_CACHE_CHECK(
- [whether link(2) dereferences a symlink specified with a trailing slash],
- jm_ac_cv_func_link_follows_symlink,
- [
- # Create a regular file.
- echo > conftest.file
- AC_TRY_RUN(
- [
+ AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
+ AC_CHECK_FUNCS_ONCE([readlink])
+ dnl Mingw lacks link, although gnulib provides a good replacement.
+ dnl However, it also lacks symlink, so there's nothing to test in
+ dnl the first place, and no reason to need to distinguish between
+ dnl linkat variants. So, we set LINK_FOLLOWS_SYMLINKS to 0.
+ gl_link_follows_symlinks=0 # assume GNU behavior
+ if test $ac_cv_func_readlink = yes; then
+ dnl Solaris has an __xpg4 variable in libc, and it determines the
+ dnl behaviour of link(): It dereferences a symlink if and only if
+ dnl __xpg4 != 0.
+ AC_CACHE_CHECK([for __xpg4], [gl_cv_have___xpg4],
+ [AC_LINK_IFELSE(
+ [AC_LANG_PROGRAM(
+ [[extern int __xpg4;]],
+ [[return __xpg4;]])],
+ [gl_cv_have___xpg4=yes],
+ [gl_cv_have___xpg4=no])
+ ])
+ if test $gl_cv_have___xpg4 = yes; then
+ gl_link_follows_symlinks=-1
+ else
+ AC_CACHE_CHECK([whether link(2) dereferences a symlink],
+ [gl_cv_func_link_follows_symlink],
+ [
+ # Create a regular file.
+ echo > conftest.file
+ AC_RUN_IFELSE(
+ [AC_LANG_SOURCE([[
# include <sys/types.h>
# include <sys/stat.h>
# include <unistd.h>
+# include <stdlib.h>
# define SAME_INODE(Stat_buf_1, Stat_buf_2) \
- ((Stat_buf_1).st_ino == (Stat_buf_2).st_ino \
- && (Stat_buf_1).st_dev == (Stat_buf_2).st_dev)
-
- int
- main ()
- {
- const char *file = "conftest.file";
- const char *sym = "conftest.sym";
- const char *hard = "conftest.hard";
- struct stat sb_file, sb_hard;
-
- /* Create a symlink to the regular file. */
- if (symlink (file, sym))
- abort ();
-
- /* Create a hard link to that symlink. */
- if (link (sym, hard))
- abort ();
-
- if (lstat (hard, &sb_hard))
- abort ();
- if (lstat (file, &sb_file))
- abort ();
-
- /* If the dev/inode of hard and file are the same, then
- the link call followed the symlink. */
- return SAME_INODE (sb_hard, sb_file) ? 0 : 1;
- }
- ],
- jm_ac_cv_func_link_follows_symlink=yes,
- jm_ac_cv_func_link_follows_symlink=no,
- jm_ac_cv_func_link_follows_symlink=yes dnl We're cross compiling.
- )
- ])
- if test $jm_ac_cv_func_link_follows_symlink = yes; then
- AC_DEFINE(LINK_FOLLOWS_SYMLINKS, 1,
- [Define if `link(2)' dereferences symbolic links.])
+ ((Stat_buf_1).st_ino == (Stat_buf_2).st_ino \
+ && (Stat_buf_1).st_dev == (Stat_buf_2).st_dev)
+
+ int
+ main ()
+ {
+ const char *file = "conftest.file";
+ const char *sym = "conftest.sym";
+ const char *hard = "conftest.hard";
+ struct stat sb_file, sb_hard;
+
+ /* Create a symlink to the regular file. */
+ if (symlink (file, sym))
+ return 2;
+
+ /* Create a hard link to that symlink. */
+ if (link (sym, hard))
+ return 3;
+
+ if (lstat (hard, &sb_hard))
+ return 4;
+ if (lstat (file, &sb_file))
+ return 5;
+
+ /* If the dev/inode of hard and file are the same, then
+ the link call followed the symlink. */
+ return SAME_INODE (sb_hard, sb_file) ? 1 : 0;
+ }
+ ]])],
+ [gl_cv_func_link_follows_symlink=no], dnl GNU behavior
+ [gl_cv_func_link_follows_symlink=yes], dnl Followed link/compile failed
+ [dnl We're cross compiling.
+ dnl The past results are "yes" on Mac OS X, FreeBSD, NetBSD,
+ dnl OpenBSD, Minix, AIX, HP-UX, OSF/1, and "no" on Linux, Cygwin.
+ case "$host_os" in
+ # On glibc/Linux we know the result.
+ linux*-gnu*) gl_cv_func_link_follows_symlink="guessing no" ;;
+ # Otherwise, we don't know.
+ *) gl_cv_func_link_follows_symlink=unknown ;;
+ esac
+ ])
+ rm -f conftest.file conftest.sym conftest.hard
+ ])
+ case "$gl_cv_func_link_follows_symlink" in
+ *yes) gl_link_follows_symlinks=1 ;;
+ *no) ;; # already defaulted to 0
+ *) gl_link_follows_symlinks=-2 ;;
+ esac
+ fi
fi
+ AC_DEFINE_UNQUOTED([LINK_FOLLOWS_SYMLINKS], [$gl_link_follows_symlinks],
+ [Define to 1 if 'link(2)' dereferences symbolic links, 0 if it
+ creates hard links to symlinks, -1 if it depends on the variable __xpg4,
+ and -2 if unknown.])
])
projects / gnulib.git / blobdiff