-#serial 1
-dnl Run a program to determine whether whether link(2) follows symlinks.
+# serial 15
+dnl Run a program to determine whether link(2) follows symlinks.
dnl Set LINK_FOLLOWS_SYMLINKS accordingly.
-AC_DEFUN(jm_AC_FUNC_LINK_FOLLOWS_SYMLINK,
+# Copyright (C) 1999-2001, 2004-2006, 2009 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.
+
+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 runtime test.
+AC_DEFUN([gl_FUNC_LINK_FOLLOWS_SYMLINK],
[dnl
- AC_CACHE_CHECK([whether link(2) follows symlinks],
- jm_ac_cv_func_link_follows_symlink,
- [
- # Create a regular file.
- echo > conftest.file
- AC_TRY_RUN(
- [
+ 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
+ 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>
-# ifdef HAVE_UNISTD_H
-# include <unistd.h>
-# endif
+# 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 \
/* Create a symlink to the regular file. */
if (symlink (file, sym))
- abort ();
+ return 2;
/* Create a hard link to that symlink. */
if (link (sym, hard))
- abort ();
+ return 3;
if (lstat (hard, &sb_hard))
- abort ();
+ return 4;
if (lstat (file, &sb_file))
- abort ();
+ 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) ? 0 : 1;
+ return SAME_INODE (sb_hard, sb_file) ? 1 : 0;
}
- ],
- jm_ac_cv_func_link_follows_symlink=yes,
- jm_ac_cv_func_link_follows_symlink=no,
- jm_ac_cv_func_link_follows_symlink=yes, We're cross compiling.
- )
- ])
+ ]])],
+ [gl_cv_func_link_follows_symlink=no], dnl GNU behavior
+ [gl_cv_func_link_follows_symlink=yes], dnl Followed link/compile failed
+ [gl_cv_func_link_follows_symlink=unknown] dnl We're cross compiling.
+ )
+ rm -f conftest.file conftest.sym conftest.hard
+ ])
+ case $gl_cv_func_link_follows_symlink in
+ yes) gl_link_follows_symlinks=1 ;;
+ no) ;; # already defaulted to 0
+ *) gl_link_follows_symlinks=-1 ;;
+ esac
+ fi
+ AC_DEFINE_UNQUOTED([LINK_FOLLOWS_SYMLINKS], [$gl_link_follows_symlinks],
+ [Define to 1 if `link(2)' dereferences symbolic links, 0 if it
+ creates hard links to symlinks, and -1 if unknown.])
])