-#serial 3
-dnl Run a program to determine whether whether link(2) follows symlinks.
+# serial 16
+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],
-[dnl
- AC_CACHE_CHECK(
- [whether link(2) dereferences a symlink specified with a trailing slash],
- jm_ac_cv_func_link_follows_symlink,
- [
- dnl poor-man's AC_REQUIRE: FIXME: repair this once autoconf-3 provides
- dnl the appropriate framework.
- test -z "$ac_cv_header_unistd_h" \
- && AC_CHECK_HEADERS(unistd.h)
+# Copyright (C) 1999-2001, 2004-2006, 2009-2011 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.
- # Create a regular file.
- echo > conftest.file
- AC_TRY_RUN(
- [
+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_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>
-# 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 \
- && (Stat_buf_1).st_dev == (Stat_buf_2).st_dev)
+ ((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;
+ 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 symlink to the regular file. */
+ if (symlink (file, sym))
+ return 2;
- /* Create a hard link to that symlink. */
- if (link (sym, hard))
- abort ();
+ /* Create a hard link to that symlink. */
+ if (link (sym, hard))
+ return 3;
- if (lstat (hard, &sb_hard))
- abort ();
- if (lstat (file, &sb_file))
- abort ();
+ 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) ? 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.])
+ /* 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
+ [gl_cv_func_link_follows_symlink=unknown] dnl We're cross compiling.
+ )
+ rm -f conftest.file conftest.sym conftest.hard
+ ])
+ case $gl_cv_func_link_follows_symlink in
+ yes) gl_link_follows_symlinks=1 ;;
+ no) ;; # already defaulted to 0
+ *) gl_link_follows_symlinks=-2 ;;
+ esac
+ fi
fi
+ AC_DEFINE_UNQUOTED([LINK_FOLLOWS_SYMLINKS], [$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.])
])