uname: Rewrite printing of Windows NT versions

[gnulib.git] / m4 / chown.m4

diff --git a/m4/chown.m4 b/m4/chown.m4
index 86c5fc7..ac76d3f 100644 (file)
--- a/m4/chown.m4
+++ b/m4/chown.m4
@@ -1,24 +1,84 @@
-#serial 8
+# serial 19
+# Determine whether we need the chown wrapper.
 
-dnl From Jim Meyering.
-dnl Determine whether chown accepts arguments of -1 for uid and gid.
-dnl If it doesn't, arrange to use the replacement function.
-dnl
+dnl Copyright (C) 1997-2001, 2003-2005, 2007, 2009
+dnl Free Software Foundation, Inc.
 
-AC_DEFUN([jm_FUNC_CHOWN],
+dnl This file is free software; the Free Software Foundation
+dnl gives unlimited permission to copy and/or distribute it,
+dnl with or without modifications, as long as this notice is preserved.
+
+# chown should accept arguments of -1 for uid and gid, and it should
+# dereference symlinks.  If it doesn't, arrange to use the replacement
+# function.
+
+# From Jim Meyering.
+
+AC_DEFUN([gl_FUNC_CHOWN],
 [
-  AC_REQUIRE([AC_TYPE_UID_T])dnl
+  AC_REQUIRE([gl_UNISTD_H_DEFAULTS])
+  AC_REQUIRE([AC_TYPE_UID_T])
   AC_REQUIRE([AC_FUNC_CHOWN])
+  AC_REQUIRE([gl_FUNC_CHOWN_FOLLOWS_SYMLINK])
+  AC_CHECK_FUNCS_ONCE([chown])
+
   if test $ac_cv_func_chown_works = no; then
-    AC_LIBOBJ(chown)
-    AC_DEFINE(chown, rpl_chown,
-      [Define to rpl_chown if the replacement function should be used.])
+    AC_DEFINE([CHOWN_FAILS_TO_HONOR_ID_OF_NEGATIVE_ONE], [1],
+      [Define if chown is not POSIX compliant regarding IDs of -1.])
+  fi
+
+  # If chown has either of the above problems, then we need the wrapper.
+  if test $ac_cv_func_chown_works$gl_cv_func_chown_follows_symlink = yesyes; then
+    : # no wrapper needed
+  else
+    REPLACE_CHOWN=1
+    AC_LIBOBJ([chown])
     gl_PREREQ_CHOWN
   fi
 ])
 
+# Determine whether chown follows symlinks (it should).
+AC_DEFUN([gl_FUNC_CHOWN_FOLLOWS_SYMLINK],
+[
+  AC_CACHE_CHECK(
+    [whether chown(2) dereferences symlinks],
+    gl_cv_func_chown_follows_symlink,
+    [
+      AC_RUN_IFELSE([AC_LANG_SOURCE([[
+#include <unistd.h>
+#include <stdlib.h>
+#include <errno.h>
+
+       int
+       main ()
+       {
+         char const *dangling_symlink = "conftest.dangle";
+
+         unlink (dangling_symlink);
+         if (symlink ("conftest.no-such", dangling_symlink))
+           abort ();
+
+         /* Exit successfully on a conforming system,
+            i.e., where chown must fail with ENOENT.  */
+         exit ( ! (chown (dangling_symlink, getuid (), getgid ()) != 0
+                   && errno == ENOENT));
+       }
+       ]])],
+       [gl_cv_func_chown_follows_symlink=yes],
+       [gl_cv_func_chown_follows_symlink=no],
+       [gl_cv_func_chown_follows_symlink=yes]
+      )
+    ]
+  )
+
+  if test $gl_cv_func_chown_follows_symlink = no; then
+    AC_DEFINE([CHOWN_MODIFIES_SYMLINK], [1],
+      [Define if chown modifies symlinks.])
+  fi
+])
+
 # Prerequisites of lib/chown.c.
 AC_DEFUN([gl_PREREQ_CHOWN],
 [
-  AC_CHECK_HEADERS_ONCE(unistd.h)
+  AC_CHECK_FUNC([fchown], , [AC_LIBOBJ([fchown-stub])])
 ])