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-rw-r--r--m4/chown.m470
1 files changed, 61 insertions, 9 deletions
diff --git a/m4/chown.m4 b/m4/chown.m4
index f723cb576..430bc8073 100644
--- a/m4/chown.m4
+++ b/m4/chown.m4
@@ -1,15 +1,24 @@
-#serial 9
-
-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
+#serial 10
+# Determine whether we need the chown wrapper. 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([AC_TYPE_UID_T])
AC_REQUIRE([AC_FUNC_CHOWN])
- if test $ac_cv_func_chown_works = no; then
+ AC_REQUIRE([gl_FUNC_CHOWN_FOLLOWS_SYMLINK])
+
+ if test $ac_cv_func_chown_works = yes; then
+ 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
AC_LIBOBJ(chown)
AC_DEFINE(chown, rpl_chown,
[Define to rpl_chown if the replacement function should be used.])
@@ -17,8 +26,51 @@ AC_DEFUN([gl_FUNC_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([[
+#ifdef HAVE_UNISTD_H
+# include <unistd.h>
+#endif
+#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=no]
+ )
+ ]
+ )
+
+ 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_HEADERS_ONCE(unistd.h fcntl.h)
+ AC_CHECK_FUNC([fchown], , [AC_LIBOBJ(fchown-stub)])
])