Re: Fix sanitizer error in fchownat.m4

[Bruno Haible <bruno@clisp.org>]

Tim Rühsen wrote:
> configure:55268: checking whether fchownat works with AT_SYMLINK_NOFOLLOW
> SUMMARY: UndefinedBehaviorSanitizer: implicit-integer-sign-change
> conftest.c:812:50 in
> configure:55326: checking whether fchownat works with an empty file name
> SUMMARY: UndefinedBehaviorSanitizer: implicit-integer-sign-change
> conftest.c:817:37 in

This patch should fix it.


2020-05-21  Bruno Haible  <bruno@clisp.org>

	fchownat: Support clang -fsanitize=implicit-integer-sign-change better.
	Reported by Tim Rühsen in
	<https://lists.gnu.org/archive/html/bug-gnulib/2020-05/msg00207.html>.
	* m4/fchownat.m4 (gl_FUNC_FCHOWNAT_DEREF_BUG,
	gl_FUNC_FCHOWNAT_EMPTY_FILENAME_BUG): Cast -1 to uid_t or git_t,
	respectively.

diff --git a/m4/fchownat.m4 b/m4/fchownat.m4
index cd5c301..0a5d637 100644
--- a/m4/fchownat.m4
+++ b/m4/fchownat.m4
@@ -1,4 +1,4 @@
-# fchownat.m4 serial 5
+# fchownat.m4 serial 6
 dnl Copyright (C) 2004-2020 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -64,7 +64,7 @@ AC_DEFUN([gl_FUNC_FCHOWNAT_DEREF_BUG],
 int
 main ()
 {
-  return (fchownat (AT_FDCWD, "$gl_dangle", -1, getgid (),
+  return (fchownat (AT_FDCWD, "$gl_dangle", (uid_t)(-1), getgid (),
                     AT_SYMLINK_NOFOLLOW) != 0
           && errno == ENOENT);
 }
@@ -98,7 +98,7 @@ AC_DEFUN([gl_FUNC_FCHOWNAT_EMPTY_FILENAME_BUG],
             fd = open ("conftestdir", O_RDONLY);
             if (fd < 0)
               return 3;
-            ret = fchownat (fd, "", -1, -1, 0);
+            ret = fchownat (fd, "", (uid_t)(-1), (gid_t)(-1), 0);
             close (fd);
             rmdir ("conftestdir");
             return ret == 0;