Provide <bits/unistd_ext.h> as a sysdeps header exclusively

Non-sysdeps headers cannot be overriden by sysdeps headers across the
entire build, so it is necessary to turn such extension headers into
sysdeps headers themselves.  The approach here follows the existing
<bits/shm.h> header (although it uses sysdeps/gnu instead of
sysdeps/generic).

Fixes commit 1d0fc213824eaa2a8f8c4385daaa698ee8fb7c92 ("Linux: Add
gettid system call wrapper [BZ #6399]") and commit
8f89ab216f205c2ffd90d1fc8454efdfc0b01dee ("posix: Fix missing wrapper
header for <bits/unistd_ext.h>").

1 files changed, 21 insertions, 0 deletions

diff --git a/sysdeps/generic/bits/unistd_ext.h b/sysdeps/generic/bits/unistd_ext.h
new file mode 100644
index 0000000000..d6e88f3bd4
--- /dev/null
+++ b/sysdeps/generic/bits/unistd_ext.h
@@ -0,0 +1,21 @@
+/* System-specific extensions of <unistd.h>, generic version.
+   Copyright (C) 2019 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#ifndef _UNISTD_H
+# error "Never include <bits/unistd_ext.h> directly; use <unistd.h> instead."
+#endif