os: wrap socket(SOCK_CLOEXEC) calls

Some system C libraries do not offer SOCK_CLOEXEC flag.

Add a new header for OS compatibility wrappers. Wrap socket() calls into
wl_os_socket_cloexec() which makes sure the O_CLOEXEC flag gets set on
the file descriptor.

On systems having SOCK_CLOEXEC this uses the old socket() call, and
falls back if it fails due to the flag (kernel not supporting it).

wayland-os.h is private and not exported.

Add close-on-exec tests for both normal and forced fallback paths.

Signed-off-by: Pekka Paalanen <ppaalanen@gmail.com>

src/wayland-os.h

@@ -0,0 +1,29 @@
+/*
+ * Copyright © 2012 Collabora, Ltd.
+ *
+ * Permission to use, copy, modify, distribute, and sell this software and its
+ * documentation for any purpose is hereby granted without fee, provided that
+ * the above copyright notice appear in all copies and that both that copyright
+ * notice and this permission notice appear in supporting documentation, and
+ * that the name of the copyright holders not be used in advertising or
+ * publicity pertaining to distribution of the software without specific,
+ * written prior permission.  The copyright holders make no representations
+ * about the suitability of this software for any purpose.  It is provided "as
+ * is" without express or implied warranty.
+ *
+ * THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
+ * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
+ * EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY SPECIAL, INDIRECT OR
+ * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
+ * DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
+ * TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
+ * OF THIS SOFTWARE.
+ */
+
+#ifndef WAYLAND_OS_H
+#define WAYLAND_OS_H
+
+int
+wl_os_socket_cloexec(int domain, int type, int protocol);
+
+#endif