compositor: turn weston main() into a lib

This takes everything that was in 'weston' the executable a turns it into
library. A new trivial 'weston' executable is written.

Creating the library will allow future improvements:

- we can link weston plugins against the library, meaning that they no longer
  need unresolved symbols to be allowed during linking

- tests do not have to fork() and exec() 'weston', they can just link to the
  library and call wet_main() after setting things up; this will help with
  using a debugger

install_rpath is set so that we can install the library into weston's module
directory, away from the normal libraries in a system. This is one library we
do not intend for others to use.

The library has no stable ABI and is not versioned.

Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.com>

compositor/executable.c

@@ -0,0 +1,34 @@
+/*
+ * Copyright © 2019 Collabora, Ltd.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the
+ * next paragraph) shall be included in all copies or substantial
+ * portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT.  IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include "config.h"
+
+#include "weston.h"
+
+int
+main(int argc, char *argv[])
+{
+	return wet_main(argc, argv);
+}

compositor/main.c

@@ -3101,7 +3101,8 @@ weston_log_subscribe_to_scopes(struct weston_log_context *log_ctx,
 	}
 }
 
-int main(int argc, char *argv[])
+WL_EXPORT int
+wet_main(int argc, char *argv[])
 {
 	int ret = EXIT_FAILURE;
 	char *cmdline;

compositor/meson.build

@@ -26,12 +26,27 @@ if get_option('xwayland')
 	config_h.set_quoted('XSERVER_PATH', get_option('xwayland-path'))
 endif
 
+libexec_weston = shared_library(
+	'exec_weston',
+	sources: srcs_weston,
+	include_directories: common_inc,
+	dependencies: deps_weston,
+	install_dir: dir_module_weston,
+	install: true,
+	version: '0.0.0',
+	soversion: 0
+)
+dep_libexec_weston = declare_dependency(
+	link_with: libexec_weston,
+	include_directories: [ include_directories('.'), public_inc ],
+	dependencies: dep_libweston_public
+)
 exe_weston = executable(
 	'weston',
-	srcs_weston,
+	'executable.c',
 	include_directories: common_inc,
-	link_args: [ '-Wl,-export-dynamic' ],
-	dependencies: deps_weston,
+	dependencies: dep_libexec_weston,
+	install_rpath: dir_module_weston,
 	install: true
 )
 install_headers('weston.h', subdir: 'weston')

compositor/weston.h

@@ -95,6 +95,9 @@ text_backend_init(struct weston_compositor *ec);
 void
 text_backend_destroy(struct text_backend *text_backend);
 
+int
+wet_main(int argc, char *argv[]);
+
 #ifdef  __cplusplus
 }
 #endif