Use epoll-shim to emulate epoll(7) on FreeBSD

FreeBSD does not provide epoll(7) and instead requires an external library,
epoll-shim, that implements epoll() using kqueue(2)

Co-authored-by: Jan Beich <jbeich@FreeBSD.org>
Signed-off-by: Alex Richardson <Alexander.Richardson@cl.cam.ac.uk>

meson.build

@@ -43,6 +43,14 @@ foreach f: have_funcs
 endforeach
 
 if get_option('libraries')
+	if host_machine.system() == 'freebsd'
+		# When building for FreeBSD, epoll(7) is provided by a userspace
+		# wrapper around kqueue(2).
+		epoll_dep = dependency('epoll-shim')
+	else
+		# Otherwise, assume that epoll(7) is supported natively.
+		epoll_dep = []
+	endif
 	ffi_dep = dependency('libffi')
 
 	decls = [
@@ -52,7 +60,7 @@ if get_option('libraries')
 	]
 
 	foreach d: decls
-		if not cc.has_header_symbol(d['header'], d['symbol'])
+		if not cc.has_header_symbol(d['header'], d['symbol'], dependencies: epoll_dep)
 			error('@0@ is needed to compile Wayland libraries'.format(d['symbol']))
 		endif
 	endforeach

src/meson.build

@@ -89,7 +89,7 @@ if get_option('libraries')
 			'connection.c',
 			'wayland-os.c'
 		],
-		dependencies: [ ffi_dep, rt_dep ]
+		dependencies: [ epoll_dep, ffi_dep, rt_dep ]
 	)
 
 	wayland_private_dep = declare_dependency(
@@ -163,6 +163,7 @@ if get_option('libraries')
 		],
 		version: '0.1.0',
 		dependencies: [
+			epoll_dep,
 			ffi_dep,
 			wayland_private_dep,
 			wayland_util_dep,
@@ -177,7 +178,7 @@ if get_option('libraries')
 	wayland_server_dep = declare_dependency(
 		link_with: wayland_server,
 		include_directories: [ root_inc, include_directories('.') ],
-		dependencies: [ ffi_dep, mathlib_dep, threads_dep ],
+		dependencies: [ epoll_dep, ffi_dep, mathlib_dep, threads_dep ],
 		sources: [
 			wayland_server_protocol_core_h,
 			wayland_server_protocol_h
@@ -206,6 +207,7 @@ if get_option('libraries')
 		],
 		version: '0.3.0',
 		dependencies: [
+			epoll_dep,
 			ffi_dep,
 			wayland_private_dep,
 			wayland_util_dep,

tests/meson.build

@@ -9,6 +9,7 @@ test_runner = static_library(
 	dependencies: [
 		cc.find_library('dl', required: false),
 		dependency('threads'),
+		epoll_dep,
 		ffi_dep,
 		wayland_util_dep,
 		wayland_private_dep,
@@ -154,7 +155,7 @@ tests = {
 
 foreach test_name, test_extra_sources: tests
 	test_sources = [ test_name + '.c' ] + test_extra_sources
-	test_deps = [test_runner_dep]
+	test_deps = [test_runner_dep, epoll_dep]
 	bin = executable(test_name, test_sources, dependencies: test_deps)
 	test(
 		test_name,