Validate selector support at run time.

ext/io/event/selector/epoll.c

@@ -1035,7 +1035,25 @@ VALUE IO_Event_Selector_EPoll_wakeup(VALUE self) {
 	return Qfalse;
 }
 
+static int IO_Event_Selector_EPoll_supported_p(void) {
+	int fd = epoll_create1(EPOLL_CLOEXEC);
+
+	if (fd < 0) {
+		rb_warn("epoll_create1() was available at compile time but failed at run time: %s\n", strerror(errno));
+
+		return 0;
+	}
+
+	close(fd);
+
+	return 1;
+}
+
 void Init_IO_Event_Selector_EPoll(VALUE IO_Event_Selector) {
+	if (!IO_Event_Selector_EPoll_supported_p()) {
+		return;
+	}
+
 	VALUE IO_Event_Selector_EPoll = rb_define_class_under(IO_Event_Selector, "EPoll", rb_cObject);
 
 	rb_define_alloc_func(IO_Event_Selector_EPoll, IO_Event_Selector_EPoll_allocate);

ext/io/event/selector/kqueue.c

@@ -1045,7 +1045,26 @@ VALUE IO_Event_Selector_KQueue_wakeup(VALUE self) {
 	return Qfalse;
 }
 
+
+static int IO_Event_Selector_KQueue_supported_p(void) {
+	int fd = kqueue();
+
+	if (fd < 0) {
+		rb_warn("kqueue() was available at compile time but failed at run time: %s\n", strerror(errno));
+
+		return 0;
+	}
+
+	close(fd);
+
+	return 1;
+}
+
 void Init_IO_Event_Selector_KQueue(VALUE IO_Event_Selector) {
+	if (!IO_Event_Selector_KQueue_supported_p()) {
+		return;
+	}
+
 	VALUE IO_Event_Selector_KQueue = rb_define_class_under(IO_Event_Selector, "KQueue", rb_cObject);
 
 	rb_define_alloc_func(IO_Event_Selector_KQueue, IO_Event_Selector_KQueue_allocate);

ext/io/event/selector/uring.c

@@ -1175,7 +1175,26 @@ VALUE IO_Event_Selector_URing_wakeup(VALUE self) {
 
 #pragma mark - Native Methods
 
+static int IO_Event_Selector_URing_supported_p(void) {
+	struct io_uring ring;
+	int result = io_uring_queue_init(32, &ring, 0);
+
+	if (result < 0) {
+		rb_warn("io_uring_queue_init() was available at compile time but failed at run time: %s\n", strerror(-result));
+
+		return 0;
+	}
+
+	io_uring_queue_exit(&ring);
+
+	return 1;
+}
+
 void Init_IO_Event_Selector_URing(VALUE IO_Event_Selector) {
+	if (!IO_Event_Selector_URing_supported_p()) {
+		return;
+	}
+
 	VALUE IO_Event_Selector_URing = rb_define_class_under(IO_Event_Selector, "URing", rb_cObject);
 
 	rb_define_alloc_func(IO_Event_Selector_URing, IO_Event_Selector_URing_allocate);

releases.md

@@ -3,6 +3,7 @@
 ## Unreleased
 
   - `IO::Event::Profiler` is moved to dedicated gem: [fiber-profiler](https://github.com/socketry/fiber-profiler).
+  - Perform runtime checks for native selectors to ensure they are supported in the current environment. While compile-time checks determine availability, restrictions like seccomp and SELinux may still prevent them from working.
 
 ## v1.9.0