Hot-Reloading Refactor

Signed-off-by: Jason Volk <jason@zemos.net>

src/core/mods/canary.rs

@@ -0,0 +1,28 @@
+use std::sync::atomic::{AtomicI32, Ordering};
+
+const ORDERING: Ordering = Ordering::Relaxed;
+static STATIC_DTORS: AtomicI32 = AtomicI32::new(0);
+
+/// Called by Module::unload() to indicate module is about to be unloaded and
+/// static destruction is intended. This will allow verifying it actually took
+/// place.
+pub(crate) fn prepare() {
+	let count = STATIC_DTORS.fetch_sub(1, ORDERING);
+	debug_assert!(count <= 0, "STATIC_DTORS should not be greater than zero.");
+}
+
+/// Called by static destructor of a module. This call should only be found
+/// inside a mod_fini! macro. Do not call from anywhere else.
+#[inline(always)]
+pub fn report() { let _count = STATIC_DTORS.fetch_add(1, ORDERING); }
+
+/// Called by Module::unload() (see check()) with action in case a check()
+/// failed. This can allow a stuck module to be noted while allowing for other
+/// independent modules to be diagnosed.
+pub(crate) fn check_and_reset() -> bool { STATIC_DTORS.swap(0, ORDERING) == 0 }
+
+/// Called by Module::unload() after unload to verify static destruction took
+/// place. A call to prepare() must be made prior to Module::unload() and making
+/// this call.
+#[allow(dead_code)]
+pub(crate) fn check() -> bool { STATIC_DTORS.load(ORDERING) == 0 }