Publish portable Darling runtime patch snapshot and testing tools

tools/test-resource-owner-cache.cpp

@@ -0,0 +1,52 @@
+#include "../build/darling-src/src/external/metal/deps/indium/private-include/indium/resource-owner-cache.private.hpp"
+
+#include <cassert>
+#include <iostream>
+#include <random>
+
+struct Base { virtual ~Base() = default; };
+struct Resource : Base {
+    static size_t alive;
+    size_t id;
+    explicit Resource(size_t id) : id(id) { ++alive; }
+    ~Resource() { --alive; }
+};
+size_t Resource::alive = 0;
+
+int main() {
+    std::vector<std::weak_ptr<Base>> weak;
+    {
+        Indium::ResourceOwnerCache<Base, Resource> cache;
+        assert(cache.acquire({}).first == nullptr);
+        // Rehash repeatedly, then release every external owner. All earlier
+        // recorded resources must remain alive until the cache retires.
+        for (size_t i = 0; i < 10000; ++i) {
+            std::shared_ptr<Base> owner = std::make_shared<Resource>(i);
+            weak.push_back(owner);
+            auto [entry, inserted] = cache.acquire(owner);
+            assert(inserted && entry->value->id == i);
+            entry->depthFeedback = i % 2;
+            auto [same, again] = cache.acquire(owner);
+            assert(!again && entry == same);
+        }
+        assert(Resource::alive == weak.size());
+        std::mt19937 random(1234);
+        for (size_t i = 0; i < 100000; ++i) {
+            size_t index = random() % weak.size();
+            auto owner = weak[index].lock();
+            assert(owner);
+            auto [entry, inserted] = cache.acquire(owner);
+            assert(!inserted && entry->owner == owner);
+            assert(entry->value->id == index && entry->depthFeedback == bool(index % 2));
+        }
+        // A failed private cast is cached safely, while its base stays owned.
+        auto other = std::make_shared<Base>();
+        std::weak_ptr<Base> otherWeak = other;
+        assert(cache.acquire(other).first->value == nullptr);
+        other.reset();
+        assert(!otherWeak.expired());
+    }
+    assert(Resource::alive == 0);
+    for (const auto& owner : weak) assert(owner.expired());
+    std::cout << "owner-cache lifetime, rehash, repeated lookup and cast tests passed\n";
+}