From f4d834c9af6e441acb02f303eee6e4bc140f02c0 Mon Sep 17 00:00:00 2001
From: Magnus Kokk <magnus@kokk.eu>
Date: Mon, 29 Apr 2024 23:40:46 +0300
Subject: [PATCH] Test cache finalizer

---
 cache.go                         |  8 +++-----
 cache_test.go                    | 24 ++++++++++++++++++++++++
 internal/backend/backend_test.go |  4 ++--
 3 files changed, 29 insertions(+), 7 deletions(-)

diff --git a/cache.go b/cache.go
index e59f600..8bce266 100644
--- a/cache.go
+++ b/cache.go
@@ -18,14 +18,12 @@ type Cache[K comparable, V any] struct {
 
 // New creates an empty cache.
 func New[K comparable, V any](capacity int) *Cache[K, V] {
-	b := backend.NewBackend[K, V](capacity)
-
 	c := &Cache[K, V]{
-		backend: b,
+		backend: backend.NewBackend[K, V](capacity),
 	}
 
-	runtime.SetFinalizer(c, func(any) {
-		b.Close()
+	runtime.SetFinalizer(c, func(c *Cache[K, V]) {
+		c.backend.Close()
 	})
 
 	return c
diff --git a/cache_test.go b/cache_test.go
index 24c9b92..71e5e77 100644
--- a/cache_test.go
+++ b/cache_test.go
@@ -2,6 +2,7 @@ package evcache_test
 
 import (
 	"fmt"
+	"runtime"
 	"testing"
 	"time"
 
@@ -225,3 +226,26 @@ func TestExpireEdgeCase(t *testing.T) {
 		return c.Len() == 0
 	})
 }
+
+func TestCacheGoGC(t *testing.T) {
+	capacity := 1_000_000
+	c := evcache.New[int, byte](capacity)
+
+	for i := range capacity {
+		c.LoadOrStore(i, 0, 0)
+	}
+
+	var stats runtime.MemStats
+
+	runtime.ReadMemStats(&stats)
+	t.Logf("alloc before:\t%d bytes", stats.Alloc)
+
+	runtime.KeepAlive(c)
+
+	// Run GC twice to account for the finalizer.
+	runtime.GC()
+	runtime.GC()
+
+	runtime.ReadMemStats(&stats)
+	t.Logf("alloc after:\t%d bytes", stats.Alloc)
+}
diff --git a/internal/backend/backend_test.go b/internal/backend/backend_test.go
index 5980f44..f6ccf06 100644
--- a/internal/backend/backend_test.go
+++ b/internal/backend/backend_test.go
@@ -199,12 +199,12 @@ func assertCacheLen[K comparable, V any](t *testing.T, be *backend.Backend[K, V]
 	Equal(t, getMapRangeCount(be), n)
 }
 
-func fillCache(t *testing.T, b *backend.Backend[int, int], capacity int) {
+func fillCache[V any](t *testing.T, b *backend.Backend[int, V], capacity int) {
 	for i := 0; i < capacity; i++ {
 		elem := b.Reserve(i)
 		_, loaded := b.LoadOrStore(elem)
 		Equal(t, loaded, false)
-		b.Initialize(elem, 0, 0)
+		b.Initialize(elem, *new(V), 0)
 	}
 
 	assertCacheLen(t, b, capacity)