Avoid oversized cycle detector allocation

izidic.go

@@ -128,10 +128,15 @@ func (dic *container) Service(name string) (any, error) {
 	// for at least one service was attempted more than once, which implies a
 	// dependency cycle.
 	const funcName = "github.com/fgm/izidic.(*container).Service"
-	// We need a vastly oversized value to cover the case of deeply nested dic.Service() calls.
-	pcs := make([]uintptr, 1e6)
-	n := runtime.Callers(1, pcs)
-	pcs = pcs[:n]
+	pcs := make([]uintptr, 64)
+	for {
+		n := runtime.Callers(1, pcs)
+		if n < len(pcs) {
+			pcs = pcs[:n]
+			break
+		}
+		pcs = make([]uintptr, 2*len(pcs))
+	}
 	frames := runtime.CallersFrames(pcs)
 	serviceCalls := 0
 	for {

izidic_test.go

@@ -3,6 +3,7 @@ package izidic_test
 import (
 	"errors"
 	"fmt"
+	"runtime"
 	"strings"
 	"testing"
 
@@ -98,6 +99,28 @@ func TestContainer_Service(t *testing.T) {
 	}
 }
 
+func TestContainer_Service_AvoidsOversizedCycleDetectorAllocation(t *testing.T) {
+	const maxAllocatedBytes = 1 << 20
+
+	runtime.GC()
+	var before runtime.MemStats
+	runtime.ReadMemStats(&before)
+
+	dic := izidic.New()
+	dic.Register("s", s1)
+	_, err := dic.Service("s")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	var after runtime.MemStats
+	runtime.ReadMemStats(&after)
+	allocatedBytes := after.TotalAlloc - before.TotalAlloc
+	if allocatedBytes > maxAllocatedBytes {
+		t.Fatalf("Service allocated %d bytes, expected at most %d", allocatedBytes, maxAllocatedBytes)
+	}
+}
+
 func TestContainer_MustService_Missing(t *testing.T) {
 	const expectedFormat = "service not found: %q"
 	defer func() {