A decoded string owns its bytes

zap reads text zero-copy over the frame that arrived, and Call releases that
frame to the pool when it returns, so a reply's strings pointed into memory the
next call overwrites. The generated codecs already copy text for this reason;
the reflective decoder now does the same.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

internal/zapenc/alias_test.go

@@ -0,0 +1,34 @@
+package zapenc_test
+
+import (
+	"testing"
+
+	"github.com/zap-proto/zip/internal/zapenc"
+)
+
+// A decoded value owns its strings. The transport hands Unmarshal a pooled frame
+// and reuses it for the next call, so a string that still pointed into the frame
+// would change under whoever kept it.
+func TestDecodedTextOutlivesTheFrame(t *testing.T) {
+	type site struct {
+		Bucket string
+		Prefix string
+		Opt    *string
+		Inner  inner
+	}
+	s := "gone"
+	frame, err := zapenc.Marshal(&site{Bucket: "hanzo-sites", Prefix: "hanzo/bootnode", Opt: &s, Inner: inner{Slug: "bootnode"}})
+	if err != nil {
+		t.Fatal(err)
+	}
+	var got site
+	if err := zapenc.Unmarshal(frame, &got); err != nil {
+		t.Fatal(err)
+	}
+	for i := range frame {
+		frame[i] = 'x'
+	}
+	if got.Bucket != "hanzo-sites" || got.Prefix != "hanzo/bootnode" || got.Opt == nil || *got.Opt != "gone" || got.Inner.Slug != "bootnode" {
+		t.Fatalf("decoded strings follow the frame: %+v opt=%v", got, got.Opt)
+	}
+}

internal/zapenc/zapenc.go

@@ -52,6 +52,7 @@ import (
 	"math"
 	"reflect"
 	"strconv"
+	"strings"
 	"sync"
 
 	zap "github.com/zap-proto/go"
@@ -593,7 +594,10 @@ func readField(o zap.Object, f field, target reflect.Value) error {
 	case kFloat64:
 		target.SetFloat(o.Float64(f.offset))
 	case kText:
-		target.SetString(o.Text(f.offset))
+		// zap reads text zero-copy, over the frame that arrived, and the caller's
+		// transport reuses that frame once the call returns. The decoded value
+		// outlives the call, so it is copied here, as the generated codecs copy.
+		target.SetString(strings.Clone(o.Text(f.offset)))
 	case kBytes:
 		if b := o.Bytes(f.offset); len(b) > 0 {
 			target.SetBytes(append([]byte(nil), b...))