fix: wrong behaviors on nested interface

fix #359

decode_test.go

@@ -3918,3 +3918,16 @@ func TestIssue360(t *testing.T) {
 		t.Errorf("unexpected result: %v", uints)
 	}
 }
+
+func TestIssue359(t *testing.T) {
+	var a interface{} = 1
+	var b interface{} = &a
+	var c interface{} = &b
+	v, err := json.Marshal(c)
+	if err != nil {
+		t.Errorf("unexpected error: %v", err)
+	}
+	if string(v) != "1" {
+		t.Errorf("unexpected result: %v", string(v))
+	}
+}

internal/cmd/generator/vm.go.tmpl

@@ -14,6 +14,7 @@ func Run(ctx *encoder.RuntimeContext, b []byte, codeSet *encoder.OpcodeSet) ([]b
 	recursiveLevel := 0
 	ptrOffset := uintptr(0)
 	ctxptr := ctx.Ptr()
+	codeLength := uintptr(codeSet.CodeLength)
 	var code *encoder.Opcode
 	if (ctx.Option.Flag & encoder.HTMLEscapeOption) != 0 {
 		code = codeSet.EscapeKeyCode
@@ -204,8 +205,8 @@ func Run(ctx *encoder.RuntimeContext, b []byte, codeSet *encoder.OpcodeSet) ([]b
 				return nil, err
 			}
 
-			totalLength := uintptr(code.Length) + 3
-			nextTotalLength := uintptr(ifaceCodeSet.CodeLength) + 3
+			totalLength := codeLength + 4
+			nextTotalLength := uintptr(ifaceCodeSet.CodeLength) + 4
 
 			var c *encoder.Opcode
 			if (ctx.Option.Flag & encoder.HTMLEscapeOption) != 0 {
@@ -219,6 +220,8 @@ func Run(ctx *encoder.RuntimeContext, b []byte, codeSet *encoder.OpcodeSet) ([]b
 			ptrOffset += totalLength * uintptrSize
 			oldBaseIndent := ctx.BaseIndent
 			ctx.BaseIndent += code.Indent
+			oldCodeLength := codeLength
+			codeLength = uintptr(ifaceCodeSet.CodeLength)
 
 			newLen := offsetNum + totalLength + nextTotalLength
 			if curlen < newLen {
@@ -231,6 +234,7 @@ func Run(ctx *encoder.RuntimeContext, b []byte, codeSet *encoder.OpcodeSet) ([]b
 			store(ctxptr, end.Idx, oldOffset)
 			store(ctxptr, end.ElemIdx, uintptr(unsafe.Pointer(code.Next)))
 			storeIndent(ctxptr, end, uintptr(oldBaseIndent))
+			store(ctxptr, end.Offset, oldCodeLength)
 			code = c
 			recursiveLevel++
 		case encoder.OpInterfaceEnd:
@@ -239,6 +243,7 @@ func Run(ctx *encoder.RuntimeContext, b []byte, codeSet *encoder.OpcodeSet) ([]b
 			// restore ctxptr
 			offset := load(ctxptr, code.Idx)
 			restoreIndent(ctx, code, ctxptr)
+			codeLength = load(ctxptr, code.Offset)
 			ctx.SeenPtr = ctx.SeenPtr[:len(ctx.SeenPtr)-1]
 
 			codePtr := load(ctxptr, code.ElemIdx)

internal/encoder/opcode.go

@@ -385,6 +385,7 @@ func copyToInterfaceOpcode(code *Opcode) *Opcode {
 	c.Idx += uintptrSize
 	c.ElemIdx = c.Idx + uintptrSize
 	c.Length = c.Idx + 2*uintptrSize
+	c.Offset = c.Idx + 3*uintptrSize
 	c.Op = OpInterfaceEnd
 	return copied
 }