fix: account for recursion when stringing to avoid overflow

gnovm/pkg/gnolang/values_string.go

@@ -7,78 +7,115 @@
 	"strings"
 )
 
+const recursed string = "<recursed>"
+
 func (v StringValue) String() string {
 	return strconv.Quote(string(v))
 }
 
-func (bv BigintValue) String() string {
-	return bv.V.String()
+func (v BigintValue) String() string {
+	return v.V.String()
+}
+
+func (v BigdecValue) String() string {
+	return v.V.String()
 }
 
-func (bv BigdecValue) String() string {
-	return bv.V.String()
+func (v DataByteValue) String() string {
+	return fmt.Sprintf("(%0X)", (v.GetByte()))
 }
 
-func (dbv DataByteValue) String() string {
-	return fmt.Sprintf("(%0X)", (dbv.GetByte()))
+func (v *ArrayValue) String() string {
+	return v.ProtectedString(map[Value]struct{}{})
 }
 
-func (av *ArrayValue) String() string {
-	ss := make([]string, len(av.List))
-	if av.Data == nil {
-		for i, e := range av.List {
-			ss[i] = e.String()
+func (v *ArrayValue) ProtectedString(seen map[Value]struct{}) string {
+	if _, ok := seen[v]; ok {
+		return recursed
+	}
+
+	seen[v] = struct{}{}
+	ss := make([]string, len(v.List))
+	if v.Data == nil {
+		for i, e := range v.List {
+			ss[i] = e.ProtectedString(seen)
 		}
 		// NOTE: we may want to unify the representation,
 		// but for now tests expect this to be different.
 		// This may be helpful for testing implementation behavior.
 		return "array[" + strings.Join(ss, ",") + "]"
 	}
-	if len(av.Data) > 256 {
-		return fmt.Sprintf("array[0x%X...]", av.Data[:256])
+	if len(v.Data) > 256 {
+		return fmt.Sprintf("array[0x%X...]", v.Data[:256])
 	}
-	return fmt.Sprintf("array[0x%X]", av.Data)
+	return fmt.Sprintf("array[0x%X]", v.Data)
 }
 
-func (sv *SliceValue) String() string {
-	if sv.Base == nil {
+func (v *SliceValue) String() string {
+	return v.ProtectedString(map[Value]struct{}{})
+}
+
+func (v *SliceValue) ProtectedString(seen map[Value]struct{}) string {
+	if v.Base == nil {
 		return "nil-slice"
 	}
-	if ref, ok := sv.Base.(RefValue); ok {
+
+	if _, ok := seen[v]; ok {
+		return recursed
+	}
+
+	if ref, ok := v.Base.(RefValue); ok {
 		return fmt.Sprintf("slice[%v]", ref)
 	}
-	vbase := sv.Base.(*ArrayValue)
+
+	seen[v] = struct{}{}
+	vbase := v.Base.(*ArrayValue)
 	if vbase.Data == nil {
-		ss := make([]string, sv.Length)
-		for i, e := range vbase.List[sv.Offset : sv.Offset+sv.Length] {
-			ss[i] = e.String()
+		ss := make([]string, v.Length)
+		for i, e := range vbase.List[v.Offset : v.Offset+v.Length] {
+			ss[i] = e.ProtectedString(seen)
 		}
 		return "slice[" + strings.Join(ss, ",") + "]"
 	}
-	if sv.Length > 256 {
-		return fmt.Sprintf("slice[0x%X...(%d)]", vbase.Data[sv.Offset:sv.Offset+256], sv.Length)
+	if v.Length > 256 {
+		return fmt.Sprintf("slice[0x%X...(%d)]", vbase.Data[v.Offset:v.Offset+256], v.Length)
 	}
-	return fmt.Sprintf("slice[0x%X]", vbase.Data[sv.Offset:sv.Offset+sv.Length])
+	return fmt.Sprintf("slice[0x%X]", vbase.Data[v.Offset:v.Offset+v.Length])
 }
 
-func (pv PointerValue) String() string {
-	// NOTE: cannot do below, due to recursion problems.
-	// TODO: create a different String2(...) function.
-	// return fmt.Sprintf("&%s", v.TypedValue.String())
-	return fmt.Sprintf("&%p.(*%s)", pv.TV, pv.TV.T.String())
+func (v PointerValue) String() string {
+	return v.ProtectedString(map[Value]struct{}{})
 }
 
-func (sv *StructValue) String() string {
-	ss := make([]string, len(sv.Fields))
-	for i, f := range sv.Fields {
-		ss[i] = f.String()
+func (v PointerValue) ProtectedString(seen map[Value]struct{}) string {
+	if _, ok := seen[v]; ok {
+		return recursed
+	}
+
+	seen[v] = struct{}{}
+	return fmt.Sprintf("&%s", v.TV.ProtectedString(seen))
+}
+
+func (v *StructValue) String() string {
+	return v.ProtectedString(map[Value]struct{}{})
+}
+
+func (v *StructValue) ProtectedString(seen map[Value]struct{}) string {
+	if _, ok := seen[v]; ok {
+		return recursed
+	}
+
+	seen[v] = struct{}{}
+	ss := make([]string, len(v.Fields))
+	for i, f := range v.Fields {
+		ss[i] = f.ProtectedString(seen)
 	}
 	return "struct{" + strings.Join(ss, ",") + "}"
 }
 
-func (fv *FuncValue) String() string {
-	name := string(fv.Name)
-	if fv.Type == nil {
+func (v *FuncValue) String() string {
+	name := string(v.Name)
+	if v.Type == nil {
 		return fmt.Sprintf("incomplete-func ?%s(?)?", name)
 	}
 	return name
@@ -103,12 +140,22 @@
 		recvT, name, params, results)
 }
 
-func (mv *MapValue) String() string {
-	if mv.List == nil {
+func (v *MapValue) String() string {
+	return v.ProtectedString(map[Value]struct{}{})
+}
+
+func (v *MapValue) ProtectedString(seen map[Value]struct{}) string {
+	if v.List == nil {
 		return "zero-map"
 	}
-	ss := make([]string, 0, mv.GetLength())
-	next := mv.List.Head
+
+	if _, ok := seen[v]; ok {
+		return recursed
+	}
+
+	seen[v] = struct{}{}
+	ss := make([]string, 0, v.GetLength())
+	next := v.List.Head
 	for next != nil {
 		ss = append(ss,
 			next.Key.String()+":"+
@@ -133,13 +180,13 @@
 		v.Type.String(), ptr)
 }
 
-func (pv *PackageValue) String() string {
-	return fmt.Sprintf("package(%s %s)", pv.PkgName, pv.PkgPath)
+func (v *PackageValue) String() string {
+	return fmt.Sprintf("package(%s %s)", v.PkgName, v.PkgPath)
 }
 
-func (nv *NativeValue) String() string {
+func (v *NativeValue) String() string {
 	return fmt.Sprintf("gonative{%v}",
-		nv.Value.Interface())
+		v.Value.Interface())
 	/*
 		return fmt.Sprintf("gonative{%v (%s)}",
 			v.Value.Interface(),
@@ -176,10 +223,21 @@
 		res := m.Eval(Call(Sel(&ConstExpr{TypedValue: *tv}, "Error")))
 		return res[0].GetString()
 	}
+
+	return tv.ProtectedSprint(map[Value]struct{}{}, true)
+}
+
+func (tv *TypedValue) ProtectedSprint(seen map[Value]struct{}, considerDeclaredType bool) string {
+
+	if _, ok := seen[tv.V]; ok {
+		return recursed
+	}
+
 	// print declared type
-	if _, ok := tv.T.(*DeclaredType); ok {
-		return tv.String()
+	if _, ok := tv.T.(*DeclaredType); ok && considerDeclaredType {
+		return tv.ProtectedString(seen)
 	}
+
 	// otherwise, default behavior.
 	switch bt := baseOf(tv.T).(type) {
 	case PrimitiveType:
@@ -223,15 +281,15 @@
 		if tv.V == nil {
 			return "invalid-pointer"
 		}
-		return tv.V.(PointerValue).String()
+		return tv.V.(PointerValue).ProtectedString(seen)
 	case *ArrayType:
-		return tv.V.(*ArrayValue).String()
+		return tv.V.(*ArrayValue).ProtectedString(seen)
 	case *SliceType:
-		return tv.V.(*SliceValue).String()
+		return tv.V.(*SliceValue).ProtectedString(seen)
 	case *StructType:
-		return tv.V.(*StructValue).String()
+		return tv.V.(*StructValue).ProtectedString(seen)
 	case *MapType:
-		return tv.V.(*MapValue).String()
+		return tv.V.(*MapValue).ProtectedString(seen)
 	case *FuncType:
 		switch fv := tv.V.(type) {
 		case nil:
@@ -281,6 +339,10 @@
 
 // For gno debugging/testing.
 func (tv TypedValue) String() string {
+	return tv.ProtectedString(map[Value]struct{}{})
+}
+
+func (tv TypedValue) ProtectedString(seen map[Value]struct{}) string {
 	if tv.IsUndefined() {
 		return "(undefined)"
 	}
@@ -317,12 +379,18 @@
 			vs = fmt.Sprintf("%v", tv.GetFloat32())
 		case Float64Type:
 			vs = fmt.Sprintf("%v", tv.GetFloat64())
+		// Complex types that require recusion protection.
 		default:
 			vs = nilStr
 		}
 	} else {
-		vs = fmt.Sprintf("%v", tv.V)
+		// vs = fmt.Sprintf("%v", tv.V)
+		vs = tv.ProtectedSprint(seen, false)
+		if base := baseOf(tv.T); base == StringType || base == UntypedStringType {
+			vs = strconv.Quote(vs)
+		}
 	}
+
 	ts := tv.T.String()
 	return fmt.Sprintf("(%s %s)", vs, ts) // TODO improve
 }