Return values as copies when converting

Previously, value conversions were made on the original value, and thus,
calling methods like `Value.Int` had the side-effect of changing the
value's type for subsequent calls to `Value.Interface`. Any conversion
required happens on value copies, which are automatically destroyed
after use.

value/value.c

@@ -93,43 +93,67 @@ void value_object_add_property(engine_value *obj, const char *key, engine_value
 }
 
 int value_get_long(engine_value *val) {
-	// Covert value to long if needed.
-	if (Z_TYPE_P(val->value) != IS_LONG) {
-		convert_to_long(val->value);
-		val->kind = Z_TYPE_P(val->value);
+	// Return value directly if already in correct type.
+	if (val->kind == IS_LONG) {
+		return Z_LVAL_P(val->value);
 	}
 
-	return Z_LVAL_P(val->value);
+	zval *tmp = value_copy(val->value);
+
+	convert_to_long(tmp);
+	long v = Z_LVAL_P(tmp);
+
+	zval_dtor(tmp);
+
+	return v;
 }
 
 double value_get_double(engine_value *val) {
-	// Covert value to double if needed.
-	if (Z_TYPE_P(val->value) != IS_DOUBLE) {
-		convert_to_double(val->value);
-		val->kind = Z_TYPE_P(val->value);
+	// Return value directly if already in correct type.
+	if (val->kind == IS_DOUBLE) {
+		return Z_DVAL_P(val->value);
 	}
 
-	return Z_DVAL_P(val->value);
+	zval *tmp = value_copy(val->value);
+
+	convert_to_double(tmp);
+	double v = Z_DVAL_P(tmp);
+
+	zval_dtor(tmp);
+
+	return v;
 }
 
 bool value_get_bool(engine_value *val) {
-	// Covert value to long if needed.
-	if (Z_TYPE_P(val->value) != IS_BOOL) {
-		convert_to_boolean(val->value);
-		val->kind = Z_TYPE_P(val->value);
+	// Return value directly if already in correct type.
+	if (val->kind == IS_BOOL) {
+		return Z_BVAL_P(val->value);
 	}
 
-	return Z_BVAL_P(val->value);
+	zval *tmp = value_copy(val->value);
+
+	convert_to_boolean(tmp);
+	bool v = Z_BVAL_P(tmp);
+
+	zval_dtor(tmp);
+
+	return v;
 }
 
 char *value_get_string(engine_value *val) {
-	// Covert value to string if needed.
-	if (Z_TYPE_P(val->value) != IS_STRING) {
-		convert_to_cstring(val->value);
-		val->kind = Z_TYPE_P(val->value);
+	// Return value directly if already in correct type.
+	if (val->kind == IS_STRING) {
+		return Z_STRVAL_P(val->value);
 	}
 
-	return Z_STRVAL_P(val->value);
+	zval *tmp = value_copy(val->value);
+
+	convert_to_cstring(tmp);
+	char *v = Z_STRVAL_P(tmp);
+
+	zval_dtor(tmp);
+
+	return v;
 }
 
 void value_destroy(engine_value *val) {

value/value.go

@@ -55,8 +55,6 @@ func (v *Value) Interface() interface{} {
 		return v.Float()
 	case Bool:
 		return v.Bool()
-	// case Array:
-	// 	return v.Map()
 	case String:
 		return v.String()
 	}

value/value.h

@@ -10,6 +10,16 @@ typedef struct _engine_value {
 	int kind;
 } engine_value;
 
+static inline zval *value_copy(zval *zv) {
+	zval *tmp;
+
+	ALLOC_ZVAL(tmp);
+	INIT_PZVAL_COPY(tmp, zv);
+	zval_copy_ctor(tmp);
+
+	return tmp;
+}
+
 engine_value *value_new(zval *zv);
 int value_kind(engine_value *val);
 void value_destroy(engine_value *val);