From 88fbe3ac3436961ffe26842080024cbf8ce64dc4 Mon Sep 17 00:00:00 2001
From: Benoit Blanchon <git@benoitblanchon.fr>
Date: Thu, 15 Apr 2021 11:21:34 +0200
Subject: [PATCH] Fixed undefined behavior in JSON serializer

---
 src/ArduinoJson/Json/TextFormatter.hpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/ArduinoJson/Json/TextFormatter.hpp b/src/ArduinoJson/Json/TextFormatter.hpp
index 23d16d03..18694f14 100644
--- a/src/ArduinoJson/Json/TextFormatter.hpp
+++ b/src/ArduinoJson/Json/TextFormatter.hpp
@@ -92,9 +92,9 @@ class TextFormatter {
     unsigned_type unsigned_value;
     if (value < 0) {
       writeRaw('-');
-      unsigned_value = static_cast<unsigned_type>(-value);
+      unsigned_value = unsigned_type(unsigned_type(~value) + 1);
     } else {
-      unsigned_value = static_cast<unsigned_type>(value);
+      unsigned_value = unsigned_type(value);
     }
     writeInteger(unsigned_value);
   }