From 09f9bd6b8bbd4e0eff123a94ad013c574797432b Mon Sep 17 00:00:00 2001
From: Benoit Blanchon <git@benoitblanchon.fr>
Date: Mon, 26 Dec 2022 10:21:57 +0100
Subject: [PATCH] Fix detection of char types

---
 extras/tests/Misc/StringAdapters.cpp           |  3 +++
 src/ArduinoJson/Serialization/serialize.hpp    |  8 ++------
 src/ArduinoJson/Strings/Adapters/RamString.hpp | 10 +++++++---
 3 files changed, 12 insertions(+), 9 deletions(-)

diff --git a/extras/tests/Misc/StringAdapters.cpp b/extras/tests/Misc/StringAdapters.cpp
index 19adab98..02282334 100644
--- a/extras/tests/Misc/StringAdapters.cpp
+++ b/extras/tests/Misc/StringAdapters.cpp
@@ -86,6 +86,8 @@ TEST_CASE("custom_string") {
   CHECK(s.size() == 5);
 }
 
+struct EmptyStruct {};
+
 TEST_CASE("IsString<T>") {
   CHECK(IsString<std::string>::value == true);
   CHECK(IsString<std::basic_string<wchar_t> >::value == false);
@@ -95,6 +97,7 @@ TEST_CASE("IsString<T>") {
   CHECK(IsString<const char[8]>::value == true);
   CHECK(IsString< ::String>::value == true);
   CHECK(IsString< ::StringSumHelper>::value == true);
+  CHECK(IsString<const EmptyStruct*>::value == false);
 }
 
 TEST_CASE("stringCompare") {
diff --git a/src/ArduinoJson/Serialization/serialize.hpp b/src/ArduinoJson/Serialization/serialize.hpp
index e65bb3a7..cc57b4c6 100644
--- a/src/ArduinoJson/Serialization/serialize.hpp
+++ b/src/ArduinoJson/Serialization/serialize.hpp
@@ -40,12 +40,8 @@ serialize(JsonVariantConst source, void* buffer, size_t bufferSize) {
 }
 
 template <template <typename> class TSerializer, typename TChar, size_t N>
-#if defined _MSC_VER && _MSC_VER < 1900
-typename enable_if<sizeof(remove_reference<TChar>::type) == 1, size_t>::type
-#else
-typename enable_if<sizeof(TChar) == 1, size_t>::type
-#endif
-serialize(JsonVariantConst source, TChar (&buffer)[N]) {
+typename enable_if<IsChar<TChar>::value, size_t>::type serialize(
+    JsonVariantConst source, TChar (&buffer)[N]) {
   return serialize<TSerializer>(source, buffer, N);
 }
 
diff --git a/src/ArduinoJson/Strings/Adapters/RamString.hpp b/src/ArduinoJson/Strings/Adapters/RamString.hpp
index fabd5e09..7a77a296 100644
--- a/src/ArduinoJson/Strings/Adapters/RamString.hpp
+++ b/src/ArduinoJson/Strings/Adapters/RamString.hpp
@@ -13,6 +13,10 @@
 
 namespace ARDUINOJSON_NAMESPACE {
 
+template <typename T>
+struct IsChar
+    : integral_constant<bool, is_integral<T>::value && sizeof(T) == 1> {};
+
 class ZeroTerminatedRamString {
  public:
   static const size_t typeSortKey = 3;
@@ -58,7 +62,7 @@ class ZeroTerminatedRamString {
 };
 
 template <typename TChar>
-struct StringAdapter<TChar*, typename enable_if<sizeof(TChar) == 1>::type> {
+struct StringAdapter<TChar*, typename enable_if<IsChar<TChar>::value>::type> {
   typedef ZeroTerminatedRamString AdaptedString;
 
   static AdaptedString adapt(const TChar* p) {
@@ -67,7 +71,7 @@ struct StringAdapter<TChar*, typename enable_if<sizeof(TChar) == 1>::type> {
 };
 
 template <typename TChar, size_t N>
-struct StringAdapter<TChar[N], typename enable_if<sizeof(TChar) == 1>::type> {
+struct StringAdapter<TChar[N], typename enable_if<IsChar<TChar>::value>::type> {
   typedef ZeroTerminatedRamString AdaptedString;
 
   static AdaptedString adapt(const TChar* p) {
@@ -128,7 +132,7 @@ class SizedRamString {
 
 template <typename TChar>
 struct SizedStringAdapter<TChar*,
-                          typename enable_if<sizeof(TChar) == 1>::type> {
+                          typename enable_if<IsChar<TChar>::value>::type> {
   typedef SizedRamString AdaptedString;
 
   static AdaptedString adapt(const TChar* p, size_t n) {