From 302e9f5f09fbd5a4bc3f1eeab12c8b45d325cb0c Mon Sep 17 00:00:00 2001
From: Matt Borland <matt@mattborland.com>
Date: Fri, 20 Jan 2023 08:48:35 -0800
Subject: [PATCH] Workaround for warning C4146

---
 include/boost/charconv/detail/apply_sign.hpp | 29 ++++++++++++++++++++
 include/boost/charconv/from_chars.hpp        | 13 +--------
 include/boost/charconv/to_chars.hpp          |  5 ++--
 3 files changed, 33 insertions(+), 14 deletions(-)
 create mode 100644 include/boost/charconv/detail/apply_sign.hpp

diff --git a/include/boost/charconv/detail/apply_sign.hpp b/include/boost/charconv/detail/apply_sign.hpp
new file mode 100644
index 0000000..244c0bb
--- /dev/null
+++ b/include/boost/charconv/detail/apply_sign.hpp
@@ -0,0 +1,29 @@
+// Copyright 2023 Matt Borland
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#ifndef BOOST_CHARCONV_DETAIL_APPLY_SIGN_HPP
+#define BOOST_CHARCONV_DETAIL_APPLY_SIGN_HPP
+
+// Workaround for warning C4146: unary minus operator applied to unsigned type, result still unsigned
+// Occurs using MSVC with pre-C++17 language standards
+
+#include <type_traits>
+
+namespace boost { namespace charconv { namespace detail {
+
+template <typename Integer, typename std::enable_if<std::is_signed<Integer>::value, bool>::type = true>
+constexpr Integer apply_sign(Integer val) noexcept
+{
+    return -val;
+}
+
+template <typename Integer, typename std::enable_if<std::is_unsigned<Integer>::value, bool>::type = true>
+constexpr Integer apply_sign(Integer val) noexcept
+{
+    return val;
+}
+
+}}} // Namespaces
+
+#endif // BOOST_CHARCONV_DETAIL_APPLY_SIGN_HPP
diff --git a/include/boost/charconv/from_chars.hpp b/include/boost/charconv/from_chars.hpp
index 9e5fcc6..4f8f040 100644
--- a/include/boost/charconv/from_chars.hpp
+++ b/include/boost/charconv/from_chars.hpp
@@ -6,6 +6,7 @@
 #ifndef BOOST_CHARCONV_FROM_CHARS_HPP_INCLUDED
 #define BOOST_CHARCONV_FROM_CHARS_HPP_INCLUDED
 
+#include <boost/charconv/detail/apply_sign.hpp>
 #include <boost/charconv/config.hpp>
 #include <boost/config.hpp>
 #include <type_traits>
@@ -67,18 +68,6 @@ constexpr unsigned char digit_from_char(char val) noexcept
     return uchar_values[static_cast<std::size_t>(val)];
 }
 
-template <typename Integer, typename std::enable_if<std::is_signed<Integer>::value, bool>::type = true>
-constexpr Integer apply_sign(Integer val) noexcept
-{
-    return -val;
-}
-
-template <typename Integer, typename std::enable_if<std::is_unsigned<Integer>::value, bool>::type = true>
-constexpr Integer apply_sign(Integer val) noexcept
-{
-    return val;
-}
-
 template <typename Integer>
 BOOST_CXX14_CONSTEXPR boost::charconv::from_chars_result from_chars_integer_impl(const char* first, const char* last, Integer& value, int base) noexcept
 {
diff --git a/include/boost/charconv/to_chars.hpp b/include/boost/charconv/to_chars.hpp
index b4e2cf6..1503c29 100644
--- a/include/boost/charconv/to_chars.hpp
+++ b/include/boost/charconv/to_chars.hpp
@@ -6,6 +6,7 @@
 #ifndef BOOST_CHARCONV_TO_CHARS_HPP_INCLUDED
 #define BOOST_CHARCONV_TO_CHARS_HPP_INCLUDED
 
+#include <boost/charconv/detail/apply_sign.hpp>
 #include <boost/charconv/detail/integer_search_trees.hpp>
 #include <boost/charconv/config.hpp>
 #include <type_traits>
@@ -109,7 +110,7 @@ BOOST_CXX14_CONSTEXPR to_chars_result to_chars_integer_impl(char* first, char* l
     {
         if (value < 0)
         {
-            value = -value;
+            value = apply_sign(value);
             is_negative = true;
         }
     }
@@ -119,7 +120,7 @@ BOOST_CXX14_CONSTEXPR to_chars_result to_chars_integer_impl(char* first, char* l
     // are present and then decompose the value into two (or more) std::uint32_t of known length so that we
     // don't have the issue of removing leading zeros from the least significant digits
     
-    // Yields: warning C4127: conditional expression is constant becuase first half the expression is constant
+    // Yields: warning C4127: conditional expression is constant becuase first half of the expression is constant
     // but we need to short circuit to avoid UB on the second half
     if (std::numeric_limits<Integer>::digits <= std::numeric_limits<std::uint32_t>::digits ||
         value <= static_cast<Integer>((std::numeric_limits<std::uint32_t>::max)()))