From dfa24289437797cb9794ecea05cb2c710c6b99de Mon Sep 17 00:00:00 2001
From: Junekey Jeon <jk_jeon@kaist.ac.kr>
Date: Fri, 8 Jan 2021 14:39:30 -0800
Subject: [PATCH] Fix an error in countr_zero (#11)

---
 include/dragonbox/dragonbox.h | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/include/dragonbox/dragonbox.h b/include/dragonbox/dragonbox.h
index 937b058..34b9983 100644
--- a/include/dragonbox/dragonbox.h
+++ b/include/dragonbox/dragonbox.h
@@ -281,7 +281,7 @@ namespace jkj::dragonbox {
 			template <class UInt>
 			inline int countr_zero(UInt n) noexcept {
 				static_assert(std::is_unsigned_v<UInt> && value_bits<UInt> <= 64);
-#if (defined(__GNUC__) || defined(__clang__)) && defined(__x86_64__)
+#if 0/*(defined(__GNUC__) || defined(__clang__)) && defined(__x86_64__)
 #define JKJ_HAS_COUNTR_ZERO_INTRINSIC 1
 				if constexpr (std::is_same_v<UInt, unsigned long>) {
 					return __builtin_ctzl(n);
@@ -307,7 +307,7 @@ namespace jkj::dragonbox {
 				else {
 					static_assert(sizeof(UInt) <= sizeof(unsigned int));
 					return int(_tzcnt_u32((unsigned int)n));
-				}
+				}*/
 #else
 #define JKJ_HAS_COUNTR_ZERO_INTRINSIC 0
 				int count;
@@ -345,6 +345,8 @@ namespace jkj::dragonbox {
 						count = value_bits<UInt>;
 					}
 				}
+
+				n32 &= (0 - n32);
 				if constexpr (value_bits<UInt> > 16) {
 					if ((n32 & 0x0000ffff) != 0) count -= 16;
 				}