From aa9904b7c41a266f70ee627d639de9af109e60e6 Mon Sep 17 00:00:00 2001
From: Junekey Jeon <jk_jeon@kaist.ac.kr>
Date: Fri, 8 Jan 2021 12:01:16 -0800
Subject: [PATCH] Fix errors in countr_zero (see #11)

---
 include/dragonbox/dragonbox.h | 27 ++++++++++++++++++++++++---
 1 file changed, 24 insertions(+), 3 deletions(-)

diff --git a/include/dragonbox/dragonbox.h b/include/dragonbox/dragonbox.h
index a744668..937b058 100644
--- a/include/dragonbox/dragonbox.h
+++ b/include/dragonbox/dragonbox.h
@@ -310,18 +310,39 @@ namespace jkj::dragonbox {
 				}
 #else
 #define JKJ_HAS_COUNTR_ZERO_INTRINSIC 0
-				int count = int(value_bits<UInt>);
-
+				int count;
 				auto n32 = std::uint32_t(n);
+
 				if constexpr (value_bits<UInt> > 32) {
 					if (n32 != 0) {
 						count = 31;
 					}
 					else {
 						n32 = std::uint32_t(n >> 32);
+						if constexpr (value_bits<UInt> == 64) {
+							if (n32 != 0) {
+								count = 63;
+							}
+							else {
+								return 64;
+							}
+						}
+						else {
+							count = value_bits<UInt>;
+						}
+					}
+				}
+				else {
+					if constexpr (value_bits<UInt> == 32) {
 						if (n32 != 0) {
-							count -= 1;
+							count = 31;
 						}
+						else {
+							return 32;
+						}
+					}
+					else {
+						count = value_bits<UInt>;
 					}
 				}
 				if constexpr (value_bits<UInt> > 16) {