tor

commit accd0ea65bb817ad8f2361c5ca06c40ac9a9a11f
parent eecfed0cd2c8c92175106e211d1662fa43fc60bc
Author: Nick Mathewson <nickm@torproject.org>
Date:   Wed, 20 Dec 2017 09:34:25 -0500

Fix the clz32 and clz64 settings on MSVC.

Fixes bug 24633; bugfix on 0.2.9.1-alpha.

Diffstat:
A
changes/bug24633
 | 
5
+++++
M
src/ext/timeouts/timeout-bitops.c
 | 
4
++--

2 files changed, 7 insertions(+), 2 deletions(-)
diff --git a/changes/bug24633 b/changes/bug24633
@@ -0,0 +1,5 @@
+  o Minor bugfixes (portability, msvc):
+    - Fix a bug in the bit-counting parts of our timing-wheel code on
+      MSVC. (Note that MSVC is still not a supported build platform,
+      due to cyptographic timing channel risks.) Fixes bug 24633;
+      bugfix on 0.2.9.1-alpha.
diff --git a/src/ext/timeouts/timeout-bitops.c b/src/ext/timeouts/timeout-bitops.c
@@ -40,7 +40,7 @@ static __inline int clz32(unsigned long val)
 {
 	DWORD zeros = 0;
 	_BitScanReverse(&zeros, val);
-	return zeros;
+	return 31 - zeros;
 }
 #ifdef _WIN64
 /* According to the documentation, these only exist on Win64. */
@@ -54,7 +54,7 @@ static __inline int clz64(uint64_t val)
 {
 	DWORD zeros = 0;
 	_BitScanReverse64(&zeros, val);
-	return zeros;
+	return 63 - zeros;
 }
 #else
 static __inline int ctz64(uint64_t val)