commit accd0ea65bb817ad8f2361c5ca06c40ac9a9a11f Author: Nick Mathewson nickm@torproject.org Date: Wed Dec 20 09:34:25 2017 -0500
Fix the clz32 and clz64 settings on MSVC.
Fixes bug 24633; bugfix on 0.2.9.1-alpha. --- changes/bug24633 | 5 +++++ src/ext/timeouts/timeout-bitops.c | 4 ++-- 2 files changed, 7 insertions(+), 2 deletions(-)
diff --git a/changes/bug24633 b/changes/bug24633 new file mode 100644 index 000000000..028c7cc14 --- /dev/null +++ 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 index a018f33b9..45466f6cb 100644 --- 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)