From: Ma Lin <malincns@163.com>
Date: Fri, 24 Sep 2021 11:40:24 +0000 (+0800)
Subject: Don't initialize the first parameter of _BitScanForward* functions
X-Git-Tag: v1.5.1~1^2~76^2~2
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=e5ba858270929080f03be821c53c93b8a05a42e0;p=thirdparty%2Fzstd.git

Don't initialize the first parameter of _BitScanForward* functions

Like the document example, no need to initialize `r` to 0.
https://docs.microsoft.com/en-us/cpp/intrinsics/bitscanforward-bitscanforward64
---

diff --git a/lib/common/entropy_common.c b/lib/common/entropy_common.c
index 6ba1f2209..dd80b2ccc 100644
--- a/lib/common/entropy_common.c
+++ b/lib/common/entropy_common.c
@@ -43,7 +43,7 @@ static U32 FSE_ctz(U32 val)
     assert(val != 0);
     {
 #   if defined(_MSC_VER)   /* Visual */
-        unsigned long r=0;
+        unsigned long r;
         return _BitScanForward(&r, val) ? (unsigned)r : 0;
 #   elif defined(__GNUC__) && (__GNUC__ >= 3)   /* GCC Intrinsic */
         return __builtin_ctz(val);
diff --git a/lib/common/zstd_internal.h b/lib/common/zstd_internal.h
index ba1b7bbc8..246022c5f 100644
--- a/lib/common/zstd_internal.h
+++ b/lib/common/zstd_internal.h
@@ -391,7 +391,7 @@ MEM_STATIC unsigned ZSTD_countTrailingZeros(size_t val)
 #           if STATIC_BMI2
                 return _tzcnt_u64(val);
 #           else
-                unsigned long r = 0;
+                unsigned long r;
                 return _BitScanForward64( &r, (U64)val ) ? (unsigned)(r >> 3) : 0;
 #           endif
 #       elif defined(__GNUC__) && (__GNUC__ >= 4)
@@ -409,7 +409,7 @@ MEM_STATIC unsigned ZSTD_countTrailingZeros(size_t val)
 #       endif
     } else { /* 32 bits */
 #       if defined(_MSC_VER)
-            unsigned long r=0;
+            unsigned long r;
             return _BitScanForward( &r, (U32)val ) ? (unsigned)(r >> 3) : 0;
 #       elif defined(__GNUC__) && (__GNUC__ >= 3)
             return (__builtin_ctz((U32)val) >> 3);
diff --git a/lib/compress/zstd_compress_internal.h b/lib/compress/zstd_compress_internal.h
index 6821c9df8..bc30daa75 100644
--- a/lib/compress/zstd_compress_internal.h
+++ b/lib/compress/zstd_compress_internal.h
@@ -672,7 +672,7 @@ static unsigned ZSTD_NbCommonBytes (size_t val)
 #           if STATIC_BMI2
                 return _tzcnt_u64(val) >> 3;
 #           else
-                unsigned long r = 0;
+                unsigned long r;
                 return _BitScanForward64( &r, (U64)val ) ? (unsigned)(r >> 3) : 0;
 #           endif
 #       elif defined(__GNUC__) && (__GNUC__ >= 4)
@@ -690,7 +690,7 @@ static unsigned ZSTD_NbCommonBytes (size_t val)
 #       endif
         } else { /* 32 bits */
 #       if defined(_MSC_VER)
-            unsigned long r=0;
+            unsigned long r;
             return _BitScanForward( &r, (U32)val ) ? (unsigned)(r >> 3) : 0;
 #       elif defined(__GNUC__) && (__GNUC__ >= 3)
             return (__builtin_ctz((U32)val) >> 3);
diff --git a/lib/compress/zstd_lazy.c b/lib/compress/zstd_lazy.c
index fef28de8d..ac84b479f 100644
--- a/lib/compress/zstd_lazy.c
+++ b/lib/compress/zstd_lazy.c
@@ -882,7 +882,7 @@ static U32 ZSTD_VecMask_next(ZSTD_VecMask val) {
     assert(val != 0);
 #   if defined(_MSC_VER) && defined(_WIN64)
     {
-        unsigned long r = 0;
+        unsigned long r;
         /* _BitScanForward64 is not defined outside of x64 */
         return _BitScanForward64(&r, val) ? (U32)r : 0;
     }
diff --git a/lib/dictBuilder/zdict.c b/lib/dictBuilder/zdict.c
index 2421f40f3..ea00eafc7 100644
--- a/lib/dictBuilder/zdict.c
+++ b/lib/dictBuilder/zdict.c
@@ -135,9 +135,8 @@ static unsigned ZDICT_NbCommonBytes (size_t val)
     if (MEM_isLittleEndian()) {
         if (MEM_64bits()) {
 #       if defined(_MSC_VER) && defined(_WIN64)
-            unsigned long r = 0;
-            _BitScanForward64( &r, (U64)val );
-            return (unsigned)(r>>3);
+            unsigned long r;
+            return _BitScanForward64(&r, (U64)val) ? (unsigned)(r >> 3) : 0;
 #       elif defined(__GNUC__) && (__GNUC__ >= 3)
             return (unsigned)(__builtin_ctzll((U64)val) >> 3);
 #       else
@@ -146,9 +145,8 @@ static unsigned ZDICT_NbCommonBytes (size_t val)
 #       endif
         } else { /* 32 bits */
 #       if defined(_MSC_VER)
-            unsigned long r=0;
-            _BitScanForward( &r, (U32)val );
-            return (unsigned)(r>>3);
+            unsigned long r;
+            return _BitScanForward(&r, (U32)val) ? (unsigned)(r >> 3) : 0;
 #       elif defined(__GNUC__) && (__GNUC__ >= 3)
             return (unsigned)(__builtin_ctz((U32)val) >> 3);
 #       else