folly/.../ExceptionTracerLib.cpp: provide less DOF fodder (avoid heap use-after-free)

[folly.git] / folly / experimental / EliasFanoCoding.h

diff --git a/folly/experimental/EliasFanoCoding.h b/folly/experimental/EliasFanoCoding.h
index 9f3b874402d6b995e6117972a97bd17e33e5dfb2..8508f3298a88b77fc34cff9b5a14901605d2de41 100644 (file)
--- a/folly/experimental/EliasFanoCoding.h
+++ b/folly/experimental/EliasFanoCoding.h
@@ -23,6 +23,7 @@
 
 #pragma once
 
+#include <algorithm>
 #include <cstdlib>
 #include <limits>
 #include <type_traits>
@@ -35,20 +36,14 @@
 #include <folly/experimental/Select64.h>
 #include <glog/logging.h>
 
-#ifndef __GNUC__
-#error EliasFanoCoding.h requires GCC
-#endif
-
 #if !FOLLY_X64
 #error EliasFanoCoding.h requires x86_64
 #endif
 
-#if __BYTE_ORDER__ != __ORDER_LITTLE_ENDIAN__
-#error EliasFanoCoding.h requires little endianness
-#endif
-
 namespace folly { namespace compression {
 
+static_assert(kIsLittleEndian, "EliasFanoCoding.h requires little endianness");
+
 template <class Pointer>
 struct EliasFanoCompressedListBase {
   EliasFanoCompressedListBase() = default;
@@ -140,7 +135,7 @@ struct EliasFanoEncoderV2 {
         forwardPointers_(reinterpret_cast<SkipValueType*>(
               result.forwardPointers)),
         result_(result) {
-    memset(result.data.data(), 0, result.data.size());
+    std::fill(result.data.begin(), result.data.end(), 0);
   }
 
   EliasFanoEncoderV2(size_t size, ValueType upperBound)
@@ -260,9 +255,7 @@ struct EliasFanoEncoderV2<Value,
       // more serialization-friendly way (upperSizeBits doesn't need
       // to be known by this function, unlike upper).
 
-      // '?: 1' is a workaround for false 'division by zero'
-      // compile-time error.
-      size_t numSkipPointers = (8 * upper - size) / (skipQuantum ?: 1);
+      size_t numSkipPointers = (8 * upper - size) / skipQuantum;
       layout.skipPointers = numSkipPointers * sizeof(SkipValueType);
     }
 
@@ -270,7 +263,7 @@ struct EliasFanoEncoderV2<Value,
     // Store (1-indexed) position of every forwardQuantum-th
     // 1-bit in upper bits sequence.
     /* static */ if (forwardQuantum != 0) {
-      size_t numForwardPointers = size / (forwardQuantum ?: 1);
+      size_t numForwardPointers = size / forwardQuantum;
       layout.forwardPointers = numForwardPointers * sizeof(SkipValueType);
     }
 
@@ -374,16 +367,13 @@ class UpperBitsReader {
 
     // Use forward pointer.
     if (Encoder::forwardQuantum > 0 && n > Encoder::forwardQuantum) {
-      // Workaround to avoid 'division by zero' compile-time error.
-      constexpr size_t q = Encoder::forwardQuantum ?: 1;
-
-      const size_t steps = position_ / q;
+      const size_t steps = position_ / Encoder::forwardQuantum;
       const size_t dest =
         folly::loadUnaligned<SkipValueType>(
             forwardPointers_ + (steps - 1) * sizeof(SkipValueType));
 
-      reposition(dest + steps * q);
-      n = position_ + 1 - steps * q;  // n is > 0.
+      reposition(dest + steps * Encoder::forwardQuantum);
+      n = position_ + 1 - steps * Encoder::forwardQuantum; // n is > 0.
       // Correct inner_ will be set at the end.
     }
 
@@ -410,15 +400,12 @@ class UpperBitsReader {
 
     // Use skip pointer.
     if (Encoder::skipQuantum > 0 && v >= value_ + Encoder::skipQuantum) {
-      // Workaround to avoid 'division by zero' compile-time error.
-      constexpr size_t q = Encoder::skipQuantum ?: 1;
-
-      const size_t steps = v / q;
+      const size_t steps = v / Encoder::skipQuantum;
       const size_t dest =
         folly::loadUnaligned<SkipValueType>(
             skipPointers_ + (steps - 1) * sizeof(SkipValueType));
 
-      reposition(dest + q * steps);
+      reposition(dest + Encoder::skipQuantum * steps);
       position_ = dest - 1;
 
       // Correct inner_ and value_ will be set during the next()