[scudo][standalone] Consolidate lists

[cryptoad]

Summary

This is a clean patch using the last diff of D69265, but using git
instead of svn, since svn went ro and arc was making my life harded
than it needed to be.

I was going to introduce a couple more lists and realized that our
lists are currently a bit all over the place. While we have a singly
linked list type relatively well defined, we are using doubly linked
lists defined on the fly for the stats and for the secondary blocks.

This CL adds a doubly linked list object, reorganizing the singly list
one to extract as much of the common code as possible. We use this
new type in the stats and the secondary. We also reorganize the list
tests to benefit from this consolidation.

There are a few side effect changes such as using for iterator loops
that are, in my opinion, cleaner in a couple of places.

[hctim]

LGTM - review done in D69265

compiler-rt/lib/scudo/standalone/list.h

 //===-- list.h --------------------------------------------------*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef SCUDO_LIST_H_
 #define SCUDO_LIST_H_
 
 #include "internal_defs.h"
 
 namespace scudo {
 
-// Intrusive POD singly-linked list.
+// Intrusive POD singly and doubly linked list.
 // An object with all zero fields should represent a valid empty list. clear()
 // should be called on all non-zero-initialized objects before using.
-template <class Item> struct IntrusiveList {
-  friend class Iterator;
+
+template <class T> class IteratorBase {
+public:
+  explicit IteratorBase(T *CurrentT) : Current(CurrentT) {}
+  IteratorBase &operator++() {
+    Current = Current->Next;
+    return *this;
+  }
+  bool operator!=(IteratorBase Other) const { return Current != Other.Current; }
+  T &operator*() { return *Current; }
+
+private:
+  T *Current;
+};
+
+template <class T> struct IntrusiveList {
+  bool empty() const { return Size == 0; }
+  uptr size() const { return Size; }
+
+  T *front() { return First; }
+  const T *front() const { return First; }
+  T *back() { return Last; }
+  const T *back() const { return Last; }
 
   void clear() {
     First = Last = nullptr;
     Size = 0;
   }
 
-  bool empty() const { return Size == 0; }
-  uptr size() const { return Size; }
+  typedef IteratorBase<T> Iterator;
+  typedef IteratorBase<const T> ConstIterator;
 
-  void push_back(Item *X) {
-    if (empty()) {
-      X->Next = nullptr;
-      First = Last = X;
-      Size = 1;
-    } else {
-      X->Next = nullptr;
+  Iterator begin() { return Iterator(First); }
+  Iterator end() { return Iterator(nullptr); }
+
+  ConstIterator begin() const { return ConstIterator(First); }
+  ConstIterator end() const { return ConstIterator(nullptr); }
+
+  void checkConsistency() const;
+
+protected:
+  uptr Size;
+  T *First;
+  T *Last;
+};
+
+template <class T> void IntrusiveList<T>::checkConsistency() const {
+  if (Size == 0) {
+    CHECK_EQ(First, nullptr);
+    CHECK_EQ(Last, nullptr);
+    uptr Count = 0;
+    for (T *I = First;; I = I->Next) {
+      Count++;
+      if (I == Last)
+        break;
+    }
+    CHECK_EQ(this->size(), Count);
+    CHECK_EQ(Last->Next, nullptr);
+  }
+}
+
+template <class T> struct SinglyLinkedList : public IntrusiveList<T> {
+  using IntrusiveList<T>::First;
+  using IntrusiveList<T>::Last;
+  using IntrusiveList<T>::Size;
+  using IntrusiveList<T>::empty;
+
+  void push_back(T *X) {
+    if (empty())
+      First = X;
+    else
       Last->Next = X;
-      Last = X;
-      Size++;
-    }
-  }
 
-  void push_front(Item *X) {
-    if (empty()) {
-      X->Next = nullptr;
-      First = Last = X;
-      Size = 1;
-    } else {
-      X->Next = First;
-      First = X;
-      Size++;
-    }
-  }
+  void push_front(T *X) {
+    if (empty())
+      Last = X;
 
   void pop_front() {
     DCHECK(!empty());
     First = First->Next;
     if (!First)
       Last = nullptr;
     Size--;
   }
 
-  void extract(Item *Prev, Item *X) {
+  void extract(T *Prev, T *X) {
     DCHECK(!empty());
     DCHECK_NE(Prev, nullptr);
     DCHECK_NE(X, nullptr);
     DCHECK_EQ(Prev->Next, X);
     Prev->Next = X->Next;
     if (Last == X)
       Last = Prev;
     Size--;
   }
 
-  Item *front() { return First; }
-  const Item *front() const { return First; }
-  Item *back() { return Last; }
-  const Item *back() const { return Last; }
-
-  void append_front(IntrusiveList<Item> *L) {
-    DCHECK_NE(this, L);
-    if (L->empty())
-      return;
-    if (empty()) {
-      *this = *L;
-    } else if (!L->empty()) {
-      L->Last->Next = First;
-      First = L->First;
-      Size += L->size();
-    }
-    L->clear();
-  }
-
-  void append_back(IntrusiveList<Item> *L) {
+  void append_back(SinglyLinkedList<T> *L) {
     DCHECK_NE(this, L);
     if (L->empty())
       return;
     if (empty()) {
       *this = *L;
     } else {
       Last->Next = L->First;
       Last = L->Last;
       Size += L->size();
     }
     L->clear();
   }
+};
 
-  void checkConsistency() {
-    if (Size == 0) {
-      CHECK_EQ(First, nullptr);
-      CHECK_EQ(Last, nullptr);
+template <class T> struct DoublyLinkedList : IntrusiveList<T> {
+  using IntrusiveList<T>::First;
+  using IntrusiveList<T>::Last;
+  using IntrusiveList<T>::Size;
+  using IntrusiveList<T>::empty;
+
+  void push_front(T *X) {
+    X->Prev = nullptr;
+    if (empty()) {
+      Last = X;
     } else {
-      uptr Count = 0;
-      for (Item *I = First;; I = I->Next) {
-        Count++;
-        if (I == Last)
-          break;
-      }
-      CHECK_EQ(size(), Count);
-      CHECK_EQ(Last->Next, nullptr);
-    }
+      DCHECK_EQ(First->Prev, nullptr);
+    X->Next = First;
+    First = X;
+    Size++;
+
+  // Inserts X before Y.
+  void insert(T *X, T *Y) {
+    if (Y == First)
+      return push_front(X);
+    T *Prev = Y->Prev;
+    // This is a hard CHECK to ensure consistency in the event of an intentional
+    // corruption of Y->Prev, to prevent a potential write-{4,8}.
+    CHECK_EQ(Prev->Next, Y);
+    Prev->Next = X;
+    X->Prev = Prev;
+    X->Next = Y;
+    Y->Prev = X;
+    Size++;
   }
 
-  template <class ItemT> class IteratorBase {
-  public:
-    explicit IteratorBase(ItemT *CurrentItem) : Current(CurrentItem) {}
-    IteratorBase &operator++() {
-      Current = Current->Next;
-      return *this;
+  void push_back(T *X) {
+    X->Next = nullptr;
+    if (empty()) {
+      First = X;
+    } else {
+      DCHECK_EQ(Last->Next, nullptr);
+      Last->Next = X;
     }
-    bool operator!=(IteratorBase Other) const {
-      return Current != Other.Current;
-    }
-    ItemT &operator*() { return *Current; }
-
-  private:
-    ItemT *Current;
-  };
-
-  typedef IteratorBase<Item> Iterator;
-  typedef IteratorBase<const Item> ConstIterator;
-
-  Iterator begin() { return Iterator(First); }
-  Iterator end() { return Iterator(nullptr); }
+    X->Prev = Last;
+    Last = X;
+    Size++;
 
-  ConstIterator begin() const { return ConstIterator(First); }
-  ConstIterator end() const { return ConstIterator(nullptr); }
+  void pop_front() {
+    DCHECK(!empty());
+    First = First->Next;
+    if (!First)
+      Last = nullptr;
+    else
+      First->Prev = nullptr;
+    Size--;
+  }
 
-private:
-  uptr Size;
-  Item *First;
-  Item *Last;
+  // The consistency of the adjacent links is aggressively checked in order to
+  // catch potential corruption attempts, that could yield a mirrored
+  // write-{4,8} primitive. nullptr checks are deemed less vital.
+  void remove(T *X) {
+    T *Prev = X->Prev;
+    T *Next = X->Next;
+    if (Prev) {
+      CHECK_EQ(Prev->Next, X);
+      Prev->Next = Next;
+    }
+    if (Next) {
+      CHECK_EQ(Next->Prev, X);
+      Next->Prev = Prev;
+    }
+    if (First == X) {
+      DCHECK_EQ(Prev, nullptr);
+      First = Next;
+    } else {
+      DCHECK_NE(Prev, nullptr);
+    }
+    if (Last == X) {
+      DCHECK_EQ(Next, nullptr);
+      Last = Prev;
+    } else {
+      DCHECK_NE(Next, nullptr);
+    }
+    Size--;
+  }
 };
 
 } // namespace scudo
 
 #endif // SCUDO_LIST_H_

compiler-rt/lib/scudo/standalone/primary32.h

struct ReleaseToOsInfo {
     uptr PushedBlocksAtLastRelease;
     uptr RangesReleased;
     uptr LastReleasedBytes;
     u64 LastReleaseAtNs;
   };
 
   struct ALIGNED(SCUDO_CACHE_LINE_SIZE) SizeClassInfo {
     HybridMutex Mutex;
-    IntrusiveList<TransferBatch> FreeList;
+    SinglyLinkedList<TransferBatch> FreeList;
     SizeClassStats Stats;
     bool CanRelease;
     u32 RandState;
     uptr AllocatedUser;
     ReleaseToOsInfo ReleaseInfo;
   };
   COMPILER_CHECK(sizeof(SizeClassInfo) % SCUDO_CACHE_LINE_SIZE == 0);
 
NOINLINE uptr releaseToOSMaybe(SizeClassInfo *Sci, uptr ClassId,
 
     // TODO(kostyak): currently not ideal as we loop over all regions and
     // iterate multiple times over the same freelist if a ClassId spans multiple
     // regions. But it will have to do for now.
     uptr TotalReleasedBytes = 0;
     for (uptr I = MinRegionIndex; I <= MaxRegionIndex; I++) {
       if (PossibleRegions[I] == ClassId) {
         ReleaseRecorder Recorder(I * RegionSize);
-        releaseFreeMemoryToOS(&Sci->FreeList, I * RegionSize,
+        releaseFreeMemoryToOS(Sci->FreeList, I * RegionSize,
                               RegionSize / PageSize, BlockSize, &Recorder);
         if (Recorder.getReleasedRangesCount() > 0) {
           Sci->ReleaseInfo.PushedBlocksAtLastRelease = Sci->Stats.PushedBlocks;
           Sci->ReleaseInfo.RangesReleased += Recorder.getReleasedRangesCount();
           Sci->ReleaseInfo.LastReleasedBytes = Recorder.getReleasedBytes();
           TotalReleasedBytes += Sci->ReleaseInfo.LastReleasedBytes;
         }
       }

compiler-rt/lib/scudo/standalone/primary64.h

struct ReleaseToOsInfo {
     uptr PushedBlocksAtLastRelease;
     uptr RangesReleased;
     uptr LastReleasedBytes;
     u64 LastReleaseAtNs;
   };
 
   struct ALIGNED(SCUDO_CACHE_LINE_SIZE) RegionInfo {
     HybridMutex Mutex;
-    IntrusiveList<TransferBatch> FreeList;
+    SinglyLinkedList<TransferBatch> FreeList;
     RegionStats Stats;
     bool CanRelease;
     bool Exhausted;
     u32 RandState;
     uptr RegionBeg;
     uptr MappedUser;    // Bytes mapped for user memory.
     uptr AllocatedUser; // Bytes allocated for user memory.
     MapPlatformData Data;
if (!Force) {
       if (Region->ReleaseInfo.LastReleaseAtNs +
               static_cast<uptr>(IntervalMs) * 1000000ULL >
           getMonotonicTime()) {
         return 0; // Memory was returned recently.
       }
     }
 
     ReleaseRecorder Recorder(Region->RegionBeg, &Region->Data);
-    releaseFreeMemoryToOS(&Region->FreeList, Region->RegionBeg,
+    releaseFreeMemoryToOS(Region->FreeList, Region->RegionBeg,
                           roundUpTo(Region->AllocatedUser, PageSize) / PageSize,
                           BlockSize, &Recorder);
 
     if (Recorder.getReleasedRangesCount() > 0) {
       Region->ReleaseInfo.PushedBlocksAtLastRelease =
           Region->Stats.PushedBlocks;
       Region->ReleaseInfo.RangesReleased += Recorder.getReleasedRangesCount();
       Region->ReleaseInfo.LastReleasedBytes = Recorder.getReleasedBytes();

compiler-rt/lib/scudo/standalone/quarantine.h

void getStats(ScopedString *Str) const {
     Str->append(
         "Stats: Quarantine: batches: %zu; bytes: %zu (user: %zu); chunks: %zu "
         "(capacity: %zu); %zu%% chunks used; %zu%% memory overhead\n",
         BatchCount, TotalBytes, TotalQuarantinedBytes, TotalQuarantineChunks,
         QuarantineChunksCapacity, ChunksUsagePercent, MemoryOverheadPercent);
   }
 
 private:
-  IntrusiveList<QuarantineBatch> List;
+  SinglyLinkedList<QuarantineBatch> List;
   atomic_uptr Size;
 
   void addToSize(uptr add) { atomic_store_relaxed(&Size, getSize() + add); }
   void subFromSize(uptr sub) { atomic_store_relaxed(&Size, getSize() - sub); }
 };
 
 // The callback interface is:
 // void Callback::recycle(Node *Ptr);

compiler-rt/lib/scudo/standalone/release.h

private:
   const uptr PageSizeLog;
   bool InRange = false;
   uptr CurrentPage = 0;
   uptr CurrentRangeStatePage = 0;
 };
 
 template <class TransferBatchT, class ReleaseRecorderT>
 NOINLINE void
-releaseFreeMemoryToOS(const IntrusiveList<TransferBatchT> *FreeList, uptr Base,
+releaseFreeMemoryToOS(const IntrusiveList<TransferBatchT> &FreeList, uptr Base,
                       uptr AllocatedPagesCount, uptr BlockSize,
                       ReleaseRecorderT *Recorder) {
   const uptr PageSize = getPageSizeCached();
 
   // Figure out the number of chunks per page and whether we can take a fast
   // path (the number of chunks per page is the same for all pages).
   uptr FullPagesBlockCountMax;
   bool SameBlockCountPerPage;
releaseFreeMemoryToOS(const IntrusiveList<TransferBatchT> &FreeList, uptr Base,
 
   const uptr PageSizeLog = getLog2(PageSize);
   const uptr End = Base + AllocatedPagesCount * PageSize;
 
   // Iterate over free chunks and count how many free chunks affect each
   // allocated page.
   if (BlockSize <= PageSize && PageSize % BlockSize == 0) {
     // Each chunk affects one page only.
-    for (auto It = FreeList->begin(); It != FreeList->end(); ++It) {
-      for (u32 I = 0; I < (*It).getCount(); I++) {
-        const uptr P = reinterpret_cast<uptr>((*It).get(I));
+    for (const auto &It : FreeList) {
+      for (u32 I = 0; I < It.getCount(); I++) {
+        const uptr P = reinterpret_cast<uptr>(It.get(I));
         if (P >= Base && P < End)
           Counters.inc((P - Base) >> PageSizeLog);
       }
     }
   } else {
     // In all other cases chunks might affect more than one page.
-    for (auto It = FreeList->begin(); It != FreeList->end(); ++It) {
-      for (u32 I = 0; I < (*It).getCount(); I++) {
-        const uptr P = reinterpret_cast<uptr>((*It).get(I));
+    for (const auto &It : FreeList) {
+      for (u32 I = 0; I < It.getCount(); I++) {
+        const uptr P = reinterpret_cast<uptr>(It.get(I));
         if (P >= Base && P < End)
           Counters.incRange((P - Base) >> PageSizeLog,
                             (P - Base + BlockSize - 1) >> PageSizeLog);
       }
     }
   }
 
   // Iterate over pages detecting ranges of pages with chunk Counters equal

compiler-rt/lib/scudo/standalone/secondary.h

 //===-- secondary.h ---------------------------------------------*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef SCUDO_SECONDARY_H_
 #define SCUDO_SECONDARY_H_
 
 #include "common.h"
+#include "list.h"
 #include "mutex.h"
 #include "stats.h"
 #include "string_utils.h"
 
 namespace scudo {
 
 // This allocator wraps the platform allocation primitives, and as such is on
 // the slower side and should preferably be used for larger sized allocations.
public:
 
   void getStats(ScopedString *Str) const;
 
   void disable() { Mutex.lock(); }
 
   void enable() { Mutex.unlock(); }
 
   template <typename F> void iterateOverBlocks(F Callback) const {
-    for (LargeBlock::Header *H = Tail; H != nullptr; H = H->Prev)
-      Callback(reinterpret_cast<uptr>(H) + LargeBlock::getHeaderSize());
+    for (const auto &H : InUseBlocks)
+      Callback(reinterpret_cast<uptr>(&H) + LargeBlock::getHeaderSize());
   }
 
 private:
   HybridMutex Mutex;
-  LargeBlock::Header *Tail;
+  DoublyLinkedList<LargeBlock::Header> InUseBlocks;
   uptr AllocatedBytes;
   uptr FreedBytes;
   uptr LargestSize;
   u32 NumberOfAllocs;
   u32 NumberOfFrees;
   LocalStats Stats;
 };
 
 } // namespace scudo
 
 #endif // SCUDO_SECONDARY_H_

compiler-rt/lib/scudo/standalone/secondary.cpp

const uptr Ptr =
                                  CommitSize, "scudo:secondary", 0, &Data));
   LargeBlock::Header *H = reinterpret_cast<LargeBlock::Header *>(Ptr);
   H->MapBase = MapBase;
   H->MapSize = MapEnd - MapBase;
   H->BlockEnd = CommitBase + CommitSize;
   H->Data = Data;
   {
     ScopedLock L(Mutex);
-    if (LIKELY(Tail)) {
-      Tail->Next = H;
-      H->Prev = Tail;
-    }
-    Tail = H;
+    InUseBlocks.push_back(H);
     AllocatedBytes += CommitSize;
     if (LargestSize < CommitSize)
       LargestSize = CommitSize;
     NumberOfAllocs++;
     Stats.add(StatAllocated, CommitSize);
     Stats.add(StatMapped, H->MapSize);
   }
   if (BlockEnd)
     *BlockEnd = CommitBase + CommitSize;
   return reinterpret_cast<void *>(Ptr + LargeBlock::getHeaderSize());
 }
 
 void MapAllocator::deallocate(void *Ptr) {
   LargeBlock::Header *H = LargeBlock::getHeader(Ptr);
   {
     ScopedLock L(Mutex);
-    LargeBlock::Header *Prev = H->Prev;
-    LargeBlock::Header *Next = H->Next;
-    if (Prev) {
-      CHECK_EQ(Prev->Next, H);
-      Prev->Next = Next;
-    }
-    if (Next) {
-      CHECK_EQ(Next->Prev, H);
-      Next->Prev = Prev;
-    }
-    if (UNLIKELY(Tail == H)) {
-      CHECK(!Next);
-      Tail = Prev;
-    } else {
-      CHECK(Next);
-    }
+    InUseBlocks.remove(H);
     const uptr CommitSize = H->BlockEnd - reinterpret_cast<uptr>(H);
     FreedBytes += CommitSize;
     NumberOfFrees++;
     Stats.sub(StatAllocated, CommitSize);
     Stats.sub(StatMapped, H->MapSize);
   }
   void *Addr = reinterpret_cast<void *>(H->MapBase);
   const uptr Size = H->MapSize;

compiler-rt/lib/scudo/standalone/stats.h

 //===-- stats.h -------------------------------------------------*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef SCUDO_STATS_H_
 #define SCUDO_STATS_H_
 
 #include "atomic_helpers.h"
+#include "list.h"
 #include "mutex.h"
 
 #include <string.h>
 
 namespace scudo {
 
 // Memory allocator statistics
 enum StatType { StatAllocated, StatFree, StatMapped, StatCount };
void sub(StatType I, uptr V) {
     V = atomic_load_relaxed(&StatsArray[I]) - V;
     atomic_store_relaxed(&StatsArray[I], V);
   }
 
   void set(StatType I, uptr V) { atomic_store_relaxed(&StatsArray[I], V); }
 
   uptr get(StatType I) const { return atomic_load_relaxed(&StatsArray[I]); }
 
-private:
-  friend class GlobalStats;
-  atomic_uptr StatsArray[StatCount];
   LocalStats *Next;
   LocalStats *Prev;
+
+private:
+  atomic_uptr StatsArray[StatCount];
 };
 
 // Global stats, used for aggregation and querying.
 class GlobalStats : public LocalStats {
 public:
-  void initLinkerInitialized() {
-    Next = this;
-    Prev = this;
-  }
+  void initLinkerInitialized() {}
   void init() {
     memset(this, 0, sizeof(*this));
     initLinkerInitialized();
   }
 
   void link(LocalStats *S) {
     ScopedLock L(Mutex);
-    S->Next = Next;
-    S->Prev = this;
-    Next->Prev = S;
-    Next = S;
+    StatsList.push_back(S);
   }
 
   void unlink(LocalStats *S) {
     ScopedLock L(Mutex);
-    S->Prev->Next = S->Next;
-    S->Next->Prev = S->Prev;
+    StatsList.remove(S);
     for (uptr I = 0; I < StatCount; I++)
       add(static_cast<StatType>(I), S->get(static_cast<StatType>(I)));
   }
 
   void get(uptr *S) const {
-    memset(S, 0, StatCount * sizeof(uptr));
     ScopedLock L(Mutex);
-    const LocalStats *Stats = this;
-    for (;;) {
-      for (uptr I = 0; I < StatCount; I++)
-        S[I] += Stats->get(static_cast<StatType>(I));
-      Stats = Stats->Next;
-      if (Stats == this)
-        break;
+      S[I] = LocalStats::get(static_cast<StatType>(I));
+    for (const auto &Stats : StatsList) {
+      for (uptr I = 0; I < StatCount; I++)
+        S[I] += Stats.get(static_cast<StatType>(I));
     }
     // All stats must be non-negative.
     for (uptr I = 0; I < StatCount; I++)
       S[I] = static_cast<sptr>(S[I]) >= 0 ? S[I] : 0;
   }
 
 private:
   mutable HybridMutex Mutex;
+  DoublyLinkedList<LocalStats> StatsList;
 };
 
 } // namespace scudo
 
 #endif // SCUDO_STATS_H_

compiler-rt/lib/scudo/standalone/tests/list_test.cpp

 //===-- list_test.cpp -------------------------------------------*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #include "scudo/standalone/list.h"
 #include "gtest/gtest.h"
 
 struct ListItem {
   ListItem *Next;
+  ListItem *Prev;
 };
 
-typedef scudo::IntrusiveList<ListItem> List;
-
-static List StaticList;
-
-static void setList(List *L, ListItem *X = nullptr, ListItem *Y = nullptr,
-                    ListItem *Z = nullptr) {
+static ListItem Items[6];
+static ListItem *X = &Items[0];
+static ListItem *Y = &Items[1];
+static ListItem *Z = &Items[2];
+static ListItem *A = &Items[3];
+static ListItem *B = &Items[4];
+static ListItem *C = &Items[5];
+
+typedef scudo::SinglyLinkedList<ListItem> SLList;
+typedef scudo::DoublyLinkedList<ListItem> DLList;
+
+template <typename ListT>
+static void setList(ListT *L, ListItem *I1 = nullptr, ListItem *I2 = nullptr,
+                    ListItem *I3 = nullptr) {
   L->clear();
-  if (X)
-    L->push_back(X);
-  if (Y)
-    L->push_back(Y);
-  if (Z)
-    L->push_back(Z);
+  if (I1)
+    L->push_back(I1);
+  if (I2)
+    L->push_back(I2);
+  if (I3)
+    L->push_back(I3);
 }
 
-static void checkList(List *L, ListItem *I1, ListItem *I2 = nullptr,
+template <typename ListT>
+static void checkList(ListT *L, ListItem *I1, ListItem *I2 = nullptr,
                       ListItem *I3 = nullptr, ListItem *I4 = nullptr,
                       ListItem *I5 = nullptr, ListItem *I6 = nullptr) {
   if (I1) {
     EXPECT_EQ(L->front(), I1);
     L->pop_front();
   }
   if (I2) {
     EXPECT_EQ(L->front(), I2);
static void checkList(ListT *L, ListItem *I1, ListItem *I2 = nullptr,
   }
   if (I6) {
     EXPECT_EQ(L->front(), I6);
     L->pop_front();
   }
   EXPECT_TRUE(L->empty());
 }
 
-TEST(ScudoListTest, IntrusiveList) {
-  ListItem Items[6];
-  EXPECT_EQ(StaticList.size(), 0U);
-
-  List L;
+template <typename ListT> static void testListCommon(void) {
+  ListT L;
   L.clear();
 
-  ListItem *X = &Items[0];
-  ListItem *Y = &Items[1];
-  ListItem *Z = &Items[2];
-  ListItem *A = &Items[3];
-  ListItem *B = &Items[4];
-  ListItem *C = &Items[5];
-
   EXPECT_EQ(L.size(), 0U);
   L.push_back(X);
   EXPECT_EQ(L.size(), 1U);
   EXPECT_EQ(L.back(), X);
   EXPECT_EQ(L.front(), X);
   L.pop_front();
   EXPECT_TRUE(L.empty());
   L.checkConsistency();
template <typename ListT> static void testListCommon(void) {
   L.pop_front();
   EXPECT_EQ(L.size(), 2U);
   EXPECT_EQ(L.front(), Y);
   EXPECT_EQ(L.back(), Z);
   L.pop_front();
   L.pop_front();
   EXPECT_TRUE(L.empty());
   L.checkConsistency();
+}
+
+TEST(ScudoListTest, LinkedListCommon) {
+  testListCommon<SLList>();
+  testListCommon<DLList>();
+}
+
+TEST(ScudoListTest, SinglyLinkedList) {
+  SLList L;
+  L.clear();
 
   L.push_back(X);
   L.push_back(Y);
   L.push_back(Z);
   L.extract(X, Y);
   EXPECT_EQ(L.size(), 2U);
   EXPECT_EQ(L.front(), X);
   EXPECT_EQ(L.back(), Z);
   L.checkConsistency();
   L.extract(X, Z);
   EXPECT_EQ(L.size(), 1U);
   EXPECT_EQ(L.front(), X);
   EXPECT_EQ(L.back(), X);
   L.checkConsistency();
   L.pop_front();
   EXPECT_TRUE(L.empty());
 
-  List L1, L2;
+  SLList L1, L2;
   L1.clear();
   L2.clear();
 
-  L1.append_front(&L2);
-  EXPECT_TRUE(L1.empty());
-  EXPECT_TRUE(L2.empty());
-
   L1.append_back(&L2);
   EXPECT_TRUE(L1.empty());
   EXPECT_TRUE(L2.empty());
 
   setList(&L1, X);
   checkList(&L1, X);
 
   setList(&L1, X, Y, Z);
   setList(&L2, A, B, C);
   L1.append_back(&L2);
   checkList(&L1, X, Y, Z, A, B, C);
   EXPECT_TRUE(L2.empty());
 
-  setList(&L1, X, Y);
-  setList(&L2);
-  L1.append_front(&L2);
-  checkList(&L1, X, Y);
-  EXPECT_TRUE(L2.empty());
+  L1.clear();
+  L2.clear();
+  L1.push_back(X);
+  L1.append_back(&L2);
+  EXPECT_EQ(L1.back(), X);
+  EXPECT_EQ(L1.front(), X);
+  EXPECT_EQ(L1.size(), 1U);
 }
 
-TEST(ScudoListTest, IntrusiveListAppendEmpty) {
-  ListItem I;
-  List L;
+TEST(ScudoListTest, DoublyLinkedList) {
+  DLList L;
   L.clear();
-  L.push_back(&I);
-  List L2;
-  L2.clear();
-  L.append_back(&L2);
-  EXPECT_EQ(L.back(), &I);
-  EXPECT_EQ(L.front(), &I);
-  EXPECT_EQ(L.size(), 1U);
-  L.append_front(&L2);
-  EXPECT_EQ(L.back(), &I);
-  EXPECT_EQ(L.front(), &I);
+
+  L.push_back(X);
+  L.push_back(Y);
+  L.push_back(Z);
+  L.remove(Y);
+  EXPECT_EQ(L.size(), 2U);
+  EXPECT_EQ(L.front(), X);
+  EXPECT_EQ(L.back(), Z);
+  L.checkConsistency();
+  L.remove(Z);
   EXPECT_EQ(L.size(), 1U);
+  EXPECT_EQ(L.front(), X);
+  EXPECT_EQ(L.back(), X);
+  L.checkConsistency();
+  L.pop_front();
+  EXPECT_TRUE(L.empty());
 }

compiler-rt/lib/scudo/standalone/tests/release_test.cpp

for (scudo::uptr I = 0; I < MaxBlocks; I++) {
         FreeArray.push_back(I * BlockSize);
     }
     if (FreeArray.empty())
       continue;
     // Shuffle the array to ensure that the order is irrelevant.
     std::shuffle(FreeArray.begin(), FreeArray.end(), R);
 
     // Build the FreeList from the FreeArray.
-    scudo::IntrusiveList<Batch> FreeList;
+    scudo::SinglyLinkedList<Batch> FreeList;
     FreeList.clear();
     Batch *CurrentBatch = nullptr;
     for (auto const &Block : FreeArray) {
       if (!CurrentBatch) {
         CurrentBatch = new Batch;
         CurrentBatch->clear();
         FreeList.push_back(CurrentBatch);
       }
       CurrentBatch->add(Block);
       if (CurrentBatch->getCount() == Batch::MaxCount)
         CurrentBatch = nullptr;
     }
 
     // Release the memory.
     ReleasedPagesRecorder Recorder;
-    releaseFreeMemoryToOS(&FreeList, 0, AllocatedPagesCount, BlockSize,
+    releaseFreeMemoryToOS(FreeList, 0, AllocatedPagesCount, BlockSize,
                           &Recorder);
 
     // Verify that there are no released pages touched by used chunks and all
     // ranges of free chunks big enough to contain the entire memory pages had
     // these pages released.
     scudo::uptr VerifiedReleasedPages = 0;
     std::set<scudo::uptr> FreeBlocks(FreeArray.begin(), FreeArray.end());