[heap] Factor out read-only-spaces.h from spaces.h

Moves ReadOnlyPage, ReadOnlyArtifacts, ReadOnlySpace and
SharedReadOnlySpace out of spaces.h and into read-only-spaces.h, as well
as creating a corresponding .cc file.

Bug: v8:10473
Change-Id: I9d8b49d61ed643fd6e16919d571a909ab6fce407
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2171197
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Dan Elphick <delphick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#67531}

BUILD.gn

@@ -2460,6 +2460,8 @@ v8_source_set("v8_base_without_compiler") {
     "src/heap/read-only-heap-inl.h",
     "src/heap/read-only-heap.cc",
     "src/heap/read-only-heap.h",
+    "src/heap/read-only-spaces.cc",
+    "src/heap/read-only-spaces.h",
     "src/heap/remembered-set.h",
     "src/heap/safepoint.cc",
     "src/heap/safepoint.h",

src/heap/heap-inl.h

@@ -23,6 +23,7 @@
 // leak heap internals to users of this interface!
 #include "src/execution/isolate-data.h"
 #include "src/execution/isolate.h"
+#include "src/heap/read-only-spaces.h"
 #include "src/heap/spaces-inl.h"
 #include "src/objects/allocation-site-inl.h"
 #include "src/objects/api-callbacks-inl.h"

src/heap/mark-compact.cc

@@ -30,6 +30,7 @@
 #include "src/heap/object-stats.h"
 #include "src/heap/objects-visiting-inl.h"
 #include "src/heap/read-only-heap.h"
+#include "src/heap/read-only-spaces.h"
 #include "src/heap/spaces-inl.h"
 #include "src/heap/sweeper.h"
 #include "src/heap/worklist.h"

src/heap/mark-compact.h

@@ -24,6 +24,7 @@ class EvacuationJobTraits;
 class HeapObjectVisitor;
 class ItemParallelJob;
 class MigrationObserver;
+class ReadOnlySpace;
 class RecordMigratedSlotVisitor;
 class UpdatingItem;
 class YoungGenerationMarkingVisitor;

src/heap/read-only-heap.cc

@@ -11,7 +11,7 @@
 #include "src/base/platform/mutex.h"
 #include "src/heap/heap-inl.h"
 #include "src/heap/heap-write-barrier-inl.h"
-#include "src/heap/spaces.h"
+#include "src/heap/read-only-spaces.h"
 #include "src/objects/heap-object-inl.h"
 #include "src/objects/objects-inl.h"
 #include "src/objects/smi.h"

src/heap/read-only-spaces.cc

@@ -0,0 +1,169 @@
+// Copyright 2020 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "src/heap/read-only-spaces.h"
+
+#include "src/base/lsan.h"
+#include "src/execution/isolate.h"
+#include "src/heap/combined-heap.h"
+#include "src/heap/heap-inl.h"
+#include "src/heap/read-only-heap.h"
+#include "src/objects/objects-inl.h"
+#include "src/objects/string.h"
+
+namespace v8 {
+namespace internal {
+
+// -----------------------------------------------------------------------------
+// ReadOnlySpace implementation
+
+ReadOnlySpace::ReadOnlySpace(Heap* heap)
+    : PagedSpace(heap, RO_SPACE, NOT_EXECUTABLE, FreeList::CreateFreeList()),
+      is_string_padding_cleared_(heap->isolate()->initialized_from_snapshot()) {
+}
+
+ReadOnlyArtifacts::~ReadOnlyArtifacts() {
+  v8::PageAllocator* page_allocator = GetPlatformPageAllocator();
+
+  MemoryChunk* next_chunk;
+  for (MemoryChunk* chunk = pages_.front(); chunk != nullptr;
+       chunk = next_chunk) {
+    void* chunk_address = reinterpret_cast<void*>(chunk->address());
+    page_allocator->SetPermissions(chunk_address, chunk->size(),
+                                   PageAllocator::kReadWrite);
+    next_chunk = chunk->list_node().next();
+    size_t size = RoundUp(chunk->size(), page_allocator->AllocatePageSize());
+    CHECK(page_allocator->FreePages(chunk_address, size));
+  }
+}
+
+void ReadOnlyArtifacts::set_read_only_heap(
+    std::unique_ptr<ReadOnlyHeap> read_only_heap) {
+  read_only_heap_ = std::move(read_only_heap);
+}
+
+SharedReadOnlySpace::~SharedReadOnlySpace() {
+  // Clear the memory chunk list before the space is deleted, so that the
+  // inherited destructors don't try to destroy the MemoryChunks themselves.
+  memory_chunk_list_ = heap::List<MemoryChunk>();
+}
+
+SharedReadOnlySpace::SharedReadOnlySpace(
+    Heap* heap, std::shared_ptr<ReadOnlyArtifacts> artifacts)
+    : ReadOnlySpace(heap) {
+  artifacts->pages().ShallowCopyTo(&memory_chunk_list_);
+  is_marked_read_only_ = true;
+  accounting_stats_ = artifacts->accounting_stats();
+}
+
+void ReadOnlySpace::DetachPagesAndAddToArtifacts(
+    std::shared_ptr<ReadOnlyArtifacts> artifacts) {
+  Heap* heap = ReadOnlySpace::heap();
+  Seal(SealMode::kDetachFromHeapAndForget);
+  artifacts->set_accounting_stats(accounting_stats_);
+  artifacts->TransferPages(std::move(memory_chunk_list_));
+  artifacts->set_shared_read_only_space(
+      std::make_unique<SharedReadOnlySpace>(heap, artifacts));
+  heap->ReplaceReadOnlySpace(artifacts->shared_read_only_space());
+}
+
+void ReadOnlyPage::MakeHeaderRelocatable() {
+  ReleaseAllocatedMemoryNeededForWritableChunk();
+  // Detached read-only space needs to have a valid marking bitmap and free list
+  // categories. Instruct Lsan to ignore them if required.
+  LSAN_IGNORE_OBJECT(categories_);
+  for (int i = kFirstCategory; i < free_list()->number_of_categories(); i++) {
+    LSAN_IGNORE_OBJECT(categories_[i]);
+  }
+  LSAN_IGNORE_OBJECT(marking_bitmap_);
+  heap_ = nullptr;
+  owner_ = nullptr;
+}
+
+void ReadOnlySpace::SetPermissionsForPages(MemoryAllocator* memory_allocator,
+                                           PageAllocator::Permission access) {
+  for (Page* p : *this) {
+    // Read only pages don't have valid reservation object so we get proper
+    // page allocator manually.
+    v8::PageAllocator* page_allocator =
+        memory_allocator->page_allocator(p->executable());
+    CHECK(SetPermissions(page_allocator, p->address(), p->size(), access));
+  }
+}
+
+// After we have booted, we have created a map which represents free space
+// on the heap.  If there was already a free list then the elements on it
+// were created with the wrong FreeSpaceMap (normally nullptr), so we need to
+// fix them.
+void ReadOnlySpace::RepairFreeListsAfterDeserialization() {
+  free_list_->RepairLists(heap());
+  // Each page may have a small free space that is not tracked by a free list.
+  // Those free spaces still contain null as their map pointer.
+  // Overwrite them with new fillers.
+  for (Page* page : *this) {
+    int size = static_cast<int>(page->wasted_memory());
+    if (size == 0) {
+      // If there is no wasted memory then all free space is in the free list.
+      continue;
+    }
+    Address start = page->HighWaterMark();
+    Address end = page->area_end();
+    if (start < end - size) {
+      // A region at the high watermark is already in free list.
+      HeapObject filler = HeapObject::FromAddress(start);
+      CHECK(filler.IsFreeSpaceOrFiller());
+      start += filler.Size();
+    }
+    CHECK_EQ(size, static_cast<int>(end - start));
+    heap()->CreateFillerObjectAt(start, size, ClearRecordedSlots::kNo);
+  }
+}
+
+void ReadOnlySpace::ClearStringPaddingIfNeeded() {
+  if (V8_ENABLE_THIRD_PARTY_HEAP_BOOL) {
+    // TODO(ulan): Revisit this once third-party heap supports iteration.
+    return;
+  }
+  if (is_string_padding_cleared_) return;
+
+  ReadOnlyHeapObjectIterator iterator(this);
+  for (HeapObject o = iterator.Next(); !o.is_null(); o = iterator.Next()) {
+    if (o.IsSeqOneByteString()) {
+      SeqOneByteString::cast(o).clear_padding();
+    } else if (o.IsSeqTwoByteString()) {
+      SeqTwoByteString::cast(o).clear_padding();
+    }
+  }
+  is_string_padding_cleared_ = true;
+}
+
+void ReadOnlySpace::Seal(SealMode ro_mode) {
+  DCHECK(!is_marked_read_only_);
+
+  FreeLinearAllocationArea();
+  is_marked_read_only_ = true;
+  auto* memory_allocator = heap()->memory_allocator();
+
+  if (ro_mode == SealMode::kDetachFromHeapAndForget) {
+    DetachFromHeap();
+    for (Page* p : *this) {
+      memory_allocator->UnregisterMemory(p);
+      static_cast<ReadOnlyPage*>(p)->MakeHeaderRelocatable();
+    }
+  }
+
+  SetPermissionsForPages(memory_allocator, PageAllocator::kRead);
+}
+
+void ReadOnlySpace::Unseal() {
+  DCHECK(is_marked_read_only_);
+  if (HasPages()) {
+    SetPermissionsForPages(heap()->memory_allocator(),
+                           PageAllocator::kReadWrite);
+  }
+  is_marked_read_only_ = false;
+}
+
+}  // namespace internal
+}  // namespace v8

src/heap/read-only-spaces.h

@@ -0,0 +1,124 @@
+// Copyright 2020 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef V8_HEAP_READ_ONLY_SPACES_H_
+#define V8_HEAP_READ_ONLY_SPACES_H_
+
+#include <memory>
+#include <utility>
+
+#include "include/v8-platform.h"
+#include "src/base/macros.h"
+#include "src/heap/list.h"
+#include "src/heap/spaces.h"
+
+namespace v8 {
+namespace internal {
+
+class ReadOnlyHeap;
+
+class ReadOnlyPage : public Page {
+ public:
+  // Clears any pointers in the header that point out of the page that would
+  // otherwise make the header non-relocatable.
+  void MakeHeaderRelocatable();
+
+ private:
+  friend class ReadOnlySpace;
+};
+
+// -----------------------------------------------------------------------------
+// Artifacts used to construct a new SharedReadOnlySpace
+class ReadOnlyArtifacts {
+ public:
+  ~ReadOnlyArtifacts();
+
+  void set_accounting_stats(const AllocationStats& stats) { stats_ = stats; }
+
+  void set_shared_read_only_space(
+      std::unique_ptr<SharedReadOnlySpace> shared_space) {
+    shared_read_only_space_ = std::move(shared_space);
+  }
+  SharedReadOnlySpace* shared_read_only_space() {
+    return shared_read_only_space_.get();
+  }
+
+  heap::List<MemoryChunk>& pages() { return pages_; }
+  void TransferPages(heap::List<MemoryChunk>&& pages) {
+    pages_ = std::move(pages);
+  }
+
+  const AllocationStats& accounting_stats() const { return stats_; }
+
+  void set_read_only_heap(std::unique_ptr<ReadOnlyHeap> read_only_heap);
+  ReadOnlyHeap* read_only_heap() { return read_only_heap_.get(); }
+
+ private:
+  heap::List<MemoryChunk> pages_;
+  AllocationStats stats_;
+  std::unique_ptr<SharedReadOnlySpace> shared_read_only_space_;
+  std::unique_ptr<ReadOnlyHeap> read_only_heap_;
+};
+
+// -----------------------------------------------------------------------------
+// Read Only space for all Immortal Immovable and Immutable objects
+class ReadOnlySpace : public PagedSpace {
+ public:
+  explicit ReadOnlySpace(Heap* heap);
+
+  // Detach the pages and them to artifacts for using in creating a
+  // SharedReadOnlySpace.
+  void DetachPagesAndAddToArtifacts(
+      std::shared_ptr<ReadOnlyArtifacts> artifacts);
+
+  ~ReadOnlySpace() override { Unseal(); }
+
+  bool writable() const { return !is_marked_read_only_; }
+
+  bool Contains(Address a) = delete;
+  bool Contains(Object o) = delete;
+
+  V8_EXPORT_PRIVATE void ClearStringPaddingIfNeeded();
+
+  enum class SealMode { kDetachFromHeapAndForget, kDoNotDetachFromHeap };
+
+  // Seal the space by marking it read-only, optionally detaching it
+  // from the heap and forgetting it for memory bookkeeping purposes (e.g.
+  // prevent space's memory from registering as leaked).
+  void Seal(SealMode ro_mode);
+
+  // During boot the free_space_map is created, and afterwards we may need
+  // to write it into the free list nodes that were already created.
+  void RepairFreeListsAfterDeserialization();
+
+  size_t Available() override { return 0; }
+
+ protected:
+  void SetPermissionsForPages(MemoryAllocator* memory_allocator,
+                              PageAllocator::Permission access);
+
+  bool is_marked_read_only_ = false;
+
+ private:
+  // Unseal the space after is has been sealed, by making it writable.
+  // TODO(v8:7464): Only possible if the space hasn't been detached.
+  void Unseal();
+
+  //
+  // String padding must be cleared just before serialization and therefore the
+  // string padding in the space will already have been cleared if the space was
+  // deserialized.
+  bool is_string_padding_cleared_;
+};
+
+class SharedReadOnlySpace : public ReadOnlySpace {
+ public:
+  SharedReadOnlySpace(Heap* heap, std::shared_ptr<ReadOnlyArtifacts> artifacts);
+  ~SharedReadOnlySpace() override;
+};
+
+}  // namespace internal
+}  // namespace v8
+
+#endif  // V8_HEAP_READ_ONLY_SPACES_H_

src/heap/spaces.cc

@@ -9,7 +9,6 @@
 #include <utility>
 
 #include "src/base/bits.h"
-#include "src/base/lsan.h"
 #include "src/base/macros.h"
 #include "src/base/optional.h"
 #include "src/base/platform/semaphore.h"
@@ -3997,155 +3996,5 @@ void MapSpace::SortFreeList() {
 void MapSpace::VerifyObject(HeapObject object) { CHECK(object.IsMap()); }
 #endif
 
-// -----------------------------------------------------------------------------
-// ReadOnlySpace implementation
-
-ReadOnlySpace::ReadOnlySpace(Heap* heap)
-    : PagedSpace(heap, RO_SPACE, NOT_EXECUTABLE, FreeList::CreateFreeList()),
-      is_string_padding_cleared_(heap->isolate()->initialized_from_snapshot()) {
-}
-
-ReadOnlyArtifacts::~ReadOnlyArtifacts() {
-  v8::PageAllocator* page_allocator = GetPlatformPageAllocator();
-
-  MemoryChunk* next_chunk;
-  for (MemoryChunk* chunk = pages_.front(); chunk != nullptr;
-       chunk = next_chunk) {
-    void* chunk_address = reinterpret_cast<void*>(chunk->address());
-    page_allocator->SetPermissions(chunk_address, chunk->size(),
-                                   PageAllocator::kReadWrite);
-    next_chunk = chunk->list_node().next();
-    size_t size = RoundUp(chunk->size(), page_allocator->AllocatePageSize());
-    CHECK(page_allocator->FreePages(chunk_address, size));
-  }
-}
-
-void ReadOnlyArtifacts::set_read_only_heap(
-    std::unique_ptr<ReadOnlyHeap> read_only_heap) {
-  read_only_heap_ = std::move(read_only_heap);
-}
-
-SharedReadOnlySpace::~SharedReadOnlySpace() {
-  // Clear the memory chunk list before the space is deleted, so that the
-  // inherited destructors don't try to destroy the MemoryChunks themselves.
-  memory_chunk_list_ = heap::List<MemoryChunk>();
-}
-
-SharedReadOnlySpace::SharedReadOnlySpace(
-    Heap* heap, std::shared_ptr<ReadOnlyArtifacts> artifacts)
-    : ReadOnlySpace(heap) {
-  artifacts->pages().ShallowCopyTo(&memory_chunk_list_);
-  is_marked_read_only_ = true;
-  accounting_stats_ = artifacts->accounting_stats();
-}
-
-void ReadOnlySpace::DetachPagesAndAddToArtifacts(
-    std::shared_ptr<ReadOnlyArtifacts> artifacts) {
-  Heap* heap = ReadOnlySpace::heap();
-  Seal(SealMode::kDetachFromHeapAndForget);
-  artifacts->set_accounting_stats(accounting_stats_);
-  artifacts->TransferPages(std::move(memory_chunk_list_));
-  artifacts->set_shared_read_only_space(
-      std::make_unique<SharedReadOnlySpace>(heap, artifacts));
-  heap->ReplaceReadOnlySpace(artifacts->shared_read_only_space());
-}
-
-void ReadOnlyPage::MakeHeaderRelocatable() {
-  ReleaseAllocatedMemoryNeededForWritableChunk();
-  // Detached read-only space needs to have a valid marking bitmap and free list
-  // categories. Instruct Lsan to ignore them if required.
-  LSAN_IGNORE_OBJECT(categories_);
-  for (int i = kFirstCategory; i < free_list()->number_of_categories(); i++) {
-    LSAN_IGNORE_OBJECT(categories_[i]);
-  }
-  LSAN_IGNORE_OBJECT(marking_bitmap_);
-  heap_ = nullptr;
-  owner_ = nullptr;
-}
-
-void ReadOnlySpace::SetPermissionsForPages(MemoryAllocator* memory_allocator,
-                                           PageAllocator::Permission access) {
-  for (Page* p : *this) {
-    // Read only pages don't have valid reservation object so we get proper
-    // page allocator manually.
-    v8::PageAllocator* page_allocator =
-        memory_allocator->page_allocator(p->executable());
-    CHECK(SetPermissions(page_allocator, p->address(), p->size(), access));
-  }
-}
-
-// After we have booted, we have created a map which represents free space
-// on the heap.  If there was already a free list then the elements on it
-// were created with the wrong FreeSpaceMap (normally nullptr), so we need to
-// fix them.
-void ReadOnlySpace::RepairFreeListsAfterDeserialization() {
-  free_list_->RepairLists(heap());
-  // Each page may have a small free space that is not tracked by a free list.
-  // Those free spaces still contain null as their map pointer.
-  // Overwrite them with new fillers.
-  for (Page* page : *this) {
-    int size = static_cast<int>(page->wasted_memory());
-    if (size == 0) {
-      // If there is no wasted memory then all free space is in the free list.
-      continue;
-    }
-    Address start = page->HighWaterMark();
-    Address end = page->area_end();
-    if (start < end - size) {
-      // A region at the high watermark is already in free list.
-      HeapObject filler = HeapObject::FromAddress(start);
-      CHECK(filler.IsFreeSpaceOrFiller());
-      start += filler.Size();
-    }
-    CHECK_EQ(size, static_cast<int>(end - start));
-    heap()->CreateFillerObjectAt(start, size, ClearRecordedSlots::kNo);
-  }
-}
-
-void ReadOnlySpace::ClearStringPaddingIfNeeded() {
-  if (V8_ENABLE_THIRD_PARTY_HEAP_BOOL) {
-    // TODO(ulan): Revisit this once third-party heap supports iteration.
-    return;
-  }
-  if (is_string_padding_cleared_) return;
-
-  ReadOnlyHeapObjectIterator iterator(this);
-  for (HeapObject o = iterator.Next(); !o.is_null(); o = iterator.Next()) {
-    if (o.IsSeqOneByteString()) {
-      SeqOneByteString::cast(o).clear_padding();
-    } else if (o.IsSeqTwoByteString()) {
-      SeqTwoByteString::cast(o).clear_padding();
-    }
-  }
-  is_string_padding_cleared_ = true;
-}
-
-void ReadOnlySpace::Seal(SealMode ro_mode) {
-  DCHECK(!is_marked_read_only_);
-
-  FreeLinearAllocationArea();
-  is_marked_read_only_ = true;
-  auto* memory_allocator = heap()->memory_allocator();
-
-  if (ro_mode == SealMode::kDetachFromHeapAndForget) {
-    DetachFromHeap();
-    for (Page* p : *this) {
-      memory_allocator->UnregisterMemory(p);
-      static_cast<ReadOnlyPage*>(p)->MakeHeaderRelocatable();
-    }
-  }
-
-  SetPermissionsForPages(memory_allocator, PageAllocator::kRead);
-}
-
-void ReadOnlySpace::Unseal() {
-  DCHECK(is_marked_read_only_);
-  if (HasPages()) {
-    SetPermissionsForPages(heap()->memory_allocator(),
-                           PageAllocator::kReadWrite);
-  }
-  is_marked_read_only_ = false;
-}
-
 }  // namespace internal
 }  // namespace v8

src/heap/spaces.h

@@ -1117,16 +1117,6 @@ class Page : public MemoryChunk {
   friend class MemoryAllocator;
 };
 
-class ReadOnlyPage : public Page {
- public:
-  // Clears any pointers in the header that point out of the page that would
-  // otherwise make the header non-relocatable.
-  void MakeHeaderRelocatable();
-
- private:
-  friend class ReadOnlySpace;
-};
-
 // Validate our estimates on the header size.
 STATIC_ASSERT(sizeof(BasicMemoryChunk) <= BasicMemoryChunk::kHeaderSize);
 STATIC_ASSERT(sizeof(MemoryChunk) <= MemoryChunk::kHeaderSize);
@@ -3208,97 +3198,6 @@ class V8_EXPORT_PRIVATE OffThreadSpace : public LocalSpace {
   void RefillFreeList() override;
 };
 
-// -----------------------------------------------------------------------------
-// Artifacts used to construct a new SharedReadOnlySpace
-class ReadOnlyArtifacts {
- public:
-  ~ReadOnlyArtifacts();
-
-  void set_accounting_stats(const AllocationStats& stats) { stats_ = stats; }
-
-  void set_shared_read_only_space(
-      std::unique_ptr<SharedReadOnlySpace> shared_space) {
-    shared_read_only_space_ = std::move(shared_space);
-  }
-  SharedReadOnlySpace* shared_read_only_space() {
-    return shared_read_only_space_.get();
-  }
-
-  heap::List<MemoryChunk>& pages() { return pages_; }
-  void TransferPages(heap::List<MemoryChunk>&& pages) {
-    pages_ = std::move(pages);
-  }
-
-  const AllocationStats& accounting_stats() const { return stats_; }
-
-  void set_read_only_heap(std::unique_ptr<ReadOnlyHeap> read_only_heap);
-  ReadOnlyHeap* read_only_heap() { return read_only_heap_.get(); }
-
- private:
-  heap::List<MemoryChunk> pages_;
-  AllocationStats stats_;
-  std::unique_ptr<SharedReadOnlySpace> shared_read_only_space_;
-  std::unique_ptr<ReadOnlyHeap> read_only_heap_;
-};
-
-// -----------------------------------------------------------------------------
-// Read Only space for all Immortal Immovable and Immutable objects
-
-class ReadOnlySpace : public PagedSpace {
- public:
-  explicit ReadOnlySpace(Heap* heap);
-
-  // Detach the pages and them to artifacts for using in creating a
-  // SharedReadOnlySpace.
-  void DetachPagesAndAddToArtifacts(
-      std::shared_ptr<ReadOnlyArtifacts> artifacts);
-
-  ~ReadOnlySpace() override { Unseal(); }
-
-  bool writable() const { return !is_marked_read_only_; }
-
-  bool Contains(Address a) = delete;
-  bool Contains(Object o) = delete;
-
-  V8_EXPORT_PRIVATE void ClearStringPaddingIfNeeded();
-
-  enum class SealMode { kDetachFromHeapAndForget, kDoNotDetachFromHeap };
-
-  // Seal the space by marking it read-only, optionally detaching it
-  // from the heap and forgetting it for memory bookkeeping purposes (e.g.
-  // prevent space's memory from registering as leaked).
-  void Seal(SealMode ro_mode);
-
-  // During boot the free_space_map is created, and afterwards we may need
-  // to write it into the free list nodes that were already created.
-  void RepairFreeListsAfterDeserialization();
-
-  size_t Available() override { return 0; }
-
- protected:
-  void SetPermissionsForPages(MemoryAllocator* memory_allocator,
-                              PageAllocator::Permission access);
-
-  bool is_marked_read_only_ = false;
-
- private:
-  // Unseal the space after is has been sealed, by making it writable.
-  // TODO(v8:7464): Only possible if the space hasn't been detached.
-  void Unseal();
-
-  //
-  // String padding must be cleared just before serialization and therefore the
-  // string padding in the space will already have been cleared if the space was
-  // deserialized.
-  bool is_string_padding_cleared_;
-};
-
-class SharedReadOnlySpace : public ReadOnlySpace {
- public:
-  SharedReadOnlySpace(Heap* heap, std::shared_ptr<ReadOnlyArtifacts> artifacts);
-  ~SharedReadOnlySpace() override;
-};
-
 // Iterates over the chunks (pages and large object pages) that can contain
 // pointers to new space or to evacuation candidates.
 class OldGenerationMemoryChunkIterator {

test/cctest/test-debug-helper.cc

@@ -4,6 +4,7 @@
 
 #include "src/api/api-inl.h"
 #include "src/flags/flags.h"
+#include "src/heap/read-only-spaces.h"
 #include "src/heap/spaces.h"
 #include "test/cctest/cctest.h"
 #include "tools/debug_helper/debug-helper.h"