src: add debugging array allocator

Add a subclass of `ArrayBufferAllocator` that performs additional
debug checking, which in particular verifies that:

- All `ArrayBuffer` backing stores have been allocated with this
  allocator, or have been explicitly marked as coming from a
  compatible source.
- All memory allocated by the allocator has been freed once it is
  destroyed.

PR-URL: https://github.com/nodejs/node/pull/26207
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>

1 files changed, 23 insertions, 0 deletions

diff --git a/src/node_internals.h b/src/node_internals.h
index 6f09708371..9ac2b0a331 100644
--- a/src/node_internals.h
+++ b/src/node_internals.h
@@ -109,11 +109,34 @@ class ArrayBufferAllocator : public v8::ArrayBuffer::Allocator {
   void* AllocateUninitialized(size_t size) override
     { return node::UncheckedMalloc(size); }
   void Free(void* data, size_t) override { free(data); }
+  virtual void* Reallocate(void* data, size_t old_size, size_t size) {
+    return static_cast<void*>(
+        UncheckedRealloc<char>(static_cast<char*>(data), size));
+  }
+  virtual void RegisterPointer(void* data, size_t size) {}
+  virtual void UnregisterPointer(void* data, size_t size) {}
 
  private:
   uint32_t zero_fill_field_ = 1;  // Boolean but exposed as uint32 to JS land.
 };
 
+class DebuggingArrayBufferAllocator final : public ArrayBufferAllocator {
+ public:
+  ~DebuggingArrayBufferAllocator() override;
+  void* Allocate(size_t size) override;
+  void* AllocateUninitialized(size_t size) override;
+  void Free(void* data, size_t size) override;
+  void* Reallocate(void* data, size_t old_size, size_t size) override;
+  void RegisterPointer(void* data, size_t size) override;
+  void UnregisterPointer(void* data, size_t size) override;
+
+ private:
+  void RegisterPointerInternal(void* data, size_t size);
+  void UnregisterPointerInternal(void* data, size_t size);
+  Mutex mutex_;
+  std::unordered_map<void*, size_t> allocations_;
+};
+
 namespace Buffer {
 v8::MaybeLocal<v8::Object> Copy(Environment* env, const char* data, size_t len);
 v8::MaybeLocal<v8::Object> New(Environment* env, size_t size);