lib,src: support values > 4GB in heap statistics

We were transporting the heap statistics as uint32 values to JS land but
those wrap around for values > 4 GB.  Use 64 bits floats instead, those
should last us a while.

Fixes: https://github.com/nodejs/node/issues/10185
PR-URL: https://github.com/nodejs/node/pull/10186
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Evan Lucas <evanlucas@me.com>

lib/v8.js

@@ -18,7 +18,7 @@ const v8binding = process.binding('v8');
 
 // Properties for heap statistics buffer extraction.
 const heapStatisticsBuffer =
-    new Uint32Array(v8binding.heapStatisticsArrayBuffer);
+    new Float64Array(v8binding.heapStatisticsArrayBuffer);
 const kTotalHeapSizeIndex = v8binding.kTotalHeapSizeIndex;
 const kTotalHeapSizeExecutableIndex = v8binding.kTotalHeapSizeExecutableIndex;
 const kTotalPhysicalSizeIndex = v8binding.kTotalPhysicalSizeIndex;
@@ -28,7 +28,7 @@ const kHeapSizeLimitIndex = v8binding.kHeapSizeLimitIndex;
 
 // Properties for heap space statistics buffer extraction.
 const heapSpaceStatisticsBuffer =
-    new Uint32Array(v8binding.heapSpaceStatisticsArrayBuffer);
+    new Float64Array(v8binding.heapSpaceStatisticsArrayBuffer);
 const kHeapSpaces = v8binding.kHeapSpaces;
 const kNumberOfHeapSpaces = kHeapSpaces.length;
 const kHeapSpaceStatisticsPropertiesCount =

src/env-inl.h

@@ -396,22 +396,22 @@ inline std::vector<int64_t>* Environment::destroy_ids_list() {
   return &destroy_ids_list_;
 }
 
-inline uint32_t* Environment::heap_statistics_buffer() const {
+inline double* Environment::heap_statistics_buffer() const {
   CHECK_NE(heap_statistics_buffer_, nullptr);
   return heap_statistics_buffer_;
 }
 
-inline void Environment::set_heap_statistics_buffer(uint32_t* pointer) {
+inline void Environment::set_heap_statistics_buffer(double* pointer) {
   CHECK_EQ(heap_statistics_buffer_, nullptr);  // Should be set only once.
   heap_statistics_buffer_ = pointer;
 }
 
-inline uint32_t* Environment::heap_space_statistics_buffer() const {
+inline double* Environment::heap_space_statistics_buffer() const {
   CHECK_NE(heap_space_statistics_buffer_, nullptr);
   return heap_space_statistics_buffer_;
 }
 
-inline void Environment::set_heap_space_statistics_buffer(uint32_t* pointer) {
+inline void Environment::set_heap_space_statistics_buffer(double* pointer) {
   CHECK_EQ(heap_space_statistics_buffer_, nullptr);  // Should be set only once.
   heap_space_statistics_buffer_ = pointer;
 }

src/env.h

@@ -458,11 +458,11 @@ class Environment {
   // List of id's that have been destroyed and need the destroy() cb called.
   inline std::vector<int64_t>* destroy_ids_list();
 
-  inline uint32_t* heap_statistics_buffer() const;
-  inline void set_heap_statistics_buffer(uint32_t* pointer);
+  inline double* heap_statistics_buffer() const;
+  inline void set_heap_statistics_buffer(double* pointer);
 
-  inline uint32_t* heap_space_statistics_buffer() const;
-  inline void set_heap_space_statistics_buffer(uint32_t* pointer);
+  inline double* heap_space_statistics_buffer() const;
+  inline void set_heap_space_statistics_buffer(double* pointer);
 
   inline char* http_parser_buffer() const;
   inline void set_http_parser_buffer(char* buffer);
@@ -578,8 +578,8 @@ class Environment {
            &HandleCleanup::handle_cleanup_queue_> handle_cleanup_queue_;
   int handle_cleanup_waiting_;
 
-  uint32_t* heap_statistics_buffer_ = nullptr;
-  uint32_t* heap_space_statistics_buffer_ = nullptr;
+  double* heap_statistics_buffer_ = nullptr;
+  double* heap_space_statistics_buffer_ = nullptr;
 
   char* http_parser_buffer_;
 

src/node_v8.cc

@@ -54,8 +54,8 @@ void UpdateHeapStatisticsArrayBuffer(const FunctionCallbackInfo<Value>& args) {
   Environment* env = Environment::GetCurrent(args);
   HeapStatistics s;
   env->isolate()->GetHeapStatistics(&s);
-  uint32_t* const buffer = env->heap_statistics_buffer();
-#define V(index, name, _) buffer[index] = static_cast<uint32_t>(s.name());
+  double* const buffer = env->heap_statistics_buffer();
+#define V(index, name, _) buffer[index] = static_cast<double>(s.name());
   HEAP_STATISTICS_PROPERTIES(V)
 #undef V
 }
@@ -65,13 +65,13 @@ void UpdateHeapSpaceStatisticsBuffer(const FunctionCallbackInfo<Value>& args) {
   Environment* env = Environment::GetCurrent(args);
   HeapSpaceStatistics s;
   Isolate* const isolate = env->isolate();
-  uint32_t* buffer = env->heap_space_statistics_buffer();
+  double* buffer = env->heap_space_statistics_buffer();
 
   for (size_t i = 0; i < number_of_heap_spaces; i++) {
     isolate->GetHeapSpaceStatistics(&s, i);
     size_t const property_offset = i * kHeapSpaceStatisticsPropertiesCount;
 #define V(index, name, _) buffer[property_offset + index] = \
-                              static_cast<uint32_t>(s.name());
+                              static_cast<double>(s.name());
       HEAP_SPACE_STATISTICS_PROPERTIES(V)
 #undef V
   }
@@ -100,7 +100,7 @@ void InitializeV8Bindings(Local<Object> target,
                  "updateHeapStatisticsArrayBuffer",
                  UpdateHeapStatisticsArrayBuffer);
 
-  env->set_heap_statistics_buffer(new uint32_t[kHeapStatisticsPropertiesCount]);
+  env->set_heap_statistics_buffer(new double[kHeapStatisticsPropertiesCount]);
 
   const size_t heap_statistics_buffer_byte_length =
       sizeof(*env->heap_statistics_buffer()) * kHeapStatisticsPropertiesCount;
@@ -146,7 +146,7 @@ void InitializeV8Bindings(Local<Object> target,
                  UpdateHeapSpaceStatisticsBuffer);
 
   env->set_heap_space_statistics_buffer(
-    new uint32_t[kHeapSpaceStatisticsPropertiesCount * number_of_heap_spaces]);
+    new double[kHeapSpaceStatisticsPropertiesCount * number_of_heap_spaces]);
 
   const size_t heap_space_statistics_buffer_byte_length =
       sizeof(*env->heap_space_statistics_buffer()) *