From 8a4432cc2e55e19797e7d068ca32bbecd1fcce10 Mon Sep 17 00:00:00 2001
From: Artem Pavlenko <artem@mapnik.org>
Date: Wed, 13 Nov 2019 18:42:39 +0000
Subject: Adjust external memory after freeing image buffer (ref ##15915)

---
 platform/node/src/node_map.cpp | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/platform/node/src/node_map.cpp b/platform/node/src/node_map.cpp
index fbdd194472..a8ef14f5f7 100644
--- a/platform/node/src/node_map.cpp
+++ b/platform/node/src/node_map.cpp
@@ -542,12 +542,18 @@ void NodeMap::renderFinished() {
         auto image_size = img.bytes();
         v8::Local<v8::Object> pixels =
             Nan::NewBuffer(
-                reinterpret_cast<char*>(img.data.get()), image_size, [](char* buf, void*) { delete[] buf; }, nullptr)
-                .ToLocalChecked();
+                reinterpret_cast<char*>(img.data.get()), image_size,
+                [](char* buf, void* hint) {
+                    delete[] buf;
+                    std::int64_t* mem_freed = reinterpret_cast<std::int64_t*>(hint);
+                    Nan::AdjustExternalMemory(-(*mem_freed + sizeof(std::int64_t)));
+                    delete mem_freed;
+                }, new std::int64_t(image_size))
+            .ToLocalChecked();
         if (!pixels.IsEmpty()) {
             img.data.release();
         }
-        Nan::AdjustExternalMemory(image_size);
+        Nan::AdjustExternalMemory(image_size + sizeof(std::int64_t));
         v8::Local<v8::Value> argv[] = {
             Nan::Null(),
             pixels
-- 
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