scratch: minimal cppgc MakeGarbageCollected addon repro (arm64 macOS)

Author: romgrk

.github/workflows/cppgc-repro.yml

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+name: cppgc-repro
+
+on:
+  push:
+    branches: [scratch/cppgc-arm64-repro]
+
+jobs:
+  repro:
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest, macos-latest, windows-latest]
+    runs-on: ${{ matrix.os }}
+    defaults:
+      run:
+        working-directory: cppgc-repro
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 22
+      - name: build
+        run: npx node-gyp configure build
+      - name: run
+        run: node test.js
+      - name: lldb backtrace (macOS)
+        if: always() && runner.os == 'macOS'
+        run: |
+          lldb --batch -o run -k "thread backtrace" -k "quit" -- "$(command -v node)" test.js || true

cppgc-repro/binding.cc

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+// Minimal reproduction: cppgc::MakeGarbageCollected crashes inside an addon on
+// arm64 macOS. Build with node-gyp; call `make()` from JS.
+#include <cstdio>
+#include <node.h>
+#include <v8.h>
+
+#include "cppgc/allocation.h"
+#include "cppgc/garbage-collected.h"
+#include "cppgc/visitor.h"
+#include "v8-cppgc.h"
+
+class Wrappable final : public cppgc::GarbageCollected<Wrappable> {
+ public:
+  void Trace(cppgc::Visitor*) const {}
+};
+
+static void Make(const v8::FunctionCallbackInfo<v8::Value>& info) {
+  v8::Isolate* isolate = info.GetIsolate();
+
+  v8::CppHeap* heap = isolate->GetCppHeap();
+  fprintf(stderr, "[repro] isolate->GetCppHeap() = %p\n", (void*)heap);
+  fflush(stderr);
+  if (heap == nullptr) {
+    fprintf(stderr, "[repro] CppHeap is null\n");
+    fflush(stderr);
+    return;
+  }
+
+  cppgc::AllocationHandle& handle = heap->GetAllocationHandle();
+  fprintf(stderr, "[repro] &GetAllocationHandle() = %p\n", (void*)&handle);
+  fflush(stderr);
+
+  // Crashes here (EXC_BAD_ACCESS) on arm64 macOS; works on x64 Linux/Windows.
+  Wrappable* w = cppgc::MakeGarbageCollected<Wrappable>(handle);
+  fprintf(stderr, "[repro] MakeGarbageCollected = %p\n", (void*)w);
+  fflush(stderr);
+}
+
+static void Init(v8::Local<v8::Object> exports) {
+  NODE_SET_METHOD(exports, "make", Make);
+}
+
+NODE_MODULE(NODE_GYP_MODULE_NAME, Init)

cppgc-repro/binding.gyp

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+{
+  "targets": [
+    {
+      "target_name": "cppgc_repro",
+      "sources": [ "binding.cc" ]
+    }
+  ]
+}

cppgc-repro/package.json

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+{
+  "name": "cppgc-repro",
+  "version": "1.0.0",
+  "private": true,
+  "gypfile": true
+}

cppgc-repro/test.js

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+const addon = require('./build/Release/cppgc_repro.node')
+console.log('node', process.versions.node, 'arch', process.arch, 'platform', process.platform)
+addon.make()
+console.log('OK: no crash')