From 271276be81c4913aa98970b6843744a94ab542db Mon Sep 17 00:00:00 2001
From: Project516 <138796702+Project516@users.noreply.github.com>
Date: Sun, 1 Nov 2026 12:22:07 -0600
Subject: [PATCH 1/2] Make System.gc collect under the java-web command, which
 node starts without --expose-gc.

---
 src/node.ts           | 11 +++++++++++
 test/programs.test.ts |  7 +++++++
 2 files changed, 18 insertions(+)

diff --git a/src/node.ts b/src/node.ts
index 71f9c31..86d05c0 100644
--- a/src/node.ts
+++ b/src/node.ts
@@ -4,6 +4,8 @@ import { isAssertionFlag, parseAssertions } from "./assertions.ts";
 import * as fs from "node:fs";
 import * as os from "node:os";
 import * as path from "node:path";
+import { setFlagsFromString } from "node:v8";
+import { runInNewContext } from "node:vm";
 import { fileURLToPath, pathToFileURL } from "node:url";
 import { VFS } from "./fs.ts";
 import type { Backend, Stat } from "./fs.ts";
@@ -180,7 +182,16 @@ function fixedInput(data: Uint8Array) {
 const bridges = new WeakMap<object, Bridge>();
 
 // The host file system is the VFS root, with the JDK image mounted at /jdk.
+// System.gc() calls globalThis.gc, which node defines only under --expose-gc
+function exposeGc() {
+  const g = globalThis as { gc?: unknown };
+  if (typeof g.gc === "function") return;
+  setFlagsFromString("--expose-gc");
+  g.gc = runInNewContext("gc");
+}
+
 function nodeVm(o: NodeRunOptions): JVM {
+  exposeGc();
   const vfs = new VFS();
   vfs.mount("/", new NodeBackend("/", true));
   // built as dist/node.js, it reads the packaged image next to it
diff --git a/test/programs.test.ts b/test/programs.test.ts
index 448e6cc..436893b 100644
--- a/test/programs.test.ts
+++ b/test/programs.test.ts
@@ -56,6 +56,13 @@ for (const file of files) {
   });
 }
 
+// the java-web command, which node starts without --expose-gc
+test("System.gc collects under the command", () => {
+  const ref = spawnSync(hotspot("java"), ["-cp", out, "Refs"], { encoding: "utf8" });
+  const got = spawnSync(process.execPath, [join(root, "src", "node.ts"), "-cp", out, "Refs"], { encoding: "utf8" });
+  assert.deepEqual({ stdout: got.stdout, code: got.status }, { stdout: ref.stdout, code: ref.status });
+});
+
 function flags(file: string, tool: string): string[] {
   const m = new RegExp(`^// ${tool}: (.*)$`, "m").exec(readFileSync(join(src, file), "utf8"));
   return m ? m[1].split(" ") : [];

From f8cf6839ec2f867c4fb225bf5f197174d5955eb4 Mon Sep 17 00:00:00 2001
From: Project516 <138796702+Project516@users.noreply.github.com>
Date: Sun, 1 Nov 2026 12:30:58 -0600
Subject: [PATCH 2/2] Leave V8 flags alone when they are frozen or gc is
 renamed, and require Refs to run in the command test.

---
 src/node.ts           | 6 +++++-
 test/programs.test.ts | 3 ++-
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/src/node.ts b/src/node.ts
index 86d05c0..b182677 100644
--- a/src/node.ts
+++ b/src/node.ts
@@ -186,8 +186,12 @@ const bridges = new WeakMap<object, Bridge>();
 function exposeGc() {
   const g = globalThis as { gc?: unknown };
   if (typeof g.gc === "function") return;
+  // V8 aborts on a flag change once flags are frozen
+  if (/(^|\s)--freeze-flags-after-init\b/.test([...process.execArgv, process.env.NODE_OPTIONS ?? ""].join(" "))) return;
   setFlagsFromString("--expose-gc");
-  g.gc = runInNewContext("gc");
+  // absent when --expose-gc-as gave it another name
+  const gc = runInNewContext("typeof gc === 'function' ? gc : undefined");
+  if (gc) g.gc = gc;
 }
 
 function nodeVm(o: NodeRunOptions): JVM {
diff --git a/test/programs.test.ts b/test/programs.test.ts
index 436893b..4c848b7 100644
--- a/test/programs.test.ts
+++ b/test/programs.test.ts
@@ -57,8 +57,9 @@ for (const file of files) {
 }
 
 // the java-web command, which node starts without --expose-gc
-test("System.gc collects under the command", () => {
+test("System.gc collects under the command", { skip: !files.includes("Refs.java") }, () => {
   const ref = spawnSync(hotspot("java"), ["-cp", out, "Refs"], { encoding: "utf8" });
+  assert.equal(ref.status, 0);
   const got = spawnSync(process.execPath, [join(root, "src", "node.ts"), "-cp", out, "Refs"], { encoding: "utf8" });
   assert.deepEqual({ stdout: got.stdout, code: got.status }, { stdout: ref.stdout, code: ref.status });
 });