inspect, pretty_format, ipc, yaml: harden recursive walkers against stack overflow and dangling state

src/jsc/ConsoleObject.rs

@@ -1729,10 +1729,7 @@ pub mod formatter {
                 ordered_properties: false,
                 custom_formatted_object: CustomFormattedObject::default(),
                 disable_inspect_custom: false,
-                // `StackCheck::default()` has `cached_stack_end = 0` ⇒ the
-                // check always passes; callers that want a real bound
-                // overwrite with `StackCheck::init()` explicitly.
-                stack_check: StackCheck::default(),
+                stack_check: StackCheck::init(),
                 can_throw_stack_overflow: false,
                 error_display_level: ErrorDisplayLevel::Full,
                 format_buffer_as_text: false,
@@ -2010,6 +2007,7 @@ pub mod formatter {
                     | Tag::Error
                     | Tag::Class
                     | Tag::Event
+                    | Tag::JSX
             )
         }
     }
@@ -3387,9 +3385,6 @@ pub mod formatter {
             if self.global_this.has_exception() {
                 return Err(jsc::JsError::Thrown);
             }
-            if !can_circ {
-                return Ok(true);
-            }
 
             if !self.stack_check.is_safe_to_recurse() {
                 self.failed = true;
@@ -3399,6 +3394,10 @@ pub mod formatter {
                 return Ok(false);
             }
 
+            if !can_circ {
+                return Ok(true);
+            }
+
             if self.map_node.is_none() {
                 let mut node = core::ptr::NonNull::new(visited::Pool::get_node())
                     .expect("ObjectPool::get_node always returns a valid heap node");

src/jsc/VirtualMachine.rs

@@ -5600,8 +5600,7 @@ impl VirtualMachine {
         // re-check here with an extra `MAX_PATH_BYTES * 3` of slack on Windows
         // to cover the transpiler's nested path buffers — same parity-level
         // protection the Object path gets from C++ `forEachProperty`'s
-        // `vm.isSafeToRecurse()`. The formatter's `stack_check` was seated by
-        // the caller (`format2` / `Bun.inspect`).
+        // `vm.isSafeToRecurse()`.
         let extra_headroom: usize = if cfg!(windows) {
             // 3× PathBuffer ≈ 288 KB — empirically enough for the
             // `remap_zig_exception` → `transpile_source_code` chain on the

src/jsc/ipc.rs

@@ -372,7 +372,14 @@ mod advanced {
                 }
 
                 let message = &data[HEADER_LENGTH..][..message_len as usize];
-                let deserialized = JSValue::deserialize(message, global)?;
+                let deserialized = match JSValue::deserialize(message, global) {
+                    Ok(v) => v,
+                    Err(JsError::Thrown) => {
+                        global.clear_exception();
+                        return Err(IPCDecodeError::InvalidFormat);
+                    }
+                    Err(e) => return Err(e.into()),
+                };
 
                 Ok(DecodeIPCMessageResult {
                     bytes_consumed: HEADER_LENGTH_U32 + message_len,

src/runtime/api/YAMLObject.rs

@@ -132,8 +132,10 @@ impl AnchorAlias {
             name: match origin {
                 ValueOrigin::Root => AnchorAliasName::Root,
                 ValueOrigin::ArrayItem => AnchorAliasName::ArrayItem(0),
+                // `prop_name` is a borrow of the iterator's `PropertyNameArray`
+                // entry; take a ref so it outlives that iterator.
                 ValueOrigin::PropValue(prop_name) => AnchorAliasName::PropValue {
-                    prop_name,
+                    prop_name: OwnedString::new(prop_name.dupe_ref()),
                     counter: 0,
                 },
             },
@@ -146,7 +148,7 @@ pub(crate) enum AnchorAliasName {
     Root,
     ArrayItem(usize),
     PropValue {
-        prop_name: BunString,
+        prop_name: OwnedString,
         // added after the name
         counter: usize,
     },
@@ -408,7 +410,7 @@ impl Stringifier {
                         self.builder.append_latin1(b"value");
                         self.builder.append_usize(*counter);
                     } else {
-                        self.builder.append_string(*prop_name);
+                        self.builder.append_string(prop_name.get());
                         if *counter != 0 {
                             self.builder.append_usize(*counter);
                         }

src/runtime/test_runner/pretty_format.rs

@@ -3,7 +3,7 @@ use crate::test_runner::expect::JSValueTestExt;
 use core::ffi::c_void;
 
 use bun_collections::HashMap;
-use bun_core::{fmt as bun_fmt, Output};
+use bun_core::{fmt as bun_fmt, Output, StackCheck};
 use bun_jsc::{
     self as jsc, ComptimeStringMapExt as _, JSGlobalObject, JSObject,
     JSPropertyIterator, JSType, JSValue, JsError, JsResult, VM,
@@ -342,6 +342,7 @@ pub struct Formatter<'a> {
     pub failed: bool,
     pub estimated_line_length: usize,
     pub always_newline_scope: bool,
+    pub stack_check: StackCheck,
 }
 
 impl<'a> Formatter<'a> {
@@ -357,6 +358,7 @@ impl<'a> Formatter<'a> {
             failed: false,
             estimated_line_length: 0,
             always_newline_scope: false,
+            stack_check: StackCheck::init(),
         }
     }
 
@@ -504,7 +506,7 @@ impl Tag {
 
     #[inline]
     pub const fn can_have_circular_references(self) -> bool {
-        matches!(self, Tag::Array | Tag::Object | Tag::Map | Tag::Set)
+        matches!(self, Tag::Array | Tag::Object | Tag::Map | Tag::Set | Tag::JSX)
     }
 }
 
@@ -1156,6 +1158,11 @@ impl<'a> Formatter<'a> {
         if self.failed {
             return Ok(());
         }
+        if !self.stack_check.is_safe_to_recurse() {
+            self.failed = true;
+            let _ = writer_.write_all(b"...");
+            return Ok(());
+        }
         // reshaped for borrowck — `WrappedWriter` borrows both writer_
         // and &mut self.estimated_line_length; we use a local wrapper and sync
         // `failed` at scope exit. estimated_line_length is unused by WrappedWriter

test/js/bun/spawn/spawn.ipc.test.ts

@@ -157,6 +157,40 @@ describe("ipc mode advanced", () => {
       expect(exitCode).toBe(0);
     },
   );
+
+  it("a malformed SerializedScriptValue payload closes the channel without leaving an uncaught TypeError", async () => {
+    // type=SerializedMessage (0x02), len=4, payload = SSV version 0xFFFFFFFF (> CurrentVersion)
+    // so CloneDeserializer throws TypeError("Unable to deserialize data."). The decoder must
+    // clear that exception and treat the frame as InvalidFormat; previously it left the
+    // exception pending and the parent saw it as an uncaught error.
+    const parent = `
+      const child = Bun.spawn({
+        cmd: [
+          process.execPath, "-e",
+          'require("fs").writeSync(3, Buffer.from([0x02, 0x04, 0x00, 0x00, 0x00, 0xff, 0xff, 0xff, 0xff]))',
+        ],
+        stdio: ["ignore", "inherit", "inherit"],
+        serialization: "advanced",
+        ipc(msg) { console.error("UNEXPECTED_IPC_MESSAGE", msg); },
+      });
+      await child.exited;
+      console.log("PARENT_OK");
+    `;
+
+    await using proc = Bun.spawn({
+      cmd: [bunExe(), "-e", parent],
+      env: bunEnv,
+      stdout: "pipe",
+      stderr: "pipe",
+    });
+
+    const [stdout, stderr, exitCode] = await Promise.all([proc.stdout.text(), proc.stderr.text(), proc.exited]);
+
+    expect(stdout.trim()).toBe("PARENT_OK");
+    expect(stderr).not.toContain("Unable to deserialize data");
+    expect(stderr).not.toContain("UNEXPECTED_IPC_MESSAGE");
+    expect(exitCode).toBe(0);
+  });
 });
 
 // getIPCInstance error path: on Windows, windowsConfigureClient can open the

test/js/bun/test/pretty-format-overflow.test.ts

@@ -37,7 +37,7 @@ test("deep nesting", () => {
       env: bunEnv,
       cwd: dir,
       stderr: "pipe",
-      stdout: "pipe",
+      stdout: "ignore",
     });
 
     const [stderr, exitCode] = await Promise.all([proc.stderr.text(), proc.exited]);
@@ -50,4 +50,40 @@ test("deep nesting", () => {
     // Verify it actually formatted and showed the diff (not just crashed)
     expect(stderr).toContain("expect(received).toEqual(expected)");
   }, 30000);
+
+  test.each(["array", "object"])(
+    "toEqual diff of a %s nested past the native stack limit does not crash",
+    async kind => {
+      // `b` is shallow so toEqual returns a mismatch immediately; the crash was in
+      // the diff formatter rendering `a` afterwards.
+      const build =
+        kind === "array"
+          ? "let a = []; for (let i = 0; i < 30000; i++) a = [a];"
+          : "let a = {}; for (let i = 0; i < 30000; i++) a = {x: a};";
+      const dir = tempDirWithFiles("pretty-format-stack", {
+        "deep.test.js": `
+          import { test, expect } from "bun:test";
+          test("deep", () => {
+            ${build}
+            expect(a).toEqual(${kind === "array" ? '["leaf"]' : '{ x: "leaf" }'});
+          });
+        `,
+      });
+
+      await using proc = Bun.spawn({
+        cmd: [bunExe(), "test", "deep.test.js"],
+        env: bunEnv,
+        cwd: dir,
+        stderr: "pipe",
+        stdout: "ignore",
+      });
+      const [stderr, exitCode] = await Promise.all([proc.stderr.text(), proc.exited]);
+
+      // The diff formatter stopped at the stack limit and the matcher threw its
+      // normal mismatch error, so the runner reports a failing test.
+      expect(stderr).toContain("expect(received).toEqual(expected)");
+      expect(stderr).toContain("1 fail");
+      expect(exitCode).toBe(1);
+    },
+  );
 });

test/js/bun/util/inspect.test.js

@@ -316,6 +316,73 @@
   expect(input).toBe(output);
 });
 
+// Without the fix these overflow the native stack and segfault, so they run in a
+// subprocess and assert on exit code + output rather than bringing down the runner.
+describe("deep / self-referencing values do not overflow the formatter stack", () => {
+  it("self-referencing JSX element prints [Circular]", async () => {
+    await using proc = Bun.spawn({
+      cmd: [
+        bunExe(),
+        "-e",
+        `
+          const a = { $$typeof: Symbol.for("react.element"), type: "div", props: null, key: null };
+          a.props = { children: a };
+          console.log(Bun.inspect(a));
+        `,
+      ],
+      env: bunEnv,
+      stdout: "pipe",
+      stderr: "pipe",
+    });
+    const [stdout, stderr, exitCode] = await Promise.all([proc.stdout.text(), proc.stderr.text(), proc.exited]);
+    expect(stdout).toContain("[Circular]");
+    expect(exitCode).toBe(0);
+  });
+
+  it.each([
+    [
+      "a deep JSX tree",
+      `let x = "leaf"; for (let i = 0; i < 100000; i++) x = { $$typeof: Symbol.for("react.element"), type: "div", props: { children: x }, key: null };`,
+    ],
+    ["a deep Proxy chain", `let x = {}; for (let i = 0; i < 100000; i++) x = new Proxy(x, {});`],
+  ])("console.log of %s throws RangeError instead of crashing", async (_, setup) => {
+    await using proc = Bun.spawn({
+      cmd: [bunExe(), "-e", `${setup} try { console.log(x); } catch (e) { process.stdout.write("CAUGHT:" + e.name); }`],
+      env: bunEnv,
+      stdout: "pipe",
+      stderr: "pipe",
+    });
+    const [stdout, stderr, exitCode] = await Promise.all([proc.stdout.text(), proc.stderr.text(), proc.exited]);
+    expect(stdout).toEndWith("CAUGHT:RangeError");
+    expect(exitCode).toBe(0);
+  });
+
+  it("throwing a deeply nested array as an uncaught exception does not crash the printer", async () => {
+    await using proc = Bun.spawn({
+      cmd: [bunExe(), "-e", `let a = []; for (let i = 0; i < 60000; i++) a = [a]; throw a;`],
+      env: bunEnv,
+      stdout: "pipe",
+      stderr: "pipe",
+    });
+    const [stdout, stderr, exitCode] = await Promise.all([proc.stdout.text(), proc.stderr.text(), proc.exited]);
+    // Uncaught throw exits 1 (not a segfault's 139/11) and the error printer ran.
+    expect(stderr).toContain("error");
+    expect(exitCode).toBe(1);
+  });
+
+  it("rejecting a deeply nested array as an unhandled rejection does not crash the printer", async () => {
+    await using proc = Bun.spawn({
+      cmd: [bunExe(), "-e", `let a = []; for (let i = 0; i < 60000; i++) a = [a]; Promise.reject(a);`],
+      env: bunEnv,
+      stdout: "pipe",
+      stderr: "pipe",
+    });
+    const [stdout, stderr, exitCode] = await Promise.all([proc.stdout.text(), proc.stderr.text(), proc.exited]);
+    expect(stderr).toContain("error");
+    expect(exitCode).toBe(1);
+  });
+});
+
 it("inspect", () => {
   expect(Bun.inspect(new TypeError("what")).includes("TypeError: what")).toBe(true);
   expect(Bun.inspect("hi")).toBe('"hi"');

test/js/bun/yaml/yaml.test.ts

@@ -2516,6 +2516,54 @@ config:
   });
 
   describe("stringify", () => {
+    test.skipIf(!isASAN)(
+      "anchor name derived from a property name survives a GC between the anchor scan and emit",
+      async () => {
+        // The anchor name for a shared value is the first property name it was seen under,
+        // stored as a BunString that borrowed the scan iterator's PropertyNameArray entry
+        // without a ref. A Proxy whose ownKeys returns fresh strings is the one case where
+        // nothing else holds that StringImpl; once the inner iterator drops and a later
+        // getter GCs, the emit pass reads freed bytes. Malloc=1 routes WTF allocations
+        // through system malloc so ASAN sees the free.
+        await using proc = Bun.spawn({
+          cmd: [
+            bunExe(),
+            "-e",
+            `
+            const shared = { x: 1 };
+            function keys() {
+              const out = [];
+              for (let i = 0; i < 8; i++) out.push("freshkey_padding_to_avoid_small_string_" + i);
+              return out;
+            }
+            const inner = new Proxy({}, {
+              ownKeys: keys,
+              getOwnPropertyDescriptor() { return { enumerable: true, configurable: true, value: shared }; },
+              has() { return true; },
+              get() { return shared; },
+            });
+            const outer = { inner };
+            Object.defineProperty(outer, "zz", {
+              enumerable: true,
+              get() { Bun.gc(true); Bun.gc(true); Bun.gc(true); return shared; },
+            });
+            const anchor = keys()[0];
+            const out = Bun.YAML.stringify(outer);
+            if (!out.includes("&" + anchor)) throw new Error("anchor name corrupted");
+            if (!out.includes("*" + anchor)) throw new Error("alias name corrupted");
+            process.stdout.write("ok");
+          `,
+          ],
+          env: { ...bunEnv, Malloc: "1" },
+          stdout: "pipe",
+          stderr: "pipe",
+        });
+        const [stdout, stderr, exitCode] = await Promise.all([proc.stdout.text(), proc.stderr.text(), proc.exited]);
+        expect({ stdout, exitCode }).toEqual({ stdout: "ok", exitCode: 0 });
+        expect(stderr).not.toContain("AddressSanitizer");
+      },
+    );
+
     // Basic data type tests
     test("stringifies null", () => {
       expect(YAML.stringify(null)).toBe("null");