node child process maxbuf support (#18293)

.vscode/launch.json

@@ -1118,7 +1118,11 @@
       "request": "attach",
       "name": "rr",
       "trace": "Off",
-      "setupCommands": ["handle SIGPWR nostop noprint pass"],
+      "setupCommands": [
+        "handle SIGPWR nostop noprint pass",
+        "source ${workspaceFolder}/misctools/gdb/std_gdb_pretty_printers.py",
+        "source ${workspaceFolder}/misctools/gdb/zig_gdb_pretty_printers.py",
+      ],
     },
   ],
   "inputs": [

docs/api/spawn.md

@@ -253,6 +253,19 @@ const proc = Bun.spawn({
 
 The `killSignal` option also controls which signal is sent when an AbortSignal is aborted.
 
+## Using maxBuffer
+
+For spawnSync, you can limit the maximum number of bytes of output before the process is killed:
+
+```ts
+// KIll 'yes' after it emits over 100 bytes of output
+const result = Bun.spawnSync({
+  cmd: ["yes"], // or ["bun", "exec", "yes"] on windows
+  maxBuffer: 100,
+});
+// process exits
+```
+
 ## Inter-process communication (IPC)
 
 Bun supports direct inter-process communication channel between two `bun` processes. To receive messages from a spawned Bun subprocess, specify an `ipc` handler.
@@ -423,6 +436,7 @@ namespace SpawnOptions {
     signal?: AbortSignal;
     timeout?: number;
     killSignal?: string | number;
+    maxBuffer?: number;
   }
 
   type Readable =

misctools/gdb/std_gdb_pretty_printers.py

@@ -0,0 +1,142 @@
+# pretty printing for the standard library.
+# put "source /path/to/stage2_gdb_pretty_printers.py" in ~/.gdbinit to load it automatically.
+import re
+import gdb.printing
+
+# Handles both ArrayList and ArrayListUnmanaged.
+class ArrayListPrinter:
+    def __init__(self, val):
+        self.val = val
+
+    def to_string(self):
+        type = self.val.type.name[len('std.array_list.'):]
+        type = re.sub(r'^ArrayListAligned(Unmanaged)?\((.*),null\)$', r'ArrayList\1(\2)', type)
+        return '%s of length %s, capacity %s' % (type, self.val['items']['len'], self.val['capacity'])
+
+    def children(self):
+        for i in range(self.val['items']['len']):
+            item = self.val['items']['ptr'] + i
+            yield ('[%d]' % i, item.dereference())
+
+    def display_hint(self):
+        return 'array'
+
+class MultiArrayListPrinter:
+    def __init__(self, val):
+        self.val = val
+
+    def child_type(self):
+        (helper_fn, _) = gdb.lookup_symbol('%s.dbHelper' % self.val.type.name)
+        return helper_fn.type.fields()[1].type.target()
+
+    def to_string(self):
+        type = self.val.type.name[len('std.multi_array_list.'):]
+        return '%s of length %s, capacity %s' % (type, self.val['len'], self.val['capacity'])
+
+    def slice(self):
+        fields = self.child_type().fields()
+        base = self.val['bytes']
+        cap = self.val['capacity']
+        len = self.val['len']
+
+        if len == 0:
+            return
+
+        fields = sorted(fields, key=lambda field: field.type.alignof, reverse=True)
+
+        for field in fields:
+            ptr = base.cast(field.type.pointer()).dereference().cast(field.type.array(len - 1))
+            base += field.type.sizeof * cap
+            yield (field.name, ptr)
+
+    def children(self):
+        for i, (name, ptr) in enumerate(self.slice()):
+            yield ('[%d]' % i, name)
+            yield ('[%d]' % i, ptr)
+
+    def display_hint(self):
+        return 'map'
+
+# Handles both HashMap and HashMapUnmanaged.
+class HashMapPrinter:
+    def __init__(self, val):
+        self.type = val.type
+        is_managed = re.search(r'^std\.hash_map\.HashMap\(', self.type.name)
+        self.val = val['unmanaged'] if is_managed else val
+
+    def header_ptr_type(self):
+        (helper_fn, _) = gdb.lookup_symbol('%s.dbHelper' % self.val.type.name)
+        return helper_fn.type.fields()[1].type
+
+    def header(self):
+        if self.val['metadata'] == 0:
+            return None
+        return (self.val['metadata'].cast(self.header_ptr_type()) - 1).dereference()
+
+    def to_string(self):
+        type = self.type.name[len('std.hash_map.'):]
+        type = re.sub(r'^HashMap(Unmanaged)?\((.*),std.hash_map.AutoContext\(.*$', r'AutoHashMap\1(\2)', type)
+        hdr = self.header()
+        if hdr is not None:
+            cap = hdr['capacity']
+        else:
+            cap = 0
+        return '%s of length %s, capacity %s' % (type, self.val['size'], cap)
+
+    def children(self):
+        hdr = self.header()
+        if hdr is None:
+            return
+        is_map = self.display_hint() == 'map'
+        for i in range(hdr['capacity']):
+            metadata = self.val['metadata'] + i
+            if metadata.dereference()['used'] == 1:
+                yield ('[%d]' % i, (hdr['keys'] + i).dereference())
+                if is_map:
+                    yield ('[%d]' % i, (hdr['values'] + i).dereference())
+
+    def display_hint(self):
+        for field in self.header_ptr_type().target().fields():
+            if field.name == 'values':
+                return 'map'
+        return 'array'
+
+# Handles both ArrayHashMap and ArrayHashMapUnmanaged.
+class ArrayHashMapPrinter:
+    def __init__(self, val):
+        self.type = val.type
+        is_managed = re.search(r'^std\.array_hash_map\.ArrayHashMap\(', self.type.name)
+        self.val = val['unmanaged'] if is_managed else val
+
+    def to_string(self):
+        type = self.type.name[len('std.array_hash_map.'):]
+        type = re.sub(r'^ArrayHashMap(Unmanaged)?\((.*),std.array_hash_map.AutoContext\(.*$', r'AutoArrayHashMap\1(\2)', type)
+        return '%s of length %s' % (type, self.val['entries']['len'])
+
+    def children(self):
+        entries = MultiArrayListPrinter(self.val['entries'])
+        len = self.val['entries']['len']
+        fields = {}
+        for name, ptr in entries.slice():
+            fields[str(name)] = ptr
+
+        for i in range(len):
+            if 'key' in fields:
+                yield ('[%d]' % i, fields['key'][i])
+            else:
+                yield ('[%d]' % i, '{}')
+            if 'value' in fields:
+                yield ('[%d]' % i, fields['value'][i])
+
+    def display_hint(self):
+        for name, ptr in MultiArrayListPrinter(self.val['entries']).slice():
+            if name == 'value':
+                return 'map'
+        return 'array'
+
+pp = gdb.printing.RegexpCollectionPrettyPrinter('Zig standard library')
+pp.add_printer('ArrayList', r'^std\.array_list\.ArrayListAligned(Unmanaged)?\(.*\)$', ArrayListPrinter)
+pp.add_printer('MultiArrayList', r'^std\.multi_array_list\.MultiArrayList\(.*\)$', MultiArrayListPrinter)
+pp.add_printer('HashMap', r'^std\.hash_map\.HashMap(Unmanaged)?\(.*\)$', HashMapPrinter)
+pp.add_printer('ArrayHashMap', r'^std\.array_hash_map\.ArrayHashMap(Unmanaged)?\(.*\)$', ArrayHashMapPrinter)
+gdb.printing.register_pretty_printer(gdb.current_objfile(), pp)

misctools/gdb/zig_gdb_pretty_printers.py

@@ -0,0 +1,63 @@
+# pretty printing for the language.
+# put "source /path/to/zig_gdb_pretty_printers.py" in ~/.gdbinit to load it automatically.
+import gdb.printing
+
+
+class ZigPrettyPrinter(gdb.printing.PrettyPrinter):
+    def __init__(self):
+        super().__init__('Zig')
+
+    def __call__(self, val):
+        tag = val.type.tag
+        if tag is None:
+            return None
+        if tag == '[]u8':
+            return StringPrinter(val)
+        if tag.startswith('[]'):
+            return SlicePrinter(val)
+        if tag.startswith('?'):
+            return OptionalPrinter(val)
+        return None
+
+
+class SlicePrinter:
+    def __init__(self, val):
+        self.val = val
+
+    def to_string(self):
+        return f"{self.val['len']} items at {self.val['ptr']}"
+
+    def children(self):
+        def it(val):
+            for i in range(int(val['len'])):
+                item = val['ptr'] + i
+                yield (f'[{i}]', item.dereference())
+        return it(self.val)
+
+    def display_hint(self):
+        return 'array'
+
+
+class StringPrinter:
+    def __init__(self, val):
+        self.val = val
+
+    def to_string(self):
+        return self.val['ptr'].string(length=int(self.val['len']))
+
+    def display_hint(self):
+        return 'string'
+
+
+class OptionalPrinter:
+    def __init__(self, val):
+        self.val = val
+
+    def to_string(self):
+        if self.val['some']:
+            return self.val['data']
+        else:
+            return 'null'
+
+
+gdb.printing.register_pretty_printer(gdb.current_objfile(), ZigPrettyPrinter())

packages/bun-types/bun.d.ts

@@ -6587,7 +6587,8 @@ declare module "bun" {
       timeout?: number;
 
       /**
-       * The signal to use when killing the process after a timeout or when the AbortSignal is aborted.
+       * The signal to use when killing the process after a timeout, when the AbortSignal is aborted,
+       * or when the process goes over the `maxBuffer` limit.
        *
        * @default "SIGTERM" (signal 15)
        *
@@ -6602,6 +6603,14 @@ declare module "bun" {
        * ```
        */
       killSignal?: string | number;
+
+      /**
+       * The maximum number of bytes the process may output. If the process goes over this limit,
+       * it is killed with signal `killSignal` (defaults to SIGTERM).
+       *
+       * @default undefined (no limit)
+       */
+      maxBuffer?: number;
     }
 
     type OptionsToSubprocess<Opts extends OptionsObject> =
@@ -6847,7 +6856,8 @@ declare module "bun" {
     resourceUsage: ResourceUsage;
 
     signalCode?: string;
-    exitedDueToTimeout?: true;
+    exitedDueToTimeout?: boolean;
+    exitedDueToMaxBuffer?: boolean;
     pid: number;
   }
 

src/bun.js/MaxBuf.zig

@@ -0,0 +1,84 @@
+const Subprocess = @import("api/bun/subprocess.zig");
+const MaxBuf = @This();
+const bun = @import("root").bun;
+const std = @import("std");
+
+pub const Kind = enum {
+    stdout,
+    stderr,
+};
+// null after subprocess finalize
+owned_by_subprocess: ?*Subprocess,
+// null after pipereader finalize
+owned_by_reader: bool,
+// if this goes negative, onMaxBuffer is called on the subprocess
+remaining_bytes: i64,
+// (once both are null, it is freed)
+
+pub fn createForSubprocess(owner: *Subprocess, ptr: *?*MaxBuf, initial: ?i64) void {
+    if (initial == null) {
+        ptr.* = null;
+        return;
+    }
+    const maxbuf = bun.default_allocator.create(MaxBuf) catch bun.outOfMemory();
+    maxbuf.* = .{
+        .owned_by_subprocess = owner,
+        .owned_by_reader = false,
+        .remaining_bytes = initial.?,
+    };
+    ptr.* = maxbuf;
+}
+fn disowned(this: *MaxBuf) bool {
+    return this.owned_by_subprocess != null and this.owned_by_reader == false;
+}
+fn destroy(this: *MaxBuf) void {
+    bun.assert(this.disowned());
+    bun.default_allocator.destroy(this);
+}
+pub fn removeFromSubprocess(ptr: *?*MaxBuf) void {
+    if (ptr.* == null) return;
+    const this = ptr.*.?;
+    bun.assert(this.owned_by_subprocess != null);
+    this.owned_by_subprocess = null;
+    ptr.* = null;
+    if (this.disowned()) {
+        this.destroy();
+    }
+}
+pub fn addToPipereader(value: ?*MaxBuf, ptr: *?*MaxBuf) void {
+    if (value == null) return;
+    bun.assert(ptr.* == null);
+    ptr.* = value;
+    bun.assert(!value.?.owned_by_reader);
+    value.?.owned_by_reader = true;
+}
+pub fn removeFromPipereader(ptr: *?*MaxBuf) void {
+    if (ptr.* == null) return;
+    const this = ptr.*.?;
+    bun.assert(this.owned_by_reader);
+    this.owned_by_reader = false;
+    ptr.* = null;
+    if (this.disowned()) {
+        this.destroy();
+    }
+}
+pub fn transferToPipereader(prev: *?*MaxBuf, next: *?*MaxBuf) void {
+    if (prev.* == null) return;
+    next.* = prev.*;
+    prev.* = null;
+}
+pub fn onReadBytes(this: *MaxBuf, bytes: u64) void {
+    this.remaining_bytes = std.math.sub(i64, this.remaining_bytes, std.math.cast(i64, bytes) orelse 0) catch -1;
+    if (this.remaining_bytes < 0 and this.owned_by_subprocess != null) {
+        const owned_by = this.owned_by_subprocess.?;
+        if (owned_by.stderr_maxbuf == this) {
+            MaxBuf.removeFromSubprocess(&owned_by.stderr_maxbuf);
+            owned_by.onMaxBuffer(.stderr);
+        } else if (owned_by.stdout_maxbuf == this) {
+            MaxBuf.removeFromSubprocess(&owned_by.stdout_maxbuf);
+            owned_by.onMaxBuffer(.stdout);
+        } else {
+            bun.assert(false);
+        }
+    }
+}

src/bun.js/api/bun/spawn/stdio.zig

@@ -87,7 +87,7 @@ pub const Stdio = union(enum) {
         }
     }
 
-    pub fn canUseMemfd(this: *const @This(), is_sync: bool) bool {
+    pub fn canUseMemfd(this: *const @This(), is_sync: bool, has_max_buffer: bool) bool {
         if (comptime !Environment.isLinux) {
             return false;
         }
@@ -95,7 +95,7 @@ pub const Stdio = union(enum) {
         return switch (this.*) {
             .blob => !this.blob.needsToReadFile(),
             .memfd, .array_buffer => true,
-            .pipe => is_sync,
+            .pipe => is_sync and !has_max_buffer,
             else => false,
         };
     }

src/bun.js/api/bun/subprocess.zig

@@ -1,6 +1,7 @@
 //! The Subprocess object is returned by `Bun.spawn`. This file also holds the
 //! code for `Bun.spawnSync`
 const Subprocess = @This();
+const MaxBuf = @import("../../MaxBuf.zig");
 pub usingnamespace JSC.Codegen.JSSubprocess;
 pub usingnamespace bun.NewRefCounted(@This(), deinit, null);
 
@@ -40,6 +41,10 @@ event_loop_timer: JSC.API.Bun.Timer.EventLoopTimer = .{
 },
 killSignal: SignalCode,
 
+stdout_maxbuf: ?*MaxBuf = null,
+stderr_maxbuf: ?*MaxBuf = null,
+exited_due_to_maxbuf: ?MaxBuf.Kind = null,
+
 pub const Flags = packed struct {
     is_sync: bool = false,
     killed: bool = false,
@@ -177,7 +182,6 @@ pub fn appendEnvpFromJS(globalThis: *JSC.JSGlobalObject, object: *JSC.JSObject,
 }
 
 const log = Output.scoped(.Subprocess, false);
-const default_max_buffer_size = 1024 * 1024 * 4;
 pub const StdioKind = enum {
     stdin,
     stdout,
@@ -412,24 +416,11 @@ const Readable = union(enum) {
         }
     }
 
-    pub fn init(stdio: Stdio, event_loop: *JSC.EventLoop, process: *Subprocess, result: StdioResult, allocator: std.mem.Allocator, max_size: u32, is_sync: bool) Readable {
+    pub fn init(stdio: Stdio, event_loop: *JSC.EventLoop, process: *Subprocess, result: StdioResult, allocator: std.mem.Allocator, max_size: ?*MaxBuf, is_sync: bool) Readable {
         _ = allocator; // autofix
-        _ = max_size; // autofix
         _ = is_sync; // autofix
         assertStdioResult(result);
 
-        if (Environment.isWindows) {
-            return switch (stdio) {
-                .inherit => Readable{ .inherit = {} },
-                .ignore, .ipc, .path, .memfd => Readable{ .ignore = {} },
-                .fd => |fd| Readable{ .fd = fd },
-                .dup2 => |dup2| Readable{ .fd = dup2.out.toFd() },
-                .pipe => Readable{ .pipe = PipeReader.create(event_loop, process, result) },
-                .array_buffer, .blob => Output.panic("TODO: implement ArrayBuffer & Blob support in Stdio readable", .{}),
-                .capture => Output.panic("TODO: implement capture support in Stdio readable", .{}),
-            };
-        }
-
         if (comptime Environment.isPosix) {
             if (stdio == .pipe) {
                 _ = bun.sys.setNonblocking(result.?);
@@ -439,12 +430,12 @@ const Readable = union(enum) {
         return switch (stdio) {
             .inherit => Readable{ .inherit = {} },
             .ignore, .ipc, .path => Readable{ .ignore = {} },
-            .fd => Readable{ .fd = result.? },
-            .memfd => Readable{ .memfd = stdio.memfd },
-            .pipe => Readable{ .pipe = PipeReader.create(event_loop, process, result) },
+            .fd => |fd| if (Environment.isPosix) Readable{ .fd = result.? } else Readable{ .fd = fd },
+            .memfd => if (Environment.isPosix) Readable{ .memfd = stdio.memfd } else Readable{ .ignore = {} },
+            .dup2 => |dup2| if (Environment.isPosix) Output.panic("TODO: implement dup2 support in Stdio readable", .{}) else Readable{ .fd = dup2.out.toFd() },
+            .pipe => Readable{ .pipe = PipeReader.create(event_loop, process, result, max_size) },
             .array_buffer, .blob => Output.panic("TODO: implement ArrayBuffer & Blob support in Stdio readable", .{}),
             .capture => Output.panic("TODO: implement capture support in Stdio readable", .{}),
-            .dup2 => Output.panic("TODO: implement dup2 support in Stdio readable", .{}),
         };
     }
 
@@ -637,6 +628,11 @@ pub fn timeoutCallback(this: *Subprocess) JSC.API.Bun.Timer.EventLoopTimer.Arm {
     return .disarm;
 }
 
+pub fn onMaxBuffer(this: *Subprocess, kind: MaxBuf.Kind) void {
+    this.exited_due_to_maxbuf = kind;
+    _ = this.tryKill(this.killSignal);
+}
+
 fn parseSignal(arg: JSC.JSValue, globalThis: *JSC.JSGlobalObject) !SignalCode {
     if (arg.getNumber()) |sig64| {
         // Node does this:
@@ -1039,7 +1035,6 @@ pub const PipeReader = struct {
         err: bun.sys.Error,
     } = .{ .pending = {} },
     stdio_result: StdioResult,
-
     pub const IOReader = bun.io.BufferedReader;
     pub const Poll = IOReader;
 
@@ -1061,13 +1056,14 @@ pub const PipeReader = struct {
         this.deref();
     }
 
-    pub fn create(event_loop: *JSC.EventLoop, process: *Subprocess, result: StdioResult) *PipeReader {
+    pub fn create(event_loop: *JSC.EventLoop, process: *Subprocess, result: StdioResult, limit: ?*MaxBuf) *PipeReader {
         var this = PipeReader.new(.{
             .process = process,
             .reader = IOReader.init(@This()),
             .event_loop = event_loop,
             .stdio_result = result,
         });
+        MaxBuf.addToPipereader(limit, &this.reader.maxbuf);
         if (Environment.isWindows) {
             this.reader.source = .{ .pipe = this.stdio_result.buffer };
         }
@@ -1754,6 +1750,9 @@ pub fn finalize(this: *Subprocess) callconv(.C) void {
     }
     this.setEventLoopTimerRefd(false);
 
+    MaxBuf.removeFromSubprocess(&this.stdout_maxbuf);
+    MaxBuf.removeFromSubprocess(&this.stderr_maxbuf);
+
     this.flags.finalized = true;
     this.deref();
 }
@@ -1947,6 +1946,7 @@ pub fn spawnMaybeSync(
     var ipc_channel: i32 = -1;
     var timeout: ?i32 = null;
     var killSignal: SignalCode = SignalCode.default;
+    var maxBuffer: ?i64 = null;
 
     var windows_hide: bool = false;
     var windows_verbatim_arguments: bool = false;
@@ -2139,7 +2139,7 @@ pub fn spawnMaybeSync(
             }
 
             if (try args.get(globalThis, "timeout")) |val| {
-                if (val.isNumber()) {
+                if (val.isNumber() and val.isFinite()) {
                     timeout = @max(val.coerce(i32, globalThis), 1);
                 }
             }
@@ -2147,18 +2147,26 @@ pub fn spawnMaybeSync(
             if (try args.get(globalThis, "killSignal")) |val| {
                 killSignal = try parseSignal(val, globalThis);
             }
+
+            if (try args.get(globalThis, "maxBuffer")) |val| {
+                if (val.isNumber() and val.isFinite()) { // 'Infinity' does not set maxBuffer
+                    maxBuffer = val.coerce(i64, globalThis);
+                }
+            }
         } else {
             try getArgv(globalThis, cmd_value, PATH, cwd, &argv0, allocator, &argv);
         }
     }
 
+    log("spawn maxBuffer: {?d}", .{maxBuffer});
+
     if (!override_env and env_array.items.len == 0) {
         env_array.items = jsc_vm.transpiler.env.map.createNullDelimitedEnvMap(allocator) catch |err| return globalThis.throwError(err, "in Bun.spawn") catch return .zero;
         env_array.capacity = env_array.items.len;
     }
 
     inline for (0..stdio.len) |fd_index| {
-        if (stdio[fd_index].canUseMemfd(is_sync)) {
+        if (stdio[fd_index].canUseMemfd(is_sync, fd_index > 0 and maxBuffer != null)) {
             stdio[fd_index].useMemfd(fd_index);
         }
     }
@@ -2310,6 +2318,9 @@ pub fn spawnMaybeSync(
     else
         bun.invalid_fd;
 
+    MaxBuf.createForSubprocess(subprocess, &subprocess.stderr_maxbuf, maxBuffer);
+    MaxBuf.createForSubprocess(subprocess, &subprocess.stdout_maxbuf, maxBuffer);
+
     // When run synchronously, subprocess isn't garbage collected
     subprocess.* = Subprocess{
         .globalThis = globalThis,
@@ -2330,7 +2341,7 @@ pub fn spawnMaybeSync(
             subprocess,
             spawned.stdout,
             jsc_vm.allocator,
-            default_max_buffer_size,
+            subprocess.stdout_maxbuf,
             is_sync,
         ),
         .stderr = Readable.init(
@@ -2339,7 +2350,7 @@ pub fn spawnMaybeSync(
             subprocess,
             spawned.stderr,
             jsc_vm.allocator,
-            default_max_buffer_size,
+            subprocess.stderr_maxbuf,
             is_sync,
         ),
         // 1. JavaScript.
@@ -2357,6 +2368,8 @@ pub fn spawnMaybeSync(
             .is_sync = is_sync,
         },
         .killSignal = killSignal,
+        .stderr_maxbuf = subprocess.stderr_maxbuf,
+        .stdout_maxbuf = subprocess.stdout_maxbuf,
     };
 
     subprocess.process.setExitHandler(subprocess);
@@ -2544,6 +2557,7 @@ pub fn spawnMaybeSync(
     const stderr = try subprocess.stderr.toBufferedValue(globalThis);
     const resource_usage: JSValue = if (!globalThis.hasException()) subprocess.createResourceUsageObject(globalThis) else .zero;
     const exitedDueToTimeout = subprocess.event_loop_timer.state == .FIRED;
+    const exitedDueToMaxBuffer = subprocess.exited_due_to_maxbuf;
     const resultPid = JSC.JSValue.jsNumberFromInt32(subprocess.pid());
     subprocess.finalize();
 
@@ -2561,7 +2575,8 @@ pub fn spawnMaybeSync(
     sync_value.put(globalThis, JSC.ZigString.static("stderr"), stderr);
     sync_value.put(globalThis, JSC.ZigString.static("success"), JSValue.jsBoolean(exitCode.isInt32() and exitCode.asInt32() == 0));
     sync_value.put(globalThis, JSC.ZigString.static("resourceUsage"), resource_usage);
-    if (exitedDueToTimeout) sync_value.put(globalThis, JSC.ZigString.static("exitedDueToTimeout"), JSC.JSValue.true);
+    if (timeout != null) sync_value.put(globalThis, JSC.ZigString.static("exitedDueToTimeout"), if (exitedDueToTimeout) JSC.JSValue.true else JSC.JSValue.false);
+    if (maxBuffer != null) sync_value.put(globalThis, JSC.ZigString.static("exitedDueToMaxBuffer"), if (exitedDueToMaxBuffer != null) JSC.JSValue.true else JSC.JSValue.false);
     sync_value.put(globalThis, JSC.ZigString.static("pid"), resultPid);
 
     return sync_value;

src/bun.js/bindings/ErrorCode.cpp

@@ -2001,6 +2001,14 @@ JSC_DEFINE_HOST_FUNCTION(Bun::jsFunctionMakeErrorWithCode, (JSC::JSGlobalObject
         return JSC::JSValue::encode(createError(globalObject, ErrorCode::ERR_AMBIGUOUS_ARGUMENT, message));
     }
 
+    case Bun::ErrorCode::ERR_CHILD_PROCESS_STDIO_MAXBUFFER: {
+        auto arg0 = callFrame->argument(1);
+        auto str0 = arg0.toWTFString(globalObject);
+        RETURN_IF_EXCEPTION(scope, {});
+        auto message = makeString(str0, " maxBuffer length exceeded"_s);
+        return JSC::JSValue::encode(createError(globalObject, ErrorCode::ERR_CHILD_PROCESS_STDIO_MAXBUFFER, message));
+    }
+
     case ErrorCode::ERR_IPC_DISCONNECTED:
         return JSC::JSValue::encode(createError(globalObject, ErrorCode::ERR_IPC_DISCONNECTED, "IPC channel is already disconnected"_s));
     case ErrorCode::ERR_SERVER_NOT_RUNNING:

src/bun.js/bindings/ErrorCode.ts

@@ -26,6 +26,7 @@ const errors: ErrorCodeMapping = [
   ["ERR_BUFFER_OUT_OF_BOUNDS", RangeError],
   ["ERR_BUFFER_TOO_LARGE", RangeError],
   ["ERR_CHILD_PROCESS_IPC_REQUIRED", Error],
+  ["ERR_CHILD_PROCESS_STDIO_MAXBUFFER", RangeError],
   ["ERR_CLOSED_MESSAGE_PORT", Error],
   ["ERR_CONSOLE_WRITABLE_STREAM", TypeError, "TypeError"],
   ["ERR_CONSTRUCT_CALL_INVALID", TypeError],

src/bun.js/node/node_util_binding.zig

@@ -113,6 +113,10 @@ pub fn etimedoutErrorCode(_: *JSC.JSGlobalObject, _: *JSC.CallFrame) bun.JSError
     return JSC.JSValue.jsNumberFromInt32(-bun.C.UV_ETIMEDOUT);
 }
 
+pub fn enobufsErrorCode(_: *JSC.JSGlobalObject, _: *JSC.CallFrame) bun.JSError!JSC.JSValue {
+    return JSC.JSValue.jsNumberFromInt32(-bun.C.UV_ENOBUFS);
+}
+
 /// `extractedSplitNewLines` for ASCII/Latin1 strings. Panics if passed a non-string.
 /// Returns `undefined` if param is utf8 or utf16 and not fully ascii.
 ///

src/io/PipeReader.zig

@@ -5,6 +5,7 @@ const Source = @import("./source.zig").Source;
 
 const ReadState = @import("./pipes.zig").ReadState;
 const FileType = @import("./pipes.zig").FileType;
+const MaxBuf = @import("../bun.js/MaxBuf.zig");
 
 const PollOrFd = @import("./pipes.zig").PollOrFd;
 
@@ -92,6 +93,8 @@ const PosixBufferedReader = struct {
     _offset: usize = 0,
     vtable: BufferedReaderVTable,
     flags: Flags = .{},
+    count: usize = 0,
+    maxbuf: ?*MaxBuf = null,
 
     const Flags = packed struct {
         is_done: bool = false,
@@ -139,6 +142,7 @@ const PosixBufferedReader = struct {
         other.flags.is_done = true;
         other.handle = .{ .closed = {} };
         other._offset = 0;
+        MaxBuf.transferToPipereader(&other.maxbuf, &to.maxbuf);
         to.handle.setOwner(to);
 
         // note: the caller is supposed to drain the buffer themselves
@@ -184,14 +188,6 @@ const PosixBufferedReader = struct {
         }
     }
 
-    fn _onReadChunk(this: *PosixBufferedReader, chunk: []u8, hasMore: ReadState) bool {
-        if (hasMore == .eof) {
-            this.flags.received_eof = true;
-        }
-
-        return this.vtable.onReadChunk(chunk, hasMore);
-    }
-
     pub fn getFd(this: *PosixBufferedReader) bun.FileDescriptor {
         return this.handle.getFd();
     }
@@ -266,6 +262,7 @@ const PosixBufferedReader = struct {
     }
 
     pub fn deinit(this: *PosixBufferedReader) void {
+        MaxBuf.removeFromPipereader(&this.maxbuf);
         this.buffer().clearAndFree();
         this.closeWithoutReporting();
     }
@@ -468,6 +465,7 @@ const PosixBufferedReader = struct {
                         parent._offset,
                     )) {
                         .result => |bytes_read| {
+                            if (parent.maxbuf) |l| l.onReadBytes(bytes_read);
                             parent._offset += bytes_read;
                             buf = stack_buffer_head[0..bytes_read];
                             stack_buffer_head = stack_buffer_head[bytes_read..];
@@ -560,6 +558,7 @@ const PosixBufferedReader = struct {
 
             switch (sys_fn(fd, buf, parent._offset)) {
                 .result => |bytes_read| {
+                    if (parent.maxbuf) |l| l.onReadBytes(bytes_read);
                     parent._offset += bytes_read;
                     buf = buf[0..bytes_read];
                     resizable_buffer.items.len += bytes_read;
@@ -678,6 +677,7 @@ pub const WindowsBufferedReader = struct {
     _buffer: std.ArrayList(u8) = std.ArrayList(u8).init(bun.default_allocator),
     // for compatibility with Linux
     flags: Flags = .{},
+    maxbuf: ?*MaxBuf = null,
 
     parent: *anyopaque = undefined,
     vtable: WindowsOutputReaderVTable = undefined,
@@ -741,6 +741,7 @@ pub const WindowsBufferedReader = struct {
         other._offset = 0;
         other.buffer().* = std.ArrayList(u8).init(bun.default_allocator);
         other.source = null;
+        MaxBuf.transferToPipereader(&other.maxbuf, &to.maxbuf);
         to.setParent(parent);
     }
 
@@ -802,6 +803,7 @@ pub const WindowsBufferedReader = struct {
     }
 
     fn _onReadChunk(this: *WindowsOutputReader, buf: []u8, hasMore: ReadState) bool {
+        if (this.maxbuf) |m| m.onReadBytes(buf.len);
         this.flags.has_inflight_read = false;
         if (hasMore == .eof) {
             this.flags.received_eof = true;
@@ -867,6 +869,7 @@ pub const WindowsBufferedReader = struct {
     }
 
     pub fn deinit(this: *WindowsOutputReader) void {
+        MaxBuf.removeFromPipereader(&this.maxbuf);
         this.buffer().deinit();
         const source = this.source orelse return;
         if (!source.isClosed()) {

src/js/builtins.d.ts

@@ -488,7 +488,7 @@ declare function $createCommonJSModule(
 ): JSCommonJSModule;
 declare function $evaluateCommonJSModule(
   moduleToEvaluate: JSCommonJSModule,
-  sourceModule: JSCommonJSModule
+  sourceModule: JSCommonJSModule,
 ): JSCommonJSModule[];
 
 declare function $overridableRequire(this: JSCommonJSModule, id: string): any;
@@ -644,6 +644,7 @@ declare function $ERR_BUFFER_OUT_OF_BOUNDS(name?: string): RangeError;
 declare function $ERR_CRYPTO_INVALID_KEY_OBJECT_TYPE(value, expected): TypeError;
 declare function $ERR_CRYPTO_INCOMPATIBLE_KEY(name, value): Error;
 declare function $ERR_CHILD_PROCESS_IPC_REQUIRED(where): Error;
+declare function $ERR_CHILD_PROCESS_STDIO_MAXBUFFER(message): Error;
 declare function $ERR_INVALID_ASYNC_ID(name, value): RangeError;
 declare function $ERR_ASYNC_TYPE(name): TypeError;
 declare function $ERR_ASYNC_CALLBACK(name): TypeError;

src/js/internal/cluster/child.ts

@@ -38,6 +38,7 @@ cluster._setupWorker = function () {
   // before calling, check if the channel is refd. if it isn't, then unref it after calling process.once();
   $newZigFunction("node_cluster_binding.zig", "channelIgnoreOneDisconnectEventListener", 0)();
   process.once("disconnect", () => {
+    process.channel = null;
     worker.emit("disconnect");
 
     if (!worker.exitedAfterDisconnect) {

src/js/internal/cluster/primary.ts

@@ -153,6 +153,7 @@ cluster.fork = function (env) {
   });
 
   worker.process.once("disconnect", () => {
+    worker.process.channel = null;
     /*
      * Now is a good time to remove the handles
      * associated with this worker because it is

src/js/node/child_process.ts

@@ -241,6 +241,7 @@ function execFile(file, args, options, callback) {
     windowsVerbatimArguments: options.windowsVerbatimArguments,
     shell: options.shell,
     signal: options.signal,
+    maxBuffer: options.maxBuffer,
   });
 
   let encoding;
@@ -270,16 +271,15 @@ function execFile(file, args, options, callback) {
 
     if (!callback) return;
 
-    const readableEncoding = child?.stdout?.readableEncoding;
     // merge chunks
     let stdout;
     let stderr;
-    if (encoding || (child.stdout && readableEncoding)) {
+    if (child.stdout?.readableEncoding) {
       stdout = ArrayPrototypeJoin.$call(_stdout, "");
     } else {
       stdout = BufferConcat(_stdout);
     }
-    if (encoding || (child.stderr && readableEncoding)) {
+    if (child.stderr?.readableEncoding) {
       stderr = ArrayPrototypeJoin.$call(_stderr, "");
     } else {
       stderr = BufferConcat(_stderr);
@@ -339,84 +339,50 @@ function execFile(file, args, options, callback) {
     }, options.timeout).unref();
   }
 
-  const onData = (array, kind) => {
-    let total = 0;
-    let encodedLength;
-    return encoding
-      ? function onDataEncoded(chunk) {
-          total += chunk.length;
+  function addOnDataListener(child_buffer, _buffer, kind) {
+    if (encoding) child_buffer.setEncoding(encoding);
 
-          if (total > maxBuffer) {
-            const out = child[kind];
-            const encoding = out.readableEncoding;
-            const actualLen = Buffer.byteLength(chunk, encoding);
-            if (encodedLength === undefined) {
-              encodedLength = 0;
+    let totalLen = 0;
+    if (maxBuffer === Infinity) {
+      child_buffer.on("data", function onDataNoMaxBuf(chunk) {
+        $arrayPush(_buffer, chunk);
+      });
+      return;
+    }
+    child_buffer.on("data", function onData(chunk) {
+      const encoding = child_buffer.readableEncoding;
+      if (encoding) {
+        const length = Buffer.byteLength(chunk, encoding);
+        totalLen += length;
 
-              for (let i = 0, length = array.length; i < length; i++) {
-                encodedLength += Buffer.byteLength(array[i], encoding);
-              }
-            }
+        if (totalLen > maxBuffer) {
+          const truncatedLen = maxBuffer - (totalLen - length);
+          $arrayPush(_buffer, String.prototype.slice.$call(chunk, 0, truncatedLen));
 
-            encodedLength += actualLen;
-
-            if (encodedLength > maxBuffer) {
-              const joined = ArrayPrototypeJoin.$call(array, "");
-              let combined = joined + chunk;
-              combined = StringPrototypeSlice.$call(combined, 0, maxBuffer);
-              array.length = 1;
-              array[0] = combined;
-              ex = ERR_CHILD_PROCESS_STDIO_MAXBUFFER(kind);
-              kill();
-            } else {
-              const val = ArrayPrototypeJoin.$call(array, "") + chunk;
-              array.length = 1;
-              array[0] = val;
-            }
-          } else {
-            $arrayPush(array, chunk);
-          }
+          ex = $ERR_CHILD_PROCESS_STDIO_MAXBUFFER(kind);
+          kill();
+        } else {
+          $arrayPush(_buffer, chunk);
         }
-      : function onDataRaw(chunk) {
-          total += chunk.length;
+      } else {
+        const length = chunk.length;
+        totalLen += length;
 
-          if (total > maxBuffer) {
-            const truncatedLen = maxBuffer - (total - chunk.length);
-            $arrayPush(array, chunk.slice(0, truncatedLen));
+        if (totalLen > maxBuffer) {
+          const truncatedLen = maxBuffer - (totalLen - length);
+          $arrayPush(_buffer, chunk.slice(0, truncatedLen));
 
-            ex = ERR_CHILD_PROCESS_STDIO_MAXBUFFER(kind);
-            kill();
-          } else {
-            $arrayPush(array, chunk);
-          }
-        };
-  };
-
-  if (child.stdout) {
-    if (encoding) child.stdout.setEncoding(encoding);
-
-    child.stdout.on(
-      "data",
-      maxBuffer === Infinity
-        ? function onUnlimitedSizeBufferedData(chunk) {
-            $arrayPush(_stdout, chunk);
-          }
-        : onData(_stdout, "stdout"),
-    );
+          ex = $ERR_CHILD_PROCESS_STDIO_MAXBUFFER(kind);
+          kill();
+        } else {
+          $arrayPush(_buffer, chunk);
+        }
+      }
+    });
   }
 
-  if (child.stderr) {
-    if (encoding) child.stderr.setEncoding(encoding);
-
-    child.stderr.on(
-      "data",
-      maxBuffer === Infinity
-        ? function onUnlimitedSizeBufferedData(chunk) {
-            $arrayPush(_stderr, chunk);
-          }
-        : onData(_stderr, "stderr"),
-    );
-  }
+  if (child.stdout) addOnDataListener(child.stdout, _stdout, "stdout");
+  if (child.stderr) addOnDataListener(child.stderr, _stderr, "stderr");
 
   child.addListener("close", exitHandler);
   child.addListener("error", errorHandler);
@@ -563,6 +529,7 @@ function spawnSync(file, args, options) {
       exitCode,
       signalCode,
       exitedDueToTimeout,
+      exitedDueToMaxBuffer,
       pid,
     } = Bun.spawnSync({
       // normalizeSpawnargs has already prepended argv0 to the spawnargs array
@@ -577,6 +544,7 @@ function spawnSync(file, args, options) {
       argv0: options.args[0],
       timeout: options.timeout,
       killSignal: options.killSignal,
+      maxBuffer: options.maxBuffer,
     });
   } catch (err) {
     error = err;
@@ -616,6 +584,15 @@ function spawnSync(file, args, options) {
       "ETIMEDOUT",
     );
   }
+  if (exitedDueToMaxBuffer && error == null) {
+    result.error = new SystemError(
+      "spawnSync " + options.file + " ENOBUFS (stdout or stderr buffer reached maxBuffer size limit)",
+      options.file,
+      "spawnSync " + options.file,
+      enobufsErrorCode(),
+      "ENOBUFS",
+    );
+  }
 
   if (result.error) {
     result.error.syscall = "spawnSync " + options.file;
@@ -625,6 +602,7 @@ function spawnSync(file, args, options) {
   return result;
 }
 const etimedoutErrorCode = $newZigFunction("node_util_binding.zig", "etimedoutErrorCode", 0);
+const enobufsErrorCode = $newZigFunction("node_util_binding.zig", "enobufsErrorCode", 0);
 
 /**
  * Spawns a file as a shell synchronously.
@@ -1336,6 +1314,7 @@ class ChildProcess extends EventEmitter {
         argv0: spawnargs[0],
         windowsHide: !!options.windowsHide,
         windowsVerbatimArguments: !!options.windowsVerbatimArguments,
+        maxBuffer: options.maxBuffer,
       });
       this.pid = this.#handle.pid;
 
@@ -1348,6 +1327,15 @@ class ChildProcess extends EventEmitter {
       if (has_ipc) {
         this.send = this.#send;
         this.disconnect = this.#disconnect;
+        this.channel = new Control();
+        Object.defineProperty(this, "_channel", {
+          get() {
+            return this.channel;
+          },
+          set(value) {
+            this.channel = value;
+          },
+        });
         if (options[kFromNode]) this.#closesNeeded += 1;
       }
 
@@ -1416,8 +1404,8 @@ class ChildProcess extends EventEmitter {
       return;
     }
     $assert(!this.connected);
-    this.#maybeClose();
     process.nextTick(() => this.emit("disconnect"));
+    process.nextTick(() => this.#maybeClose());
   }
   #disconnect() {
     if (!this.connected) {
@@ -1425,6 +1413,7 @@ class ChildProcess extends EventEmitter {
       return;
     }
     this.#handle.disconnect();
+    this.channel = null;
   }
 
   kill(sig?) {
@@ -1612,6 +1601,12 @@ function abortChildProcess(child, killSignal, reason) {
   }
 }
 
+class Control extends EventEmitter {
+  constructor() {
+    super();
+  }
+}
+
 class ShimmedStdin extends EventEmitter {
   constructor() {
     super();
@@ -1882,12 +1877,6 @@ function genericNodeError(message, errorProperties) {
 //   TypeError
 // );
 
-function ERR_CHILD_PROCESS_STDIO_MAXBUFFER(stdio) {
-  const err = Error(`${stdio} maxBuffer length exceeded`);
-  err.code = "ERR_CHILD_PROCESS_STDIO_MAXBUFFER";
-  return err;
-}
-
 function ERR_UNKNOWN_SIGNAL(name) {
   const err = new TypeError(`Unknown signal: ${name}`);
   err.code = "ERR_UNKNOWN_SIGNAL";

test/js/bun/spawn/spawn-maxbuf.test.ts

@@ -0,0 +1,154 @@
+import { bunExe } from "harness";
+
+const { isWindows } = require("../../node/test/common");
+
+async function toUtf8(out: ReadableStream<Uint8Array>): Promise<string> {
+  const stream = new TextDecoderStream();
+  out.pipeTo(stream.writable);
+  let result = "";
+  for await (const chunk of stream.readable) {
+    result += chunk;
+  }
+  return result;
+}
+
+describe("yes is killed", () => {
+  // TODO
+  test("Bun.spawn", async () => {
+    const timeStart = Date.now();
+    const proc = Bun.spawn([bunExe(), "exec", "yes"], {
+      maxBuffer: 256,
+      killSignal: isWindows ? "SIGKILL" : "SIGHUP",
+      stdio: ["pipe", "pipe", "pipe"],
+    });
+    await proc.exited;
+    expect(proc.exitCode).toBe(null);
+    expect(proc.signalCode).toBe(isWindows ? "SIGKILL" : "SIGHUP");
+    const timeEnd = Date.now();
+    expect(timeEnd - timeStart).toBeLessThan(100); // make sure it's not waiting a full tick
+    const result = await toUtf8(proc.stdout);
+    expect(result).toStartWith("y\n".repeat(128));
+    const stderr = await toUtf8(proc.stderr);
+    expect(stderr).toBe("");
+  });
+
+  test("Bun.spawnSync", () => {
+    const timeStart = Date.now();
+    const proc = Bun.spawnSync([bunExe(), "exec", "yes"], {
+      maxBuffer: 256,
+      killSignal: isWindows ? "SIGKILL" : "SIGHUP",
+      stdio: ["pipe", "pipe", "pipe"],
+    });
+    expect(proc.exitedDueToMaxBuffer).toBe(true);
+    expect(proc.exitCode).toBe(null);
+    expect(proc.signalCode).toBe(isWindows ? "SIGKILL" : "SIGHUP");
+    const timeEnd = Date.now();
+    expect(timeEnd - timeStart).toBeLessThan(100); // make sure it's not waiting a full tick
+    const result = proc.stdout.toString("utf-8");
+    expect(result).toStartWith("y\n".repeat(128));
+    const stderr = proc.stderr.toString("utf-8");
+    expect(stderr).toBe("");
+  });
+});
+
+describe("maxBuffer infinity does not limit the number of bytes", () => {
+  const sample = "this is a long example string\n";
+  const sample_repeat_count = 10000;
+  test("Bun.spawn", async () => {
+    const proc = Bun.spawn([bunExe(), "-e", `console.log(${JSON.stringify(sample)}.repeat(${sample_repeat_count}))`], {
+      maxBuffer: Infinity,
+    });
+    await proc.exited;
+    expect(proc.exitCode).toBe(0);
+    const result = await toUtf8(proc.stdout);
+    expect(result).toBe(sample.repeat(sample_repeat_count) + "\n");
+  });
+
+  test("Bun.spawnSync", () => {
+    const proc = Bun.spawnSync(
+      [bunExe(), "-e", `console.log(${JSON.stringify(sample)}.repeat(${sample_repeat_count}))`],
+      {
+        maxBuffer: Infinity,
+      },
+    );
+    expect(proc.exitCode).toBe(0);
+    const result = proc.stdout.toString("utf-8");
+    expect(result).toBe(sample.repeat(sample_repeat_count) + "\n");
+  });
+});
+
+describe("timeout kills the process", () => {
+  test("Bun.spawn", async () => {
+    const timeStart = Date.now();
+    const proc = Bun.spawn([bunExe(), "exec", "sleep 5"], {
+      timeout: 100,
+      killSignal: isWindows ? "SIGKILL" : "SIGHUP",
+      stdio: ["pipe", "pipe", "pipe"],
+    });
+    await proc.exited;
+    expect(proc.exitCode).toBe(null);
+    expect(proc.signalCode).toBe(isWindows ? "SIGKILL" : "SIGHUP");
+    const timeEnd = Date.now();
+    expect(timeEnd - timeStart).toBeLessThan(200); // make sure it's terminating early
+    const result = await toUtf8(proc.stdout);
+    expect(result).toBe("");
+    const stderr = await toUtf8(proc.stderr);
+    expect(stderr).toBe("");
+  });
+
+  test("Bun.spawnSync", () => {
+    const timeStart = Date.now();
+    const proc = Bun.spawnSync([bunExe(), "exec", "sleep 5"], {
+      timeout: 100,
+      killSignal: isWindows ? "SIGKILL" : "SIGHUP",
+      stdio: ["pipe", "pipe", "pipe"],
+    });
+    expect(proc.exitedDueToTimeout).toBe(true);
+    expect(proc.exitCode).toBe(null);
+    expect(proc.signalCode).toBe(isWindows ? "SIGKILL" : "SIGHUP");
+    const timeEnd = Date.now();
+    expect(timeEnd - timeStart).toBeGreaterThan(100); // make sure it actually waits
+    expect(timeEnd - timeStart).toBeLessThan(200); // make sure it's terminating early
+    const result = proc.stdout.toString("utf-8");
+    expect(result).toBe("");
+    const stderr = proc.stderr.toString("utf-8");
+    expect(stderr).toBe("");
+  });
+});
+
+describe("timeout Infinity does not kill the process", () => {
+  test("Bun.spawn", async () => {
+    const timeStart = Date.now();
+    const proc = Bun.spawn([bunExe(), "exec", "sleep 1"], {
+      timeout: Infinity,
+      killSignal: isWindows ? "SIGKILL" : "SIGHUP",
+      stdio: ["pipe", "pipe", "pipe"],
+    });
+    await proc.exited;
+    expect(proc.exitCode).toBe(0);
+    const timeEnd = Date.now();
+    expect(timeEnd - timeStart).toBeGreaterThan(1000); // make sure it actually waits
+    expect(timeEnd - timeStart).toBeLessThan(1500); // make sure it's terminating early
+    const result = await toUtf8(proc.stdout);
+    expect(result).toBe("");
+    const stderr = await toUtf8(proc.stderr);
+    expect(stderr).toBe("");
+  });
+
+  test("Bun.spawnSync", () => {
+    const timeStart = Date.now();
+    const proc = Bun.spawnSync([bunExe(), "exec", "sleep 1"], {
+      timeout: Infinity,
+      killSignal: isWindows ? "SIGKILL" : "SIGHUP",
+      stdio: ["pipe", "pipe", "pipe"],
+    });
+    expect(proc.exitCode).toBe(0);
+    const timeEnd = Date.now();
+    expect(timeEnd - timeStart).toBeGreaterThan(1000); // make sure it actually waits
+    expect(timeEnd - timeStart).toBeLessThan(1500);
+    const result = proc.stdout.toString("utf-8");
+    expect(result).toBe("");
+    const stderr = proc.stderr.toString("utf-8");
+    expect(stderr).toBe("");
+  });
+});

test/js/node/test/parallel/test-child-process-exec-abortcontroller-promisified.js

@@ -0,0 +1,88 @@
+'use strict';
+const common = require('../common');
+const assert = require('assert');
+const exec = require('child_process').exec;
+const { promisify } = require('util');
+
+const execPromisifed = promisify(exec);
+const invalidArgTypeError = {
+  code: 'ERR_INVALID_ARG_TYPE',
+  name: 'TypeError'
+};
+
+const waitCommand = common.isWindows ?
+  // `"` is forbidden for Windows paths, no need for escaping.
+  `"${process.execPath}" -e "setInterval(()=>{}, 99)"` :
+  'sleep 2m';
+
+{
+  const ac = new AbortController();
+  const signal = ac.signal;
+  const promise = execPromisifed(waitCommand, { signal });
+  ac.abort();
+  assert.rejects(promise, {
+    name: 'AbortError',
+    cause: ac.signal.reason,
+  }).then(common.mustCall());
+}
+
+{
+  const err = new Error('boom');
+  const ac = new AbortController();
+  const signal = ac.signal;
+  const promise = execPromisifed(waitCommand, { signal });
+  assert.rejects(promise, {
+    name: 'AbortError',
+    cause: err
+  }).then(common.mustCall());
+  ac.abort(err);
+}
+
+{
+  const ac = new AbortController();
+  const signal = ac.signal;
+  const promise = execPromisifed(waitCommand, { signal });
+  assert.rejects(promise, {
+    name: 'AbortError',
+    cause: 'boom'
+  }).then(common.mustCall());
+  ac.abort('boom');
+}
+
+{
+  assert.throws(() => {
+    execPromisifed(waitCommand, { signal: {} });
+  }, invalidArgTypeError);
+}
+
+{
+  function signal() {}
+  assert.throws(() => {
+    execPromisifed(waitCommand, { signal });
+  }, invalidArgTypeError);
+}
+
+{
+  const signal = AbortSignal.abort(); // Abort in advance
+  const promise = execPromisifed(waitCommand, { signal });
+
+  assert.rejects(promise, { name: 'AbortError' })
+        .then(common.mustCall());
+}
+
+{
+  const err = new Error('boom');
+  const signal = AbortSignal.abort(err); // Abort in advance
+  const promise = execPromisifed(waitCommand, { signal });
+
+  assert.rejects(promise, { name: 'AbortError', cause: err })
+        .then(common.mustCall());
+}
+
+{
+  const signal = AbortSignal.abort('boom'); // Abort in advance
+  const promise = execPromisifed(waitCommand, { signal });
+
+  assert.rejects(promise, { name: 'AbortError', cause: 'boom' })
+        .then(common.mustCall());
+}

test/js/node/test/parallel/test-child-process-exec-maxbuf.js

@@ -0,0 +1,146 @@
+'use strict';
+const common = require('../common');
+const assert = require('assert');
+const cp = require('child_process');
+
+function runChecks(err, stdio, streamName, expected) {
+  assert.strictEqual(err.message, `${streamName} maxBuffer length exceeded`);
+  assert(err instanceof RangeError);
+  assert.strictEqual(err.code, 'ERR_CHILD_PROCESS_STDIO_MAXBUFFER');
+  assert.deepStrictEqual(stdio[streamName], expected);
+}
+
+// The execPath might contain chars that should be escaped in a shell context.
+// On non-Windows, we can pass the path via the env; `"` is not a valid char on
+// Windows, so we can simply pass the path.
+const execNode = (args, optionsOrCallback, callback) => {
+  const [cmd, opts] = common.escapePOSIXShell`"${process.execPath}" `;
+  let options = optionsOrCallback;
+  if (typeof optionsOrCallback === 'function') {
+    options = undefined;
+    callback = optionsOrCallback;
+  }
+  return cp.exec(
+    cmd + args,
+    { ...opts, ...options },
+    callback,
+  );
+};
+
+// default value
+{
+  execNode(`-e "console.log('a'.repeat(1024 * 1024))"`, common.mustCall((err) => {
+    assert(err instanceof RangeError);
+    assert.strictEqual(err.message, 'stdout maxBuffer length exceeded');
+    assert.strictEqual(err.code, 'ERR_CHILD_PROCESS_STDIO_MAXBUFFER');
+  }));
+}
+
+// default value
+{
+  execNode(`-e "console.log('a'.repeat(1024 * 1024 - 1))"`, common.mustSucceed((stdout, stderr) => {
+    assert.strictEqual(stdout.trim(), 'a'.repeat(1024 * 1024 - 1));
+    assert.strictEqual(stderr, '');
+  }));
+}
+
+{
+  const options = { maxBuffer: Infinity };
+
+  execNode(`-e "console.log('hello world');"`, options, common.mustSucceed((stdout, stderr) => {
+    assert.strictEqual(stdout.trim(), 'hello world');
+    assert.strictEqual(stderr, '');
+  }));
+}
+
+{
+  const cmd = 'echo hello world';
+
+  cp.exec(
+    cmd,
+    { maxBuffer: 5 },
+    common.mustCall((err, stdout, stderr) => {
+      runChecks(err, { stdout, stderr }, 'stdout', 'hello');
+    })
+  );
+}
+
+// default value
+{
+  execNode(
+    `-e "console.log('a'.repeat(1024 * 1024))"`,
+    common.mustCall((err, stdout, stderr) => {
+      runChecks(
+        err,
+        { stdout, stderr },
+        'stdout',
+        'a'.repeat(1024 * 1024)
+      );
+    })
+  );
+}
+
+// default value
+{
+  execNode(`-e "console.log('a'.repeat(1024 * 1024 - 1))"`, common.mustSucceed((stdout, stderr) => {
+    assert.strictEqual(stdout.trim(), 'a'.repeat(1024 * 1024 - 1));
+    assert.strictEqual(stderr, '');
+  }));
+}
+
+const unicode = '中文测试'; // length = 4, byte length = 12
+
+{
+  execNode(
+    `-e "console.log('${unicode}');"`,
+    { maxBuffer: 10 },
+    common.mustCall((err, stdout, stderr) => {
+      runChecks(err, { stdout, stderr }, 'stdout', '中文测试\n');
+    })
+  );
+}
+
+{
+  execNode(
+    `-e "console.error('${unicode}');"`,
+    { maxBuffer: 3 },
+    common.mustCall((err, stdout, stderr) => {
+      runChecks(err, { stdout, stderr }, 'stderr', '中文测');
+    })
+  );
+}
+
+{
+  const child = execNode(
+    `-e "console.log('${unicode}');"`,
+    { encoding: null, maxBuffer: 10 },
+    common.mustCall((err, stdout, stderr) => {
+      runChecks(err, { stdout, stderr }, 'stdout', '中文测试\n');
+    })
+  );
+
+  child.stdout.setEncoding('utf-8');
+}
+
+{
+  const child = execNode(
+    `-e "console.error('${unicode}');"`,
+    { encoding: null, maxBuffer: 3 },
+    common.mustCall((err, stdout, stderr) => {
+      runChecks(err, { stdout, stderr }, 'stderr', '中文测');
+    })
+  );
+
+  child.stderr.setEncoding('utf-8');
+}
+
+{
+  execNode(
+    `-e "console.error('${unicode}');"`,
+    { encoding: null, maxBuffer: 5 },
+    common.mustCall((err, stdout, stderr) => {
+      const buf = Buffer.from(unicode).slice(0, 5);
+      runChecks(err, { stdout, stderr }, 'stderr', buf);
+    })
+  );
+}

test/js/node/test/parallel/test-child-process-execfile-maxbuf.js

@@ -0,0 +1,92 @@
+'use strict';
+const common = require('../common');
+const assert = require('assert');
+const { execFile } = require('child_process');
+
+function checkFactory(streamName) {
+  return common.mustCall((err) => {
+    assert(err instanceof RangeError);
+    assert.strictEqual(err.message, `${streamName} maxBuffer length exceeded`);
+    assert.strictEqual(err.code, 'ERR_CHILD_PROCESS_STDIO_MAXBUFFER');
+  });
+}
+
+// default value
+{
+  execFile(
+    process.execPath,
+    ['-e', 'console.log("a".repeat(1024 * 1024))'],
+    checkFactory('stdout')
+  );
+}
+
+// default value
+{
+  execFile(
+    process.execPath,
+    ['-e', 'console.log("a".repeat(1024 * 1024 - 1))'],
+    common.mustSucceed((stdout, stderr) => {
+      assert.strictEqual(stdout.trim(), 'a'.repeat(1024 * 1024 - 1));
+      assert.strictEqual(stderr, '');
+    })
+  );
+}
+
+{
+  const options = { maxBuffer: Infinity };
+
+  execFile(
+    process.execPath,
+    ['-e', 'console.log("hello world");'],
+    options,
+    common.mustSucceed((stdout, stderr) => {
+      assert.strictEqual(stdout.trim(), 'hello world');
+      assert.strictEqual(stderr, '');
+    })
+  );
+}
+
+{
+  execFile('echo', ['hello world'], { maxBuffer: 5 }, checkFactory('stdout'));
+}
+
+const unicode = '中文测试'; // length = 4, byte length = 12
+
+{
+  execFile(
+    process.execPath,
+    ['-e', `console.log('${unicode}');`],
+    { maxBuffer: 10 },
+    checkFactory('stdout'));
+}
+
+{
+  execFile(
+    process.execPath,
+    ['-e', `console.error('${unicode}');`],
+    { maxBuffer: 10 },
+    checkFactory('stderr')
+  );
+}
+
+{
+  const child = execFile(
+    process.execPath,
+    ['-e', `console.log('${unicode}');`],
+    { encoding: null, maxBuffer: 10 },
+    checkFactory('stdout')
+  );
+
+  child.stdout.setEncoding('utf-8');
+}
+
+{
+  const child = execFile(
+    process.execPath,
+    ['-e', `console.error('${unicode}');`],
+    { encoding: null, maxBuffer: 10 },
+    checkFactory('stderr')
+  );
+
+  child.stderr.setEncoding('utf-8');
+}

test/js/node/test/parallel/test-child-process-execfilesync-maxbuf.js

@@ -0,0 +1,53 @@
+'use strict';
+require('../common');
+
+// This test checks that the maxBuffer option for child_process.execFileSync()
+// works as expected.
+
+const assert = require('assert');
+const { getSystemErrorName } = require('util');
+const { execFileSync } = require('child_process');
+const msgOut = 'this is stdout';
+const msgOutBuf = Buffer.from(`${msgOut}\n`);
+
+const args = [
+  '-e',
+  `console.log("${msgOut}");`,
+];
+
+// Verify that an error is returned if maxBuffer is surpassed.
+{
+  assert.throws(() => {
+    execFileSync(process.execPath, args, { maxBuffer: 1 });
+  }, (e) => {
+    assert.ok(e, 'maxBuffer should error');
+    assert.strictEqual(e.code, 'ENOBUFS');
+    assert.strictEqual(getSystemErrorName(e.errno), 'ENOBUFS');
+    // We can have buffers larger than maxBuffer because underneath we alloc 64k
+    // that matches our read sizes.
+    assert.deepStrictEqual(e.stdout, msgOutBuf);
+    return true;
+  });
+}
+
+// Verify that a maxBuffer size of Infinity works.
+{
+  const ret = execFileSync(process.execPath, args, { maxBuffer: Infinity });
+
+  assert.deepStrictEqual(ret, msgOutBuf);
+}
+
+// Default maxBuffer size is 1024 * 1024.
+{
+  assert.throws(() => {
+    execFileSync(
+      process.execPath,
+      ['-e', "console.log('a'.repeat(1024 * 1024))"]
+    );
+  }, (e) => {
+    assert.ok(e, 'maxBuffer should error');
+    assert.strictEqual(e.code, 'ENOBUFS');
+    assert.strictEqual(getSystemErrorName(e.errno), 'ENOBUFS');
+    return true;
+  });
+}

test/js/node/test/parallel/test-child-process-execsync-maxbuf.js

@@ -0,0 +1,60 @@
+'use strict';
+const { escapePOSIXShell } = require('../common');
+
+// This test checks that the maxBuffer option for child_process.spawnSync()
+// works as expected.
+
+const assert = require('assert');
+const { getSystemErrorName } = require('util');
+const { execSync } = require('child_process');
+const msgOut = 'this is stdout';
+const msgOutBuf = Buffer.from(`${msgOut}\n`);
+
+const [cmd, opts] = escapePOSIXShell`"${process.execPath}" -e "${`console.log('${msgOut}')`}"`;
+
+// Verify that an error is returned if maxBuffer is surpassed.
+{
+  assert.throws(() => {
+    execSync(cmd, { ...opts, maxBuffer: 1 });
+  }, (e) => {
+    assert.ok(e, 'maxBuffer should error');
+    assert.strictEqual(e.code, 'ENOBUFS');
+    assert.strictEqual(getSystemErrorName(e.errno), 'ENOBUFS');
+    // We can have buffers larger than maxBuffer because underneath we alloc 64k
+    // that matches our read sizes.
+    assert.deepStrictEqual(e.stdout, msgOutBuf);
+    return true;
+  });
+}
+
+// Verify that a maxBuffer size of Infinity works.
+{
+  const ret = execSync(
+    cmd,
+    { ...opts, maxBuffer: Infinity },
+  );
+
+  assert.deepStrictEqual(ret, msgOutBuf);
+}
+
+// Default maxBuffer size is 1024 * 1024.
+{
+  assert.throws(() => {
+    execSync(...escapePOSIXShell`"${process.execPath}" -e "console.log('a'.repeat(1024 * 1024))"`);
+  }, (e) => {
+    assert.ok(e, 'maxBuffer should error');
+    assert.strictEqual(e.code, 'ENOBUFS');
+    assert.strictEqual(getSystemErrorName(e.errno), 'ENOBUFS');
+    return true;
+  });
+}
+
+// Default maxBuffer size is 1024 * 1024.
+{
+  const ret = execSync(...escapePOSIXShell`"${process.execPath}" -e "console.log('a'.repeat(1024 * 1024 - 1))"`);
+
+  assert.deepStrictEqual(
+    ret.toString().trim(),
+    'a'.repeat(1024 * 1024 - 1)
+  );
+}

test/js/node/test/parallel/test-child-process-fork-closed-channel-segfault.js

@@ -0,0 +1,88 @@
+'use strict';
+const common = require('../common');
+
+// Before https://github.com/nodejs/node/pull/2847 a child process trying
+// (asynchronously) to use the closed channel to it's creator caused a segfault.
+
+const assert = require('assert');
+const cluster = require('cluster');
+const net = require('net');
+
+if (!cluster.isPrimary) {
+  // Exit on first received handle to leave the queue non-empty in primary
+  process.on('message', function() {
+    process.exit(1);
+  });
+  return;
+}
+
+const server = net
+  .createServer(function(s) {
+    if (common.isWindows) {
+      s.on('error', function(err) {
+        // Prevent possible ECONNRESET errors from popping up
+        if (err.code !== 'ECONNRESET') throw err;
+      });
+    }
+    setTimeout(function() {
+      s.destroy();
+    }, 100);
+  })
+  .listen(0, function() {
+    const worker = cluster.fork();
+
+    worker.on('error', function(err) {
+      if (
+        err.code !== 'ECONNRESET' &&
+        err.code !== 'ECONNREFUSED' &&
+        err.code !== 'EMFILE'
+      ) {
+        throw err;
+      }
+    });
+
+    function send(callback) {
+      const s = net.connect(server.address().port, function() {
+        worker.send({}, s, callback);
+      });
+
+      // https://github.com/nodejs/node/issues/3635#issuecomment-157714683
+      // ECONNREFUSED or ECONNRESET errors can happen if this connection is
+      // still establishing while the server has already closed.
+      // EMFILE can happen if the worker __and__ the server had already closed.
+      s.on('error', function(err) {
+        if (
+          err.code !== 'ECONNRESET' &&
+          err.code !== 'ECONNREFUSED' &&
+          err.code !== 'EMFILE'
+        ) {
+          throw err;
+        }
+      });
+    }
+
+    worker.process.once(
+      'close',
+      common.mustCall(function() {
+        // Otherwise the crash on `channel.fd` access may happen
+        assert.strictEqual(worker.process.channel, null);
+        server.close();
+      })
+    );
+
+    worker.on('online', function() {
+      send(function(err) {
+        assert.ifError(err);
+        send(function(err) {
+          // Ignore errors when sending the second handle because the worker
+          // may already have exited.
+          if (err && err.code !== 'ERR_IPC_CHANNEL_CLOSED' &&
+                     err.code !== 'ECONNRESET' &&
+                     err.code !== 'ECONNREFUSED' &&
+                     err.code !== 'EMFILE') {
+            throw err;
+          }
+        });
+      });
+    });
+  });

test/js/node/test/parallel/test-child-process-spawnsync-maxbuf.js

@@ -0,0 +1,58 @@
+'use strict';
+require('../common');
+
+// This test checks that the maxBuffer option for child_process.spawnSync()
+// works as expected.
+
+const assert = require('assert');
+const spawnSync = require('child_process').spawnSync;
+const { getSystemErrorName } = require('util');
+const msgOut = 'this is stdout';
+const msgOutBuf = Buffer.from(`${msgOut}\n`);
+
+const args = [
+  '-e',
+  `console.log("${msgOut}");`,
+];
+
+// Verify that an error is returned if maxBuffer is surpassed.
+{
+  const ret = spawnSync(process.execPath, args, { maxBuffer: 1 });
+
+  assert.ok(ret.error, 'maxBuffer should error');
+  assert.strictEqual(ret.error.code, 'ENOBUFS');
+  assert.strictEqual(getSystemErrorName(ret.error.errno), 'ENOBUFS');
+  // We can have buffers larger than maxBuffer because underneath we alloc 64k
+  // that matches our read sizes.
+  assert.deepStrictEqual(ret.stdout, msgOutBuf);
+}
+
+// Verify that a maxBuffer size of Infinity works.
+{
+  const ret = spawnSync(process.execPath, args, { maxBuffer: Infinity });
+
+  assert.ifError(ret.error);
+  assert.deepStrictEqual(ret.stdout, msgOutBuf);
+}
+
+// Default maxBuffer size is 1024 * 1024.
+{
+  const args = ['-e', "console.log('a'.repeat(1024 * 1024))"];
+  const ret = spawnSync(process.execPath, args);
+
+  assert.ok(ret.error, 'maxBuffer should error');
+  assert.strictEqual(ret.error.code, 'ENOBUFS');
+  assert.strictEqual(getSystemErrorName(ret.error.errno), 'ENOBUFS');
+}
+
+// Default maxBuffer size is 1024 * 1024.
+{
+  const args = ['-e', "console.log('a'.repeat(1024 * 1024 - 1))"];
+  const ret = spawnSync(process.execPath, args);
+
+  assert.ifError(ret.error);
+  assert.deepStrictEqual(
+    ret.stdout.toString().trim(),
+    'a'.repeat(1024 * 1024 - 1)
+  );
+}