promisify(fs.X) over a named or namespace import of node:fs lowers as
the fs/promises member of the same name for access, appendFile, chmod,
chown, copyFile, lchown, link, lstat, lutimes, mkdir, mkdtemp, readFile,
readdir, readlink, realpath, rename, rm, rmdir, stat, statfs, symlink,
truncate, unlink, utimes and writeFile. For these, Node's promisified
callback form settles with the callback's single result and rejects
with the same errors as the fs/promises call. Calls through the bound
function accept the forms the fs/promises lowering accepts and refuse
the others by name.
fs.open (an fd number where fs/promises.open gives a FileHandle),
fs.exists (a custom promisify) and fs.read/fs.write (multi-value
callbacks) remain refused.
`const parsed: { score: number }[] = JSON.parse(doc)` printed a different
checksum from Node: the checked conversion (and the schema-directed
JSON.parse fast path) stored only the declared fields of each object in
its native record, so JSON.stringify(parsed) silently dropped `id`,
`name` and `active`, and every other reflective surface agreed.
A closed record converted from an ordinary object now keeps the source's
own properties beside it when the object has undeclared keys or holds the
declared ones out of declaration order. The runtime keeps a per-thread
table from the native record to a view of the source's own keys
(placeholders for declared keys, which the record still owns), released
through the native dispose hook when the record is freed:
- the checked record builder notes its source (scr_record_source_note);
- the schema parser parses undeclared members into the view instead of
declining, so typed parses keep their one-pass fast path;
- typed JSON.stringify writes such records in source key order, declared
fields through a generated per-shape field writer and the others through
the dyn writer;
- record capsules adopt the view and refresh it in place, so untyped reads
and writes see and persist undeclared properties;
- util.inspect and Object.keys/values/entries answer through the live view
(values/entries check the extra values into their static result type and
throw the checked-conversion TypeError when one does not fit).
Copies made by object spread, Object.assign, rest destructuring or
conversion to another record type still hold only the declared fields;
the limitations page documents this.
The partial for the "TLS ciphers" section was tls-cipher.mdx, while the
limitations tooling names a section's partial after its heading's slug
(tls-ciphers). It is renamed, so a join and split of the page leaves the
docs unchanged.
dgram.Socket's setBroadcast, setTTL, setMulticastTTL,
setMulticastLoopback, setMulticastInterface, addMembership,
dropMembership, get/setRecvBufferSize, get/setSendBufferSize,
getSendQueueSize, getSendQueueCount and disconnect were refused at
compile time. They now lower to scr_dgram.c and match Node:
- The TTL setters and setMulticastLoopback return their argument. The
value checks run first: a TTL outside 1-255 (0-255 for multicast,
after ToInt32) throws "setTTL EINVAL" with code, errno and syscall.
- A socket that has not been bound has no descriptor yet, so the
options throw EBADF, and the buffer size methods throw Node's
ERR_SOCKET_BUFFER_SIZE SystemError.
- After close(), the members that read Node's null handle throw its
TypeError ("Cannot read properties of null (reading 'setTTL')"), and
setMulticastInterface and the membership calls throw "Not running".
- Buffer sizes must be uint32 values (ERR_SOCKET_BAD_BUFFER_SIZE), 0
reads the current size, and sizes past the int32 range fail as EINVAL.
- IPv6 interfaces and groups go to the IPv6 socket options, so a udp4
socket answers ENOPROTOOPT as in Node.
- disconnect() throws ERR_SOCKET_DGRAM_NOT_CONNECTED until 'connect' was
emitted, and dissolves the association with an AF_UNSPEC connect.
addMembership and dropMembership before bind() throw SC2020, where
Node binds the socket to an ephemeral port first; the limitations page
documents it, along with the missing info object on the buffer size
SystemError. Corpus 5655 and 5656 and the node-types fixture
dgram-options.ts cover each method.
A const binding of promisify(exec) now lowers like promisify(execFile):
each call runs the command line with /bin/sh -c, as execSync does, and
settles with { stdout, stderr }. A non-zero exit, a missing command (the
shell's 127) or a timeout rejects with Node's "Command failed: <command>\n
<stderr>" message. The options are the execFile slice: encoding utf8,
cwd, env (inline spread included), timeout, and maxBuffer accepted.
Three gaps closed for both targets along the way:
- the { stdout, stderr } result maps as a record when it is held in a
variable, passed or returned, instead of only when destructured at the
await (it is an anonymous literal in @types/node and in the fallback);
- a namespace member is a recognized target (promisify(cp.exec));
- util.promisify(...) through a namespace or default import is
recognized like the named import.
Every release of a LifetimeRegion, and every retry at region creation, ran
scr_collect_cycles(): full cycle-collector passes over the thread's heap, to
a fixpoint, before checking any region, in case dead cycles of ordinary
objects held counted references into it. Freeing a region ran them again
whenever the owned ordinary objects left counts behind after the region
released its fields. Next to a large heap of candidates (a type checker
beside per-file emit regions) those passes cost far more than the regions.
A retry now checks the due regions first. A region whose references are all
explained frees without a pass; only when one would be kept does the heap
get the full pass, after which every due region is judged as before. The
first check leaves a region it cannot free as it was, so the backoff, the
kept report and SCRIPTC_REGION_DEBUG see only the check after the pass. It
keeps what its walk found: a region whose counted references the pass did not
change is judged from that, without walking it again. A pass that freed a dead
cycle referring only to an owned object leaves the count unchanged; such a
region waits for its next attempt.
After a region releases its instances' fields, what can still hold counts
is the owned ordinary objects' cycles. Each has a member that lost a
reference in those releases and is buffered as a candidate, and the release
walk entered every cycle member. The cycle collector gains a pass limited to
a set of candidates (scr_cyc_collect_set): it takes the set's members out of
the buffers up to a given generation, reading only the buffers' pointers, so
the candidates it leaves are not touched, and it walks at full depth without
moving the schedule's baselines. A dead object such a pass reaches through a
candidate it did not take leaves its buffer before it is freed. Freeing a
region runs these passes over the walk's objects from the youngest buffer
out, and the whole heap only if counts remain.
SCRIPTC_REGION_STATS also prints, per thread at exit, how many full passes
over the heap regions needed.
When the main thread's script ends, the executable released every module
global and ran a full cycle collection before exiting, which takes time
proportional to everything the program still holds (about 15 ms for
1.5 million live objects) and frees memory the operating system reclaims
anyway. The main thread now skips those releases, the exit-time
collection and the collector's buffer cleanup. Exit listeners and output
flushing run as before. Worker threads still free their heaps when they
exit, since later threads reuse their arenas, and builds that check for
leaks (the RC audit, AddressSanitizer) free everything as before, as does
any process run with SCRIPTC_EXIT_FREE=1 for external leak checkers.
SCRIPTC_WORKER_STATS=1 reports, as each worker thread exits, how long it
took to start, to run its script and to exit.
Buffer.from of strings, arrays and Uint8Arrays, Buffer.allocUnsafe and
Buffer.concat now return views into a per-thread pool slab of
Buffer.poolSize bytes (64 KiB by default) when the size is below
Buffer.poolSize >>> 1, following Node's allocate, fromStringFast and
fromArrayLike: 8-byte aligned offsets, a new slab when a request does not
fit, and the four-bytes-per-unit reservation for strings. Buffer.poolSize
can be read and set, and Buffer.allocUnsafeSlow returns an unpooled Buffer.
A slab lives while any of its views does. Its ArrayBuffer cannot be
transferred, and structuredClone of a typed array view copies the whole
ArrayBuffer and keeps the view's offset. Buffer.alloc, allocUnsafe and
allocUnsafeSlow validate sizes with Node's ERR_OUT_OF_RANGE error.
The first pooled allocation finds the startup slab, which has the
default 64 KiB size. A request it cannot hold gets a slab of the current
Buffer.poolSize, as in Node, and the room is checked after every new
slab, so a Buffer.poolSize raised before the first pooled allocation
cannot place a reservation past the end of a 64 KiB slab. A reservation
larger than a fresh slab traps instead of writing past it.
Corpus 5531 (typed) and 5532 (untyped) raise Buffer.poolSize before the
first pooled allocation and allocate just under the new threshold
through each pooled path, each case in a fresh child process, and also
shrink Buffer.poolSize and change it between allocations. The
node-types fenced fixture no longer lists Buffer.poolSize, which now
compiles.
node:test's mock.fn(original[, implementation]) and t.mock.fn compile.
A Mock<F> is the function-with-properties record { %call, mock }: the
callable is a wrapper closure that shares the mock context with the mock
field. The context records each call's arguments, result, error and this,
and keeps the current implementation, the original and the one-time
implementations by call index. fn.mock supports, as in Node 24.22:
- calls, read as a copy of the log;
- callCount();
- mockImplementation(fn);
- mockImplementationOnce(fn[, onCall]), for the next call by default, a
later registration for the same index replacing the earlier one;
- resetCalls();
- restore(), which brings back the original.
A throwing implementation records the error and rethrows it. Functions
with fixed parameters or a single rest array parameter are supported; a
union return type needs an undefined arm. mock.fn() without an original,
mock.method, the tracker's reset and restoreAll, and t.mock.method are
refused with SC2020.
The node:test fixture mock-fn compares the behavior with Node, and
tests/diagnostics/mock-fences.ts covers the refusals.
Atomics operations on 8-, 16- and 32-bit integer arrays are sequentially
consistent atomic instructions on the element, and no longer take the
process-wide shared-memory lock. Other reads and writes of shared storage
are relaxed atomic accesses: element reads and writes access the element,
and copies, fills, conversions, searches and sorts read shared bytes into
a private copy and write back only the range they change, so concurrent
accesses to the same bytes are free of data races. Non-shared storage
keeps its plain memory accesses. Atomics.wait and Atomics.notify queue
waiters in buckets chosen by location, each with its own lock and
condition variable, so waiting threads no longer serialize other Atomics.
Atomics.store answers +0 for a value that truncates to -0, as Node does.
The shared storage runtime test also runs under ThreadSanitizer.
fs.createReadStream, fs.createWriteStream and FileHandle
createReadStream, createWriteStream and readLines return runtime
Readable and Writable streams (scr_fs_stream.c), as do new fs.ReadStream
and new fs.WriteStream in JavaScript sources. They follow
lib/internal/fs/streams.js on the stream engine:
- _construct opens the file, then emits 'open' (with the fd) and
'ready'; _read reads up to end; _write retries short writes as
writeAll does; _destroy waits for I/O in flight, then closes (with
fsync first for the flush option). Every open, read, write, fsync and
close runs on the shared worker pool.
- Options are checked in Node's order: getOptions, options.fd or the
path, start, end, then highWaterMark, encoding, emitClose and
autoClose. flags and mode are checked when the file opens, so their
errors arrive as 'error' events.
- bytesRead, bytesWritten, pending, path and close(cb) compile, also
through untyped values (close() there).
A FileHandle stream holds a reference on the handle; closing the stream
releases it and closes the handle unless autoClose is false.
FileHandle.close() follows Node's reference count: it waits for the
streams over the handle and runs their close(). readLines is a readline
Interface over createReadStream with crlfDelay: Infinity.
The stream engine gains Node's _construct (reads, buffered writes,
finish and _destroy wait for construction; destroy errors combine with
aggregateTwoErrors) and _writev, both internal. Writable.destroy() now
runs the buffered write callbacks and end() callbacks (errorBuffer),
which it dropped before. highWaterMark in a dynamic options record is
checked as getHighWaterMark does, and for await over a constructing
stream waits for construction.
Numeric flags, the fs, signal and windowsHandle options, non-UTF-8
write encodings, option functions that replace the file implementation,
and instanceof fs.ReadStream/WriteStream are refused.
Corpus 5546, 5547 and 5554 cover both lanes against Node 24.22.
node:test changes, matching Node 24.22:
- t.before, t.after, t.beforeEach and t.afterEach lower. t.before runs
when it is called; a throw fails the test and the subtests that follow,
which skip their body and beforeEach hooks and run their afterEach hooks.
t.beforeEach and t.afterEach wrap every descendant subtest. t.after runs
after the test's afterEach chain, also when the body throws, and a throw
fails the test.
- t.plan(count) counts the test's t.assert calls and subtests. A mismatch
fails the test with Node's "plan expected N assertions but received M"
string, unless an assertion failed first.
- t.fullName joins the names from the outermost suite or test with " > ".
- Tests and suites under a todo suite or test are todo, with a bare TODO
directive, unless they are skipped or carry their own todo message. A
todo suite reports its directive.
- describe.only, suite.only and { only: true } on a suite mark it. At each
level, when a child is marked or contains a marked test or suite, only
those children run.
- The failing-tests section lists failures in completion order, so
subtests come before the test that ran them, and prints thrown strings
quoted, as Node inspects them.
The fixtures ctx-hooks, ctx-plan, todo-suites, suite-variants,
only-nested and thrown-values compare the reporter output and exit code
with Node.
pipeline() accepts a source function (an async generator function called
with { signal }) and a destination async function, following
pipeline.js: the destination's promise value resolves the
stream/promises form and reaches the callback's second argument, and
pipeline() answers a PassThrough for it. A rejected destination destroys
that PassThrough with the reason and fails the pipeline.
Stages may take the { signal } argument: the pipeline creates its own
AbortController when one does, and aborts it when the pipeline finishes
or fails, as finishImpl does. Stage functions take the source and
{ signal } through the closure ABI, and the PassThrough and the value
are released with the pipeline.
The stream unit now links the emitter unit whenever it links, so a
pipeline of functions builds without constructing a stream. An async
generator destination and reading the PassThrough a function destination
returns are refused at compile time.
Encoding an array key added each element's size to a running length
with unchecked arithmetic, and wrote into a fixed stack buffer whenever
the sum fit. A sparse array with a large length (2^29 elements or more)
wrapped the sum on 32-bit targets, so the write landed before the buffer;
on every target the encoder also visited every index of such an array.
Array keys now have at most 65536 elements, and their encoding at most
2^31 - 1 bytes. The size is computed first with sums that cannot wrap,
the buffer is sized to it, and keys over either limit make the lookup or
insert throw a TypeError before anything is read or written. The Node.js
implementation throws the same TypeError for keys of more than 65536
elements. Sparse elements are walked in one pass in index order, and the
index growth computation checks its size arithmetic too.
InternTable keys can be arrays of numbers or of strings, compared by their
elements: numbers by SameValueZero, strings by content, and holes equal to
each other only. The runtime stores an array key as one byte string that
encodes its elements; the Node.js implementation encodes it into a Map key
the same way.
Replaced table indexes are now freed. Every thread that uses a table
records the epoch it read at the start of each lookup and insert, and an
index retired in an earlier epoch than every recorded one is freed. Worker
threads stop holding retirements back when they exit.
Number indexes keep a tag byte per slot ahead of the key and value pairs,
so a lookup of an absent key reads the dense tag bytes instead of pairs.
getOrInsertComputed lowers an arrow callback with an expression body in
place, with its parameter bound to the key, so interning through
`(key) => new T(...)` creates no closure.
@scriptc/experimental exports InternTable<K, V>: a named table that every
thread of a scriptc program shares and that each thread has its own copy
of under Node.js. Keys are strings or numbers with Map equality; values are
published (@scriptc/threads) when stored, and the first stored value of a
key is kept. Members are get, has, size, getOrInsert and
getOrInsertComputed.
The runtime table (scr_itable.c) splits each table into 64 segments.
Lookups take no lock and do not write; inserts take a segment's spin lock
for a probe and a few stores, and callbacks run without a lock. Number
tables keep keys and values in the index; string tables keep entries in
segment-owned chunks behind tagged slots. Replaced indexes are kept.
The compiler lowers the class to a synthetic class with one f64 handle
field and five intrinsics, with interned helpers per member and type and
an in-place lowering of getOrInsertComputed that creates a function
expression callback only on a miss. Stored values go through the publish
intrinsic, so their types get the write guard. scriptc refuses names that
are not string literals, one name opened with different type arguments,
and key or value types a table cannot store.
scr_publish walks small graphs in inline buffers and reads
SCRIPTC_PUBLISH_TRACE once, instead of allocating and calling getenv on
every call.
Chris Tate