Jeong, YunWon 86d9407b3d Raise where the fuzzer found aborts and stack overflows, and collect with the count in the object header (#8551)
* Correct what the non-unix frame stack is for

The comment said non-unix threading builds have no stop-the-world.
CollectStopTheWorld is gated on `feature = "threading"` alone, and
sys._current_frames stops the world on both paths; the field is the
fallback a reader uses when there is no `top_iframe` to materialize from.

Assisted-by: Claude

* Seek by the whole file position on Windows

`SetFilePointer` answers with the low half of the new position and signals
failure with INVALID_SET_FILE_POINTER, which is also that half of a
position four gigabytes in; telling them apart takes the error code, which
this did not read, so such a seek was reported as an error. Deciding
seekability from it also called such a file unseekable.

`SetFilePointerEx` returns the whole position and a success flag of its
own, which also removes the transmute of the position into halves.

Assisted-by: Claude

* memoryview: tell a value of the wrong kind from one that does not fit

Assigning an item reported every packing failure as a TypeError, so
m[0] = 300 on a 'B' view said the value was the wrong type rather than out
of range. Packing now says which of the two it was, and whether the value's
own code raised, in which case that error is the answer as it is:

    m[0] = 300                       ValueError: invalid value for format 'B'
    m[0] = "x"                       TypeError: invalid type for format 'B'
    m[0] = <__index__ that raises>   the raised error

`struct` reports both as `struct.error` and is unchanged; the kind travels
beside the exception for the caller that tells them apart.

Also: None was read as a deletion, so m[0] = None answered "cannot delete
memory" instead of packing it; and deleting through the mapping protocol
never reached the read-only check, which comes first.

Assisted-by: Claude

* Raise MemoryError for allocations sized by Python input

os.read, _RawIOBase.read, int.to_bytes, struct.pack, ctypes array
creation and the _ssl RAND functions sized a Vec from a Python-supplied
length with vec![], which calls handle_alloc_error and, under
panic = "abort", ends the process. They now allocate through
vm.new_zeroed_bytes and raise MemoryError.

itertools.product built its pools without checking that
len(iterables) * repeat is representable; it now raises OverflowError
"repeat argument too large" and reserves the pool and index vectors
fallibly. repeat is read as isize, so a negative one raises ValueError
"repeat argument cannot be negative" instead of the conversion's message.

_ssl.RAND_bytes and RAND_pseudo_bytes read n as i32, matching the int
they are declared with.

Assisted-by: Claude

* Collect with the count in the object header

A collection kept the count it was working with in a table keyed by the
object's address, and the objects it had proved reachable in a second one.
Between them they were hashed once per candidate and twice per edge in the
heap, which is where most of a collection over a live heap went.

The count now lives in `PyInner::gc_refs`, with `GcBits::COLLECTING` saying
it is meaningful, and reachability is `gc_refs == GC_REACHABLE` rather than
membership in a set. Step 5 splits the candidates and clears the bit in one
pass. gcbench, five interleaved pairs, median: a live heap of 423k objects
goes from 0.101s to 0.055s and a dead one from 0.402s to 0.383s.

The bits, generation, owner and count take eight bytes between them. A
64-bit header had those eight as the padding its alignment forces, so it is
unchanged at 48 bytes; a 32-bit header grows from 24 to 28.

Assisted-by: Claude

* Take an explicit thread stack size as a floor in debug builds

A debug build already started Python threads on 8 MiB rather than Rust's
2 MiB default, but an explicit threading.stack_size(N) went through
verbatim. test_threading asks for 256 KiB, and starting a thread on that
walked off the end of the stack: the guard page fault landed in the
prologue of ExecutingFrame::run.

Unoptimized, that prologue reserves 80,848 bytes where the optimized one
reserves 656 -- execute_instruction is #[inline(always)] and LLVM only
colors stack slots from opt-level 1, so the frame is the sum of all 200
instruction arms' temporaries rather than the largest. A Python call costs
88,672 bytes of native stack there, and threading's bootstrap is six
frames deep, so 256 KiB holds less than half of what starting a thread
takes.

The floor reaches thread::Builder only; threading.stack_size() still
answers with what was asked for, and release builds are unchanged.

Assisted-by: Claude

* Check the native stack on every frame entry

The C-stack guard ran on one frame entry in eight. That asks the margin to
cover eight frames rather than one, and it does not: an unoptimized frame
entered through native code takes 88,672 bytes against a debug margin of
262,144. A recursion whose steps re-enter that way -- `__add__` calling
itself, a sort key that sorts -- ran off the end of the stack instead of
raising RecursionError. On a debug build `class Add: __add__ = lambda s, o:
s + o; Add() + 1` segfaulted on the main thread; it now raises, as it does
under CPython and in release builds.

enter_iframe checked and then called enter_iframe_unchecked, which checked
again; it now leaves the check to the one call.

Measured on a call-dominated benchmark, five interleaved pairs: instructions
retired go up 0.17%, about four per call, which is the stack pointer read
and the compare.

Assisted-by: Claude

* Take an iterable's length hint when a list is filled from it

`map_py_iter` read `__length_hint__` only to pass it to `PyIterIter`, and
returned an empty vector when the hint was `isize::MAX` or more. Collecting
through `PyResult` dropped the iterator's lower bound, so nothing reserved
the room the hint asked for.

`list()`, `list.extend()` and `list.__iadd__()` now reserve it and report a
hint they cannot honour as `MemoryError`; a hint that leaves no room for the
elements the list already holds is passed over, as `list_extend()` does.
`tuple()` and the other callers keep filling up without reserving.

`length_hint_opt` errors other than the `TypeError` it already turns into
`None` now reach the caller instead of being dropped.

`__iadd__` and `inplace_concat` went through `extract_cloned`, which reads
`__len__` and not `__length_hint__`; both call `PyList::extend` now, the way
`list_inplace_concat()` calls `list_extend()`.

The tuple, list and dict fast paths of `extract_elements_inner` reserve their
known length, which the `collect()` they used dropped.

Assisted-by: Claude

* Drop map.__length_hint__

`map_methods` has no `__length_hint__`, so `operator.length_hint()` on a map
answers 0, not the length of what it draws from.

The method walked into the length hint of every iterator it holds, and a
chain of maps 10000 long overflowed the native stack answering for the
outermost one. It also took the longest of its iterators, where a map stops
at the shortest.

Assisted-by: Claude

* Ask for a length hint where each caller asks for it

`map_py_iter` asked the iterable it was handed, for every caller, and reported
what asking raised. Only some callers ask it: `list_extend()` and
`_PyBytes_FromIterator()` ask the iterable, `PySequence_Tuple()` asks the
iterator, and the bytearray constructor asks nothing. `tuple()`, `min()`,
`max()`, `collections.deque()` and `f(*x)` raised for an iterable whose
`__len__` or `__length_hint__` does, where they answer.

Which object is asked is now the caller's to say. `sorted()` asks the iterable,
being `PySequence_List()`.

`bytes_from_object()` stood in for `PyBytes_FromObject()`, for
`bytearray_extend()` and for the bytearray constructor, which do not agree on
this: the first two ask, the last does not. It is split, and assigning to a
bytearray slice takes the constructor's side with `PyByteArray_FromObject()`.

`list.extend()` counted what it held before the iterable had been asked, where
`list_extend()` reads `Py_SIZE(self)` after. A `__length_hint__` that adds to
the list made the overflow guard read a count too small and raise `MemoryError`
where nothing is wrong; one that empties it made the guard skip a reservation
that cannot be served.

Assisted-by: Claude

* Settle product's pool count before it reads its arguments

`product_new()` checks `repeat` and works out `npools` before it calls
`PySequence_Tuple()` on any argument, and fills the pools `npools` times.

The pools were filled by repeating the arguments `repeat` times instead, which
walks that many steps even with no arguments to repeat: `product(repeat=2**62)`
counted up to it rather than answering `[()]`. The count was also worked out
after the arguments had been read, so a repeat too large to serve ran their
code first.

Assisted-by: Claude

* Let the bool format answer with the error its value raised

`pack_single()` leaves `'?'` to `PyObject_IsTrue()` and returns what that
raised. Packing classified the error instead, so a `ValueError` from a
`__bool__` came back as "memoryview: invalid value for format '?'".

Assisted-by: Claude

* Release a cell's old value after the lock

`PyCell::set` dropped what it replaced while still holding the mutex guarding
the cell contents. A `__del__` running from that drop and reading the same cell
waited on a lock its own caller held, so `del it` on a closure variable whose
value has such a `__del__` deadlocked.

The replaced value is now released once the guard is gone, as `Py_XSETREF`
stores before it decrefs.

Assisted-by: Claude

* Have a set iterator hold the set it iterates

The iterator kept only a reference to the inner hash table, so in
`it = iter(A(*args))` the `A()` temporary was the last owner and died as the
call returned, before `it` was bound. A `__del__` reading `it` there saw an
unbound name and its error was printed and ignored.

The iterator now holds the set object, as `si_set` does, and releases it once
exhausted. That release happens after the lock is dropped, where
`setiter_iternext()` puts its `Py_DECREF(so)` past `Py_END_CRITICAL_SECTION()`,
so a `__del__` that iterates again does not wait on a lock the call holds.

Assisted-by: Claude

* Release an exhausted iterator's container after the lock

`PositionIterInternal::_next` overwrote its `IterStatus::Active` while the
caller still held the mutex around it. Dropping the container there ran any
`__del__` under that lock, and a `__del__` that iterated the same object again
blocked on it.

`exhaust()` now hands the container back instead of dropping it, and
`locked_step()` releases it after the guard. list, list_reverseiterator, tuple,
str, dict and its views and reverse views, bytes, bytearray, memoryview,
array, deque, and the enumerate and sequence iterators all go through it.

Assisted-by: Claude

* Unskip test_free_after_iterating

Assisted-by: Claude

* Stop listing test_set as an environment polluter

`check_free_after_iterating` no longer leaves an ignored exception behind, and
the job that reruns the listed tests ten times fails once one of them stops
polluting.

Assisted-by: Claude

* Drop winsound imports left unused

`TryFromBorrowedObject`, `exceptions`, and `ToWideString` have no reference in
the module, which fails the Windows clippy line under `-Dwarnings`.

Assisted-by: Claude

* Ask nothing where the caller takes no room

`map_py_iter` asked the iterator for a length hint on behalf of every caller
that does not reserve, and reported what asking raised. Those callers ask
nothing at all: `tuple()`, `f(*x)`, `bytearray(x)`, `min()`, `max()` and
`collections.deque()` answer for an iterator whose `__length_hint__` raises,
where they had been raising it.

The answer was also never spent. It reached `PyIterIter` for a `size_hint()`
the push loop does not read, so the lookup and any call it made were work
thrown away: `tuple()` over a generator drops 22% of its instructions, and 17%
over an iterator with a `__length_hint__` written in Python.

Assisted-by: Claude

* Stop asking an iterator how long it is to walk it

`PyIter::iter` and `PyIter::into_iter` asked for a length hint and reported
what asking raised. Nothing spent the answer: it reached `PyIterIter` for a
`size_hint()` that every caller either loops past or drops, since collecting
into a `Result` reports no lower bound.

23 operations answered for an iterator whose `__length_hint__` raises, where
they had been raising it: `set`, `frozenset` and the nine `set` methods that
take an iterable, `dict.fromkeys` and the dict view operators, `array` and
`array.extend`, `all`, `any`, `sum`, `io.writelines`, `math.fsum`,
`math.prod`, and `csv.writerow` and `writerows`.

Over a generator, `set()` drops 16% of its instructions and `all()` 23%.

`str.join` and `bytes.join` do ask, reaching their elements through
`PySequence_Fast()`, which fills a list from the iterator. They take
`iter_sized()`, which is now the only way to ask. `iter_without_hint` is gone,
its callers being what `iter` already does.

Assisted-by: Claude

* Name the matrix jobs rather than let the matrix name them

A generated job name lists every value in the matrix entry, so `cargo check`
carried the booleans its dependencies and `skip_ssl` keys expand to, and the
snippets job carried its test arguments and timeout. Adding or removing a key
renames the check, which drops it from the required list until that list is
edited to match. Emptying `env_polluting_tests` renamed three checks this way.

`Run rust tests` and `clippy` keep the names they had. `cargo check` drops the
booleans from six of its nine, and the snippets job drops its arguments and
timeout from all three.

Assisted-by: Claude

* Keep a sequence iterator active when an element raises

`PositionIterInternal::_next` exhausted the iterator for any non-`Return`
result, so an error from `__getitem__` ended the walk. `iter_iternext()`
lets go of its sequence for `IndexError` and `StopIteration` alone, and
`PyIterReturn::from_getitem_result` has already turned the first of those
into the second, so only `StopIteration` exhausts now.

Both deque iterators keep exhausting on their own mutation guard, which
`deque_iternext()` does by zeroing the counter before it raises; they
share one step function for it, and the message it raises is lowercased
to match the three other sites in the module.

Assisted-by: Claude

* Name the caller in the bytes conversion TypeError

An object with no iteration protocol reached `PyObject_GetIter`'s "not
iterable" message, and `bytearray.extend()` reported bytes. Each entry
point now checks for the protocol first and names itself:

    bytes(object())               cannot convert 'object' object to bytes
    bytearray(object())           cannot convert 'object' object to bytearray
    bytearray().extend(object())  can't extend bytearray with object

Assisted-by: Claude

* Take a strong count too large to hold as reachable

`start_gc_refs` clipped a count at `GC_REACHABLE - 1`, a number the
per-reference subtraction could still walk down to zero and collect a
live object. It now stores `GC_REACHABLE`, and `subtract_gc_ref` leaves
that value alone.

Assisted-by: Claude

* Raise AssertionError where a snippet asserts False

`assert False` is removed under `-O`, which the snippet suite may run.

Assisted-by: Claude

* Keep raising for a collection that moved under its iterator

A deque, set or dict iterator raised once and then read as spent. The
guard is sticky: `deque_iternext()` looks at the deque's state before the
count it keeps, and `dictiter_iternextkey()` and `setiter_iternext()`
write a size no collection can have, so every later call finds the same
thing and raises again. `dequereviter_next()` is the one exception,
looking at its count first, so it runs out after the first raise.

Both deque iterators now carry `dequeiterobject.counter` rather than
reading a length back from the deque, and the dict and set iterators
compare the size they captured against the collection's own every time
they are asked how much is left, which is what makes that answer nothing
from the moment the collection changes rather than only once the
iterator has raised.

The set's message is capitalized to match `setiter_iternext()`.

Measured against 3.14.6, for each of deque, reversed deque, set, dict
and a reversed dict view: the hint after the change, the error, the hint
after the error, and what a later call answers.

Assisted-by: Claude

* Give apt-get update a deadline to fail on

The step waits on `apt-get update`, which has no deadline of its own, so
a source that takes the connection and then stops answering holds the
job until the workflow's own timeout. The retry that disables the
Microsoft and azure-cli sources runs only when the update exits
non-zero, which a held connection never does; three jobs on this branch
sat on this step for 20 minutes to five and a half hours.

Each attempt is now bounded, and the transports are given a timeout, so
a source that stops answering reaches the retry.

Assisted-by: Claude
2026-08-20 07:08:03 +09:00
2025-07-04 23:47:05 +09:00
2026-07-18 16:48:32 +09:00
2020-07-06 18:25:10 +00:00
2025-07-01 04:40:58 +09:00
2020-09-13 06:58:57 +09:00
2021-03-14 12:50:00 -05:00
2022-08-23 01:50:04 -05:00
2019-03-07 20:00:02 +01:00
2020-03-13 08:04:33 -05:00
2020-03-13 08:04:33 -05:00
2026-05-16 19:01:40 +09:00
2026-04-13 12:49:32 +09:00
2019-03-22 18:09:05 -05:00
2021-10-02 21:13:14 +09:00
2023-03-10 02:05:52 +09:00
2025-02-26 11:48:22 -08:00
2026-03-16 11:32:27 +09:00

RustPython

A Python-3 (CPython >= 3.14.0) Interpreter written in Rust 🐍 😱 🤘.

Build Status codecov License: MIT Contributors Discord Shield docs.rs Crates.io dependency status Open in Gitpod

Usage

Check out our online demo running on WebAssembly.

RustPython requires Rust latest stable version (e.g 1.67.1 at February 7th 2023). If you don't currently have Rust installed on your system you can do so by following the instructions at rustup.rs.

To check the version of Rust you're currently running, use rustc --version. If you wish to update, rustup update stable will update your Rust installation to the most recent stable release.

To build RustPython locally, first, clone the source code:

git clone https://github.com/RustPython/RustPython

RustPython uses symlinks to manage python libraries in Lib/. If on windows, running the following helps:

git config core.symlinks true

Then you can change into the RustPython directory and run the demo (Note: --release is needed to prevent stack overflow on Windows):

$ cd RustPython
$ cargo run --release -- -c 'print("Hello, RustPython!")'
Hello, RustPython!

Or use the interactive shell:

$ cargo run --release
Welcome to rustpython
>>>>> 2+2
4

NOTE: For windows users, please set RUSTPYTHONPATH environment variable as Lib path in project directory. (e.g. When RustPython directory is C:\RustPython, set RUSTPYTHONPATH as C:\RustPython\Lib)

You can also install and run RustPython with the following:

$ cargo install --git https://github.com/RustPython/RustPython rustpython
$ rustpython
Welcome to the magnificent Rust Python interpreter
>>>>>

venv

Because RustPython currently doesn't provide a well-packaged installation, using venv helps to use pip easier.

$ rustpython -m venv <your_env_name>
$ . <your_env_name>/bin/activate
$ python # now `python` is the alias of the RustPython for the new env

PIP

If you'd like to make https requests, you can enable the ssl feature, which also lets you install the pip package manager. Note that on Windows, you may need to install OpenSSL, or you can enable the ssl-openssl-vendor feature instead, which compiles OpenSSL for you but requires a C compiler, perl, and make. OpenSSL version 3 is expected and tested in CI. Older versions may not work.

Once you've installed rustpython with SSL support, you can install pip by running:

cargo install --git https://github.com/RustPython/RustPython
rustpython --install-pip

You can also install RustPython through the conda package manager, though this isn't officially supported and may be out of date:

conda install rustpython -c conda-forge
rustpython

SSL provider

For HTTPS requests, ssl-rustls-aws-lc is enabled by default for the RustPython binary. Embedders can use rustpython-stdlib's provider-agnostic ssl-rustls feature and install their own rustls crypto provider, or replace rustls with ssl-openssl if their environment requires OpenSSL. Note that to use OpenSSL on Windows, you may need to install OpenSSL, or you can enable the ssl-openssl-vendor feature instead, which compiles OpenSSL for you but requires a C compiler, perl, and make. OpenSSL version 3 is expected and tested in CI. Older versions may not work.

WASI

You can compile RustPython to a standalone WebAssembly WASI module so it can run anywhere.

Build

cargo build --target wasm32-wasip1 --no-default-features --features freeze-stdlib,stdlib --release

Run by wasmer

wasmer run --dir `pwd` -- target/wasm32-wasip1/release/rustpython.wasm `pwd`/extra_tests/snippets/stdlib_random.py

Run by wapm

$ wapm install rustpython
$ wapm run rustpython
>>>>> 2+2
4

Building the WASI file

You can build the WebAssembly WASI file with:

cargo build --release --target wasm32-wasip1 --features="freeze-stdlib"

Note: we use the freeze-stdlib to include the standard library inside the binary. You also have to run once rustup target add wasm32-wasip1.

JIT (Just in time) compiler

RustPython has a very experimental JIT compiler that compile python functions into native code.

Building

By default the JIT compiler isn't enabled, it's enabled with the jit cargo feature.

cargo run --features jit

This requires autoconf, automake, libtool, and clang to be installed.

Using

To compile a function, call __jit__() on it.

def foo():
    a = 5
    return 10 + a

foo.__jit__()  # this will compile foo to native code and subsequent calls will execute that native code
assert foo() == 15

Embedding RustPython into your Rust Applications

Interested in exposing Python scripting in an application written in Rust, perhaps to allow quickly tweaking logic where Rust's compile times would be inhibitive? Then examples/hello_embed.rs and examples/mini_repl.rs may be of some assistance.

Disclaimer

RustPython is in development, and while the interpreter certainly can be used in interesting use cases like running Python in WASM and embedding into a Rust project, do note that RustPython is not totally production-ready.

Contribution is more than welcome! See our contribution section for more information on this.

Conference videos

Checkout those talks on conferences:

Use cases

Although RustPython is a fairly young project, a few people have used it to make cool projects:

  • GreptimeDB: an open-source, cloud-native, distributed time-series database. Using RustPython for embedded scripting.
  • pyckitup: a game engine written in rust.
  • Robot Rumble: an arena-based AI competition platform
  • Ruff: an extremely fast Python linter, written in Rust

Goals

  • Full Python-3 environment entirely in Rust (not CPython bindings)
  • A clean implementation without compatibility hacks

Documentation

Currently along with other areas of the project, documentation is still in an early phase.

You can read the online documentation for the latest release, or the user guide.

You can also generate documentation locally by running:

cargo doc # Including documentation for all dependencies
cargo doc --no-deps --all # Excluding all dependencies

Documentation HTML files can then be found in the target/doc directory or you can append --open to the previous commands to have the documentation open automatically on your default browser.

For a high level overview of the components, see the architecture document.

Contributing

Contributions are welcome and highly appreciated. To get started, check out the contributing guidelines.

You can also join us on Discord.

Compiling to WebAssembly

See this doc

Community

Discord Banner

Chat with us on Discord.

Code of conduct

Our code of conduct can be found here.

Credit

The initial work was based on windelbouwman/rspython and shinglyu/RustPython

These are some useful links to related projects:

License

This project is licensed under the MIT license. Please see the LICENSE file for more details.

The project logo is licensed under the CC-BY-4.0 license. Please see the LICENSE-logo file for more details.

Languages
Rust 87%
Python 12.5%
JavaScript 0.2%
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