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Store SyntaxError members in struct fields instead of the instance dict #8348

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172292a
Store SyntaxError members in struct fields instead of class attributes
devyubin Jul 22, 2026
c0fccaa
Coerce SyntaxError location argument from any sequence
devyubin Jul 23, 2026
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1 change: 0 additions & 1 deletion Lib/test/test_exceptions.py
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Original file line number Diff line number Diff line change
Expand Up @@ -2527,7 +2527,6 @@ def test_incorrect_constructor(self):
args = ("bad.py", 1, 2, "abcdefg", 1)
self.assertRaises(TypeError, SyntaxError, "bad bad", args)

@unittest.expectedFailure # TODO: RUSTPYTHON; AssertionError: 2 is not None
def test_syntax_error_memory_leak(self):
# gh-146250: memory leak with re-initialization of SyntaxError
e = SyntaxError("msg", ("file.py", 1, 2, "txt", 2, 3))
Expand Down
288 changes: 224 additions & 64 deletions crates/vm/src/exceptions.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -9,7 +9,7 @@ use crate::{
},
class::{PyClassImpl, StaticType},
convert::{IntoPyException, ToPyException, ToPyObject},
function::{ArgIterable, FuncArgs, IntoFuncArgs, PySetterValue},
function::{ArgIterable, FuncArgs, IntoFuncArgs},
py_io::{self, Write},
stdlib::sys,
suggestion::offer_suggestions,
Expand Down Expand Up @@ -1029,21 +1029,7 @@ impl ExceptionZoo {
excs.python_finalization_error
);

extend_exception!(PySyntaxError, ctx, excs.syntax_error, {
"msg" => ctx.new_static_getset(
"msg",
excs.syntax_error,
make_arg_getter(0),
syntax_error_set_msg,
),
// TODO: members
"filename" => ctx.none(),
"lineno" => ctx.none(),
"end_lineno" => ctx.none(),
"offset" => ctx.none(),
"end_offset" => ctx.none(),
"text" => ctx.none(),
});
extend_exception!(PySyntaxError, ctx, excs.syntax_error);
extend_exception!(PyIncompleteInputError, ctx, excs.incomplete_input_error);
extend_exception!(PyIndentationError, ctx, excs.indentation_error);
extend_exception!(PyTabError, ctx, excs.tab_error);
Expand Down Expand Up @@ -1082,20 +1068,6 @@ fn make_arg_getter(idx: usize) -> impl Fn(PyBaseExceptionRef) -> Option<PyObject
move |exc| exc.get_arg(idx)
}

fn syntax_error_set_msg(exc: PyBaseExceptionRef, value: PySetterValue, vm: &VirtualMachine) {
let mut args = exc.args.write();
let mut new_args = args.as_slice().to_vec();
// Ensure the message slot at index 0 always exists for SyntaxError.args.
if new_args.is_empty() {
new_args.push(vm.ctx.none());
}
match value {
PySetterValue::Assign(value) => new_args[0] = value,
PySetterValue::Delete => new_args[0] = vm.ctx.none(),
}
*args = PyTuple::new_ref(new_args, &vm.ctx);
}

#[cfg(feature = "serde")]
pub struct SerializeException<'vm, 's> {
vm: &'vm VirtualMachine,
Expand Down Expand Up @@ -2551,12 +2523,64 @@ pub(super) mod types {
#[repr(transparent)]
pub struct PyPythonFinalizationError(PyRuntimeError);

#[pyexception(name, base = PyException, ctx = "syntax_error")]
#[derive(Debug)]
#[repr(transparent)]
pub struct PySyntaxError(PyException);
#[pyexception(name, base = PyException, ctx = "syntax_error", traverse = "manual")]
#[repr(C)]
pub struct PySyntaxError {
base: PyException,
msg: PyAtomicRef<Option<PyObject>>,
filename: PyAtomicRef<Option<PyObject>>,
lineno: PyAtomicRef<Option<PyObject>>,
offset: PyAtomicRef<Option<PyObject>>,
text: PyAtomicRef<Option<PyObject>>,
end_lineno: PyAtomicRef<Option<PyObject>>,
end_offset: PyAtomicRef<Option<PyObject>>,
print_file_and_line: PyAtomicRef<Option<PyObject>>,
}

#[pyexception(with(Initializer))]
impl crate::class::PySubclass for PySyntaxError {
type Base = PyException;
fn as_base(&self) -> &Self::Base {
&self.base
}
}

impl core::fmt::Debug for PySyntaxError {
fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
f.debug_struct("PySyntaxError").finish_non_exhaustive()
}
}

unsafe impl Traverse for PySyntaxError {
fn traverse(&self, tracer_fn: &mut TraverseFn<'_>) {
self.base.0.traverse(tracer_fn);
if let Some(obj) = self.msg.deref() {
tracer_fn(obj);
}
if let Some(obj) = self.filename.deref() {
tracer_fn(obj);
}
if let Some(obj) = self.lineno.deref() {
tracer_fn(obj);
}
if let Some(obj) = self.offset.deref() {
tracer_fn(obj);
}
if let Some(obj) = self.text.deref() {
tracer_fn(obj);
}
if let Some(obj) = self.end_lineno.deref() {
tracer_fn(obj);
}
if let Some(obj) = self.end_offset.deref() {
tracer_fn(obj);
}
if let Some(obj) = self.print_file_and_line.deref() {
tracer_fn(obj);
}
}
}

#[pyexception(with(Constructor, Initializer))]
impl PySyntaxError {
#[pymethod]
fn __str__(zelf: &Py<PyBaseException>, vm: &VirtualMachine) -> PyStrRef {
Expand Down Expand Up @@ -2620,58 +2644,194 @@ pub(super) mod types {

vm.ctx.new_str(msg_with_location_info)
}

#[pygetset]
fn msg(&self) -> Option<PyObjectRef> {
self.msg.to_owned()
}

#[pygetset(setter)]
fn set_msg(&self, value: PySetterValue, vm: &VirtualMachine) {
let value = match value {
PySetterValue::Assign(v) => Some(v),
PySetterValue::Delete => None,
};
self.msg.swap_to_temporary_refs(value, vm);
}

#[pygetset]
fn filename(&self) -> Option<PyObjectRef> {
self.filename.to_owned()
}

#[pygetset(setter)]
fn set_filename(&self, value: PySetterValue, vm: &VirtualMachine) {
let value = match value {
PySetterValue::Assign(v) => Some(v),
PySetterValue::Delete => None,
};
self.filename.swap_to_temporary_refs(value, vm);
}

#[pygetset]
fn lineno(&self) -> Option<PyObjectRef> {
self.lineno.to_owned()
}

#[pygetset(setter)]
fn set_lineno(&self, value: PySetterValue, vm: &VirtualMachine) {
let value = match value {
PySetterValue::Assign(v) => Some(v),
PySetterValue::Delete => None,
};
self.lineno.swap_to_temporary_refs(value, vm);
}

#[pygetset]
fn offset(&self) -> Option<PyObjectRef> {
self.offset.to_owned()
}

#[pygetset(setter)]
fn set_offset(&self, value: PySetterValue, vm: &VirtualMachine) {
let value = match value {
PySetterValue::Assign(v) => Some(v),
PySetterValue::Delete => None,
};
self.offset.swap_to_temporary_refs(value, vm);
}

#[pygetset]
fn text(&self) -> Option<PyObjectRef> {
self.text.to_owned()
}

#[pygetset(setter)]
fn set_text(&self, value: PySetterValue, vm: &VirtualMachine) {
let value = match value {
PySetterValue::Assign(v) => Some(v),
PySetterValue::Delete => None,
};
self.text.swap_to_temporary_refs(value, vm);
}

#[pygetset]
fn end_lineno(&self) -> Option<PyObjectRef> {
self.end_lineno.to_owned()
}

#[pygetset(setter)]
fn set_end_lineno(&self, value: PySetterValue, vm: &VirtualMachine) {
let value = match value {
PySetterValue::Assign(v) => Some(v),
PySetterValue::Delete => None,
};
self.end_lineno.swap_to_temporary_refs(value, vm);
}

#[pygetset]
fn end_offset(&self) -> Option<PyObjectRef> {
self.end_offset.to_owned()
}

#[pygetset(setter)]
fn set_end_offset(&self, value: PySetterValue, vm: &VirtualMachine) {
let value = match value {
PySetterValue::Assign(v) => Some(v),
PySetterValue::Delete => None,
};
self.end_offset.swap_to_temporary_refs(value, vm);
}

#[pygetset]
fn print_file_and_line(&self) -> Option<PyObjectRef> {
self.print_file_and_line.to_owned()
}

#[pygetset(setter)]
fn set_print_file_and_line(&self, value: PySetterValue, vm: &VirtualMachine) {
let value = match value {
PySetterValue::Assign(v) => Some(v),
PySetterValue::Delete => None,
};
self.print_file_and_line.swap_to_temporary_refs(value, vm);
}
}

impl Constructor for PySyntaxError {
type Args = FuncArgs;

fn py_new(_cls: &Py<PyType>, args: FuncArgs, vm: &VirtualMachine) -> PyResult<Self> {
let msg = args.args.first().cloned();
let base_exception = PyBaseException::new(args.args, vm);
Ok(Self {
base: PyException(base_exception),
msg: msg.into(),
filename: None.into(),
lineno: None.into(),
offset: None.into(),
text: None.into(),
end_lineno: None.into(),
end_offset: None.into(),
print_file_and_line: None.into(),
})
}
}

impl Initializer for PySyntaxError {
type Args = FuncArgs;

fn slot_init(zelf: PyObjectRef, args: FuncArgs, vm: &VirtualMachine) -> PyResult<()> {
let len = args.args.len();
let new_args = args;
let msg = args.args.first().cloned();
let location_arg = (args.args.len() == 2).then(|| args.args[1].clone());

zelf.set_attr("print_file_and_line", vm.ctx.none(), vm)?;
PyBaseException::slot_init(zelf.clone(), args, vm)?;
let exc: &Py<Self> = zelf.downcast_ref::<Self>().unwrap();

if len == 2
&& let Ok(location_tuple) = new_args.args[1]
.clone()
.downcast::<crate::builtins::PyTuple>()
{
let location_tup_len = location_tuple.len();
if let Some(msg) = msg {
exc.msg.swap_to_temporary_refs(Some(msg), vm);
}

match location_tup_len {
// SyntaxError(msg, (filename, lineno, offset, text[, end_lineno, end_offset]))
// The location argument is coerced from any sequence like CPython's
// PySequence_Tuple; a non-sequence raises TypeError.
if let Some(location_arg) = location_arg {
let location: Vec<PyObjectRef> = location_arg.try_to_value(vm)?;

match location.len() {
4 | 6 => {}
5 => {
return Err(vm.new_type_error(
"end_offset must be provided when end_lineno is provided",
));
}
_ => {
len => {
return Err(vm.new_type_error(format!(
"function takes exactly 4 or 6 arguments ({location_tup_len} given)"
"function takes exactly 4 or 6 arguments ({len} given)"
)));
}
}

for (i, &attr) in [
"filename",
"lineno",
"offset",
"text",
"end_lineno",
"end_offset",
]
.iter()
.enumerate()
{
if location_tup_len > i {
zelf.set_attr(attr, location_tuple[i].to_owned(), vm)?;
} else {
break;
}
exc.end_lineno.swap_to_temporary_refs(None, vm);
exc.end_offset.swap_to_temporary_refs(None, vm);

exc.filename
.swap_to_temporary_refs(Some(location[0].clone()), vm);
exc.lineno
.swap_to_temporary_refs(Some(location[1].clone()), vm);
exc.offset
.swap_to_temporary_refs(Some(location[2].clone()), vm);
exc.text
.swap_to_temporary_refs(Some(location[3].clone()), vm);
if location.len() == 6 {
exc.end_lineno
.swap_to_temporary_refs(Some(location[4].clone()), vm);
exc.end_offset
.swap_to_temporary_refs(Some(location[5].clone()), vm);
}
}

PyBaseException::slot_init(zelf, new_args, vm)
Ok(())
}

fn init(_zelf: PyRef<Self>, _args: Self::Args, _vm: &VirtualMachine) -> PyResult<()> {
Expand Down
11 changes: 5 additions & 6 deletions crates/vm/src/vm/vm_new.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -341,12 +341,11 @@ impl VirtualMachine {
/// [`vm.invoke_exception()`][Self::invoke_exception] or
/// [`exceptions::ExceptionCtor`][crate::exceptions::ExceptionCtor] instead.
pub fn new_exception(&self, exc_type: PyTypeRef, args: Vec<PyObjectRef>) -> PyBaseExceptionRef {
debug_assert_eq!(
exc_type.slots.basicsize,
core::mem::size_of::<PyBaseException>(),
"vm.new_exception() is only for exception types without additional payload. The given type '{}' is not allowed. Use vm.new_os_subtype_error() for OSError subtypes.",
exc_type.name()
);
if exc_type.slots.basicsize != core::mem::size_of::<PyBaseException>() {
return self
.invoke_exception(&exc_type, args)
.expect("vm.new_exception() called with an invalid exception type");
}

PyBaseException::new(args, self)
.into_ref_with_type_lazy_dict(self, exc_type)
Expand Down
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