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Object header slimming: prefix allocation for ObjExt #7334

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Merged
youknowone merged 6 commits into from
Mar 5, 2026
Merged

Object header slimming: prefix allocation for ObjExt #7334

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f3df446
Object header slimming: prefix allocation for ObjExt
youknowone Mar 3, 2026
75d8a3a
Add HAS_WEAKREF to _asyncio Future/Task, rename weakref helpers
youknowone Mar 3, 2026
2ee043e
Add HAS_WEAKREF to array, deque, _grouper; remove expectedFailure mar…
youknowone Mar 3, 2026
de37c01
Add HAS_WEAKREF to code, union, partial, lock, IO, mmap, sre, sqlite3…
youknowone Mar 3, 2026
fb20298
Add HAS_DICT to type flags and handle non-METHOD/CLASS in descr_get
youknowone Mar 4, 2026
a2fe158
Fix ext detection, HeapMethodDef ownership, WASM error
youknowone Mar 4, 2026
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Add HAS_WEAKREF to _asyncio Future/Task, rename weakref helpers 
- Add HAS_WEAKREF flag to PyFuture and PyTask (matches CPython)
- Rename subtype_getweakref/setweakref to subtype_get_weakref/set_weakref
  to fix cspell unknown word lint
  • Loading branch information
@youknowone
youknowone committed Mar 5, 2026
commit 75d8a3a60c30dcecf2b439c27e7cf2a7ce13ac9b
4 changes: 2 additions & 2 deletions crates/stdlib/src/_asyncio.rs
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Expand Up @@ -160,7 +160,7 @@ pub(crate) mod _asyncio {
}

#[pyclass(
flags(BASETYPE, HAS_DICT),
flags(BASETYPE, HAS_DICT, HAS_WEAKREF),
with(Constructor, Initializer, Destructor, Representable, Iterable)
)]
impl PyFuture {
Expand Down Expand Up @@ -1169,7 +1169,7 @@ pub(crate) mod _asyncio {
}

#[pyclass(
flags(BASETYPE, HAS_DICT),
flags(BASETYPE, HAS_DICT, HAS_WEAKREF),
with(Constructor, Initializer, Destructor, Representable, Iterable)
)]
impl PyTask {
Expand Down
12 changes: 6 additions & 6 deletions crates/vm/src/builtins/type.rs
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Expand Up @@ -1981,8 +1981,8 @@ impl Constructor for PyType {
let descriptor = vm.ctx.new_getset(
"__weakref__",
&typ,
subtype_getweakref,
subtype_setweakref,
subtype_get_weakref,
subtype_set_weakref,
);
typ.attributes
.write()
Expand Down Expand Up @@ -2426,15 +2426,15 @@ fn subtype_set_dict(obj: PyObjectRef, value: PyObjectRef, vm: &VirtualMachine) -
}
}

// subtype_getweakref
fn subtype_getweakref(obj: PyObjectRef, vm: &VirtualMachine) -> PyResult {
// subtype_get_weakref
fn subtype_get_weakref(obj: PyObjectRef, vm: &VirtualMachine) -> PyResult {
// Return the first weakref in the weakref list, or None
let weakref = obj.get_weakrefs();
Ok(weakref.unwrap_or_else(|| vm.ctx.none()))
}

// subtype_setweakref: __weakref__ is read-only
fn subtype_setweakref(obj: PyObjectRef, _value: PyObjectRef, vm: &VirtualMachine) -> PyResult<()> {
// subtype_set_weakref: __weakref__ is read-only
fn subtype_set_weakref(obj: PyObjectRef, _value: PyObjectRef, vm: &VirtualMachine) -> PyResult<()> {
Err(vm.new_attribute_error(format!(
"attribute '__weakref__' of '{}' objects is not writable",
obj.class().name()
Expand Down
7 changes: 6 additions & 1 deletion crates/vm/src/object/core.rs
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Expand Up @@ -292,7 +292,12 @@ unsafe impl Link for GcLink {
/// Extension fields for objects that need dict, weakref list, or member slots.
/// Allocated as a prefix before PyInner when needed (prefix allocation pattern).
/// Access via `PyInner::ext_ref()` using negative offset from the object pointer.
#[repr(C)]
///
/// align(8) ensures size_of::<ObjExt>() is always a multiple of 8,
/// so the offset from Layout::extend equals size_of::<ObjExt>() for any
/// PyInner<T> alignment (important on wasm32 where pointers are 4 bytes
/// but some payloads like PyWeak have align 8 due to i64 fields).
#[repr(C, align(8))]
pub(super) struct ObjExt {
pub(super) dict: Option<InstanceDict>,
pub(super) weak_list: WeakRefList,
Expand Down