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rust: prefer NonNull::new to assertions

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Do not use new_unchecked; the effect is the same, but the
code is easier to read and unsafe regions become smaller.
Likewise, NonNull::new can be used instead of assertion and
followed by as_ref() or as_mut() instead of dereferencing the
pointer.

Suggested-by: Zhao Liu <zhao1.liu@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2025-01-23 11:25:22 +01:00
parent 24f0e8d818
commit 7d0520398f
5 changed files with 35 additions and 47 deletions
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12
rust/qemu-api/src/qdev.rs
View file

@ -4,7 +4,7 @@
//! Bindings to create devices and access device functionality from Rust.
use std::ffi::CStr;
use std::{ffi::CStr, ptr::NonNull};
pub use bindings::{DeviceClass, DeviceState, Property};
@ -55,9 +55,8 @@ pub trait DeviceImpl {
/// can be downcasted to type `T`. We also expect the device is
/// readable/writeable from one thread at any time.
unsafe extern "C" fn rust_realize_fn<T: DeviceImpl>(dev: *mut DeviceState, _errp: *mut *mut Error) {
assert!(!dev.is_null());
let state = dev.cast::<T>();
T::REALIZE.unwrap()(unsafe { &mut *state });
let state = NonNull::new(dev).unwrap().cast::<T>();
T::REALIZE.unwrap()(unsafe { state.as_ref() });
}
/// # Safety
@ -66,9 +65,8 @@ unsafe extern "C" fn rust_realize_fn<T: DeviceImpl>(dev: *mut DeviceState, _errp
/// can be downcasted to type `T`. We also expect the device is
/// readable/writeable from one thread at any time.
unsafe extern "C" fn rust_reset_fn<T: DeviceImpl>(dev: *mut DeviceState) {
assert!(!dev.is_null());
let state = dev.cast::<T>();
T::RESET.unwrap()(unsafe { &mut *state });
let mut state = NonNull::new(dev).unwrap().cast::<T>();
T::RESET.unwrap()(unsafe { state.as_mut() });
}
impl<T> ClassInitImpl<DeviceClass> for T

21
rust/qemu-api/src/qom.rs
View file

@ -58,6 +58,7 @@ use std::{
fmt,
ops::{Deref, DerefMut},
os::raw::c_void,
ptr::NonNull,
};
pub use bindings::{Object, ObjectClass};
@ -153,27 +154,34 @@ impl<T: fmt::Display + ObjectType> fmt::Display for ParentField<T> {
}
unsafe extern "C" fn rust_instance_init<T: ObjectImpl>(obj: *mut Object) {
let mut state = NonNull::new(obj).unwrap().cast::<T>();
// SAFETY: obj is an instance of T, since rust_instance_init<T>
// is called from QOM core as the instance_init function
// for class T
unsafe { T::INSTANCE_INIT.unwrap()(&mut *obj.cast::<T>()) }
unsafe {
T::INSTANCE_INIT.unwrap()(state.as_mut());
}
}
unsafe extern "C" fn rust_instance_post_init<T: ObjectImpl>(obj: *mut Object) {
let state = NonNull::new(obj).unwrap().cast::<T>();
// SAFETY: obj is an instance of T, since rust_instance_post_init<T>
// is called from QOM core as the instance_post_init function
// for class T
T::INSTANCE_POST_INIT.unwrap()(unsafe { &*obj.cast::<T>() })
T::INSTANCE_POST_INIT.unwrap()(unsafe { state.as_ref() });
}
unsafe extern "C" fn rust_class_init<T: ObjectType + ClassInitImpl<T::Class>>(
klass: *mut ObjectClass,
_data: *mut c_void,
) {
let mut klass = NonNull::new(klass)
.unwrap()
.cast::<<T as ObjectType>::Class>();
// SAFETY: klass is a T::Class, since rust_class_init<T>
// is called from QOM core as the class_init function
// for class T
T::class_init(unsafe { &mut *klass.cast::<T::Class>() })
T::class_init(unsafe { klass.as_mut() })
}
unsafe extern "C" fn drop_object<T: ObjectImpl>(obj: *mut Object) {
@ -581,11 +589,8 @@ pub trait ClassInitImpl<T> {
/// can be downcasted to type `T`. We also expect the device is
/// readable/writeable from one thread at any time.
unsafe extern "C" fn rust_unparent_fn<T: ObjectImpl>(dev: *mut Object) {
unsafe {
assert!(!dev.is_null());
let state = core::ptr::NonNull::new_unchecked(dev.cast::<T>());
T::UNPARENT.unwrap()(state.as_ref());
}
let state = NonNull::new(dev).unwrap().cast::<T>();
T::UNPARENT.unwrap()(unsafe { state.as_ref() });
}
impl<T> ClassInitImpl<ObjectClass> for T