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rust: make properties array immutable

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Now that device_class_set_props() takes a const pointer, the only part of
"define_property!" that needs to be non-const is the call to try_into().
This in turn will only break if offset_of returns a value with the most
significant bit set (i.e. a struct size that is >=2^31 or >= 2^63,
respectively on 32- and 64-bit system), which is impossible.

Just use a cast and clean everything up to remove the run-time
initialization.  This also removes a use of OnceLock, which was only
stabilized in 1.70.0.

Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2024-10-18 15:22:59 +02:00
parent 03a573b960
commit c92c447ff0
1 changed files with 8 additions and 34 deletions
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42
rust/qemu-api/src/device_class.rs
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@ -2,10 +2,6 @@
// Author(s): Manos Pitsidianakis <manos.pitsidianakis@linaro.org> // Author(s): Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
// SPDX-License-Identifier: GPL-2.0-or-later // SPDX-License-Identifier: GPL-2.0-or-later
use std::sync::OnceLock;
use crate::bindings::Property;
#[macro_export] #[macro_export]
macro_rules! device_class_init { macro_rules! device_class_init {
($func:ident, props => $props:ident, realize_fn => $realize_fn:expr, legacy_reset_fn => $legacy_reset_fn:expr, vmsd => $vmsd:ident$(,)*) => { ($func:ident, props => $props:ident, realize_fn => $realize_fn:expr, legacy_reset_fn => $legacy_reset_fn:expr, vmsd => $vmsd:ident$(,)*) => {
@ -19,7 +15,7 @@ macro_rules! device_class_init {
dc.as_mut().realize = $realize_fn; dc.as_mut().realize = $realize_fn;
dc.as_mut().vmsd = &$vmsd; dc.as_mut().vmsd = &$vmsd;
$crate::bindings::device_class_set_legacy_reset(dc.as_mut(), $legacy_reset_fn); $crate::bindings::device_class_set_legacy_reset(dc.as_mut(), $legacy_reset_fn);
$crate::bindings::device_class_set_props(dc.as_mut(), $props.as_mut_ptr()); $crate::bindings::device_class_set_props(dc.as_mut(), $props.as_ptr());
} }
} }
}; };
@ -32,9 +28,7 @@ macro_rules! define_property {
// use associated function syntax for type checking // use associated function syntax for type checking
name: ::core::ffi::CStr::as_ptr($name), name: ::core::ffi::CStr::as_ptr($name),
info: $prop, info: $prop,
offset: ::core::mem::offset_of!($state, $field) offset: ::core::mem::offset_of!($state, $field) as isize,
.try_into()
.expect("Could not fit offset value to type"),
set_default: true, set_default: true,
defval: $crate::bindings::Property__bindgen_ty_1 { u: $defval as u64 }, defval: $crate::bindings::Property__bindgen_ty_1 { u: $defval as u64 },
..unsafe { ::core::mem::MaybeUninit::<$crate::bindings::Property>::zeroed().assume_init() } ..unsafe { ::core::mem::MaybeUninit::<$crate::bindings::Property>::zeroed().assume_init() }
@ -45,47 +39,27 @@ macro_rules! define_property {
// use associated function syntax for type checking // use associated function syntax for type checking
name: ::core::ffi::CStr::as_ptr($name), name: ::core::ffi::CStr::as_ptr($name),
info: $prop, info: $prop,
offset: ::core::mem::offset_of!($state, $field) offset: ::core::mem::offset_of!($state, $field) as isize,
.try_into()
.expect("Could not fit offset value to type"),
set_default: false, set_default: false,
..unsafe { ::core::mem::MaybeUninit::<$crate::bindings::Property>::zeroed().assume_init() } ..unsafe { ::core::mem::MaybeUninit::<$crate::bindings::Property>::zeroed().assume_init() }
} }
}; };
} }
#[repr(C)]
pub struct Properties<const N: usize>(pub OnceLock<[Property; N]>, pub fn() -> [Property; N]);
impl<const N: usize> Properties<N> {
pub fn as_mut_ptr(&mut self) -> *mut Property {
_ = self.0.get_or_init(self.1);
self.0.get_mut().unwrap().as_mut_ptr()
}
}
#[macro_export] #[macro_export]
macro_rules! declare_properties { macro_rules! declare_properties {
($ident:ident, $($prop:expr),*$(,)*) => { ($ident:ident, $($prop:expr),*$(,)*) => {
pub static $ident: [$crate::bindings::Property; {
const fn _calc_prop_len() -> usize {
let mut len = 1; let mut len = 1;
$({ $({
_ = stringify!($prop); _ = stringify!($prop);
len += 1; len += 1;
})* })*
len len
} }] = [
const PROP_LEN: usize = _calc_prop_len(); $($prop),*,
unsafe { ::core::mem::MaybeUninit::<$crate::bindings::Property>::zeroed().assume_init() },
fn _make_properties() -> [$crate::bindings::Property; PROP_LEN] { ];
[
$($prop),*,
unsafe { ::core::mem::MaybeUninit::<$crate::bindings::Property>::zeroed().assume_init() },
]
}
pub static mut $ident: $crate::device_class::Properties<PROP_LEN> = $crate::device_class::Properties(::std::sync::OnceLock::new(), _make_properties);
}; };
} }