| Message ID | 20241104172721.180255-33-pbonzini@redhat.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [PULL,01/40] qdev: make properties array "const" | expand |
On Mon, 04 Nov 2024 17:27, Paolo Bonzini <pbonzini@redhat.com> wrote: >From: Junjie Mao <junjie.mao@hotmail.com> > >offset_of! was stabilized in Rust 1.77.0. Use an alternative implemenation >that was found on the Rust forums, and whose author agreed to license as >MIT for use in QEMU. > >The alternative allows only one level of field access, but apart >from this can be used just by replacing core::mem::offset_of! with >qemu_api::offset_of!. > >The actual implementation of offset_of! is done in a declarative macro, >but for simplicity and to avoid introducing an extra level of indentation, >the trigger is a procedural macro #[derive(offsets)]. > >The procedural macro is perhaps a bit overengineered, but it helps >introducing some idioms that will be useful in the future as well. > >Signed-off-by: Junjie Mao <junjie.mao@hotmail.com> >Co-developed-by: Paolo Bonzini <pbonzini@redhat.com> >Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> >--- > rust/Cargo.lock | 1 + > rust/hw/char/pl011/src/device.rs | 2 +- > rust/qemu-api-macros/Cargo.toml | 2 +- > rust/qemu-api-macros/src/lib.rs | 75 +++++++- > rust/qemu-api/Cargo.toml | 6 +- > rust/qemu-api/build.rs | 9 + > rust/qemu-api/meson.build | 12 +- > rust/qemu-api/src/device_class.rs | 8 +- > rust/qemu-api/src/lib.rs | 4 + > rust/qemu-api/src/offset_of.rs | 161 ++++++++++++++++++ > rust/qemu-api/src/vmstate.rs | 10 +- > rust/qemu-api/tests/tests.rs | 1 + > subprojects/packagefiles/syn-2-rs/meson.build | 1 + > 13 files changed, 274 insertions(+), 18 deletions(-) > create mode 100644 rust/qemu-api/src/offset_of.rs > >diff --git a/rust/Cargo.lock b/rust/Cargo.lock >index 9f43b33e8b8..c0c6069247a 100644 >--- a/rust/Cargo.lock >+++ b/rust/Cargo.lock >@@ -93,6 +93,7 @@ name = "qemu_api" > version = "0.1.0" > dependencies = [ > "qemu_api_macros", >+ "version_check", > ] > > [[package]] >diff --git a/rust/hw/char/pl011/src/device.rs b/rust/hw/char/pl011/src/device.rs >index 2d225d544de..bca727e37f0 100644 >--- a/rust/hw/char/pl011/src/device.rs >+++ b/rust/hw/char/pl011/src/device.rs >@@ -55,7 +55,7 @@ impl DeviceId { > } > > #[repr(C)] >-#[derive(Debug, qemu_api_macros::Object)] >+#[derive(Debug, qemu_api_macros::Object, qemu_api_macros::offsets)] > /// PL011 Device Model in QEMU > pub struct PL011State { > pub parent_obj: SysBusDevice, >diff --git a/rust/qemu-api-macros/Cargo.toml b/rust/qemu-api-macros/Cargo.toml >index f8d6d03609f..a8f7377106b 100644 >--- a/rust/qemu-api-macros/Cargo.toml >+++ b/rust/qemu-api-macros/Cargo.toml >@@ -19,4 +19,4 @@ proc-macro = true > [dependencies] > proc-macro2 = "1" > quote = "1" >-syn = "2" >+syn = { version = "2", features = ["extra-traits"] } >diff --git a/rust/qemu-api-macros/src/lib.rs b/rust/qemu-api-macros/src/lib.rs >index a4bc5d01ee8..cf99ac04b8f 100644 >--- a/rust/qemu-api-macros/src/lib.rs >+++ b/rust/qemu-api-macros/src/lib.rs >@@ -3,8 +3,34 @@ > // SPDX-License-Identifier: GPL-2.0-or-later > > use proc_macro::TokenStream; >-use quote::quote; >-use syn::{parse_macro_input, DeriveInput}; >+use proc_macro2::Span; >+use quote::{quote, quote_spanned}; >+use syn::{ >+ parse_macro_input, parse_quote, punctuated::Punctuated, token::Comma, Data, DeriveInput, Field, >+ Fields, Ident, Type, Visibility, >+}; >+ >+struct CompileError(String, Span); >+ >+impl From<CompileError> for proc_macro2::TokenStream { >+ fn from(err: CompileError) -> Self { >+ let CompileError(msg, span) = err; >+ quote_spanned! { span => compile_error!(#msg); } >+ } >+} >+ >+fn is_c_repr(input: &DeriveInput, msg: &str) -> Result<(), CompileError> { >+ let expected = parse_quote! { #[repr(C)] }; >+ >+ if input.attrs.iter().any(|attr| attr == &expected) { >+ Ok(()) >+ } else { >+ Err(CompileError( >+ format!("#[repr(C)] required for {}", msg), >+ input.ident.span(), >+ )) >+ } >+} > > #[proc_macro_derive(Object)] > pub fn derive_object(input: TokenStream) -> TokenStream { >@@ -21,3 +47,48 @@ pub fn derive_object(input: TokenStream) -> TokenStream { > > TokenStream::from(expanded) > } >+ >+fn get_fields(input: &DeriveInput) -> Result<&Punctuated<Field, Comma>, CompileError> { >+ if let Data::Struct(s) = &input.data { >+ if let Fields::Named(fs) = &s.fields { >+ Ok(&fs.named) >+ } else { >+ Err(CompileError( >+ "Cannot generate offsets for unnamed fields.".to_string(), >+ input.ident.span(), >+ )) >+ } >+ } else { >+ Err(CompileError( >+ "Cannot generate offsets for union or enum.".to_string(), >+ input.ident.span(), >+ )) >+ } >+} >+ >+#[rustfmt::skip::macros(quote)] >+fn derive_offsets_or_error(input: DeriveInput) -> Result<proc_macro2::TokenStream, CompileError> { >+ is_c_repr(&input, "#[derive(offsets)]")?; >+ >+ let name = &input.ident; >+ let fields = get_fields(&input)?; >+ let field_names: Vec<&Ident> = fields.iter().map(|f| f.ident.as_ref().unwrap()).collect(); >+ let field_types: Vec<&Type> = fields.iter().map(|f| &f.ty).collect(); >+ let field_vis: Vec<&Visibility> = fields.iter().map(|f| &f.vis).collect(); >+ >+ Ok(quote! { >+ ::qemu_api::with_offsets! { >+ struct #name { >+ #(#field_vis #field_names: #field_types,)* >+ } >+ } >+ }) >+} >+ >+#[proc_macro_derive(offsets)] >+pub fn derive_offsets(input: TokenStream) -> TokenStream { >+ let input = parse_macro_input!(input as DeriveInput); >+ let expanded = derive_offsets_or_error(input).unwrap_or_else(Into::into); >+ >+ TokenStream::from(expanded) >+} >diff --git a/rust/qemu-api/Cargo.toml b/rust/qemu-api/Cargo.toml >index e092f61e8f3..cc716d75d46 100644 >--- a/rust/qemu-api/Cargo.toml >+++ b/rust/qemu-api/Cargo.toml >@@ -16,9 +16,13 @@ categories = [] > [dependencies] > qemu_api_macros = { path = "../qemu-api-macros" } > >+[build-dependencies] >+version_check = "~0.9" >+ > [features] > default = [] > allocator = [] > > [lints.rust] >-unexpected_cfgs = { level = "warn", check-cfg = ['cfg(MESON)', 'cfg(HAVE_GLIB_WITH_ALIGNED_ALLOC)'] } >+unexpected_cfgs = { level = "warn", check-cfg = ['cfg(MESON)', 'cfg(HAVE_GLIB_WITH_ALIGNED_ALLOC)', >+ 'cfg(has_offset_of)'] } >diff --git a/rust/qemu-api/build.rs b/rust/qemu-api/build.rs >index 419b154c2d2..20f8f718b90 100644 >--- a/rust/qemu-api/build.rs >+++ b/rust/qemu-api/build.rs >@@ -4,6 +4,8 @@ > > use std::path::Path; > >+use version_check as rustc; >+ > fn main() { > if !Path::new("src/bindings.rs").exists() { > panic!( >@@ -11,4 +13,11 @@ fn main() { > (`ninja bindings.rs`) and copy them to src/bindings.rs, or build through meson." > ); > } >+ >+ // Check for available rustc features >+ if rustc::is_min_version("1.77.0").unwrap_or(false) { >+ println!("cargo:rustc-cfg=has_offset_of"); >+ } >+ >+ println!("cargo:rerun-if-changed=build.rs"); > } >diff --git a/rust/qemu-api/meson.build b/rust/qemu-api/meson.build >index c950b008d59..6f637af7b1b 100644 >--- a/rust/qemu-api/meson.build >+++ b/rust/qemu-api/meson.build >@@ -1,3 +1,9 @@ >+_qemu_api_cfg = ['--cfg', 'MESON'] >+# _qemu_api_cfg += ['--cfg', 'feature="allocator"'] >+if rustc.version().version_compare('>=1.77.0') >+ _qemu_api_cfg += ['--cfg', 'has_offset_of'] >+endif >+ > _qemu_api_rs = static_library( > 'qemu_api', > structured_sources( >@@ -6,6 +12,7 @@ _qemu_api_rs = static_library( > 'src/c_str.rs', > 'src/definitions.rs', > 'src/device_class.rs', >+ 'src/offset_of.rs', > 'src/vmstate.rs', > 'src/zeroable.rs', > ], >@@ -13,10 +20,7 @@ _qemu_api_rs = static_library( > ), > override_options: ['rust_std=2021', 'build.rust_std=2021'], > rust_abi: 'rust', >- rust_args: [ >- '--cfg', 'MESON', >- # '--cfg', 'feature="allocator"', >- ], >+ rust_args: _qemu_api_cfg, > ) > > rust.test('rust-qemu-api-tests', _qemu_api_rs, >diff --git a/rust/qemu-api/src/device_class.rs b/rust/qemu-api/src/device_class.rs >index cb4573ca6ef..56608c7f7fc 100644 >--- a/rust/qemu-api/src/device_class.rs >+++ b/rust/qemu-api/src/device_class.rs >@@ -23,23 +23,23 @@ macro_rules! device_class_init { > > #[macro_export] > macro_rules! define_property { >- ($name:expr, $state:ty, $field:expr, $prop:expr, $type:expr, default = $defval:expr$(,)*) => { >+ ($name:expr, $state:ty, $field:ident, $prop:expr, $type:expr, default = $defval:expr$(,)*) => { > $crate::bindings::Property { > // use associated function syntax for type checking > name: ::std::ffi::CStr::as_ptr($name), > info: $prop, >- offset: ::core::mem::offset_of!($state, $field) as isize, >+ offset: $crate::offset_of!($state, $field) as isize, > set_default: true, > defval: $crate::bindings::Property__bindgen_ty_1 { u: $defval as u64 }, > ..$crate::zeroable::Zeroable::ZERO > } > }; >- ($name:expr, $state:ty, $field:expr, $prop:expr, $type:expr$(,)*) => { >+ ($name:expr, $state:ty, $field:ident, $prop:expr, $type:expr$(,)*) => { > $crate::bindings::Property { > // use associated function syntax for type checking > name: ::std::ffi::CStr::as_ptr($name), > info: $prop, >- offset: ::core::mem::offset_of!($state, $field) as isize, >+ offset: $crate::offset_of!($state, $field) as isize, > set_default: false, > ..$crate::zeroable::Zeroable::ZERO > } >diff --git a/rust/qemu-api/src/lib.rs b/rust/qemu-api/src/lib.rs >index e6bd953e10b..aa8d16ec94b 100644 >--- a/rust/qemu-api/src/lib.rs >+++ b/rust/qemu-api/src/lib.rs >@@ -32,6 +32,7 @@ unsafe impl Sync for bindings::VMStateInfo {} > pub mod c_str; > pub mod definitions; > pub mod device_class; >+pub mod offset_of; > pub mod vmstate; > pub mod zeroable; > >@@ -169,3 +170,6 @@ unsafe fn dealloc(&self, ptr: *mut u8, layout: Layout) { > } > } > } >+ >+#[cfg(has_offset_of)] >+pub use core::mem::offset_of; >diff --git a/rust/qemu-api/src/offset_of.rs b/rust/qemu-api/src/offset_of.rs >new file mode 100644 >index 00000000000..075e98f986b >--- /dev/null >+++ b/rust/qemu-api/src/offset_of.rs >@@ -0,0 +1,161 @@ >+// SPDX-License-Identifier: MIT >+ >+/// This macro provides the same functionality as `core::mem::offset_of`, >+/// except that only one level of field access is supported. The declaration >+/// of the struct must be wrapped with `with_offsets! { }`. >+/// >+/// It is needed because `offset_of!` was only stabilized in Rust 1.77. >+#[cfg(not(has_offset_of))] >+#[macro_export] >+macro_rules! offset_of { >+ ($Container:ty, $field:ident) => { >+ <$Container>::OFFSET_TO__.$field >+ }; >+} >+ >+/// A wrapper for struct declarations, that allows using `offset_of!` in >+/// versions of Rust prior to 1.77 >+#[macro_export] >+macro_rules! with_offsets { >+ // This method to generate field offset constants comes from: >+ // >+ // https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=10a22a9b8393abd7b541d8fc844bc0df >+ // >+ // used under MIT license with permission of Yandros aka Daniel Henry-Mantilla >+ ( >+ $(#[$struct_meta:meta])* >+ $struct_vis:vis >+ struct $StructName:ident { >+ $( >+ $(#[$field_meta:meta])* >+ $field_vis:vis >+ $field_name:ident : $field_ty:ty >+ ),* >+ $(,)? >+ } >+ ) => ( >+ #[cfg(not(has_offset_of))] >+ const _: () = { >+ struct StructOffsetsHelper<T>(std::marker::PhantomData<T>); >+ const END_OF_PREV_FIELD: usize = 0; >+ >+ // populate StructOffsetsHelper<T> with associated consts, >+ // one for each field >+ $crate::with_offsets! { >+ @struct $StructName >+ @names [ $($field_name)* ] >+ @tys [ $($field_ty ,)*] >+ } >+ >+ // now turn StructOffsetsHelper<T>'s consts into a single struct, >+ // applying field visibility. This provides better error messages >+ // than if offset_of! used StructOffsetsHelper::<T> directly. >+ pub >+ struct StructOffsets { >+ $( >+ $field_vis >+ $field_name: usize, >+ )* >+ } >+ impl $StructName { >+ pub >+ const OFFSET_TO__: StructOffsets = StructOffsets { >+ $( >+ $field_name: StructOffsetsHelper::<$StructName>::$field_name, >+ )* >+ }; >+ } >+ }; >+ ); >+ >+ ( >+ @struct $StructName:ident >+ @names [] >+ @tys [] >+ ) => (); >+ >+ ( >+ @struct $StructName:ident >+ @names [$field_name:ident $($other_names:tt)*] >+ @tys [$field_ty:ty , $($other_tys:tt)*] >+ ) => ( >+ #[allow(non_local_definitions)] >+ #[allow(clippy::modulo_one)] >+ impl StructOffsetsHelper<$StructName> { >+ #[allow(nonstandard_style)] >+ const $field_name: usize = { >+ const ALIGN: usize = std::mem::align_of::<$field_ty>(); >+ const TRAIL: usize = END_OF_PREV_FIELD % ALIGN; >+ END_OF_PREV_FIELD + (if TRAIL == 0 { 0usize } else { ALIGN - TRAIL }) >+ }; >+ } >+ const _: () = { >+ const END_OF_PREV_FIELD: usize = >+ StructOffsetsHelper::<$StructName>::$field_name + >+ std::mem::size_of::<$field_ty>() >+ ; >+ $crate::with_offsets! { >+ @struct $StructName >+ @names [$($other_names)*] >+ @tys [$($other_tys)*] >+ } >+ }; >+ ); >+} >+ >+#[cfg(test)] >+mod tests { >+ use crate::offset_of; >+ >+ #[repr(C)] >+ struct Foo { >+ a: u16, >+ b: u32, >+ c: u64, >+ d: u16, >+ } >+ >+ #[repr(C)] >+ struct Bar { >+ pub a: u16, >+ pub b: u64, >+ c: Foo, >+ d: u64, >+ } >+ >+ crate::with_offsets! { >+ #[repr(C)] >+ struct Bar { >+ pub a: u16, >+ pub b: u64, >+ c: Foo, >+ d: u64, >+ } >+ } >+ >+ #[repr(C)] >+ pub struct Baz { >+ b: u32, >+ a: u8, >+ } >+ crate::with_offsets! { >+ #[repr(C)] >+ pub struct Baz { >+ b: u32, >+ a: u8, >+ } >+ } >+ >+ #[test] >+ fn test_offset_of() { >+ const OFFSET_TO_C: usize = offset_of!(Bar, c); >+ >+ assert_eq!(offset_of!(Bar, a), 0); >+ assert_eq!(offset_of!(Bar, b), 8); >+ assert_eq!(OFFSET_TO_C, 16); >+ assert_eq!(offset_of!(Bar, d), 40); >+ >+ assert_eq!(offset_of!(Baz, b), 0); >+ assert_eq!(offset_of!(Baz, a), 4); >+ } >+} >diff --git a/rust/qemu-api/src/vmstate.rs b/rust/qemu-api/src/vmstate.rs >index 9c252ce18ef..bedcf1e8f39 100644 >--- a/rust/qemu-api/src/vmstate.rs >+++ b/rust/qemu-api/src/vmstate.rs >@@ -58,7 +58,7 @@ macro_rules! vmstate_single_test { > .as_bytes() > .as_ptr() as *const ::std::os::raw::c_char, > err_hint: ::core::ptr::null(), >- offset: ::core::mem::offset_of!($struct_name, $field_name), >+ offset: $crate::offset_of!($struct_name, $field_name), > size: $size, > start: 0, > num: 0, >@@ -135,7 +135,7 @@ macro_rules! vmstate_array { > .as_bytes() > .as_ptr() as *const ::std::os::raw::c_char, > err_hint: ::core::ptr::null(), >- offset: ::core::mem::offset_of!($struct_name, $field_name), >+ offset: $crate::offset_of!($struct_name, $field_name), > size: $size, > start: 0, > num: $length as _, >@@ -183,7 +183,7 @@ macro_rules! vmstate_struct_pointer_v { > .as_bytes() > .as_ptr() as *const ::std::os::raw::c_char, > err_hint: ::core::ptr::null(), >- offset: ::core::mem::offset_of!($struct_name, $field_name), >+ offset: $crate::offset_of!($struct_name, $field_name), > size: ::core::mem::size_of::<*const $type>(), > start: 0, > num: 0, >@@ -212,7 +212,7 @@ macro_rules! vmstate_array_of_pointer { > info: unsafe { $info }, > size: ::core::mem::size_of::<*const $type>(), > flags: VMStateFlags(VMStateFlags::VMS_ARRAY.0 | VMStateFlags::VMS_ARRAY_OF_POINTER.0), >- offset: ::core::mem::offset_of!($struct_name, $field_name), >+ offset: $crate::offset_of!($struct_name, $field_name), > err_hint: ::core::ptr::null(), > start: 0, > num_offset: 0, >@@ -241,7 +241,7 @@ macro_rules! vmstate_array_of_pointer_to_struct { > | VMStateFlags::VMS_STRUCT.0 > | VMStateFlags::VMS_ARRAY_OF_POINTER.0, > ), >- offset: ::core::mem::offset_of!($struct_name, $field_name), >+ offset: $crate::offset_of!($struct_name, $field_name), > err_hint: ::core::ptr::null(), > start: 0, > num_offset: 0, >diff --git a/rust/qemu-api/tests/tests.rs b/rust/qemu-api/tests/tests.rs >index 381ac84657b..7442f695646 100644 >--- a/rust/qemu-api/tests/tests.rs >+++ b/rust/qemu-api/tests/tests.rs >@@ -21,6 +21,7 @@ fn test_device_decl_macros() { > ..Zeroable::ZERO > }; > >+ #[derive(qemu_api_macros::offsets)] > #[repr(C)] > #[derive(qemu_api_macros::Object)] > pub struct DummyState { >diff --git a/subprojects/packagefiles/syn-2-rs/meson.build b/subprojects/packagefiles/syn-2-rs/meson.build >index a53335f3092..9f56ce1c24d 100644 >--- a/subprojects/packagefiles/syn-2-rs/meson.build >+++ b/subprojects/packagefiles/syn-2-rs/meson.build >@@ -24,6 +24,7 @@ _syn_rs = static_library( > '--cfg', 'feature="printing"', > '--cfg', 'feature="clone-impls"', > '--cfg', 'feature="proc-macro"', >+ '--cfg', 'feature="extra-traits"', > ], > dependencies: [ > quote_dep, >-- >2.47.0 > Compilation fails for me, on macos / rustc 1.80.1 error[E0369]: binary operation `==` cannot be applied to type `&Attribute` --> ../rust/qemu-api-macros/src/lib.rs:25:43 | 25 | if input.attrs.iter().any(|attr| attr == &expected) { | ---- ^^ --------- &_ | | | &Attribute error: aborting due to 1 previous error
> Compilation fails for me, on macos / rustc 1.80.1 > > error[E0369]: binary operation `==` cannot be applied to type > `&Attribute` > --> ../rust/qemu-api-macros/src/lib.rs:25:43 > | > 25 | if input.attrs.iter().any(|attr| attr == &expected) { > | ---- ^^ --------- &_ > | | > | &Attribute > > error: aborting due to 1 previous error You need "meson subprojects update --reset" as mentioned in the cover letter. Paolo
On Thu, 07 Nov 2024 11:31, Paolo Bonzini <pbonzini@redhat.com> wrote: >> Compilation fails for me, on macos / rustc 1.80.1 >> >> error[E0369]: binary operation `==` cannot be applied to type >> `&Attribute` >> --> ../rust/qemu-api-macros/src/lib.rs:25:43 >> | >> 25 | if input.attrs.iter().any(|attr| attr == &expected) { >> | ---- ^^ --------- &_ >> | | >> | &Attribute >> >> error: aborting due to 1 previous error > >You need "meson subprojects update --reset" as mentioned in >the cover letter. > >Paolo > I did already, also purged the build dir. I had to delete the cached syn subproject (`rm -rf subprojects/syn-2.0.66`) to make it work FYI
diff --git a/rust/Cargo.lock b/rust/Cargo.lock index 9f43b33e8b8..c0c6069247a 100644 --- a/rust/Cargo.lock +++ b/rust/Cargo.lock @@ -93,6 +93,7 @@ name = "qemu_api" version = "0.1.0" dependencies = [ "qemu_api_macros", + "version_check", ] [[package]] diff --git a/rust/hw/char/pl011/src/device.rs b/rust/hw/char/pl011/src/device.rs index 2d225d544de..bca727e37f0 100644 --- a/rust/hw/char/pl011/src/device.rs +++ b/rust/hw/char/pl011/src/device.rs @@ -55,7 +55,7 @@ impl DeviceId { } #[repr(C)] -#[derive(Debug, qemu_api_macros::Object)] +#[derive(Debug, qemu_api_macros::Object, qemu_api_macros::offsets)] /// PL011 Device Model in QEMU pub struct PL011State { pub parent_obj: SysBusDevice, diff --git a/rust/qemu-api-macros/Cargo.toml b/rust/qemu-api-macros/Cargo.toml index f8d6d03609f..a8f7377106b 100644 --- a/rust/qemu-api-macros/Cargo.toml +++ b/rust/qemu-api-macros/Cargo.toml @@ -19,4 +19,4 @@ proc-macro = true [dependencies] proc-macro2 = "1" quote = "1" -syn = "2" +syn = { version = "2", features = ["extra-traits"] } diff --git a/rust/qemu-api-macros/src/lib.rs b/rust/qemu-api-macros/src/lib.rs index a4bc5d01ee8..cf99ac04b8f 100644 --- a/rust/qemu-api-macros/src/lib.rs +++ b/rust/qemu-api-macros/src/lib.rs @@ -3,8 +3,34 @@ // SPDX-License-Identifier: GPL-2.0-or-later use proc_macro::TokenStream; -use quote::quote; -use syn::{parse_macro_input, DeriveInput}; +use proc_macro2::Span; +use quote::{quote, quote_spanned}; +use syn::{ + parse_macro_input, parse_quote, punctuated::Punctuated, token::Comma, Data, DeriveInput, Field, + Fields, Ident, Type, Visibility, +}; + +struct CompileError(String, Span); + +impl From<CompileError> for proc_macro2::TokenStream { + fn from(err: CompileError) -> Self { + let CompileError(msg, span) = err; + quote_spanned! { span => compile_error!(#msg); } + } +} + +fn is_c_repr(input: &DeriveInput, msg: &str) -> Result<(), CompileError> { + let expected = parse_quote! { #[repr(C)] }; + + if input.attrs.iter().any(|attr| attr == &expected) { + Ok(()) + } else { + Err(CompileError( + format!("#[repr(C)] required for {}", msg), + input.ident.span(), + )) + } +} #[proc_macro_derive(Object)] pub fn derive_object(input: TokenStream) -> TokenStream { @@ -21,3 +47,48 @@ pub fn derive_object(input: TokenStream) -> TokenStream { TokenStream::from(expanded) } + +fn get_fields(input: &DeriveInput) -> Result<&Punctuated<Field, Comma>, CompileError> { + if let Data::Struct(s) = &input.data { + if let Fields::Named(fs) = &s.fields { + Ok(&fs.named) + } else { + Err(CompileError( + "Cannot generate offsets for unnamed fields.".to_string(), + input.ident.span(), + )) + } + } else { + Err(CompileError( + "Cannot generate offsets for union or enum.".to_string(), + input.ident.span(), + )) + } +} + +#[rustfmt::skip::macros(quote)] +fn derive_offsets_or_error(input: DeriveInput) -> Result<proc_macro2::TokenStream, CompileError> { + is_c_repr(&input, "#[derive(offsets)]")?; + + let name = &input.ident; + let fields = get_fields(&input)?; + let field_names: Vec<&Ident> = fields.iter().map(|f| f.ident.as_ref().unwrap()).collect(); + let field_types: Vec<&Type> = fields.iter().map(|f| &f.ty).collect(); + let field_vis: Vec<&Visibility> = fields.iter().map(|f| &f.vis).collect(); + + Ok(quote! { + ::qemu_api::with_offsets! { + struct #name { + #(#field_vis #field_names: #field_types,)* + } + } + }) +} + +#[proc_macro_derive(offsets)] +pub fn derive_offsets(input: TokenStream) -> TokenStream { + let input = parse_macro_input!(input as DeriveInput); + let expanded = derive_offsets_or_error(input).unwrap_or_else(Into::into); + + TokenStream::from(expanded) +} diff --git a/rust/qemu-api/Cargo.toml b/rust/qemu-api/Cargo.toml index e092f61e8f3..cc716d75d46 100644 --- a/rust/qemu-api/Cargo.toml +++ b/rust/qemu-api/Cargo.toml @@ -16,9 +16,13 @@ categories = [] [dependencies] qemu_api_macros = { path = "../qemu-api-macros" } +[build-dependencies] +version_check = "~0.9" + [features] default = [] allocator = [] [lints.rust] -unexpected_cfgs = { level = "warn", check-cfg = ['cfg(MESON)', 'cfg(HAVE_GLIB_WITH_ALIGNED_ALLOC)'] } +unexpected_cfgs = { level = "warn", check-cfg = ['cfg(MESON)', 'cfg(HAVE_GLIB_WITH_ALIGNED_ALLOC)', + 'cfg(has_offset_of)'] } diff --git a/rust/qemu-api/build.rs b/rust/qemu-api/build.rs index 419b154c2d2..20f8f718b90 100644 --- a/rust/qemu-api/build.rs +++ b/rust/qemu-api/build.rs @@ -4,6 +4,8 @@ use std::path::Path; +use version_check as rustc; + fn main() { if !Path::new("src/bindings.rs").exists() { panic!( @@ -11,4 +13,11 @@ fn main() { (`ninja bindings.rs`) and copy them to src/bindings.rs, or build through meson." ); } + + // Check for available rustc features + if rustc::is_min_version("1.77.0").unwrap_or(false) { + println!("cargo:rustc-cfg=has_offset_of"); + } + + println!("cargo:rerun-if-changed=build.rs"); } diff --git a/rust/qemu-api/meson.build b/rust/qemu-api/meson.build index c950b008d59..6f637af7b1b 100644 --- a/rust/qemu-api/meson.build +++ b/rust/qemu-api/meson.build @@ -1,3 +1,9 @@ +_qemu_api_cfg = ['--cfg', 'MESON'] +# _qemu_api_cfg += ['--cfg', 'feature="allocator"'] +if rustc.version().version_compare('>=1.77.0') + _qemu_api_cfg += ['--cfg', 'has_offset_of'] +endif + _qemu_api_rs = static_library( 'qemu_api', structured_sources( @@ -6,6 +12,7 @@ _qemu_api_rs = static_library( 'src/c_str.rs', 'src/definitions.rs', 'src/device_class.rs', + 'src/offset_of.rs', 'src/vmstate.rs', 'src/zeroable.rs', ], @@ -13,10 +20,7 @@ _qemu_api_rs = static_library( ), override_options: ['rust_std=2021', 'build.rust_std=2021'], rust_abi: 'rust', - rust_args: [ - '--cfg', 'MESON', - # '--cfg', 'feature="allocator"', - ], + rust_args: _qemu_api_cfg, ) rust.test('rust-qemu-api-tests', _qemu_api_rs, diff --git a/rust/qemu-api/src/device_class.rs b/rust/qemu-api/src/device_class.rs index cb4573ca6ef..56608c7f7fc 100644 --- a/rust/qemu-api/src/device_class.rs +++ b/rust/qemu-api/src/device_class.rs @@ -23,23 +23,23 @@ macro_rules! device_class_init { #[macro_export] macro_rules! define_property { - ($name:expr, $state:ty, $field:expr, $prop:expr, $type:expr, default = $defval:expr$(,)*) => { + ($name:expr, $state:ty, $field:ident, $prop:expr, $type:expr, default = $defval:expr$(,)*) => { $crate::bindings::Property { // use associated function syntax for type checking name: ::std::ffi::CStr::as_ptr($name), info: $prop, - offset: ::core::mem::offset_of!($state, $field) as isize, + offset: $crate::offset_of!($state, $field) as isize, set_default: true, defval: $crate::bindings::Property__bindgen_ty_1 { u: $defval as u64 }, ..$crate::zeroable::Zeroable::ZERO } }; - ($name:expr, $state:ty, $field:expr, $prop:expr, $type:expr$(,)*) => { + ($name:expr, $state:ty, $field:ident, $prop:expr, $type:expr$(,)*) => { $crate::bindings::Property { // use associated function syntax for type checking name: ::std::ffi::CStr::as_ptr($name), info: $prop, - offset: ::core::mem::offset_of!($state, $field) as isize, + offset: $crate::offset_of!($state, $field) as isize, set_default: false, ..$crate::zeroable::Zeroable::ZERO } diff --git a/rust/qemu-api/src/lib.rs b/rust/qemu-api/src/lib.rs index e6bd953e10b..aa8d16ec94b 100644 --- a/rust/qemu-api/src/lib.rs +++ b/rust/qemu-api/src/lib.rs @@ -32,6 +32,7 @@ unsafe impl Sync for bindings::VMStateInfo {} pub mod c_str; pub mod definitions; pub mod device_class; +pub mod offset_of; pub mod vmstate; pub mod zeroable; @@ -169,3 +170,6 @@ unsafe fn dealloc(&self, ptr: *mut u8, layout: Layout) { } } } + +#[cfg(has_offset_of)] +pub use core::mem::offset_of; diff --git a/rust/qemu-api/src/offset_of.rs b/rust/qemu-api/src/offset_of.rs new file mode 100644 index 00000000000..075e98f986b --- /dev/null +++ b/rust/qemu-api/src/offset_of.rs @@ -0,0 +1,161 @@ +// SPDX-License-Identifier: MIT + +/// This macro provides the same functionality as `core::mem::offset_of`, +/// except that only one level of field access is supported. The declaration +/// of the struct must be wrapped with `with_offsets! { }`. +/// +/// It is needed because `offset_of!` was only stabilized in Rust 1.77. +#[cfg(not(has_offset_of))] +#[macro_export] +macro_rules! offset_of { + ($Container:ty, $field:ident) => { + <$Container>::OFFSET_TO__.$field + }; +} + +/// A wrapper for struct declarations, that allows using `offset_of!` in +/// versions of Rust prior to 1.77 +#[macro_export] +macro_rules! with_offsets { + // This method to generate field offset constants comes from: + // + // https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=10a22a9b8393abd7b541d8fc844bc0df + // + // used under MIT license with permission of Yandros aka Daniel Henry-Mantilla + ( + $(#[$struct_meta:meta])* + $struct_vis:vis + struct $StructName:ident { + $( + $(#[$field_meta:meta])* + $field_vis:vis + $field_name:ident : $field_ty:ty + ),* + $(,)? + } + ) => ( + #[cfg(not(has_offset_of))] + const _: () = { + struct StructOffsetsHelper<T>(std::marker::PhantomData<T>); + const END_OF_PREV_FIELD: usize = 0; + + // populate StructOffsetsHelper<T> with associated consts, + // one for each field + $crate::with_offsets! { + @struct $StructName + @names [ $($field_name)* ] + @tys [ $($field_ty ,)*] + } + + // now turn StructOffsetsHelper<T>'s consts into a single struct, + // applying field visibility. This provides better error messages + // than if offset_of! used StructOffsetsHelper::<T> directly. + pub + struct StructOffsets { + $( + $field_vis + $field_name: usize, + )* + } + impl $StructName { + pub + const OFFSET_TO__: StructOffsets = StructOffsets { + $( + $field_name: StructOffsetsHelper::<$StructName>::$field_name, + )* + }; + } + }; + ); + + ( + @struct $StructName:ident + @names [] + @tys [] + ) => (); + + ( + @struct $StructName:ident + @names [$field_name:ident $($other_names:tt)*] + @tys [$field_ty:ty , $($other_tys:tt)*] + ) => ( + #[allow(non_local_definitions)] + #[allow(clippy::modulo_one)] + impl StructOffsetsHelper<$StructName> { + #[allow(nonstandard_style)] + const $field_name: usize = { + const ALIGN: usize = std::mem::align_of::<$field_ty>(); + const TRAIL: usize = END_OF_PREV_FIELD % ALIGN; + END_OF_PREV_FIELD + (if TRAIL == 0 { 0usize } else { ALIGN - TRAIL }) + }; + } + const _: () = { + const END_OF_PREV_FIELD: usize = + StructOffsetsHelper::<$StructName>::$field_name + + std::mem::size_of::<$field_ty>() + ; + $crate::with_offsets! { + @struct $StructName + @names [$($other_names)*] + @tys [$($other_tys)*] + } + }; + ); +} + +#[cfg(test)] +mod tests { + use crate::offset_of; + + #[repr(C)] + struct Foo { + a: u16, + b: u32, + c: u64, + d: u16, + } + + #[repr(C)] + struct Bar { + pub a: u16, + pub b: u64, + c: Foo, + d: u64, + } + + crate::with_offsets! { + #[repr(C)] + struct Bar { + pub a: u16, + pub b: u64, + c: Foo, + d: u64, + } + } + + #[repr(C)] + pub struct Baz { + b: u32, + a: u8, + } + crate::with_offsets! { + #[repr(C)] + pub struct Baz { + b: u32, + a: u8, + } + } + + #[test] + fn test_offset_of() { + const OFFSET_TO_C: usize = offset_of!(Bar, c); + + assert_eq!(offset_of!(Bar, a), 0); + assert_eq!(offset_of!(Bar, b), 8); + assert_eq!(OFFSET_TO_C, 16); + assert_eq!(offset_of!(Bar, d), 40); + + assert_eq!(offset_of!(Baz, b), 0); + assert_eq!(offset_of!(Baz, a), 4); + } +} diff --git a/rust/qemu-api/src/vmstate.rs b/rust/qemu-api/src/vmstate.rs index 9c252ce18ef..bedcf1e8f39 100644 --- a/rust/qemu-api/src/vmstate.rs +++ b/rust/qemu-api/src/vmstate.rs @@ -58,7 +58,7 @@ macro_rules! vmstate_single_test { .as_bytes() .as_ptr() as *const ::std::os::raw::c_char, err_hint: ::core::ptr::null(), - offset: ::core::mem::offset_of!($struct_name, $field_name), + offset: $crate::offset_of!($struct_name, $field_name), size: $size, start: 0, num: 0, @@ -135,7 +135,7 @@ macro_rules! vmstate_array { .as_bytes() .as_ptr() as *const ::std::os::raw::c_char, err_hint: ::core::ptr::null(), - offset: ::core::mem::offset_of!($struct_name, $field_name), + offset: $crate::offset_of!($struct_name, $field_name), size: $size, start: 0, num: $length as _, @@ -183,7 +183,7 @@ macro_rules! vmstate_struct_pointer_v { .as_bytes() .as_ptr() as *const ::std::os::raw::c_char, err_hint: ::core::ptr::null(), - offset: ::core::mem::offset_of!($struct_name, $field_name), + offset: $crate::offset_of!($struct_name, $field_name), size: ::core::mem::size_of::<*const $type>(), start: 0, num: 0, @@ -212,7 +212,7 @@ macro_rules! vmstate_array_of_pointer { info: unsafe { $info }, size: ::core::mem::size_of::<*const $type>(), flags: VMStateFlags(VMStateFlags::VMS_ARRAY.0 | VMStateFlags::VMS_ARRAY_OF_POINTER.0), - offset: ::core::mem::offset_of!($struct_name, $field_name), + offset: $crate::offset_of!($struct_name, $field_name), err_hint: ::core::ptr::null(), start: 0, num_offset: 0, @@ -241,7 +241,7 @@ macro_rules! vmstate_array_of_pointer_to_struct { | VMStateFlags::VMS_STRUCT.0 | VMStateFlags::VMS_ARRAY_OF_POINTER.0, ), - offset: ::core::mem::offset_of!($struct_name, $field_name), + offset: $crate::offset_of!($struct_name, $field_name), err_hint: ::core::ptr::null(), start: 0, num_offset: 0, diff --git a/rust/qemu-api/tests/tests.rs b/rust/qemu-api/tests/tests.rs index 381ac84657b..7442f695646 100644 --- a/rust/qemu-api/tests/tests.rs +++ b/rust/qemu-api/tests/tests.rs @@ -21,6 +21,7 @@ fn test_device_decl_macros() { ..Zeroable::ZERO }; + #[derive(qemu_api_macros::offsets)] #[repr(C)] #[derive(qemu_api_macros::Object)] pub struct DummyState { diff --git a/subprojects/packagefiles/syn-2-rs/meson.build b/subprojects/packagefiles/syn-2-rs/meson.build index a53335f3092..9f56ce1c24d 100644 --- a/subprojects/packagefiles/syn-2-rs/meson.build +++ b/subprojects/packagefiles/syn-2-rs/meson.build @@ -24,6 +24,7 @@ _syn_rs = static_library( '--cfg', 'feature="printing"', '--cfg', 'feature="clone-impls"', '--cfg', 'feature="proc-macro"', + '--cfg', 'feature="extra-traits"', ], dependencies: [ quote_dep,