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bazel / crubit / dfcb19c4d11eac86fe8a240d86c90c17f287c016 / . / cc_bindings_from_rs / bindings.rs
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// Part of the Crubit project, under the Apache License v2.0 with LLVM
// Exceptions. See /LICENSE for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
#![feature(rustc_private)]
#![deny(rustc::internal)]
extern crate rustc_attr;
extern crate rustc_hir;
extern crate rustc_infer;
extern crate rustc_middle;
extern crate rustc_span;
extern crate rustc_target;
extern crate rustc_trait_selection;
extern crate rustc_type_ir;
use arc_anyhow::{Context, Error, Result};
use code_gen_utils::{
escape_non_identifier_chars, format_cc_ident, format_cc_includes, make_rs_ident, CcInclude,
NamespaceQualifier,
};
use error_report::{anyhow, bail, ensure, ErrorReporting};
use itertools::Itertools;
use proc_macro2::{Ident, Literal, TokenStream};
use quote::{format_ident, quote, ToTokens};
use rustc_attr::find_deprecation;
use rustc_hir::def::{DefKind, Res};
use rustc_hir::{AssocItemKind, HirId, Item, ItemKind, Node, Safety, UseKind, UsePath};
use rustc_infer::infer::TyCtxtInferExt;
use rustc_middle::dep_graph::DepContext;
use rustc_middle::mir::Mutability;
use rustc_middle::ty::{self, Ty, TyCtxt}; // See <internal link>/ty.html#import-conventions
use rustc_span::def_id::{DefId, LocalDefId, LOCAL_CRATE};
use rustc_span::symbol::{kw, sym, Symbol};
use rustc_target::abi::{
Abi, AddressSpace, FieldsShape, Integer, Layout, Pointer, Primitive, Scalar,
};
use rustc_trait_selection::infer::InferCtxtExt;
use rustc_type_ir::RegionKind;
use std::collections::{BTreeSet, HashMap, HashSet};
use std::hash::{Hash, Hasher};
use std::iter::once;
use std::ops::AddAssign;
use std::rc::Rc;
use std::slice;
memoized::query_group! {
trait BindingsGenerator<'tcx> {
/// Compilation context for the crate that the bindings should be generated
/// for.
#[input]
fn tcx(&self) -> TyCtxt<'tcx>;
/// Format specifier for `#include` Crubit C++ support library headers,
/// using `{header}` as the place holder. Example:
/// `<crubit/support/{header}>` results in `#include
/// <crubit/support/hdr.h>`.
#[input]
fn crubit_support_path_format(&self) -> Rc<str>;
/// A map from a crate name to the include paths of the corresponding C++
/// headers This is used when formatting a type exported from another
/// crate.
// TODO(b/271857814): A crate name might not be globally unique - the key needs to also cover
// a "hash" of the crate version and compilation flags.
#[input]
fn crate_name_to_include_paths(&self) -> Rc<HashMap<Rc<str>, Vec<CcInclude>>>;
/// Error collector for generating reports of errors encountered during the generation of bindings.
#[input]
fn errors(&self) -> Rc<dyn ErrorReporting>;
#[input]
fn no_thunk_name_mangling(&self) -> bool;
// TODO(b/262878759): Provide a set of enabled/disabled Crubit features.
#[input]
fn _features(&self) -> ();
fn support_header(&self, suffix: &'tcx str) -> CcInclude;
fn repr_attrs(&self, did: DefId) -> Rc<[rustc_attr::ReprAttr]>;
fn format_ty_for_cc(
&self,
ty: SugaredTy<'tcx>,
location: TypeLocation,
) -> Result<CcSnippet>;
fn format_default_ctor(
&self,
core: Rc<AdtCoreBindings<'tcx>>,
) -> Result<ApiSnippets, ApiSnippets>;
fn format_copy_ctor_and_assignment_operator(
&self,
core: Rc<AdtCoreBindings<'tcx>>,
) -> Result<ApiSnippets, ApiSnippets>;
fn format_move_ctor_and_assignment_operator(
&self,
core: Rc<AdtCoreBindings<'tcx>>,
) -> Result<ApiSnippets, ApiSnippets>;
fn format_item(&self, def_id: LocalDefId) -> Result<Option<ApiSnippets>>;
fn format_fn(&self, local_def_id: LocalDefId) -> Result<ApiSnippets>;
fn format_adt_core(&self, def_id: DefId) -> Result<Rc<AdtCoreBindings<'tcx>>>;
}
pub struct Database;
}
fn support_header<'tcx>(db: &dyn BindingsGenerator<'tcx>, suffix: &'tcx str) -> CcInclude {
CcInclude::support_lib_header(db.crubit_support_path_format(), suffix.into())
}
pub struct Output {
pub h_body: TokenStream,
pub rs_body: TokenStream,
}
pub fn generate_bindings(db: &Database) -> Result<Output> {
let tcx = db.tcx();
let top_comment = {
let crate_name = tcx.crate_name(LOCAL_CRATE);
let txt = format!(
"Automatically @generated C++ bindings for the following Rust crate:\n\
{crate_name}"
);
quote! { __COMMENT__ #txt __NEWLINE__ }
};
let Output { h_body, rs_body } = format_crate(db).unwrap_or_else(|err| {
let txt = format!("Failed to generate bindings for the crate: {err}");
let src = quote! { __COMMENT__ #txt };
Output { h_body: src.clone(), rs_body: src }
});
let h_body = quote! {
#top_comment
// TODO(b/251445877): Replace `#pragma once` with include guards.
__HASH_TOKEN__ pragma once __NEWLINE__
__NEWLINE__
#h_body
};
let rs_body = quote! {
#top_comment
// `rust_builtin_type_abi_assumptions.md` documents why the generated
// bindings need to relax the `improper_ctypes_definitions` warning
// for `char` (and possibly for other built-in types in the future).
#![allow(improper_ctypes_definitions)] __NEWLINE__
__NEWLINE__
#rs_body
};
Ok(Output { h_body, rs_body })
}
#[derive(Clone, Debug, Default)]
struct CcPrerequisites {
/// Set of `#include`s that a `CcSnippet` depends on. For example if
/// `CcSnippet::tokens` expands to `std::int32_t`, then `includes`
/// need to cover the `#include <cstdint>`.
includes: BTreeSet<CcInclude>,
/// Set of local definitions that a `CcSnippet` depends on. For example if
/// `CcSnippet::tokens` expands to `void foo(S s) { ... }` then the
/// definition of `S` should have appeared earlier - in this case `defs`
/// will include the `LocalDefId` corresponding to `S`. Note that the
/// definition of `S` is covered by `ApiSnippets::main_api` (i.e. the
/// predecessor of a toposort edge is `ApiSnippets::main_api` - it is not
/// possible to depend on `ApiSnippets::cc_details`).
defs: HashSet<LocalDefId>,
/// Set of forward declarations that a `CcSnippet` depends on. For example
/// if `CcSnippet::tokens` expands to `void foo(S* s)` then a forward
/// declaration of `S` should have appeared earlier - in this case
/// `fwd_decls` will include the `LocalDefId` corresponding to `S`.
/// Note that in this particular example the *definition* of `S` does
/// *not* need to appear earlier (and therefore `defs` will *not*
/// contain `LocalDefId` corresponding to `S`).
fwd_decls: HashSet<LocalDefId>,
}
impl CcPrerequisites {
#[cfg(test)]
fn is_empty(&self) -> bool {
let &Self { ref includes, ref defs, ref fwd_decls } = self;
includes.is_empty() && defs.is_empty() && fwd_decls.is_empty()
}
/// Weakens all dependencies to only require a forward declaration. Example
/// usage scenarios:
/// - Computing prerequisites of pointer types (the pointee type can just be
/// forward-declared),
/// - Computing prerequisites of function declarations (parameter types and
/// return type can just be forward-declared).
fn move_defs_to_fwd_decls(&mut self) {
self.fwd_decls.extend(std::mem::take(&mut self.defs))
}
}
impl AddAssign for CcPrerequisites {
fn add_assign(&mut self, rhs: Self) {
let Self { mut includes, defs, fwd_decls } = rhs;
// `BTreeSet::append` is used because it _seems_ to be more efficient than
// calling `extend`. This is because `extend` takes an iterator
// (processing each `rhs` include one-at-a-time) while `append` steals
// the whole backing data store from `rhs.includes`. OTOH, this is a bit
// speculative, since the (expected / guessed) performance difference is
// not documented at
// https://doc.rust-lang.org/std/collections/struct.BTreeSet.html#method.append
self.includes.append(&mut includes);
self.defs.extend(defs);
self.fwd_decls.extend(fwd_decls);
}
}
#[derive(Clone, Debug, Default)]
struct CcSnippet {
tokens: TokenStream,
prereqs: CcPrerequisites,
}
impl CcSnippet {
/// Consumes `self` and returns its `tokens`, while preserving
/// its `prereqs` into `prereqs_accumulator`.
fn into_tokens(self, prereqs_accumulator: &mut CcPrerequisites) -> TokenStream {
let Self { tokens, prereqs } = self;
*prereqs_accumulator += prereqs;
tokens
}
/// Creates a new CcSnippet (with no `CcPrerequisites`).
fn new(tokens: TokenStream) -> Self {
Self { tokens, ..Default::default() }
}
/// Creates a CcSnippet that depends on a single `CcInclude`.
fn with_include(tokens: TokenStream, include: CcInclude) -> Self {
let mut prereqs = CcPrerequisites::default();
prereqs.includes.insert(include);
Self { tokens, prereqs }
}
}
impl AddAssign for CcSnippet {
fn add_assign(&mut self, rhs: Self) {
self.tokens.extend(rhs.into_tokens(&mut self.prereqs));
}
}
/// Represents the fully qualified name of a Rust item (e.g. of a `struct` or a
/// function).
struct FullyQualifiedName {
/// Name of the crate that defines the item.
/// For example, this would be `std` for `std::cmp::Ordering`.
krate: Symbol,
/// Path to the module where the item is located.
/// For example, this would be `cmp` for `std::cmp::Ordering`.
/// The path may contain multiple modules - e.g. `foo::bar::baz`.
mod_path: NamespaceQualifier,
/// Name of the item.
/// For example, this would be:
/// * `Some("Ordering")` for `std::cmp::Ordering`.
/// * `None` for `ItemKind::Use` - e.g.: `use submodule::*`
name: Option<Symbol>,
/// The fully-qualified C++ type to use for this, if this was originally a
/// C++ type.
///
/// For example, if a type has `#[__crubit::annotate(cpp_type="x::y")]`,
/// then cpp_type will be `Some(x::y)`.
cpp_type: Option<Symbol>,
/// The C++ name to use for the symbol.
///
/// For example, the following struct
/// ```
/// #[__crubit::annotate(cpp_name="Bar")]
/// struct Foo { ... }
/// ```
/// will be generated as a C++ struct named `Bar` instead of `Foo`.
cpp_name: Option<Symbol>,
}
impl FullyQualifiedName {
/// Computes a `FullyQualifiedName` for `def_id`.
///
/// May panic if `def_id` is an invalid id.
// TODO(b/259724276): This function's results should be memoized.
fn new(tcx: TyCtxt, def_id: DefId) -> Self {
let krate = tcx.crate_name(def_id.krate);
// Crash OK: these attributes are introduced by crubit itself, and "should
// never" be malformed.
let attributes = crubit_attr::get(tcx, def_id).unwrap();
let cpp_type = attributes.cpp_type;
let mut full_path = tcx.def_path(def_id).data; // mod_path + name
let name = full_path.pop().expect("At least the item's name should be present");
let name = name.data.get_opt_name();
let cpp_name = attributes.cpp_name.map(|s| Symbol::intern(s.as_str())).or(name);
let mod_path = NamespaceQualifier::new(
full_path
.into_iter()
.filter_map(|p| p.data.get_opt_name())
.map(|s| Rc::<str>::from(s.as_str())),
);
Self { krate, mod_path, name, cpp_type, cpp_name }
}
fn format_for_cc(&self) -> Result<TokenStream> {
if let Some(path) = self.cpp_type {
let path = format_cc_ident(path.as_str())?;
return Ok(quote! {#path});
}
let name = self.cpp_name.as_ref().unwrap_or_else(|| {
self.name.as_ref().expect("`format_for_cc` can't be called on name-less item kinds")
});
let top_level_ns = format_cc_ident(self.krate.as_str())?;
let ns_path = self.mod_path.format_for_cc()?;
let name = format_cc_ident(name.as_str())?;
Ok(quote! { :: #top_level_ns :: #ns_path #name })
}
fn format_for_rs(&self) -> TokenStream {
let name =
self.name.as_ref().expect("`format_for_rs` can't be called on name-less item kinds");
let krate = make_rs_ident(self.krate.as_str());
let mod_path = self.mod_path.format_for_rs();
let name = make_rs_ident(name.as_str());
quote! { :: #krate :: #mod_path #name }
}
}
mod sugared_ty {
use super::*;
/// A Ty, optionally attached to its `hir::Ty` counterpart, if any.
///
/// The rustc_hir::Ty is used only for detecting type aliases (or other
/// optional sugar), unrelated to the actual concrete type. It
/// necessarily disappears if, for instance, the type is plugged in from
/// a generic. There's no way to tell, in the bindings for
/// Vec<c_char>::len(), that `T` came from the type alias
/// `c_char`, instead of a plain `i8` or `u8`.
#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
pub(super) struct SugaredTy<'tcx> {
mid: Ty<'tcx>,
/// The HirId of the corresponding HirTy. We store it as a HirId so that
/// it's hashable.
hir_id: Option<HirId>,
}
impl<'tcx> std::fmt::Display for SugaredTy<'tcx> {
fn fmt(&self, f: &mut std::fmt::Formatter) -> Result<(), std::fmt::Error> {
std::fmt::Display::fmt(&self.mid, f)
}
}
impl<'tcx> SugaredTy<'tcx> {
pub fn new(mid: Ty<'tcx>, hir: Option<&rustc_hir::Ty<'tcx>>) -> Self {
Self { mid, hir_id: hir.map(|hir| hir.hir_id) }
}
/// Returns the rustc_middle::Ty this represents.
pub fn mid(&self) -> Ty<'tcx> {
self.mid
}
/// Returns the rustc_hir::Ty this represents, if any.
pub fn hir(&self, db: &dyn BindingsGenerator<'tcx>) -> Option<&'tcx rustc_hir::Ty<'tcx>> {
let hir_id = self.hir_id?;
let hir_ty = db.tcx().hir_node(hir_id).expect_ty();
debug_assert_eq!(hir_ty.hir_id, hir_id);
Some(hir_ty)
}
}
}
use sugared_ty::SugaredTy;
/// Whether functions using `extern "C"` ABI can safely handle values of type
/// `ty` (e.g. when passing by value arguments or return values of such type).
fn is_c_abi_compatible_by_value(ty: Ty) -> bool {
match ty.kind() {
// `improper_ctypes_definitions` warning doesn't complain about the following types:
ty::TyKind::Bool |
ty::TyKind::Float{..} |
ty::TyKind::Int{..} |
ty::TyKind::Uint{..} |
ty::TyKind::Never |
ty::TyKind::RawPtr{..} |
ty::TyKind::Ref{..} |
ty::TyKind::FnPtr{..} => true,
ty::TyKind::Tuple(types) if types.len() == 0 => true,
// Crubit assumes that `char` is compatible with a certain `extern "C"` ABI.
// See `rust_builtin_type_abi_assumptions.md` for more details.
ty::TyKind::Char => true,
// TODO(b/271016831): When launching `&[T]` (not just `*const T`), consider returning
// `true` for `TyKind::Ref` and document the rationale for such decision - maybe
// something like this will be sufficient:
// - In general `TyKind::Ref` should have the same ABI as `TyKind::RawPtr`
// - References to slices (`&[T]`) or strings (`&str`) rely on assumptions
// spelled out in `rust_builtin_type_abi_assumptions.md`.
ty::TyKind::Slice{..} => false,
// Crubit's C++ bindings for tuples, structs, and other ADTs may not preserve
// their ABI (even if they *do* preserve their memory layout). For example:
// - In System V ABI replacing a field with a fixed-length array of bytes may affect
// whether the whole struct is classified as an integer and passed in general purpose
// registers VS classified as SSE2 and passed in floating-point registers like xmm0).
// See also b/270454629.
// - To replicate field offsets, Crubit may insert explicit padding fields. These
// extra fields may also impact the ABI of the generated bindings.
//
// TODO(lukasza): In the future, some additional performance gains may be realized by
// returning `true` in a few limited cases (this may require additional complexity to
// ensure that `format_adt` never injects explicit padding into such structs):
// - `#[repr(C)]` structs and unions,
// - `#[repr(transparent)]` struct that wraps an ABI-safe type,
// - Discriminant-only enums (b/259984090).
ty::TyKind::Tuple{..} | // An empty tuple (`()` - the unit type) is handled above.
ty::TyKind::Adt{..} => false,
// These kinds of reference-related types are not implemented yet - `is_c_abi_compatible_by_value`
// should never need to handle them, because `format_ty_for_cc` fails for such types.
ty::TyKind::Str |
ty::TyKind::Array{..} => unimplemented!(),
// `format_ty_for_cc` is expected to fail for other kinds of types
// and therefore `is_c_abi_compatible_by_value` should never be called for
// these other types
_ => unimplemented!(),
}
}
/// Location where a type is used.
#[derive(PartialEq, Eq, Hash, Copy, Clone, Debug)]
enum TypeLocation {
/// The top-level return type.
///
/// The "top-level" part can be explained by looking at an example of `fn
/// foo() -> *const T`:
/// - The top-level return type `*const T` is in the `FnReturn` location
/// - The nested pointee type `T` is in the `Other` location
FnReturn,
/// The top-level parameter type.
///
/// The "top-level" part can be explained by looking at an example of:
/// `fn foo(param: *const T)`:
/// - The top-level parameter type `*const T` is in the `FnParam` location
/// - The nested pointee type `T` is in the `Other` location
// TODO(b/278141494, b/278141418): Once `const` and `static` items are supported,
// we may want to apply parameter-like formatting to their types (e.g. have
// `format_ty_for_cc` emit `T&` rather than `T*`).
FnParam,
/// Other location (e.g. pointee type, field type, etc.).
Other,
}
fn format_pointer_or_reference_ty_for_cc<'tcx>(
db: &dyn BindingsGenerator<'tcx>,
pointee: SugaredTy<'tcx>,
mutability: rustc_middle::mir::Mutability,
pointer_sigil: TokenStream,
) -> Result<CcSnippet> {
let tcx = db.tcx();
let const_qualifier = match mutability {
Mutability::Mut => quote! {},
Mutability::Not => quote! { const },
};
if pointee.mid().is_c_void(tcx) {
return Ok(CcSnippet { tokens: quote! { #const_qualifier void* }, ..Default::default() });
}
let CcSnippet { tokens, mut prereqs } = db.format_ty_for_cc(pointee, TypeLocation::Other)?;
prereqs.move_defs_to_fwd_decls();
Ok(CcSnippet { prereqs, tokens: quote! { #tokens #const_qualifier #pointer_sigil } })
}
fn format_slice_pointer_for_cc<'tcx>(
db: &dyn BindingsGenerator<'tcx>,
slice_ty: SugaredTy<'tcx>,
mutability: rustc_middle::mir::Mutability,
) -> Result<CcSnippet> {
let const_qualifier = match mutability {
Mutability::Mut => quote! {},
Mutability::Not => quote! { const },
};
let CcSnippet { tokens, mut prereqs } =
db.format_ty_for_cc(slice_ty, TypeLocation::Other).with_context(|| {
format!("Failed to format the inner type of the slice type `{slice_ty}`")
})?;
prereqs.includes.insert(db.support_header("rs_std/slice_ref.h"));
Ok(CcSnippet {
prereqs,
tokens: quote! {
rs_std::SliceRef<
#const_qualifier #tokens
>
},
})
}
/// Checks that `ty` has the same ABI as `rs_std::SliceRef`.
fn check_slice_layout<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) {
// Check the assumption from `rust_builtin_type_abi_assumptions.md` that Rust's
// slice has the same ABI as `rs_std::SliceRef`.
let layout = tcx
.layout_of(ty::ParamEnv::empty().and(ty))
.expect("`layout_of` is expected to succeed for `{ty}` type")
.layout;
assert_eq!(8, layout.align().abi.bytes());
assert_eq!(16, layout.size().bytes());
assert!(matches!(
layout.abi(),
Abi::ScalarPair(
Scalar::Initialized { value: Pointer(AddressSpace(_)), .. },
Scalar::Initialized {
value: Primitive::Int(Integer::I64, /* signedness = */ false),
..
}
)
));
}
/// Formats `ty` into a `CcSnippet` that represents how the type should be
/// spelled in a C++ declaration of a function parameter or field.
fn format_ty_for_cc<'tcx>(
db: &dyn BindingsGenerator<'tcx>,
ty: SugaredTy<'tcx>,
location: TypeLocation,
) -> Result<CcSnippet> {
let tcx = db.tcx();
fn cstdint(tokens: TokenStream) -> CcSnippet {
CcSnippet::with_include(tokens, CcInclude::cstdint())
}
fn keyword(tokens: TokenStream) -> CcSnippet {
CcSnippet::new(tokens)
}
if let Some(alias) = format_core_alias_for_cc(db, ty) {
return Ok(alias);
}
Ok(match ty.mid().kind() {
ty::TyKind::Never => match location {
TypeLocation::FnReturn => keyword(quote! { void }),
_ => {
// TODO(b/254507801): Maybe translate into `crubit::Never`?
bail!("The never type `!` is only supported as a return type (b/254507801)");
}
},
ty::TyKind::Tuple(types) => {
if types.len() == 0 {
match location {
TypeLocation::FnReturn => keyword(quote! { void }),
_ => {
// TODO(b/254507801): Maybe translate into `crubit::Unit`?
bail!("`()` / `void` is only supported as a return type (b/254507801)");
}
}
} else {
// TODO(b/254099023): Add support for tuples.
bail!("Tuples are not supported yet: {} (b/254099023)", ty);
}
}
// https://rust-lang.github.io/unsafe-code-guidelines/layout/scalars.html#bool documents
// that "Rust's bool has the same layout as C17's _Bool". The details (e.g. size, valid
// bit patterns) are implementation-defined, but this is okay, because `bool` in the
// `extern "C"` functions in the generated `..._cc_api.h` will also be the C17's _Bool.
ty::TyKind::Bool => keyword(quote! { bool }),
// https://rust-lang.github.io/unsafe-code-guidelines/layout/scalars.html#fixed-width-floating-point-types
// documents that "When the platforms' "math.h" header defines the __STDC_IEC_559__ macro,
// Rust's floating-point types are safe to use directly in C FFI where the appropriate C
// types are expected (f32 for float, f64 for double)."
//
// TODO(b/255768062): Generated bindings should explicitly check `__STDC_IEC_559__`
ty::TyKind::Float(ty::FloatTy::F32) => keyword(quote! { float }),
ty::TyKind::Float(ty::FloatTy::F64) => keyword(quote! { double }),
// ABI compatibility and other details are described in the doc comments in
// `crubit/support/rs_std/rs_char.h` and `crubit/support/rs_std/char_test.cc` (search for
// "Layout tests").
ty::TyKind::Char => {
// Asserting that the target architecture meets the assumption from Crubit's
// `rust_builtin_type_abi_assumptions.md` - we assume that Rust's `char` has the
// same ABI as `u32`.
let layout = tcx
.layout_of(ty::ParamEnv::empty().and(ty.mid()))
.expect("`layout_of` is expected to succeed for the builtin `char` type")
.layout;
assert_eq!(4, layout.align().abi.bytes());
assert_eq!(4, layout.size().bytes());
assert!(matches!(
layout.abi(),
Abi::Scalar(Scalar::Initialized {
value: Primitive::Int(Integer::I32, /* signedness = */ false),
..
})
));
CcSnippet::with_include(
quote! { rs_std::rs_char },
db.support_header("rs_std/rs_char.h"),
)
}
// https://rust-lang.github.io/unsafe-code-guidelines/layout/scalars.html#isize-and-usize
// documents that "Rust's signed and unsigned fixed-width integer types {i,u}{8,16,32,64}
// have the same layout the C fixed-width integer types from the <stdint.h> header
// {u,}int{8,16,32,64}_t. These fixed-width integer types are therefore safe to use
// directly in C FFI where the corresponding C fixed-width integer types are expected.
//
// https://rust-lang.github.io/unsafe-code-guidelines/layout/scalars.html#layout-compatibility-with-c-native-integer-types
// documents that "Rust does not support C platforms on which the C native integer type are
// not compatible with any of Rust's fixed-width integer type (e.g. because of
// padding-bits, lack of 2's complement, etc.)."
ty::TyKind::Int(ty::IntTy::I8) => cstdint(quote! { std::int8_t }),
ty::TyKind::Int(ty::IntTy::I16) => cstdint(quote! { std::int16_t }),
ty::TyKind::Int(ty::IntTy::I32) => cstdint(quote! { std::int32_t }),
ty::TyKind::Int(ty::IntTy::I64) => cstdint(quote! { std::int64_t }),
ty::TyKind::Uint(ty::UintTy::U8) => cstdint(quote! { std::uint8_t }),
ty::TyKind::Uint(ty::UintTy::U16) => cstdint(quote! { std::uint16_t }),
ty::TyKind::Uint(ty::UintTy::U32) => cstdint(quote! { std::uint32_t }),
ty::TyKind::Uint(ty::UintTy::U64) => cstdint(quote! { std::uint64_t }),
// https://rust-lang.github.io/unsafe-code-guidelines/layout/scalars.html#isize-and-usize
// documents that "The isize and usize types are [...] layout compatible with C's uintptr_t
// and intptr_t types.".
ty::TyKind::Int(ty::IntTy::Isize) => cstdint(quote! { std::intptr_t }),
ty::TyKind::Uint(ty::UintTy::Usize) => cstdint(quote! { std::uintptr_t }),
ty::TyKind::Int(ty::IntTy::I128) | ty::TyKind::Uint(ty::UintTy::U128) => {
// Note that "the alignment of Rust's {i,u}128 is unspecified and allowed to
// change" according to
// https://rust-lang.github.io/unsafe-code-guidelines/layout/scalars.html#fixed-width-integer-types
//
// TODO(b/254094650): Consider mapping this to Clang's (and GCC's) `__int128`
// or to `absl::in128`.
bail!("C++ doesn't have a standard equivalent of `{ty}` (b/254094650)");
}
ty::TyKind::Adt(adt, substs) => {
ensure!(substs.len() == 0, "Generic types are not supported yet (b/259749095)");
ensure!(
is_directly_public(tcx, adt.did()),
"Not directly public type (re-exports are not supported yet - b/262052635)"
);
let def_id = adt.did();
let mut prereqs = CcPrerequisites::default();
if def_id.krate == LOCAL_CRATE {
prereqs.defs.insert(def_id.expect_local());
} else {
let other_crate_name = tcx.crate_name(def_id.krate);
let crate_name_to_include_paths = db.crate_name_to_include_paths();
let includes = crate_name_to_include_paths
.get(other_crate_name.as_str())
.ok_or_else(|| {
anyhow!(
"Type `{ty}` comes from the `{other_crate_name}` crate, \
but no `--crate-header` was specified for this crate"
)
})?;
prereqs.includes.extend(includes.iter().cloned());
}
// Verify if definition of `ty` can be succesfully imported and bail otherwise.
db.format_adt_core(def_id).with_context(|| {
format!("Failed to generate bindings for the definition of `{ty}`")
})?;
CcSnippet { tokens: FullyQualifiedName::new(tcx, def_id).format_for_cc()?, prereqs }
}
ty::TyKind::RawPtr(pointee_mid, mutbl) => {
if let ty::TyKind::Slice(slice_ty) = pointee_mid.kind() {
check_slice_layout(db.tcx(), ty.mid());
let mut slice_hir_ty = None;
if let Some(hir) = ty.hir(db) {
if let rustc_hir::TyKind::Ptr(pointee) = &hir.kind {
if let rustc_hir::TyKind::Slice(slice_ty) = &pointee.ty.kind {
slice_hir_ty = Some(*slice_ty);
}
}
}
return format_slice_pointer_for_cc(
db,
SugaredTy::new(*slice_ty, slice_hir_ty),
*mutbl,
);
}
let mut pointee_hir = None;
if let Some(hir) = ty.hir(db) {
if let rustc_hir::TyKind::Ptr(mut_p) = hir.kind {
pointee_hir = Some(mut_p.ty);
}
}
let pointee = SugaredTy::new(*pointee_mid, pointee_hir);
format_pointer_or_reference_ty_for_cc(db, pointee, *mutbl, quote! { * }).with_context(
|| format!("Failed to format the pointee of the pointer type `{ty}`"),
)?
}
ty::TyKind::Ref(region, referent_mid, mutability) => {
if let ty::TyKind::Slice(_) = referent_mid.kind() {
check_slice_layout(db.tcx(), ty.mid());
}
let mut referent_hir = None;
if let Some(hir) = ty.hir(db) {
if let rustc_hir::TyKind::Ref(_, mut_p, ..) = &hir.kind {
referent_hir = Some(mut_p.ty);
}
}
let referent = SugaredTy::new(*referent_mid, referent_hir);
match location {
TypeLocation::FnReturn | TypeLocation::FnParam => (),
TypeLocation::Other => bail!(
"Can't format `{ty}`, because references are only supported in \
function parameter types and return types (b/286256327)",
),
};
let lifetime = format_region_as_cc_lifetime(region);
format_pointer_or_reference_ty_for_cc(db, referent, *mutability, quote! { & #lifetime })
.with_context(|| {
format!("Failed to format the referent of the reference type `{ty}`")
})?
}
fn_ptr @ ty::TyKind::FnPtr { .. } => {
// Temporary support for both before / after FnPtr was split in two.
// TODO(jeanpierreda): Delete the dead branch after the commit is deployed everywhere.
#[cfg(not(
google3_internal_rustc_contains_commit_9859bf27fd9892f48725c59b56aeee2be1d2fbad
))]
let sig = {
let ty::TyKind::FnPtr(sig) = fn_ptr else {
unreachable!();
};
match sig.no_bound_vars() {
None => bail!("Generic functions are not supported yet (b/259749023)"),
Some(sig) => sig,
}
};
#[cfg(google3_internal_rustc_contains_commit_9859bf27fd9892f48725c59b56aeee2be1d2fbad)]
let sig = {
let ty::TyKind::FnPtr(sig_tys, fn_header) = fn_ptr else {
unreachable!();
};
let sig_tys = match sig_tys.no_bound_vars() {
None => bail!("Generic functions are not supported yet (b/259749023)"),
Some(sig_tys) => sig_tys,
};
rustc_middle::ty::FnSig {
inputs_and_output: sig_tys.inputs_and_output,
c_variadic: fn_header.c_variadic,
safety: fn_header.safety,
abi: fn_header.abi,
}
};
check_fn_sig(&sig)?;
is_thunk_required(&sig).context("Function pointers can't have a thunk")?;
// `is_thunk_required` check above implies `extern "C"` (or `"C-unwind"`).
// This assertion reinforces that the generated C++ code doesn't need
// to use calling convention attributes like `_stdcall`, etc.
assert!(matches!(sig.abi, rustc_target::spec::abi::Abi::C { .. }));
// C++ references are not rebindable and therefore can't be used to replicate
// semantics of Rust field types (or, say, element types of Rust
// arrays). Because of this, C++ references are only used for
// top-level return types and parameter types (and pointers are used
// in other locations).
let ptr_or_ref_sigil = match location {
TypeLocation::FnReturn | TypeLocation::FnParam => quote! { & },
TypeLocation::Other => quote! { * },
};
let mut prereqs = CcPrerequisites::default();
prereqs.includes.insert(db.support_header("internal/cxx20_backports.h"));
let mut sig_hir = None;
if let Some(hir) = ty.hir(db) {
if let rustc_hir::TyKind::BareFn(bare_fn) = &hir.kind {
sig_hir = Some(bare_fn.decl);
}
}
let ret_type = format_ret_ty_for_cc(db, &sig, sig_hir)?.into_tokens(&mut prereqs);
let param_types = format_param_types_for_cc(db, &sig, sig_hir)?
.into_iter()
.map(|snippet| snippet.into_tokens(&mut prereqs));
let tokens = quote! {
crubit::type_identity_t<
#ret_type( #( #param_types ),* )
> #ptr_or_ref_sigil
};
CcSnippet { tokens, prereqs }
}
// TODO(b/260268230, b/260729464): When recursively processing nested types (e.g. an
// element type of an Array, a referent of a Ref, a parameter type of an FnPtr, etc), one
// should also 1) propagate `CcPrerequisites::defs`, 2) cover `CcPrerequisites::defs` in
// `test_format_ty_for_cc...`. For ptr/ref it might be possible to use
// `CcPrerequisites::move_defs_to_fwd_decls`.
_ => bail!("The following Rust type is not supported yet: {ty}"),
})
}
/// Returns `Some(CcSnippet)` if `ty` is a special-cased alias type from
/// `core::ffi` (AKA `std::ffi`).
///
/// TODO(b/283258442): Also handle `libc` aliases.
fn format_core_alias_for_cc<'tcx>(
db: &dyn BindingsGenerator<'tcx>,
ty: SugaredTy<'tcx>,
) -> Option<CcSnippet> {
let tcx = db.tcx();
let hir_ty = ty.hir(db)?;
let rustc_hir::TyKind::Path(rustc_hir::QPath::Resolved(None, path)) = &hir_ty.kind else {
return None;
};
let rustc_hir::def::Res::Def(rustc_hir::def::DefKind::TyAlias, alias_def_id) = &path.res else {
return None;
};
let def_path = tcx.def_path(*alias_def_id);
// Note: the `std::ffi` aliases are still originally defined in `core::ffi`, so
// we only need to check for a crate name of `core` here.
if tcx.crate_name(def_path.krate) != sym::core {
return None;
};
let [module, item] = def_path.data.as_slice() else {
return None;
};
if module.data != rustc_hir::definitions::DefPathData::TypeNs(sym::ffi) {
return None;
};
let rustc_hir::definitions::DefPathData::TypeNs(item) = item.data else {
return None;
};
let cpp_type = match item.as_str() {
"c_char" => quote! { char},
"c_schar" => quote! { signed char},
"c_uchar" => quote! { unsigned char},
"c_short" => quote! { short},
"c_ushort" => quote! { unsigned short},
"c_int" => quote! { int},
"c_uint" => quote! { unsigned int},
"c_long" => quote! { long},
"c_ulong" => quote! { unsigned long},
"c_longlong" => quote! { long long},
"c_ulonglong" => quote! { unsigned long long},
_ => return None,
};
Some(CcSnippet::new(cpp_type))
}
/// Returns the C++ return type.
///
/// `sig_hir` is the optional HIR `FnDecl`, if available. This is used to
/// retrieve alias information.
fn format_ret_ty_for_cc<'tcx>(
db: &dyn BindingsGenerator<'tcx>,
sig_mid: &ty::FnSig<'tcx>,
sig_hir: Option<&rustc_hir::FnDecl<'tcx>>,
) -> Result<CcSnippet> {
let hir = sig_hir.and_then(|sig_hir| match sig_hir.output {
rustc_hir::FnRetTy::Return(hir_ty) => Some(hir_ty),
_ => None,
});
db.format_ty_for_cc(SugaredTy::new(sig_mid.output(), hir), TypeLocation::FnReturn)
.context("Error formatting function return type")
}
/// Returns the C++ parameter types.
///
/// `sig_hir` is the optional HIR FnSig, if available. This is used to retrieve
/// alias information.
fn format_param_types_for_cc<'tcx>(
db: &dyn BindingsGenerator<'tcx>,
sig_mid: &ty::FnSig<'tcx>,
sig_hir: Option<&rustc_hir::FnDecl<'tcx>>,
) -> Result<Vec<CcSnippet>> {
if let Some(sig_hir) = sig_hir {
assert_eq!(
sig_mid.inputs().len(),
sig_hir.inputs.len(),
"internal error: MIR and HIR function signatures do not line up"
);
}
sig_mid
.inputs()
.iter()
.enumerate()
.map(|(i, &mid)| {
let hir = sig_hir.map(|sig_hir| &sig_hir.inputs[i]);
db.format_ty_for_cc(SugaredTy::new(mid, hir), TypeLocation::FnParam)
.with_context(|| format!("Error handling parameter #{i}"))
})
.collect()
}
/// Formats `ty` for Rust - to be used in `..._cc_api_impl.rs` (e.g. as a type
/// of a parameter in a Rust thunk). Because `..._cc_api_impl.rs` is a
/// distinct, separate crate, the returned `TokenStream` uses crate-qualified
/// names whenever necessary - for example: `target_crate::SomeStruct` rather
/// than just `SomeStruct`.
//
// TODO(b/259724276): This function's results should be memoized.
fn format_ty_for_rs(tcx: TyCtxt, ty: Ty) -> Result<TokenStream> {
Ok(match ty.kind() {
ty::TyKind::Bool
| ty::TyKind::Float(_)
| ty::TyKind::Char
| ty::TyKind::Int(_)
| ty::TyKind::Uint(_)
| ty::TyKind::FnPtr { .. }
| ty::TyKind::Never => ty
.to_string()
.parse()
.expect("rustc_middle::ty::Ty::to_string() should produce no parsing errors"),
ty::TyKind::Tuple(types) => {
if types.len() == 0 {
quote! { () }
} else {
// TODO(b/254099023): Add support for tuples.
bail!("Tuples are not supported yet: {} (b/254099023)", ty);
}
}
ty::TyKind::Adt(adt, substs) => {
ensure!(substs.len() == 0, "Generic types are not supported yet (b/259749095)");
FullyQualifiedName::new(tcx, adt.did()).format_for_rs()
}
ty::TyKind::RawPtr(pointee_ty, mutbl) => {
let qualifier = match mutbl {
Mutability::Mut => quote! { mut },
Mutability::Not => quote! { const },
};
let ty = format_ty_for_rs(tcx, *pointee_ty).with_context(|| {
format!("Failed to format the pointee of the pointer type `{ty}`")
})?;
quote! { * #qualifier #ty }
}
ty::TyKind::Ref(region, referent_ty, mutability) => {
let mutability = match mutability {
Mutability::Mut => quote! { mut },
Mutability::Not => quote! {},
};
let ty = format_ty_for_rs(tcx, *referent_ty).with_context(|| {
format!("Failed to format the referent of the reference type `{ty}`")
})?;
let lifetime = format_region_as_rs_lifetime(region);
quote! { & #lifetime #mutability #ty }
}
ty::TyKind::Slice(slice_ty) => {
let ty = format_ty_for_rs(tcx, *slice_ty).with_context(|| {
format!("Failed to format the element type of the slice type `{ty}`")
})?;
quote! { [#ty] }
}
_ => bail!("The following Rust type is not supported yet: {ty}"),
})
}
fn format_region_as_cc_lifetime(region: &ty::Region) -> TokenStream {
let name =
region.get_name().expect("Caller should use `liberate_and_deanonymize_late_bound_regions`");
let name = name
.as_str()
.strip_prefix('\'')
.expect("All Rust lifetimes are expected to begin with the \"'\" character");
// TODO(b/286299326): Use `$a` or `$(foo)` or `$static` syntax below.
quote! { [[clang::annotate_type("lifetime", #name)]] }
}
fn format_region_as_rs_lifetime(region: &ty::Region) -> TokenStream {
let name =
region.get_name().expect("Caller should use `liberate_and_deanonymize_late_bound_regions`");
let lifetime = syn::Lifetime::new(name.as_str(), proc_macro2::Span::call_site());
quote! { #lifetime }
}
#[derive(Clone, Debug, Default)]
struct ApiSnippets {
/// Main API - for example:
/// - A C++ declaration of a function (with a doc comment),
/// - A C++ definition of a struct (with a doc comment).
main_api: CcSnippet,
/// C++ implementation details - for example:
/// - A C++ declaration of an `extern "C"` thunk,
/// - C++ `static_assert`s about struct size, aligment, and field offsets.
cc_details: CcSnippet,
/// Rust implementation details - for exmaple:
/// - A Rust implementation of an `extern "C"` thunk,
/// - Rust `assert!`s about struct size, aligment, and field offsets.
rs_details: TokenStream,
}
impl FromIterator<ApiSnippets> for ApiSnippets {
fn from_iter<I: IntoIterator<Item = ApiSnippets>>(iter: I) -> Self {
let mut result = ApiSnippets::default();
for ApiSnippets { main_api, cc_details, rs_details } in iter.into_iter() {
result.main_api += main_api;
result.cc_details += cc_details;
result.rs_details.extend(rs_details);
}
result
}
}
/// Similar to `TyCtxt::liberate_and_name_late_bound_regions` but also replaces
/// anonymous regions with new names.
fn liberate_and_deanonymize_late_bound_regions<'tcx>(
tcx: TyCtxt<'tcx>,
sig: ty::PolyFnSig<'tcx>,
fn_def_id: DefId,
) -> ty::FnSig<'tcx> {
let mut anon_count: u32 = 0;
let mut translated_kinds: HashMap<ty::BoundVar, ty::BoundRegionKind> = HashMap::new();
let region_f = |br: ty::BoundRegion| {
let new_kind: &ty::BoundRegionKind = translated_kinds.entry(br.var).or_insert_with(|| {
let name = br.kind.get_name().unwrap_or_else(|| {
anon_count += 1;
Symbol::intern(&format!("'__anon{anon_count}"))
});
let id = br.kind.get_id().unwrap_or(fn_def_id);
ty::BoundRegionKind::BrNamed(id, name)
});
ty::Region::new_late_param(tcx, fn_def_id, *new_kind)
};
tcx.instantiate_bound_regions_uncached(sig, region_f)
}
/// Returns the rustc_middle and rustc_hir function signatures.
///
/// In the case of rustc_hir, this returns the `FnDecl`, not the
/// `rustc_hir::FnSig`, because the `FnDecl` type is used for both function
/// pointers and actual functions. This makes it a more useful vocabulary type.
/// `FnDecl` does drop information, but that information is already on the
/// rustc_middle `FnSig`, so there is no loss.
fn get_fn_sig(tcx: TyCtxt, local_def_id: LocalDefId) -> (ty::FnSig, &rustc_hir::FnDecl) {
let def_id = local_def_id.to_def_id();
let sig_mid = liberate_and_deanonymize_late_bound_regions(
tcx,
tcx.fn_sig(def_id).instantiate_identity(),
def_id,
);
let sig_hir = tcx.hir_node_by_def_id(local_def_id).fn_sig().unwrap();
(sig_mid, sig_hir.decl)
}
/// Formats a C++ function declaration of a thunk that wraps a Rust function
/// identified by `fn_def_id`. `format_thunk_impl` may panic if `fn_def_id`
/// doesn't identify a function.
fn format_thunk_decl<'tcx>(
db: &dyn BindingsGenerator<'tcx>,
fn_def_id: DefId,
sig_mid: &ty::FnSig<'tcx>,
sig_hir: Option<&rustc_hir::FnDecl<'tcx>>,
thunk_name: &TokenStream,
) -> Result<CcSnippet> {
let tcx = db.tcx();
let mut prereqs = CcPrerequisites::default();
let main_api_ret_type = format_ret_ty_for_cc(db, sig_mid, sig_hir)?.into_tokens(&mut prereqs);
let mut thunk_params = {
let cpp_types = format_param_types_for_cc(db, sig_mid, sig_hir)?;
sig_mid
.inputs()
.iter()
.zip(cpp_types.into_iter())
.map(|(&ty, cpp_type)| -> Result<TokenStream> {
let cpp_type = cpp_type.into_tokens(&mut prereqs);
if is_c_abi_compatible_by_value(ty) {
Ok(quote! { #cpp_type })
} else {
// Rust thunk will move a value via memcpy - we need to `ensure` that
// invoking the C++ destructor (on the moved-away value) is safe.
ensure!(
!ty.needs_drop(tcx, tcx.param_env(fn_def_id)),
"Only trivially-movable and trivially-destructible types \
may be passed by value over the FFI boundary"
);
Ok(quote! { #cpp_type* })
}
})
.collect::<Result<Vec<_>>>()?
};
let thunk_ret_type: TokenStream;
if is_c_abi_compatible_by_value(sig_mid.output()) {
thunk_ret_type = main_api_ret_type;
} else {
thunk_ret_type = quote! { void };
thunk_params.push(quote! { #main_api_ret_type* __ret_ptr });
};
Ok(CcSnippet {
prereqs,
tokens: quote! {
namespace __crubit_internal {
extern "C" #thunk_ret_type #thunk_name ( #( #thunk_params ),* );
}
},
})
}
/// Formats a thunk implementation in Rust that provides an `extern "C"` ABI for
/// calling a Rust function identified by `fn_def_id`. `format_thunk_impl` may
/// panic if `fn_def_id` doesn't identify a function.
///
/// `fully_qualified_fn_name` specifies how the thunk can identify the function
/// to call. Examples of valid arguments:
/// - `::crate_name::some_module::free_function`
/// - `::crate_name::some_module::SomeStruct::method`
/// - `<::crate_name::some_module::SomeStruct as
/// ::core::default::Default>::default`
fn format_thunk_impl<'tcx>(
tcx: TyCtxt<'tcx>,
fn_def_id: DefId,
sig: &ty::FnSig<'tcx>,
thunk_name: &str,
fully_qualified_fn_name: TokenStream,
) -> Result<TokenStream> {
let param_names_and_types: Vec<(Ident, Ty)> = {
let param_names = tcx.fn_arg_names(fn_def_id).iter().enumerate().map(|(i, ident)| {
if ident.as_str().is_empty() {
format_ident!("__param_{i}")
} else if ident.name == kw::SelfLower {
format_ident!("__self")
} else {
make_rs_ident(ident.as_str())
}
});
let param_types = sig.inputs().iter().copied();
param_names.zip(param_types).collect_vec()
};
let mut thunk_params = param_names_and_types
.iter()
.map(|(param_name, ty)| {
let rs_type = format_ty_for_rs(tcx, *ty)
.with_context(|| format!("Error handling parameter `{param_name}`"))?;
Ok(if is_c_abi_compatible_by_value(*ty) {
quote! { #param_name: #rs_type }
} else {
quote! { #param_name: &mut ::core::mem::MaybeUninit<#rs_type> }
})
})
.collect::<Result<Vec<_>>>()?;
let mut thunk_ret_type = format_ty_for_rs(tcx, sig.output())?;
let mut thunk_body = {
let fn_args = param_names_and_types.iter().map(|(rs_name, ty)| {
if is_c_abi_compatible_by_value(*ty) {
quote! { #rs_name }
} else if let Safety::Unsafe = sig.safety {
// The whole call will be wrapped in `unsafe` below.
quote! { #rs_name.assume_init_read() }
} else {
quote! { unsafe { #rs_name.assume_init_read() } }
}
});
quote! {
#fully_qualified_fn_name( #( #fn_args ),* )
}
};
// Wrap the call in an unsafe block, for the sake of RFC #2585
// `unsafe_block_in_unsafe_fn`.
if let Safety::Unsafe = sig.safety {
thunk_body = quote! {unsafe {#thunk_body}};
}
if !is_c_abi_compatible_by_value(sig.output()) {
thunk_params.push(quote! {
__ret_slot: &mut ::core::mem::MaybeUninit<#thunk_ret_type>
});
thunk_ret_type = quote! { () };
thunk_body = quote! { __ret_slot.write(#thunk_body); };
};
let generic_params = {
let regions = sig
.inputs()
.iter()
.copied()
.chain(std::iter::once(sig.output()))
.flat_map(|ty| {
ty.walk().filter_map(|generic_arg| match generic_arg.unpack() {
ty::GenericArgKind::Const(_) | ty::GenericArgKind::Type(_) => None,
ty::GenericArgKind::Lifetime(region) => Some(region),
})
})
.filter(|region| match region.kind() {
RegionKind::ReStatic => false,
RegionKind::ReLateParam(_) => true,
_ => panic!("Unexpected region kind: {region}"),
})
.sorted_by_key(|region| {
region
.get_name()
.expect("Caller should use `liberate_and_deanonymize_late_bound_regions`")
})
.dedup()
.collect_vec();
if regions.is_empty() {
quote! {}
} else {
let lifetimes = regions.into_iter().map(|region| format_region_as_rs_lifetime(&region));
quote! { < #( #lifetimes ),* > }
}
};
let thunk_name = make_rs_ident(thunk_name);
let unsafe_qualifier = if let Safety::Unsafe = sig.safety {
quote! {unsafe}
} else {
quote! {}
};
Ok(quote! {
#[no_mangle]
#unsafe_qualifier extern "C" fn #thunk_name #generic_params (
#( #thunk_params ),*
) -> #thunk_ret_type {
#thunk_body
}
})
}
fn check_fn_sig(sig: &ty::FnSig) -> Result<()> {
if sig.c_variadic {
// TODO(b/254097223): Add support for variadic functions.
bail!("C variadic functions are not supported (b/254097223)");
}
Ok(())
}
/// Returns `Ok(())` if no thunk is required.
/// Otherwise returns an error the describes why the thunk is needed.
fn is_thunk_required(sig: &ty::FnSig) -> Result<()> {
match sig.abi {
// "C" ABI is okay: since https://rust-lang.github.io/rfcs/2945-c-unwind-abi.html has been
// accepted, a Rust panic that "escapes" a "C" ABI function is a defined crash. See
// https://doc.rust-lang.org/nomicon/ffi.html#ffi-and-unwinding.
rustc_target::spec::abi::Abi::C { unwind: false } => (),
// This requires a thunk if the calling C++ frames use `-fno-exceptions`, as it is
// UB. However, we leave this to the caller: if you use `extern "C-unwind"`, we assume you
// know what you are doing and do not block you from integrating with exception-enabled C++.
rustc_target::spec::abi::Abi::C { unwind: true } => (),
// All other ABIs trigger thunk generation. This covers Rust ABI functions, but also
// ABIs that theoretically are understood both by C++ and Rust (e.g. see
// `format_cc_call_conv_as_clang_attribute` in `rs_bindings_from_cc/src_code_gen.rs`).
_ => bail!("Any calling convention other than `extern \"C\"` requires a thunk"),
};
ensure!(is_c_abi_compatible_by_value(sig.output()), "Return type requires a thunk");
for (i, param_ty) in sig.inputs().iter().enumerate() {
ensure!(is_c_abi_compatible_by_value(*param_ty), "Type of parameter #{i} requires a thunk");
}
Ok(())
}
#[derive(Debug, Eq, PartialEq)]
enum FunctionKind {
/// Free function (i.e. not a method).
Free,
/// Static method (i.e. the first parameter is not named `self`).
StaticMethod,
/// Instance method taking `self` by value (i.e. `self: Self`).
MethodTakingSelfByValue,
/// Instance method taking `self` by reference (i.e. `&self` or `&mut
/// self`).
MethodTakingSelfByRef,
}
impl FunctionKind {
fn has_self_param(&self) -> bool {
match self {
FunctionKind::MethodTakingSelfByValue | FunctionKind::MethodTakingSelfByRef => true,
FunctionKind::Free | FunctionKind::StaticMethod => false,
}
}
}
/// Returns the C++ deprecated tag for the item identified by `def_id`, if it is
/// deprecated. Otherwise, returns None.
fn format_deprecated_tag(tcx: TyCtxt, def_id: DefId) -> Option<TokenStream> {
if let Some(deprecated_attr) = tcx.get_attr(def_id, rustc_span::symbol::sym::deprecated) {
if let Some((deprecation, _span)) =
find_deprecation(tcx.sess(), tcx.features(), slice::from_ref(deprecated_attr))
{
let cc_deprecated_tag = match deprecation.note {
None => quote! {[[deprecated]]},
Some(note_symbol) => {
let note = note_symbol.as_str();
quote! {[[deprecated(#note)]]}
}
};
return Some(cc_deprecated_tag);
}
}
None
}
fn format_use(
db: &dyn BindingsGenerator<'_>,
using_name: &str,
use_path: &UsePath,
use_kind: &UseKind,
) -> Result<ApiSnippets> {
let tcx = db.tcx();
// TODO(b/350772554): Support multiple items with the same name in `use`
// statements.`
if use_path.res.len() != 1 {
bail!(
"use statements which resolve to multiple items with the same name are not supported yet"
);
}
match use_kind {
UseKind::Single => {}
// TODO(b/350772554): Implement `pub use foo::{x,y}` and `pub use foo::*`
UseKind::Glob | UseKind::ListStem => {
bail!("Unsupported use kind: {use_kind:?}");
}
};
let (def_kind, def_id) = match use_path.res[0] {
// TODO(b/350772554): Support PrimTy.
Res::Def(def_kind, def_id) => (def_kind, def_id),
_ => {
bail!(
"Unsupported use statement that refers to this type of the entity: {:#?}",
use_path.res[0]
);
}
};
ensure!(
is_directly_public(tcx, def_id),
"Not directly public type (re-exports are not supported yet - b/262052635)"
);
match def_kind {
DefKind::Fn => {
let mut prereqs;
// TODO(b/350772554): Support exporting private functions.
if let Some(local_id) = def_id.as_local() {
if let Ok(snippet) = db.format_fn(local_id) {
prereqs = snippet.main_api.prereqs;
} else {
bail!("Ignoring the use because the bindings for the target is not generated");
}
} else {
bail!("Unsupported checking for external function");
}
let fully_qualified_fn_name = FullyQualifiedName::new(tcx, def_id);
let unqualified_rust_fn_name =
fully_qualified_fn_name.name.expect("Functions are assumed to always have a name");
let formatted_fully_qualified_fn_name = fully_qualified_fn_name.format_for_cc()?;
let cpp_name = crubit_attr::get(tcx, def_id).unwrap().cpp_name;
let main_api_fn_name =
format_cc_ident(cpp_name.unwrap_or(unqualified_rust_fn_name).as_str())
.context("Error formatting function name")?;
let using_name = format_cc_ident(using_name).context("Error formatting using name")?;
prereqs.defs.insert(def_id.expect_local());
let tokens = if format!("{}", using_name) == format!("{}", main_api_fn_name) {
quote! {using #formatted_fully_qualified_fn_name;}
} else {
// TODO(b/350772554): Support function alias.
bail!("Unsupported function alias");
};
Ok(ApiSnippets {
main_api: CcSnippet { prereqs, tokens },
cc_details: CcSnippet::default(),
rs_details: quote! {},
})
}
DefKind::Struct | DefKind::Enum => {
// This points directly to a type definition, not an alias or compound data
// type, so we can drop the hir type.
let use_type = SugaredTy::new(tcx.type_of(def_id).instantiate_identity(), None);
create_type_alias(db, def_id, using_name, use_type)
}
_ => bail!(
"Unsupported use statement that refers to this type of the entity: {:#?}",
use_path.res
),
}
}
fn format_type_alias(
db: &dyn BindingsGenerator<'_>,
local_def_id: LocalDefId,
) -> Result<ApiSnippets> {
let tcx = db.tcx();
let def_id: DefId = local_def_id.to_def_id();
let Item { kind: ItemKind::TyAlias(hir_ty, ..), .. } = tcx.hir().expect_item(local_def_id)
else {
panic!("called format_type_alias on a non-type-alias");
};
let alias_type = SugaredTy::new(tcx.type_of(def_id).instantiate_identity(), Some(*hir_ty));
create_type_alias(db, def_id, tcx.item_name(def_id).as_str(), alias_type)
}
fn create_type_alias<'tcx>(
db: &dyn BindingsGenerator<'tcx>,
def_id: DefId,
alias_name: &str,
alias_type: SugaredTy<'tcx>,
) -> Result<ApiSnippets> {
let cc_bindings = format_ty_for_cc(db, alias_type, TypeLocation::Other)?;
let mut main_api_prereqs = CcPrerequisites::default();
let actual_type_name = cc_bindings.into_tokens(&mut main_api_prereqs);
let alias_name = format_cc_ident(alias_name).context("Error formatting type alias name")?;
let mut attributes = vec![];
if let Some(cc_deprecated_tag) = format_deprecated_tag(db.tcx(), def_id) {
attributes.push(cc_deprecated_tag);
}
let tokens = quote! {using #alias_name #(#attributes)* = #actual_type_name;};
Ok(ApiSnippets {
main_api: CcSnippet { prereqs: main_api_prereqs, tokens },
cc_details: CcSnippet::default(),
rs_details: quote! {},
})
}
/// Formats a function with the given `local_def_id`.
///
/// Will panic if `local_def_id`
/// - is invalid
/// - doesn't identify a function,
fn format_fn(db: &dyn BindingsGenerator<'_>, local_def_id: LocalDefId) -> Result<ApiSnippets> {
let tcx = db.tcx();
let def_id: DefId = local_def_id.to_def_id(); // Convert LocalDefId to DefId.
ensure!(
tcx.generics_of(def_id).count() == 0,
"Generic functions are not supported yet (b/259749023)"
);
let (sig_mid, sig_hir) = get_fn_sig(tcx, local_def_id);
check_fn_sig(&sig_mid)?;
// TODO(b/262904507): Don't require thunks for mangled extern "C" functions.
let needs_thunk = is_thunk_required(&sig_mid).is_err()
|| (tcx.get_attr(def_id, rustc_span::symbol::sym::no_mangle).is_none()
&& tcx.get_attr(def_id, rustc_span::symbol::sym::export_name).is_none());
let thunk_name = {
let symbol_name = if db.no_thunk_name_mangling() {
FullyQualifiedName::new(tcx, def_id)
.name
.expect("Functions are assumed to always have a name")
.to_string()
} else {
// Call to `mono` is ok - `generics_of` have been checked above.
let instance = ty::Instance::mono(tcx, def_id);
tcx.symbol_name(instance).name.to_string()
};
if needs_thunk {
format!("__crubit_thunk_{}", &escape_non_identifier_chars(&symbol_name))
} else {
symbol_name.to_string()
}
};
let fully_qualified_fn_name = FullyQualifiedName::new(tcx, def_id);
let unqualified_rust_fn_name =
fully_qualified_fn_name.name.expect("Functions are assumed to always have a name");
let attribute = crubit_attr::get(tcx, def_id).unwrap();
let cpp_name = attribute.cpp_name;
// The generated C++ function name.
let main_api_fn_name = format_cc_ident(cpp_name.unwrap_or(unqualified_rust_fn_name).as_str())
.context("Error formatting function name")?;
let mut main_api_prereqs = CcPrerequisites::default();
let main_api_ret_type =
format_ret_ty_for_cc(db, &sig_mid, Some(sig_hir))?.into_tokens(&mut main_api_prereqs);
struct Param<'tcx> {
cc_name: TokenStream,
cpp_type: TokenStream,
ty: Ty<'tcx>,
}
let params = {
let names = tcx.fn_arg_names(def_id).iter();
let cpp_types = format_param_types_for_cc(db, &sig_mid, Some(sig_hir))?;
names
.enumerate()
.zip(sig_mid.inputs().iter())
.zip(cpp_types)
.map(|(((i, name), &ty), cpp_type)| {
let cc_name = format_cc_ident(name.as_str())
.unwrap_or_else(|_err| format_cc_ident(&format!("__param_{i}")).unwrap());
let cpp_type = cpp_type.into_tokens(&mut main_api_prereqs);
Param { cc_name, cpp_type, ty }
})
.collect_vec()
};
let self_ty: Option<Ty> = match tcx.impl_of_method(def_id) {
Some(impl_id) => match tcx.impl_subject(impl_id).instantiate_identity() {
ty::ImplSubject::Inherent(ty) => Some(ty),
ty::ImplSubject::Trait(_) => panic!("Trait methods should be filtered by caller"),
},
None => None,
};
let method_kind = match tcx.hir_node_by_def_id(local_def_id) {
Node::Item(_) => FunctionKind::Free,
Node::ImplItem(_) => match tcx.fn_arg_names(def_id).first() {
Some(arg_name) if arg_name.name == kw::SelfLower => {
let self_ty = self_ty.expect("ImplItem => non-None `self_ty`");
if params[0].ty == self_ty {
FunctionKind::MethodTakingSelfByValue
} else {
match params[0].ty.kind() {
ty::TyKind::Ref(_, referent_ty, _) if *referent_ty == self_ty => {
FunctionKind::MethodTakingSelfByRef
}
_ => bail!("Unsupported `self` type"),
}
}
}
_ => FunctionKind::StaticMethod,
},
other => panic!("Unexpected HIR node kind: {other:?}"),
};
let method_qualifiers = match method_kind {
FunctionKind::Free | FunctionKind::StaticMethod => quote! {},
FunctionKind::MethodTakingSelfByValue => quote! { && },
FunctionKind::MethodTakingSelfByRef => match params[0].ty.kind() {
ty::TyKind::Ref(region, _, mutability) => {
let lifetime_annotation = format_region_as_cc_lifetime(region);
let mutability = match mutability {
Mutability::Mut => quote! {},
Mutability::Not => quote! { const },
};
quote! { #mutability #lifetime_annotation }
}
_ => panic!("Expecting TyKind::Ref for MethodKind...Self...Ref"),
},
};
let struct_name = match self_ty {
Some(ty) => match ty.kind() {
ty::TyKind::Adt(adt, substs) => {
assert_eq!(0, substs.len(), "Callers should filter out generics");
Some(FullyQualifiedName::new(tcx, adt.did()))
}
_ => panic!("Non-ADT `impl`s should be filtered by caller"),
},
None => None,
};
let needs_definition = unqualified_rust_fn_name.as_str() != thunk_name;
let main_api_params = params
.iter()
.skip(if method_kind.has_self_param() { 1 } else { 0 })
.map(|Param { cc_name, cpp_type, .. }| quote! { #cpp_type #cc_name })
.collect_vec();
let main_api = {
let doc_comment = {
let doc_comment = format_doc_comment(tcx, local_def_id);
quote! { __NEWLINE__ #doc_comment }
};
let mut prereqs = main_api_prereqs.clone();
prereqs.move_defs_to_fwd_decls();
let static_ = if method_kind == FunctionKind::StaticMethod {
quote! { static }
} else {
quote! {}
};
let extern_c = if !needs_definition {
quote! { extern "C" }
} else {
quote! {}
};
let mut attributes = vec![];
// Attribute: must_use
if let Some(must_use_attr) = tcx.get_attr(def_id, rustc_span::symbol::sym::must_use) {
match must_use_attr.value_str() {
None => attributes.push(quote! {[[nodiscard]]}),
Some(symbol) => {
let message = symbol.as_str();
attributes.push(quote! {[[nodiscard(#message)]]});
}
};
}
// Attribute: deprecated
if let Some(cc_deprecated_tag) = format_deprecated_tag(tcx, def_id) {
attributes.push(cc_deprecated_tag);
}
// Also check the impl block to which this function belongs (if there is one).
// Note: parent_def_id can be Some(...) even if the function is not inside an
// impl block.
if let Some(parent_def_id) = tcx.opt_parent(def_id) {
if let Some(cc_deprecated_tag) = format_deprecated_tag(tcx, parent_def_id) {
attributes.push(cc_deprecated_tag);
}
}
CcSnippet {
prereqs,
tokens: quote! {
__NEWLINE__
#doc_comment
#extern_c #(#attributes)* #static_
#main_api_ret_type #main_api_fn_name (
#( #main_api_params ),*
) #method_qualifiers;
__NEWLINE__
},
}
};
let cc_details = if !needs_definition {
CcSnippet::default()
} else {
let thunk_name = format_cc_ident(&thunk_name).context("Error formatting thunk name")?;
let struct_name = match struct_name.as_ref() {
None => quote! {},
Some(fully_qualified_name) => {
let name = fully_qualified_name.cpp_name.expect("Structs always have a name");
let name = format_cc_ident(name.as_str())
.expect("Caller of format_fn should verify struct via format_adt_core");
quote! { #name :: }
}
};
let mut prereqs = main_api_prereqs;
let thunk_decl = format_thunk_decl(db, def_id, &sig_mid, Some(sig_hir), &thunk_name)?
.into_tokens(&mut prereqs);
let mut thunk_args = params
.iter()
.enumerate()
.map(|(i, Param { cc_name, ty, .. })| {
if i == 0 && method_kind.has_self_param() {
if method_kind == FunctionKind::MethodTakingSelfByValue {
quote! { this }
} else {
quote! { *this }
}
} else if is_c_abi_compatible_by_value(*ty) {
quote! { #cc_name }
} else {
quote! { & #cc_name }
}
})
.collect_vec();
let impl_body: TokenStream;
if is_c_abi_compatible_by_value(sig_mid.output()) {
impl_body = quote! {
return __crubit_internal :: #thunk_name( #( #thunk_args ),* );
};
} else {
if let Some(adt_def) = sig_mid.output().ty_adt_def() {
let core = db.format_adt_core(adt_def.did())?;
db.format_move_ctor_and_assignment_operator(core).map_err(|_| {
anyhow!("Can't pass the return type by value without a move constructor")
})?;
}
thunk_args.push(quote! { __ret_slot.Get() });
impl_body = quote! {
crubit::ReturnValueSlot<#main_api_ret_type> __ret_slot;
__crubit_internal :: #thunk_name( #( #thunk_args ),* );
return std::move(__ret_slot).AssumeInitAndTakeValue();
};
prereqs.includes.insert(CcInclude::utility()); // for `std::move`
prereqs.includes.insert(db.support_header("internal/return_value_slot.h"));
};
CcSnippet {
prereqs,
tokens: quote! {
__NEWLINE__
#thunk_decl
inline #main_api_ret_type #struct_name #main_api_fn_name (
#( #main_api_params ),* ) #method_qualifiers {
#impl_body
}
__NEWLINE__
},
}
};
let rs_details = if !needs_thunk {
quote! {}
} else {
let fully_qualified_fn_name = match struct_name.as_ref() {
None => fully_qualified_fn_name.format_for_rs(),
Some(struct_name) => {
let fn_name = make_rs_ident(unqualified_rust_fn_name.as_str());
let struct_name = struct_name.format_for_rs();
quote! { #struct_name :: #fn_name }
}
};
format_thunk_impl(tcx, def_id, &sig_mid, &thunk_name, fully_qualified_fn_name)?
};
Ok(ApiSnippets { main_api, cc_details, rs_details })
}
/// Represents bindings for the "core" part of an algebraic data type (an ADT -
/// a struct, an enum, or a union) in a way that supports later injecting the
/// other parts like so:
///
/// ```
/// quote! {
/// #keyword #alignment #name final {
/// #core
/// #decls_of_other_parts // (e.g. struct fields, methods, etc.)
/// }
/// }
/// ```
///
/// `keyword`, `name` are stored separately, to support formatting them as a
/// forward declaration - e.g. `struct SomeStruct`.
#[derive(Clone)]
struct AdtCoreBindings<'tcx> {
/// DefId of the ADT.
def_id: DefId,
/// C++ tag - e.g. `struct`, `class`, `enum`, or `union`. This isn't always
/// a direct mapping from Rust (e.g. a Rust `enum` might end up being
/// represented as an opaque C++ `struct`).
keyword: TokenStream,
/// C++ translation of the ADT identifier - e.g. `SomeStruct`.
///
/// A _short_ name is sufficient (i.e. there is no need to use a
/// namespace-qualified name), for `CcSnippet`s that are emitted into
/// the same namespace as the ADT. (This seems to be all the snippets
/// today.)
cc_short_name: TokenStream,
/// Rust spelling of the ADT type - e.g.
/// `::some_crate::some_module::SomeStruct`.
rs_fully_qualified_name: TokenStream,
self_ty: Ty<'tcx>,
alignment_in_bytes: u64,
size_in_bytes: u64,
}
// AdtCoreBindings are a pure (and memoized...) function of the def_id.
impl<'tcx> PartialEq for AdtCoreBindings<'tcx> {
fn eq(&self, other: &Self) -> bool {
self.def_id == other.def_id
}
}
impl<'tcx> Eq for AdtCoreBindings<'tcx> {}
impl<'tcx> Hash for AdtCoreBindings<'tcx> {
fn hash<H: Hasher>(&self, state: &mut H) {
self.def_id.hash(state);
}
}
impl<'tcx> AdtCoreBindings<'tcx> {
fn needs_drop(&self, tcx: TyCtxt<'tcx>) -> bool {
self.self_ty.needs_drop(tcx, tcx.param_env(self.def_id))
}
}
/// Like `TyCtxt::is_directly_public`, but works not only with `LocalDefId`, but
/// also with `DefId`.
fn is_directly_public(tcx: TyCtxt, def_id: DefId) -> bool {
match def_id.as_local() {
None => {
// This mimics the checks in `try_print_visible_def_path_recur` in
// `compiler/rustc_middle/src/ty/print/pretty.rs`.
let actual_parent = tcx.opt_parent(def_id);
let visible_parent = tcx.visible_parent_map(()).get(&def_id).copied();
actual_parent == visible_parent
}
Some(local_def_id) => tcx.effective_visibilities(()).is_directly_public(local_def_id),
}
}
fn get_layout<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> Result<Layout<'tcx>> {
let param_env = match ty.ty_adt_def() {
None => ty::ParamEnv::empty(),
Some(adt_def) => tcx.param_env(adt_def.did()),
};
tcx.layout_of(param_env.and(ty)).map(|ty_and_layout| ty_and_layout.layout).map_err(
|layout_err| {
// Have to use `.map_err`, because `LayoutError` doesn't satisfy the
// `anyhow::context::ext::StdError` trait bound.
anyhow!("Error computing the layout: {layout_err}")
},
)
}
/// Formats the core of an algebraic data type (an ADT - a struct, an enum, or a
/// union) represented by `def_id`.
///
/// The "core" means things that are necessary for a succesful binding (e.g.
/// inability to generate a correct C++ destructor means that the ADT cannot
/// have any bindings). "core" excludes things that are A) infallible (e.g.
/// struct or union fields which can always be translated into private, opaque
/// blobs of bytes) or B) optional (e.g. a problematic instance method
/// can just be ignored, unlike a problematic destructor). The split between
/// fallible "core" and non-fallible "rest" is motivated by the need to avoid
/// cycles / infinite recursion (e.g. when processing fields that refer back to
/// the struct type, possible with an indirection of a pointer).
///
/// `format_adt_core` is used both to 1) format bindings for the core of an ADT,
/// and 2) check if formatting would have succeeded (e.g. when called from
/// `format_ty`). The 2nd case is needed for ADTs defined in any crate - this
/// is why the `def_id` parameter is a DefId rather than LocalDefId.
fn format_adt_core<'tcx>(
db: &dyn BindingsGenerator<'tcx>,
def_id: DefId,
) -> Result<Rc<AdtCoreBindings<'tcx>>> {
let tcx = db.tcx();
let self_ty = tcx.type_of(def_id).instantiate_identity();
assert!(self_ty.is_adt());
assert!(is_directly_public(tcx, def_id), "Caller should verify");
let attribute = crubit_attr::get(tcx, def_id).unwrap();
let item_name = attribute.cpp_name.unwrap_or_else(|| tcx.item_name(def_id));
let rs_fully_qualified_name = format_ty_for_rs(tcx, self_ty)?;
let cc_short_name =
format_cc_ident(item_name.as_str()).context("Error formatting item name")?;
// The check below ensures that `format_trait_thunks` will succeed for the
// `Drop`, `Default`, and/or `Clone` trait. Ideally we would directly check
// if `format_trait_thunks` or `format_ty_for_cc(..., self_ty, ...)`
// succeeds, but this would lead to infinite recursion, so we only replicate
// `format_ty_for_cc` / `TyKind::Adt` checks that are outside of
// `format_adt_core`.
FullyQualifiedName::new(tcx, def_id).format_for_cc().with_context(|| {
format!("Error formatting the fully-qualified C++ name of `{item_name}")
})?;
let adt_def = self_ty.ty_adt_def().expect("`def_id` needs to identify an ADT");
let keyword = match adt_def.adt_kind() {
ty::AdtKind::Struct | ty::AdtKind::Enum => quote! { struct },
ty::AdtKind::Union => quote! { union },
};
let layout = get_layout(tcx, self_ty)
.with_context(|| format!("Error computing the layout of #{item_name}"))?;
ensure!(layout.abi().is_sized(), "Bindings for dynamically sized types are not supported.");
let alignment_in_bytes = {
// Only the ABI-mandated alignment is considered (i.e. `AbiAndPrefAlign::pref`
// is ignored), because 1) Rust's `std::mem::align_of` returns the
// ABI-mandated alignment and 2) the generated C++'s `alignas(...)`
// should specify the minimal/mandatory alignment.
layout.align().abi.bytes()
};
let size_in_bytes = layout.size().bytes();
ensure!(size_in_bytes != 0, "Zero-sized types (ZSTs) are not supported (b/258259459)");
Ok(Rc::new(AdtCoreBindings {
def_id,
keyword,
cc_short_name,
rs_fully_qualified_name,
self_ty,
alignment_in_bytes,
size_in_bytes,
}))
}
fn repr_attrs(db: &dyn BindingsGenerator<'_>, def_id: DefId) -> Rc<[rustc_attr::ReprAttr]> {
let tcx = db.tcx();
let attrs: Vec<_> = tcx
.get_attrs(def_id, sym::repr)
.flat_map(|attr| rustc_attr::parse_repr_attr(tcx.sess(), attr))
.collect();
attrs.into()
}
fn format_fields<'tcx>(
db: &dyn BindingsGenerator<'tcx>,
core: &AdtCoreBindings<'tcx>,
) -> ApiSnippets {
let tcx = db.tcx();
// TODO(b/259749095): Support non-empty set of generic parameters.
let substs_ref = ty::List::empty();
struct FieldTypeInfo {
size: u64,
cpp_type: CcSnippet,
}
struct Field {
type_info: Result<FieldTypeInfo>,
cc_name: TokenStream,
rs_name: TokenStream,
is_public: bool,
index: usize,
offset: u64,
offset_of_next_field: u64,
doc_comment: TokenStream,
attributes: Vec<TokenStream>,
}
impl Field {
fn size(&self) -> u64 {
match self.type_info {
Err(_) => self.offset_of_next_field - self.offset,
Ok(FieldTypeInfo { size, .. }) => size,
}
}
}
let layout = get_layout(tcx, core.self_ty)
.expect("Layout should be already verified by `format_adt_core`");
let adt_def = core.self_ty.ty_adt_def().expect("`core.def_id` needs to identify an ADT");
let fields: Vec<Field> = if core.self_ty.is_enum() {
vec![Field {
type_info: Err(anyhow!("No support for bindings of individual `enum` fields")),
cc_name: quote! { __opaque_blob_of_bytes },
rs_name: quote! { __opaque_blob_of_bytes },
is_public: false,
index: 0,
offset: 0,
offset_of_next_field: core.size_in_bytes,
doc_comment: quote! {},
attributes: vec![],
}]
} else {
let rustc_hir::Node::Item(item) = tcx.hir_node_by_def_id(core.def_id.expect_local()) else {
panic!("internal error: def_id referring to an ADT was not a HIR Item.");
};
let variants = match item.kind {
rustc_hir::ItemKind::Struct(variants, _) => variants,
rustc_hir::ItemKind::Union(variants, _) => variants,
_ => panic!(
"internal error: def_id referring to a non-enum ADT was not a struct or union."
),
};
let hir_fields: Vec<_> = variants.fields().iter().sorted_by_key(|f| f.span).collect();
let mut fields = core
.self_ty
.ty_adt_def()
.expect("`core.def_id` needs to identify an ADT")
.all_fields()
.sorted_by_key(|f| tcx.def_span(f.did))
.enumerate()
.map(|(index, field_def)| {
// *Not* using zip, in order to crash on length mismatch.
let hir_field =
hir_fields.get(index).expect("HIR ADT had fewer fields than rustc_middle");
assert!(field_def.did == hir_field.def_id.to_def_id());
let ty = SugaredTy::new(field_def.ty(tcx, substs_ref), Some(hir_field.ty));
let size = get_layout(tcx, ty.mid()).map(|layout| layout.size().bytes());
let type_info = size.and_then(|size| {
Ok(FieldTypeInfo {
size,
cpp_type: db.format_ty_for_cc(ty, TypeLocation::Other)?,
})
});
let name = field_def.ident(tcx);
let cc_name = format_cc_ident(name.as_str())
.unwrap_or_else(|_err| format_ident!("__field{index}").into_token_stream());
let rs_name = {
let name_starts_with_digit = name
.as_str()
.chars()
.next()
.expect("Empty names are unexpected (here and in general)")
.is_ascii_digit();
if name_starts_with_digit {
let index = Literal::usize_unsuffixed(index);
quote! { #index }
} else {
let name = make_rs_ident(name.as_str());
quote! { #name }
}
};
// `offset` and `offset_of_next_field` will be fixed by FieldsShape::Arbitrary
// branch below.
let offset = 0;
let offset_of_next_field = 0;
// Populate attributes.
let mut attributes = vec![];
if let Some(cc_deprecated_tag) = format_deprecated_tag(tcx, field_def.did) {
attributes.push(cc_deprecated_tag);
}
Field {
type_info,
cc_name,
rs_name,
is_public: field_def.vis == ty::Visibility::Public,
index,
offset,
offset_of_next_field,
doc_comment: format_doc_comment(tcx, field_def.did.expect_local()),
attributes,
}
})
.collect_vec();
// Determine the memory layout
match layout.fields() {
FieldsShape::Arbitrary { offsets, .. } => {
for (index, offset) in offsets.iter().enumerate() {
// Documentation of `FieldsShape::Arbitrary says that the offsets are
// "ordered to match the source definition order".
// We can coorelate them with elements
// of the `fields` vector because we've explicitly `sorted_by_key` using
// `def_span`.
fields[index].offset = offset.bytes();
}
// Sort by offset first; ZSTs in the same offset are sorted by source order.
// Use `field_size` to ensure ZSTs at the same offset as
// non-ZSTs sort first to avoid weird offset issues later on.
fields.sort_by_key(|field| {
let field_size = field.type_info.as_ref().map(|info| info.size).unwrap_or(0);
(field.offset, field_size, field.index)
});
}
FieldsShape::Union(num_fields) => {
// Compute the offset of each field
for index in 0..num_fields.get() {
fields[index].offset = layout.fields().offset(index).bytes();
}
}
unexpected => panic!("Unexpected FieldsShape: {unexpected:?}"),
}
let next_offsets = fields
.iter()
.map(|Field { offset, .. }| *offset)
.skip(1)
.chain(once(core.size_in_bytes))
.collect_vec();
for (field, next_offset) in fields.iter_mut().zip(next_offsets) {
field.offset_of_next_field = next_offset;
}
fields
};
let cc_details = if fields.is_empty() {
CcSnippet::default()
} else {
let adt_cc_name = &core.cc_short_name;
let cc_assertions: TokenStream = fields
.iter()
// TODO(b/298660437): Add support for ZST fields.
.filter(|field| field.size() != 0)
.map(|Field { cc_name, offset, .. }| {
let offset = Literal::u64_unsuffixed(*offset);
quote! { static_assert(#offset == offsetof(#adt_cc_name, #cc_name)); }
})
.collect();
CcSnippet::with_include(
quote! {
inline void #adt_cc_name::__crubit_field_offset_assertions() {
#cc_assertions
}
},
CcInclude::cstddef(),
)
};
let rs_details: TokenStream = {
let adt_rs_name = &core.rs_fully_qualified_name;
fields
.iter()
// TODO(b/298660437): Even though we don't generate bindings for ZST fields, we'd still
// like to make sure we computed the offset of ZST fields correctly on the Rust side,
// so we still emit offset assertions for ZST fields here.
// TODO(b/298660437): Remove the comment above when ZST fields are supported.
.filter(|field| field.is_public)
.map(|Field { rs_name, offset, .. }| {
let expected_offset = Literal::u64_unsuffixed(*offset);
let actual_offset = quote! { ::core::mem::offset_of!(#adt_rs_name, #rs_name) };
quote! { const _: () = assert!(#actual_offset == #expected_offset); }
})
.collect()
};
let main_api = {
let assertions_method_decl = if fields.is_empty() {
quote! {}
} else {
// We put the assertions in a method so that they can read private member
// variables.
quote! { private: static void __crubit_field_offset_assertions(); }
};
// If all fields are known, and the type is repr(C), then we don't need padding
// fields, and can instead use the natural padding from alignment.
//
// Note: it does need to be repr(C) to be guaranteed, since the compiler might
// reasonably place a field later than it has to for layout
// randomization purposes. For example, in `#[repr(align(4))] struct
// Foo(i8);` there are four different places the `i8` could be.
// If it was placed in the second byte, for any reason, then we would need
// explicit padding bytes.
let repr_attrs = db.repr_attrs(core.def_id);
let always_omit_padding = repr_attrs.contains(&rustc_attr::ReprC)
&& fields.iter().all(|field| field.type_info.is_ok());
let mut prereqs = CcPrerequisites::default();
let fields: TokenStream = fields
.into_iter()
.map(|field| {
let cc_name = &field.cc_name;
match field.type_info {
Err(ref err) => {
let size = field.size();
let msg =
format!("Field type has been replaced with a blob of bytes: {err:#}");
// Empty arrays are ill-formed, but also unnecessary for padding.
if size > 0 {
let size = Literal::u64_unsuffixed(size);
quote! {
private: __NEWLINE__
__COMMENT__ #msg
unsigned char #cc_name[#size];
}
} else {
// TODO(b/258259459): Generate bindings for ZST fields.
let msg = format!(
"Skipped bindings for field `{cc_name}`: \
ZST fields are not supported (b/258259459)"
);
quote! {__NEWLINE__ __COMMENT__ #msg}
}
}
Ok(FieldTypeInfo { cpp_type, size }) => {
// Only structs require no overlaps.
let padding = match adt_def.adt_kind() {
ty::AdtKind::Struct => {
assert!((field.offset + size) <= field.offset_of_next_field);
field.offset_of_next_field - field.offset - size
}
ty::AdtKind::Union => field.offset,
ty::AdtKind::Enum => todo!(),
};
// Omit explicit padding if:
// 1. The type is repr(C) and has known types for all fields, so we can
// reuse the natural repr(C) padding.
// 2. There is no padding
// TODO(jeanpierreda): also omit padding for the final field?
let padding = if always_omit_padding || padding == 0 {
quote! {}
} else {
let padding = Literal::u64_unsuffixed(padding);
let ident = format_ident!("__padding{}", field.index);
quote! { private: unsigned char #ident[#padding]; }
};
let visibility = if field.is_public {
quote! { public: }
} else {
quote! { private: }
};
let cpp_type = cpp_type.into_tokens(&mut prereqs);
let doc_comment = field.doc_comment;
let attributes = field.attributes;
match adt_def.adt_kind() {
ty::AdtKind::Struct => quote! {
#visibility __NEWLINE__
// The anonymous union gives more control over when exactly
// the field constructors and destructors run. See also
// b/288138612.
union { __NEWLINE__
#doc_comment
#(#attributes)*
#cpp_type #cc_name;
};
#padding
},
ty::AdtKind::Union => {
if repr_attrs.contains(&rustc_attr::ReprC) {
quote! {
__NEWLINE__
#doc_comment
#cpp_type #cc_name;
}
} else {
let internal_padding = if field.offset == 0 {
quote! {}
} else {
let internal_padding_size = Literal::u64_unsuffixed(field.offset);
quote! {char __crubit_internal_padding[#internal_padding_size]}
};
quote! {
__NEWLINE__
#doc_comment
struct {
#internal_padding
#cpp_type value;
} #cc_name;
}
}
}
ty::AdtKind::Enum => todo!(),
}
}
}
})
.collect();
CcSnippet {
prereqs,
tokens: quote! {
#fields
#assertions_method_decl
},
}
};
ApiSnippets { main_api, cc_details, rs_details }
}
fn does_type_implement_trait<'tcx>(tcx: TyCtxt<'tcx>, self_ty: Ty<'tcx>, trait_id: DefId) -> bool {
assert!(tcx.is_trait(trait_id));
let generics = tcx.generics_of(trait_id);
assert!(generics.has_self);
assert_eq!(
generics.count(),
1, // Only `Self`
"Generic traits are not supported yet (b/286941486)",
);
let substs = [self_ty];
tcx.infer_ctxt()
.build()
.type_implements_trait(trait_id, substs, tcx.param_env(trait_id))
.must_apply_modulo_regions()
}
struct TraitThunks {
method_name_to_cc_thunk_name: HashMap<Symbol, TokenStream>,
cc_thunk_decls: CcSnippet,
rs_thunk_impls: TokenStream,
}
fn format_trait_thunks<'tcx>(
db: &dyn BindingsGenerator<'tcx>,
trait_id: DefId,
adt: &AdtCoreBindings<'tcx>,
) -> Result<TraitThunks> {
let tcx = db.tcx();
assert!(tcx.is_trait(trait_id));
let self_ty = adt.self_ty;
let is_drop_trait = Some(trait_id) == tcx.lang_items().drop_trait();
if is_drop_trait {
// To support "drop glue" we don't require that `self_ty` directly implements
// the `Drop` trait. Instead we require the caller to check
// `needs_drop`.
assert!(self_ty.needs_drop(tcx, tcx.param_env(adt.def_id)));
} else if !does_type_implement_trait(tcx, self_ty, trait_id) {
let trait_name = tcx.item_name(trait_id);
bail!("`{self_ty}` doesn't implement the `{trait_name}` trait");
}
let mut method_name_to_cc_thunk_name = HashMap::new();
let mut cc_thunk_decls = CcSnippet::default();
let mut rs_thunk_impls = quote! {};
let methods = tcx
.associated_items(trait_id)
.in_definition_order()
.filter(|item| item.kind == ty::AssocKind::Fn);
for method in methods {
let substs = {
let generics = tcx.generics_of(method.def_id);
if generics.own_params.iter().any(|p| p.kind.is_ty_or_const()) {
// Note that lifetime-generic methods are ok:
// * they are handled by `format_thunk_decl` and `format_thunk_impl`
// * the lifetimes are erased by `ty::Instance::mono` and *seem* to be erased by
// `ty::Instance::new`
panic!(
"So far callers of `format_trait_thunks` didn't need traits with \
methods that are type-generic or const-generic"
);
}
assert!(generics.has_self);
tcx.mk_args_trait(self_ty, std::iter::empty())
};
let thunk_name = {
if db.no_thunk_name_mangling() {
format!("__crubit_thunk_{}", &escape_non_identifier_chars(method.name.as_str()))
} else {
let instance = ty::Instance::new(method.def_id, substs);
let symbol = tcx.symbol_name(instance);
format!("__crubit_thunk_{}", &escape_non_identifier_chars(symbol.name))
}
};
method_name_to_cc_thunk_name.insert(method.name, format_cc_ident(&thunk_name)?);
let sig_mid = liberate_and_deanonymize_late_bound_regions(
tcx,
tcx.fn_sig(method.def_id).instantiate(tcx, substs),
method.def_id,
);
// TODO(b/254096006): Preserve the HIR here, if possible?
// Cannot in general (e.g. blanket impl from another crate), but should be able
// to for traits defined or implemented in the current crate.
let sig_hir = None;
cc_thunk_decls.add_assign({
let thunk_name = format_cc_ident(&thunk_name)?;
format_thunk_decl(db, method.def_id, &sig_mid, sig_hir, &thunk_name)?
});
rs_thunk_impls.extend({
let struct_name = &adt.rs_fully_qualified_name;
if is_drop_trait {
// Manually formatting (instead of depending on `format_thunk_impl`)
// to avoid https://doc.rust-lang.org/error_codes/E0040.html
let thunk_name = make_rs_ident(&thunk_name);
quote! {
#[no_mangle]
extern "C" fn #thunk_name(
__self: &mut ::core::mem::MaybeUninit<#struct_name>
) {
unsafe { __self.assume_init_drop() };
}
}
} else {
let fully_qualified_fn_name = {
let fully_qualified_trait_name =
FullyQualifiedName::new(tcx, trait_id).format_for_rs();
let method_name = make_rs_ident(method.name.as_str());
quote! { <#struct_name as #fully_qualified_trait_name>::#method_name }
};
format_thunk_impl(
tcx,
method.def_id,
&sig_mid,
&thunk_name,
fully_qualified_fn_name,
)?
}
});
}
Ok(TraitThunks { method_name_to_cc_thunk_name, cc_thunk_decls, rs_thunk_impls })
}
/// Formats a default constructor for an ADT if possible (i.e. if the `Default`
/// trait is implemented for the ADT). Returns an error otherwise (e.g. if
/// there is no `Default` impl, then the default constructor will be
/// `=delete`d in the returned snippet).
fn format_default_ctor<'tcx>(
db: &dyn BindingsGenerator<'tcx>,
core: Rc<AdtCoreBindings<'tcx>>,
) -> Result<ApiSnippets, ApiSnippets> {
fn fallible_format_default_ctor<'tcx>(
db: &dyn BindingsGenerator<'tcx>,
core: Rc<AdtCoreBindings<'tcx>>,
) -> Result<ApiSnippets> {
let tcx = db.tcx();
let trait_id = tcx
.get_diagnostic_item(sym::Default)
.ok_or(anyhow!("Couldn't find `core::default::Default`"))?;
let TraitThunks {
method_name_to_cc_thunk_name,
cc_thunk_decls,
rs_thunk_impls: rs_details,
} = format_trait_thunks(db, trait_id, &core)?;
let cc_struct_name = &core.cc_short_name;
let main_api = CcSnippet::new(quote! {
__NEWLINE__ __COMMENT__ "Default::default"
#cc_struct_name(); __NEWLINE__ __NEWLINE__
});
let cc_details = {
let thunk_name = method_name_to_cc_thunk_name
.into_values()
.exactly_one()
.expect("Expecting a single `default` method");
let mut prereqs = CcPrerequisites::default();
let cc_thunk_decls = cc_thunk_decls.into_tokens(&mut prereqs);
let tokens = quote! {
#cc_thunk_decls
inline #cc_struct_name::#cc_struct_name() {
__crubit_internal::#thunk_name(this);
}
};
CcSnippet { tokens, prereqs }
};
Ok(ApiSnippets { main_api, cc_details, rs_details })
}
fallible_format_default_ctor(db, core.clone()).map_err(|err| {
let msg = format!("{err:#}");
let adt_cc_name = &core.cc_short_name;
ApiSnippets {
main_api: CcSnippet::new(quote! {
__NEWLINE__ __COMMENT__ #msg
#adt_cc_name() = delete; __NEWLINE__
}),
..Default::default()
}
})
}
/// Formats the copy constructor and the copy-assignment operator for an ADT if
/// possible (i.e. if the `Clone` trait is implemented for the ADT). Returns an
/// error otherwise (e.g. if there is no `Clone` impl, then the copy constructor
/// and assignment operator will be `=delete`d in the returned snippet).
fn format_copy_ctor_and_assignment_operator<'tcx>(
db: &dyn BindingsGenerator<'tcx>,
core: Rc<AdtCoreBindings<'tcx>>,
) -> Result<ApiSnippets, ApiSnippets> {
fn fallible_format_copy_ctor_and_assignment_operator<'tcx>(
db: &dyn BindingsGenerator<'tcx>,
core: Rc<AdtCoreBindings<'tcx>>,
) -> Result<ApiSnippets> {
let tcx = db.tcx();
let cc_struct_name = &core.cc_short_name;
let is_copy = {
// TODO(b/259749095): Once generic ADTs are supported, `is_copy_modulo_regions`
// might need to be replaced with a more thorough check - see
// b/258249993#comment4.
core.self_ty.is_copy_modulo_regions(tcx, tcx.param_env(core.def_id))
};
if is_copy {
let msg = "Rust types that are `Copy` get trivial, `default` C++ copy constructor \
and assignment operator.";
let main_api = CcSnippet::new(quote! {
__NEWLINE__ __COMMENT__ #msg
#cc_struct_name(const #cc_struct_name&) = default; __NEWLINE__
#cc_struct_name& operator=(const #cc_struct_name&) = default;
});
let cc_details = CcSnippet::with_include(
quote! {
static_assert(std::is_trivially_copy_constructible_v<#cc_struct_name>);
static_assert(std::is_trivially_copy_assignable_v<#cc_struct_name>);
},
CcInclude::type_traits(),
);
return Ok(ApiSnippets { main_api, cc_details, rs_details: quote! {} });
}
let trait_id = tcx
.lang_items()
.clone_trait()
.ok_or_else(|| anyhow!("Can't find the `Clone` trait"))?;
let TraitThunks {
method_name_to_cc_thunk_name,
cc_thunk_decls,
rs_thunk_impls: rs_details,
} = format_trait_thunks(db, trait_id, &core)?;
let main_api = CcSnippet::new(quote! {
__NEWLINE__ __COMMENT__ "Clone::clone"
#cc_struct_name(const #cc_struct_name&); __NEWLINE__
__NEWLINE__ __COMMENT__ "Clone::clone_from"
#cc_struct_name& operator=(const #cc_struct_name&); __NEWLINE__ __NEWLINE__
});
let cc_details = {
// `unwrap` calls are okay because `Clone` trait always has these methods.
let clone_thunk_name = method_name_to_cc_thunk_name.get(&sym::clone).unwrap();
let clone_from_thunk_name = method_name_to_cc_thunk_name.get(&sym::clone_from).unwrap();
let mut prereqs = CcPrerequisites::default();
let cc_thunk_decls = cc_thunk_decls.into_tokens(&mut prereqs);
let tokens = quote! {
#cc_thunk_decls
inline #cc_struct_name::#cc_struct_name(const #cc_struct_name& other) {
__crubit_internal::#clone_thunk_name(other, this);
}
inline #cc_struct_name& #cc_struct_name::operator=(const #cc_struct_name& other) {
if (this != &other) {
__crubit_internal::#clone_from_thunk_name(*this, other);
}
return *this;
}
};
CcSnippet { tokens, prereqs }
};
Ok(ApiSnippets { main_api, cc_details, rs_details })
}
fallible_format_copy_ctor_and_assignment_operator(db, core.clone()).map_err(|err| {
let msg = format!("{err:#}");
let adt_cc_name = &core.cc_short_name;
ApiSnippets {
main_api: CcSnippet::new(quote! {
__NEWLINE__ __COMMENT__ #msg
#adt_cc_name(const #adt_cc_name&) = delete; __NEWLINE__
#adt_cc_name& operator=(const #adt_cc_name&) = delete;
}),
..Default::default()
}
})
}
/// Formats the move constructor and the move-assignment operator for an ADT if
/// possible (it depends on various factors like `needs_drop`, `is_unpin` and
/// implementations of `Default` and/or `Clone` traits). Returns an error
/// otherwise (the error's `ApiSnippets` contain a `=delete`d declaration).
fn format_move_ctor_and_assignment_operator<'tcx>(
db: &dyn BindingsGenerator<'tcx>,
core: Rc<AdtCoreBindings<'tcx>>,
) -> Result<ApiSnippets, ApiSnippets> {
fn fallible_format_move_ctor_and_assignment_operator<'tcx>(
db: &dyn BindingsGenerator<'tcx>,
core: Rc<AdtCoreBindings<'tcx>>,
) -> Result<ApiSnippets> {
let tcx = db.tcx();
let adt_cc_name = &core.cc_short_name;
if core.needs_drop(tcx) {
let has_default_ctor = db.format_default_ctor(core.clone()).is_ok();
let is_unpin = core.self_ty.is_unpin(tcx, tcx.param_env(core.def_id));
if has_default_ctor && is_unpin {
let main_api = CcSnippet::new(quote! {
#adt_cc_name(#adt_cc_name&&); __NEWLINE__
#adt_cc_name& operator=(#adt_cc_name&&); __NEWLINE__
});
let mut prereqs = CcPrerequisites::default();
prereqs.includes.insert(db.support_header("internal/memswap.h"));
prereqs.includes.insert(CcInclude::utility()); // for `std::move`
let tokens = quote! {
inline #adt_cc_name::#adt_cc_name(#adt_cc_name&& other)
: #adt_cc_name() {
*this = std::move(other);
}
inline #adt_cc_name& #adt_cc_name::operator=(#adt_cc_name&& other) {
crubit::MemSwap(*this, other);
return *this;
}
};
let cc_details = CcSnippet { tokens, prereqs };
Ok(ApiSnippets { main_api, cc_details, ..Default::default() })
} else if db.format_copy_ctor_and_assignment_operator(core).is_ok() {
// The class will have a custom copy constructor and copy assignment operator
// and *no* move constructor nor move assignment operator. This
// way, when a move is requested, a copy is performed instead
// (this is okay, this is what happens if a copyable pre-C++11
// class is compiled in C++11 mode and moved).
//
// We can't use the `=default` move constructor, because it is elementwise and
// semantically incorrect.  We can't `=delete` the move constructor because it
// would make `SomeStruct(MakeSomeStruct())` select the deleted move constructor
// and fail to compile.
Ok(ApiSnippets::default())
} else {
bail!(
"C++ moves are deleted \
because there's no non-destructive implementation available."
);
}
} else {
let main_api = CcSnippet::new(quote! {
// The generated bindings have to follow Rust move semantics:
// * All Rust types are memcpy-movable (e.g. <internal link>/constructors.html says
// that "Every type must be ready for it to be blindly memcopied to somewhere
// else in memory")
// * The only valid operation on a moved-from non-`Copy` Rust struct is to assign to
// it.
//
// The generated C++ bindings below match the required semantics because they:
// * Generate trivial` C++ move constructor and move assignment operator. Per
// <internal link>/cpp/language/move_constructor#Trivial_move_constructor: "A trivial
// move constructor is a constructor that performs the same action as the trivial
// copy constructor, that is, makes a copy of the object representation as if by
// std::memmove."
// * Generate trivial C++ destructor.
//
// In particular, note that the following C++ code and Rust code are exactly
// equivalent (except that in Rust, reuse of `y` is forbidden at compile time,
// whereas in C++, it's only prohibited by convention):
// * C++, assumming trivial move constructor and trivial destructor:
// `auto x = std::move(y);`
// * Rust, assumming non-`Copy`, no custom `Drop` or drop glue:
// `let x = y;`
//
// TODO(b/258251148): If the ADT provides a custom `Drop` impls or requires drop
// glue, then extra care should be taken to ensure the C++ destructor can handle
// the moved-from object in a way that meets Rust move semantics. For example, the
// generated C++ move constructor might need to assign `Default::default()` to the
// moved-from object.
#adt_cc_name(#adt_cc_name&&) = default; __NEWLINE__
#adt_cc_name& operator=(#adt_cc_name&&) = default; __NEWLINE__
__NEWLINE__
});
let cc_details = CcSnippet::with_include(
quote! {
static_assert(std::is_trivially_move_constructible_v<#adt_cc_name>);
static_assert(std::is_trivially_move_assignable_v<#adt_cc_name>);
},
CcInclude::type_traits(),
);
Ok(ApiSnippets { main_api, cc_details, ..Default::default() })
}
}
fallible_format_move_ctor_and_assignment_operator(db, core.clone()).map_err(|err| {
let msg = format!("{err:#}");
let adt_cc_name = &core.cc_short_name;
ApiSnippets {
main_api: CcSnippet::new(quote! {
__NEWLINE__ __COMMENT__ #msg
#adt_cc_name(#adt_cc_name&&) = delete; __NEWLINE__
#adt_cc_name& operator=(#adt_cc_name&&) = delete;
}),
..Default::default()
}
})
}
/// Formats an algebraic data type (an ADT - a struct, an enum, or a union)
/// represented by `core`. This function is infallible - after
/// `format_adt_core` returns success we have committed to emitting C++ bindings
/// for the ADT.
fn format_adt<'tcx>(
db: &dyn BindingsGenerator<'tcx>,
core: Rc<AdtCoreBindings<'tcx>>,
) -> ApiSnippets {
let tcx = db.tcx();
let adt_cc_name = &core.cc_short_name;
// `format_adt` should only be called for local ADTs.
let local_def_id = core.def_id.expect_local();
let default_ctor_snippets = db.format_default_ctor(core.clone()).unwrap_or_else(|err| err);
let destructor_snippets = if core.needs_drop(tcx) {
let drop_trait_id =
tcx.lang_items().drop_trait().expect("`Drop` trait should be present if `needs_drop");
let TraitThunks {
method_name_to_cc_thunk_name,
cc_thunk_decls,
rs_thunk_impls: rs_details,
} = format_trait_thunks(db, drop_trait_id, &core)
.expect("`format_adt_core` should have already validated `Drop` support");
let drop_thunk_name = method_name_to_cc_thunk_name
.into_values()
.exactly_one()
.expect("Expecting a single `drop` method");
let main_api = CcSnippet::new(quote! {
__NEWLINE__ __COMMENT__ "Drop::drop"
~#adt_cc_name(); __NEWLINE__
__NEWLINE__
});
let cc_details = {
let mut prereqs = CcPrerequisites::default();
let cc_thunk_decls = cc_thunk_decls.into_tokens(&mut prereqs);
let tokens = quote! {
#cc_thunk_decls
inline #adt_cc_name::~#adt_cc_name() {
__crubit_internal::#drop_thunk_name(*this);
}
};
CcSnippet { tokens, prereqs }
};
ApiSnippets { main_api, cc_details, rs_details }
} else {
let main_api = CcSnippet::new(quote! {
__NEWLINE__ __COMMENT__ "No custom `Drop` impl and no custom \"drop glue\" required"
~#adt_cc_name() = default; __NEWLINE__
});
let cc_details = CcSnippet::with_include(
quote! { static_assert(std::is_trivially_destructible_v<#adt_cc_name>); },
CcInclude::type_traits(),
);
ApiSnippets { main_api, cc_details, ..Default::default() }
};
let copy_ctor_and_assignment_snippets =
db.format_copy_ctor_and_assignment_operator(core.clone()).unwrap_or_else(|err| err);
let move_ctor_and_assignment_snippets =
db.format_move_ctor_and_assignment_operator(core.clone()).unwrap_or_else(|err| err);
let impl_items_snippets = tcx
.inherent_impls(core.def_id)
.into_iter()
.flatten()
.map(|impl_id| tcx.hir().expect_item(impl_id.expect_local()))
.flat_map(|item| match &item.kind {
ItemKind::Impl(impl_) => impl_.items,
other => panic!("Unexpected `ItemKind` from `inherent_impls`: {other:?}"),
})
.sorted_by_key(|impl_item_ref| {
let def_id = impl_item_ref.id.owner_id.def_id;
tcx.def_span(def_id)
})
.filter_map(|impl_item_ref| {
let def_id = impl_item_ref.id.owner_id.def_id;
if !tcx.effective_visibilities(()).is_directly_public(def_id) {
return None;
}