rustc_sanitizers/cfi/typeid/itanium_cxx_abi/encode.rs
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//! Encodes type metadata identifiers for LLVM CFI and cross-language LLVM CFI support using Itanium
//! C++ ABI mangling for encoding with vendor extended type qualifiers and types for Rust types that
//! are not used across the FFI boundary.
//!
//! For more information about LLVM CFI and cross-language LLVM CFI support for the Rust compiler,
//! see design document in the tracking issue #89653.
use std::fmt::Write as _;
use rustc_data_structures::base_n::{ALPHANUMERIC_ONLY, CASE_INSENSITIVE, ToBaseN};
use rustc_data_structures::fx::FxHashMap;
use rustc_hir as hir;
use rustc_middle::bug;
use rustc_middle::ty::layout::IntegerExt;
use rustc_middle::ty::{
self, Const, ExistentialPredicate, FloatTy, FnSig, GenericArg, GenericArgKind, GenericArgsRef,
IntTy, List, Region, RegionKind, TermKind, Ty, TyCtxt, TypeFoldable, UintTy,
};
use rustc_span::def_id::DefId;
use rustc_span::sym;
use rustc_target::abi::Integer;
use rustc_target::spec::abi::Abi;
use tracing::instrument;
use crate::cfi::typeid::TypeIdOptions;
use crate::cfi::typeid::itanium_cxx_abi::transform::{TransformTy, TransformTyOptions};
/// Options for encode_ty.
pub(crate) type EncodeTyOptions = TypeIdOptions;
/// Substitution dictionary key.
#[derive(Eq, Hash, PartialEq)]
pub(crate) enum DictKey<'tcx> {
Ty(Ty<'tcx>, TyQ),
Region(Region<'tcx>),
Const(Const<'tcx>),
Predicate(ExistentialPredicate<'tcx>),
}
/// Type and extended type qualifiers.
#[derive(Eq, Hash, PartialEq)]
pub(crate) enum TyQ {
None,
Const,
Mut,
}
/// Substitutes a component if found in the substitution dictionary (see
/// <https://itanium-cxx-abi.github.io/cxx-abi/abi.html#mangling-compression>).
fn compress<'tcx>(
dict: &mut FxHashMap<DictKey<'tcx>, usize>,
key: DictKey<'tcx>,
comp: &mut String,
) {
match dict.get(&key) {
Some(num) => {
comp.clear();
let _ = write!(comp, "S{}_", to_seq_id(*num));
}
None => {
dict.insert(key, dict.len());
}
}
}
/// Encodes args using the Itanium C++ ABI with vendor extended type qualifiers and types for Rust
/// types that are not used at the FFI boundary.
fn encode_args<'tcx>(
tcx: TyCtxt<'tcx>,
args: GenericArgsRef<'tcx>,
for_def: DefId,
has_erased_self: bool,
dict: &mut FxHashMap<DictKey<'tcx>, usize>,
options: EncodeTyOptions,
) -> String {
// [I<subst1..substN>E] as part of vendor extended type
let mut s = String::new();
let args: Vec<GenericArg<'_>> = args.iter().collect();
if !args.is_empty() {
s.push('I');
let def_generics = tcx.generics_of(for_def);
for (n, arg) in args.iter().enumerate() {
match arg.unpack() {
GenericArgKind::Lifetime(region) => {
s.push_str(&encode_region(region, dict));
}
GenericArgKind::Type(ty) => {
s.push_str(&encode_ty(tcx, ty, dict, options));
}
GenericArgKind::Const(c) => {
let n = n + (has_erased_self as usize);
let ct_ty =
tcx.type_of(def_generics.param_at(n, tcx).def_id).instantiate_identity();
s.push_str(&encode_const(tcx, c, ct_ty, dict, options));
}
}
}
s.push('E');
}
s
}
/// Encodes a const using the Itanium C++ ABI as a literal argument (see
/// <https://itanium-cxx-abi.github.io/cxx-abi/abi.html#mangling.literal>).
fn encode_const<'tcx>(
tcx: TyCtxt<'tcx>,
c: Const<'tcx>,
ct_ty: Ty<'tcx>,
dict: &mut FxHashMap<DictKey<'tcx>, usize>,
options: EncodeTyOptions,
) -> String {
// L<element-type>[n][<element-value>]E as literal argument
let mut s = String::from('L');
match c.kind() {
// Const parameters
ty::ConstKind::Param(..) => {
// L<element-type>E as literal argument
// Element type
s.push_str(&encode_ty(tcx, ct_ty, dict, options));
}
// Literal arguments
ty::ConstKind::Value(ct_ty, ..) => {
// L<element-type>[n]<element-value>E as literal argument
// Element type
s.push_str(&encode_ty(tcx, ct_ty, dict, options));
// The only allowed types of const values are bool, u8, u16, u32,
// u64, u128, usize i8, i16, i32, i64, i128, isize, and char. The
// bool value false is encoded as 0 and true as 1.
match ct_ty.kind() {
ty::Int(ity) => {
let bits = c.eval_bits(tcx, ty::ParamEnv::reveal_all());
let val = Integer::from_int_ty(&tcx, *ity).size().sign_extend(bits) as i128;
if val < 0 {
s.push('n');
}
let _ = write!(s, "{val}");
}
ty::Uint(_) => {
let val = c.eval_bits(tcx, ty::ParamEnv::reveal_all());
let _ = write!(s, "{val}");
}
ty::Bool => {
let val = c.try_to_bool().expect("expected monomorphic const in cfi");
let _ = write!(s, "{val}");
}
_ => {
bug!("encode_const: unexpected type `{:?}`", ct_ty);
}
}
}
_ => {
bug!("encode_const: unexpected kind `{:?}`", c.kind());
}
}
// Close the "L..E" pair
s.push('E');
compress(dict, DictKey::Const(c), &mut s);
s
}
/// Encodes a FnSig using the Itanium C++ ABI with vendor extended type qualifiers and types for
/// Rust types that are not used at the FFI boundary.
fn encode_fnsig<'tcx>(
tcx: TyCtxt<'tcx>,
fn_sig: &FnSig<'tcx>,
dict: &mut FxHashMap<DictKey<'tcx>, usize>,
options: TypeIdOptions,
) -> String {
// Function types are delimited by an "F..E" pair
let mut s = String::from("F");
let mut encode_ty_options = EncodeTyOptions::from_bits(options.bits())
.unwrap_or_else(|| bug!("encode_fnsig: invalid option(s) `{:?}`", options.bits()));
match fn_sig.abi {
Abi::C { .. } => {
encode_ty_options.insert(EncodeTyOptions::GENERALIZE_REPR_C);
}
_ => {
encode_ty_options.remove(EncodeTyOptions::GENERALIZE_REPR_C);
}
}
// Encode the return type
let transform_ty_options = TransformTyOptions::from_bits(options.bits())
.unwrap_or_else(|| bug!("encode_fnsig: invalid option(s) `{:?}`", options.bits()));
let mut type_folder = TransformTy::new(tcx, transform_ty_options);
let ty = fn_sig.output().fold_with(&mut type_folder);
s.push_str(&encode_ty(tcx, ty, dict, encode_ty_options));
// Encode the parameter types
let tys = fn_sig.inputs();
if !tys.is_empty() {
for ty in tys {
let ty = ty.fold_with(&mut type_folder);
s.push_str(&encode_ty(tcx, ty, dict, encode_ty_options));
}
if fn_sig.c_variadic {
s.push('z');
}
} else if fn_sig.c_variadic {
s.push('z');
} else {
// Empty parameter lists, whether declared as () or conventionally as (void), are
// encoded with a void parameter specifier "v".
s.push('v')
}
// Close the "F..E" pair
s.push('E');
s
}
/// Encodes a predicate using the Itanium C++ ABI with vendor extended type qualifiers and types for
/// Rust types that are not used at the FFI boundary.
fn encode_predicate<'tcx>(
tcx: TyCtxt<'tcx>,
predicate: ty::PolyExistentialPredicate<'tcx>,
dict: &mut FxHashMap<DictKey<'tcx>, usize>,
options: EncodeTyOptions,
) -> String {
// u<length><name>[I<element-type1..element-typeN>E], where <element-type> is <subst>, as vendor
// extended type.
let mut s = String::new();
match predicate.as_ref().skip_binder() {
ty::ExistentialPredicate::Trait(trait_ref) => {
let name = encode_ty_name(tcx, trait_ref.def_id);
let _ = write!(s, "u{}{}", name.len(), name);
s.push_str(&encode_args(tcx, trait_ref.args, trait_ref.def_id, true, dict, options));
}
ty::ExistentialPredicate::Projection(projection) => {
let name = encode_ty_name(tcx, projection.def_id);
let _ = write!(s, "u{}{}", name.len(), name);
s.push_str(&encode_args(tcx, projection.args, projection.def_id, true, dict, options));
match projection.term.unpack() {
TermKind::Ty(ty) => s.push_str(&encode_ty(tcx, ty, dict, options)),
TermKind::Const(c) => s.push_str(&encode_const(
tcx,
c,
tcx.type_of(projection.def_id).instantiate(tcx, projection.args),
dict,
options,
)),
}
}
ty::ExistentialPredicate::AutoTrait(def_id) => {
let name = encode_ty_name(tcx, *def_id);
let _ = write!(s, "u{}{}", name.len(), name);
}
};
compress(dict, DictKey::Predicate(*predicate.as_ref().skip_binder()), &mut s);
s
}
/// Encodes predicates using the Itanium C++ ABI with vendor extended type qualifiers and types for
/// Rust types that are not used at the FFI boundary.
fn encode_predicates<'tcx>(
tcx: TyCtxt<'tcx>,
predicates: &List<ty::PolyExistentialPredicate<'tcx>>,
dict: &mut FxHashMap<DictKey<'tcx>, usize>,
options: EncodeTyOptions,
) -> String {
// <predicate1[..predicateN]>E as part of vendor extended type
let mut s = String::new();
let predicates: Vec<ty::PolyExistentialPredicate<'tcx>> = predicates.iter().collect();
for predicate in predicates {
s.push_str(&encode_predicate(tcx, predicate, dict, options));
}
s
}
/// Encodes a region using the Itanium C++ ABI as a vendor extended type.
fn encode_region<'tcx>(region: Region<'tcx>, dict: &mut FxHashMap<DictKey<'tcx>, usize>) -> String {
// u6region[I[<region-disambiguator>][<region-index>]E] as vendor extended type
let mut s = String::new();
match region.kind() {
RegionKind::ReBound(debruijn, r) => {
s.push_str("u6regionI");
// Debruijn index, which identifies the binder, as region disambiguator
let num = debruijn.index() as u64;
if num > 0 {
s.push_str(&to_disambiguator(num));
}
// Index within the binder
let _ = write!(s, "{}", r.var.index() as u64);
s.push('E');
compress(dict, DictKey::Region(region), &mut s);
}
RegionKind::ReErased => {
s.push_str("u6region");
compress(dict, DictKey::Region(region), &mut s);
}
RegionKind::ReEarlyParam(..)
| RegionKind::ReLateParam(..)
| RegionKind::ReStatic
| RegionKind::ReError(_)
| RegionKind::ReVar(..)
| RegionKind::RePlaceholder(..) => {
bug!("encode_region: unexpected `{:?}`", region.kind());
}
}
s
}
/// Encodes a ty:Ty using the Itanium C++ ABI with vendor extended type qualifiers and types for
/// Rust types that are not used at the FFI boundary.
#[instrument(level = "trace", skip(tcx, dict))]
pub(crate) fn encode_ty<'tcx>(
tcx: TyCtxt<'tcx>,
ty: Ty<'tcx>,
dict: &mut FxHashMap<DictKey<'tcx>, usize>,
options: EncodeTyOptions,
) -> String {
let mut typeid = String::new();
match ty.kind() {
// Primitive types
// Rust's bool has the same layout as C17's _Bool, that is, its size and alignment are
// implementation-defined. Any bool can be cast into an integer, taking on the values 1
// (true) or 0 (false).
//
// (See https://rust-lang.github.io/unsafe-code-guidelines/layout/scalars.html#bool.)
ty::Bool => {
typeid.push('b');
}
ty::Int(..) | ty::Uint(..) => {
// u<length><type-name> as vendor extended type
let mut s = String::from(match ty.kind() {
ty::Int(IntTy::I8) => "u2i8",
ty::Int(IntTy::I16) => "u3i16",
ty::Int(IntTy::I32) => "u3i32",
ty::Int(IntTy::I64) => "u3i64",
ty::Int(IntTy::I128) => "u4i128",
ty::Int(IntTy::Isize) => "u5isize",
ty::Uint(UintTy::U8) => "u2u8",
ty::Uint(UintTy::U16) => "u3u16",
ty::Uint(UintTy::U32) => "u3u32",
ty::Uint(UintTy::U64) => "u3u64",
ty::Uint(UintTy::U128) => "u4u128",
ty::Uint(UintTy::Usize) => "u5usize",
_ => bug!("encode_ty: unexpected `{:?}`", ty.kind()),
});
compress(dict, DictKey::Ty(ty, TyQ::None), &mut s);
typeid.push_str(&s);
}
// Rust's f16, f32, f64, and f126 half (16-bit), single (32-bit), double (64-bit), and
// quad (128-bit) precision floating-point types have IEEE-754 binary16, binary32,
// binary64, and binary128 floating-point layouts, respectively.
//
// (See https://rust-lang.github.io/unsafe-code-guidelines/layout/scalars.html#fixed-width-floating-point-types.)
ty::Float(float_ty) => {
typeid.push_str(match float_ty {
FloatTy::F16 => "Dh",
FloatTy::F32 => "f",
FloatTy::F64 => "d",
FloatTy::F128 => "g",
});
}
ty::Char => {
// u4char as vendor extended type
let mut s = String::from("u4char");
compress(dict, DictKey::Ty(ty, TyQ::None), &mut s);
typeid.push_str(&s);
}
ty::Str => {
// u3str as vendor extended type
let mut s = String::from("u3str");
compress(dict, DictKey::Ty(ty, TyQ::None), &mut s);
typeid.push_str(&s);
}
ty::Never => {
// u5never as vendor extended type
let mut s = String::from("u5never");
compress(dict, DictKey::Ty(ty, TyQ::None), &mut s);
typeid.push_str(&s);
}
// Compound types
// () in Rust is equivalent to void return type in C
_ if ty.is_unit() => {
typeid.push('v');
}
// Sequence types
ty::Tuple(tys) => {
// u5tupleI<element-type1..element-typeN>E as vendor extended type
let mut s = String::from("u5tupleI");
for ty in tys.iter() {
s.push_str(&encode_ty(tcx, ty, dict, options));
}
s.push('E');
compress(dict, DictKey::Ty(ty, TyQ::None), &mut s);
typeid.push_str(&s);
}
ty::Array(ty0, len) => {
// A<array-length><element-type>
let len = len.try_to_target_usize(tcx).expect("expected monomorphic const in cfi");
let mut s = String::from("A");
let _ = write!(s, "{len}");
s.push_str(&encode_ty(tcx, *ty0, dict, options));
compress(dict, DictKey::Ty(ty, TyQ::None), &mut s);
typeid.push_str(&s);
}
ty::Pat(ty0, pat) => {
// u3patI<element-type><pattern>E as vendor extended type
let mut s = String::from("u3patI");
s.push_str(&encode_ty(tcx, *ty0, dict, options));
write!(s, "{:?}", **pat).unwrap();
s.push('E');
compress(dict, DictKey::Ty(ty, TyQ::None), &mut s);
typeid.push_str(&s);
}
ty::Slice(ty0) => {
// u5sliceI<element-type>E as vendor extended type
let mut s = String::from("u5sliceI");
s.push_str(&encode_ty(tcx, *ty0, dict, options));
s.push('E');
compress(dict, DictKey::Ty(ty, TyQ::None), &mut s);
typeid.push_str(&s);
}
// User-defined types
ty::Adt(adt_def, args) => {
let mut s = String::new();
let def_id = adt_def.did();
if let Some(cfi_encoding) = tcx.get_attr(def_id, sym::cfi_encoding) {
// Use user-defined CFI encoding for type
if let Some(value_str) = cfi_encoding.value_str() {
let value_str = value_str.to_string();
let str = value_str.trim();
if !str.is_empty() {
s.push_str(str);
// Don't compress user-defined builtin types (see
// https://itanium-cxx-abi.github.io/cxx-abi/abi.html#mangling-builtin and
// https://itanium-cxx-abi.github.io/cxx-abi/abi.html#mangling-compression).
let builtin_types = [
"v", "w", "b", "c", "a", "h", "s", "t", "i", "j", "l", "m", "x", "y",
"n", "o", "f", "d", "e", "g", "z", "Dh",
];
if !builtin_types.contains(&str) {
compress(dict, DictKey::Ty(ty, TyQ::None), &mut s);
}
} else {
#[allow(
rustc::diagnostic_outside_of_impl,
rustc::untranslatable_diagnostic
)]
tcx.dcx()
.struct_span_err(
cfi_encoding.span,
format!("invalid `cfi_encoding` for `{:?}`", ty.kind()),
)
.emit();
}
} else {
bug!("encode_ty: invalid `cfi_encoding` for `{:?}`", ty.kind());
}
} else if options.contains(EncodeTyOptions::GENERALIZE_REPR_C) && adt_def.repr().c() {
// For cross-language LLVM CFI support, the encoding must be compatible at the FFI
// boundary. For instance:
//
// struct type1 {};
// void foo(struct type1* bar) {}
//
// Is encoded as:
//
// _ZTSFvP5type1E
//
// So, encode any repr(C) user-defined type for extern function types with the "C"
// calling convention (or extern types [i.e., ty::Foreign]) as <length><name>, where
// <name> is <unscoped-name>.
let name = tcx.item_name(def_id).to_string();
let _ = write!(s, "{}{}", name.len(), name);
compress(dict, DictKey::Ty(ty, TyQ::None), &mut s);
} else {
// u<length><name>[I<element-type1..element-typeN>E], where <element-type> is
// <subst>, as vendor extended type.
let name = encode_ty_name(tcx, def_id);
let _ = write!(s, "u{}{}", name.len(), name);
s.push_str(&encode_args(tcx, args, def_id, false, dict, options));
compress(dict, DictKey::Ty(ty, TyQ::None), &mut s);
}
typeid.push_str(&s);
}
ty::Foreign(def_id) => {
// <length><name>, where <name> is <unscoped-name>
let mut s = String::new();
if let Some(cfi_encoding) = tcx.get_attr(*def_id, sym::cfi_encoding) {
// Use user-defined CFI encoding for type
if let Some(value_str) = cfi_encoding.value_str() {
if !value_str.to_string().trim().is_empty() {
s.push_str(value_str.to_string().trim());
} else {
#[allow(
rustc::diagnostic_outside_of_impl,
rustc::untranslatable_diagnostic
)]
tcx.dcx()
.struct_span_err(
cfi_encoding.span,
format!("invalid `cfi_encoding` for `{:?}`", ty.kind()),
)
.emit();
}
} else {
bug!("encode_ty: invalid `cfi_encoding` for `{:?}`", ty.kind());
}
} else {
let name = tcx.item_name(*def_id).to_string();
let _ = write!(s, "{}{}", name.len(), name);
}
compress(dict, DictKey::Ty(ty, TyQ::None), &mut s);
typeid.push_str(&s);
}
// Function types
ty::FnDef(def_id, args) | ty::Closure(def_id, args) => {
// u<length><name>[I<element-type1..element-typeN>E], where <element-type> is <subst>,
// as vendor extended type.
let mut s = String::new();
let name = encode_ty_name(tcx, *def_id);
let _ = write!(s, "u{}{}", name.len(), name);
s.push_str(&encode_args(tcx, args, *def_id, false, dict, options));
compress(dict, DictKey::Ty(ty, TyQ::None), &mut s);
typeid.push_str(&s);
}
ty::CoroutineClosure(def_id, args) => {
// u<length><name>[I<element-type1..element-typeN>E], where <element-type> is <subst>,
// as vendor extended type.
let mut s = String::new();
let name = encode_ty_name(tcx, *def_id);
let _ = write!(s, "u{}{}", name.len(), name);
let parent_args = tcx.mk_args(args.as_coroutine_closure().parent_args());
s.push_str(&encode_args(tcx, parent_args, *def_id, false, dict, options));
compress(dict, DictKey::Ty(ty, TyQ::None), &mut s);
typeid.push_str(&s);
}
ty::Coroutine(def_id, args, ..) => {
// u<length><name>[I<element-type1..element-typeN>E], where <element-type> is <subst>,
// as vendor extended type.
let mut s = String::new();
let name = encode_ty_name(tcx, *def_id);
let _ = write!(s, "u{}{}", name.len(), name);
// Encode parent args only
s.push_str(&encode_args(
tcx,
tcx.mk_args(args.as_coroutine().parent_args()),
*def_id,
false,
dict,
options,
));
compress(dict, DictKey::Ty(ty, TyQ::None), &mut s);
typeid.push_str(&s);
}
// Pointer types
ty::Ref(region, ty0, ..) => {
// [U3mut]u3refI<element-type>E as vendor extended type qualifier and type
let mut s = String::new();
s.push_str("u3refI");
s.push_str(&encode_ty(tcx, *ty0, dict, options));
s.push('E');
compress(dict, DictKey::Ty(Ty::new_imm_ref(tcx, *region, *ty0), TyQ::None), &mut s);
if ty.is_mutable_ptr() {
s = format!("{}{}", "U3mut", s);
compress(dict, DictKey::Ty(ty, TyQ::Mut), &mut s);
}
typeid.push_str(&s);
}
ty::RawPtr(ptr_ty, _mutbl) => {
// FIXME: This can definitely not be so spaghettified.
// P[K]<element-type>
let mut s = String::new();
s.push_str(&encode_ty(tcx, *ptr_ty, dict, options));
if !ty.is_mutable_ptr() {
s = format!("{}{}", "K", s);
compress(dict, DictKey::Ty(*ptr_ty, TyQ::Const), &mut s);
};
s = format!("{}{}", "P", s);
compress(dict, DictKey::Ty(ty, TyQ::None), &mut s);
typeid.push_str(&s);
}
ty::FnPtr(sig_tys, hdr) => {
// PF<return-type><parameter-type1..parameter-typeN>E
let mut s = String::from("P");
s.push_str(&encode_fnsig(
tcx,
&sig_tys.with(*hdr).skip_binder(),
dict,
TypeIdOptions::empty(),
));
compress(dict, DictKey::Ty(ty, TyQ::None), &mut s);
typeid.push_str(&s);
}
// Trait types
ty::Dynamic(predicates, region, kind) => {
// u3dynI<element-type1[..element-typeN]>E, where <element-type> is <predicate>, as
// vendor extended type.
let mut s = String::from(match kind {
ty::Dyn => "u3dynI",
ty::DynStar => "u7dynstarI",
});
s.push_str(&encode_predicates(tcx, predicates, dict, options));
s.push_str(&encode_region(*region, dict));
s.push('E');
compress(dict, DictKey::Ty(ty, TyQ::None), &mut s);
typeid.push_str(&s);
}
// Type parameters
ty::Param(..) => {
// u5param as vendor extended type
let mut s = String::from("u5param");
compress(dict, DictKey::Ty(ty, TyQ::None), &mut s);
typeid.push_str(&s);
}
// Unexpected types
ty::Alias(..)
| ty::Bound(..)
| ty::Error(..)
| ty::CoroutineWitness(..)
| ty::Infer(..)
| ty::Placeholder(..) => {
bug!("encode_ty: unexpected `{:?}`", ty.kind());
}
};
typeid
}
/// Encodes a ty:Ty name, including its crate and path disambiguators and names.
fn encode_ty_name(tcx: TyCtxt<'_>, def_id: DefId) -> String {
// Encode <name> for use in u<length><name>[I<element-type1..element-typeN>E], where
// <element-type> is <subst>, using v0's <path> without v0's extended form of paths:
//
// N<namespace-tagN>..N<namespace-tag1>
// C<crate-disambiguator><crate-name>
// <path-disambiguator1><path-name1>..<path-disambiguatorN><path-nameN>
//
// With additional tags for DefPathData::Impl and DefPathData::ForeignMod. For instance:
//
// pub type Type1 = impl Send;
// let _: Type1 = <Struct1<i32>>::foo;
// fn foo1(_: Type1) { }
//
// pub type Type2 = impl Send;
// let _: Type2 = <Trait1<i32>>::foo;
// fn foo2(_: Type2) { }
//
// pub type Type3 = impl Send;
// let _: Type3 = <i32 as Trait1<i32>>::foo;
// fn foo3(_: Type3) { }
//
// pub type Type4 = impl Send;
// let _: Type4 = <Struct1<i32> as Trait1<i32>>::foo;
// fn foo3(_: Type4) { }
//
// Are encoded as:
//
// _ZTSFvu29NvNIC1234_5crate8{{impl}}3fooIu3i32EE
// _ZTSFvu27NvNtC1234_5crate6Trait13fooIu3dynIu21NtC1234_5crate6Trait1Iu3i32Eu6regionES_EE
// _ZTSFvu27NvNtC1234_5crate6Trait13fooIu3i32S_EE
// _ZTSFvu27NvNtC1234_5crate6Trait13fooIu22NtC1234_5crate7Struct1Iu3i32ES_EE
//
// The reason for not using v0's extended form of paths is to use a consistent and simpler
// encoding, as the reasoning for using it isn't relevant for type metadata identifiers (i.e.,
// keep symbol names close to how methods are represented in error messages). See
// https://rust-lang.github.io/rfcs/2603-rust-symbol-name-mangling-v0.html#methods.
let mut s = String::new();
// Start and namespace tags
let mut def_path = tcx.def_path(def_id);
def_path.data.reverse();
for disambiguated_data in &def_path.data {
s.push('N');
s.push_str(match disambiguated_data.data {
hir::definitions::DefPathData::Impl => "I", // Not specified in v0's <namespace>
hir::definitions::DefPathData::ForeignMod => "F", // Not specified in v0's <namespace>
hir::definitions::DefPathData::TypeNs(..) => "t",
hir::definitions::DefPathData::ValueNs(..) => "v",
hir::definitions::DefPathData::Closure => "C",
hir::definitions::DefPathData::Ctor => "c",
hir::definitions::DefPathData::AnonConst => "k",
hir::definitions::DefPathData::OpaqueTy => "i",
hir::definitions::DefPathData::CrateRoot
| hir::definitions::DefPathData::Use
| hir::definitions::DefPathData::GlobalAsm
| hir::definitions::DefPathData::MacroNs(..)
| hir::definitions::DefPathData::LifetimeNs(..)
| hir::definitions::DefPathData::AnonAdt => {
bug!("encode_ty_name: unexpected `{:?}`", disambiguated_data.data);
}
});
}
// Crate disambiguator and name
s.push('C');
s.push_str(&to_disambiguator(tcx.stable_crate_id(def_path.krate).as_u64()));
let crate_name = tcx.crate_name(def_path.krate).to_string();
let _ = write!(s, "{}{}", crate_name.len(), crate_name);
// Disambiguators and names
def_path.data.reverse();
for disambiguated_data in &def_path.data {
let num = disambiguated_data.disambiguator as u64;
if num > 0 {
s.push_str(&to_disambiguator(num));
}
let name = disambiguated_data.data.to_string();
let _ = write!(s, "{}", name.len());
// Prepend a '_' if name starts with a digit or '_'
if let Some(first) = name.as_bytes().first() {
if first.is_ascii_digit() || *first == b'_' {
s.push('_');
}
} else {
bug!("encode_ty_name: invalid name `{:?}`", name);
}
s.push_str(&name);
}
s
}
/// Converts a number to a disambiguator (see
/// <https://rust-lang.github.io/rfcs/2603-rust-symbol-name-mangling-v0.html>).
fn to_disambiguator(num: u64) -> String {
if let Some(num) = num.checked_sub(1) {
format!("s{}_", num.to_base(ALPHANUMERIC_ONLY))
} else {
"s_".to_string()
}
}
/// Converts a number to a sequence number (see
/// <https://itanium-cxx-abi.github.io/cxx-abi/abi.html#mangle.seq-id>).
fn to_seq_id(num: usize) -> String {
if let Some(num) = num.checked_sub(1) {
(num as u64).to_base(CASE_INSENSITIVE).to_uppercase()
} else {
"".to_string()
}
}