use rustc_data_structures::stable_hasher::{HashStable, StableHasher}; use rustc_hir::def_id::CrateNum; use rustc_hir::definitions::{DefPathData, DisambiguatedDefPathData}; use rustc_middle::ty::print::{PrettyPrinter, Print, Printer}; use rustc_middle::ty::subst::{GenericArg, GenericArgKind}; use rustc_middle::ty::{self, Instance, Ty, TyCtxt, TypeVisitable}; use rustc_middle::util::common::record_time; use std::fmt::{self, Write}; use std::mem::{self, discriminant}; pub(super) fn mangle<'tcx>( tcx: TyCtxt<'tcx>, instance: Instance<'tcx>, instantiating_crate: Option, ) -> String { let def_id = instance.def_id(); // We want to compute the "type" of this item. Unfortunately, some // kinds of items (e.g., closures) don't have an entry in the // item-type array. So walk back up the find the closest parent // that DOES have an entry. let mut ty_def_id = def_id; let instance_ty; loop { let key = tcx.def_key(ty_def_id); match key.disambiguated_data.data { DefPathData::TypeNs(_) | DefPathData::ValueNs(_) => { instance_ty = tcx.type_of(ty_def_id); debug!(?instance_ty); break; } _ => { // if we're making a symbol for something, there ought // to be a value or type-def or something in there // *somewhere* ty_def_id.index = key.parent.unwrap_or_else(|| { bug!( "finding type for {:?}, encountered def-id {:?} with no \ parent", def_id, ty_def_id ); }); } } } // Erase regions because they may not be deterministic when hashed // and should not matter anyhow. let instance_ty = tcx.erase_regions(instance_ty); let hash = get_symbol_hash(tcx, instance, instance_ty, instantiating_crate); let mut printer = SymbolPrinter { tcx, path: SymbolPath::new(), keep_within_component: false }; printer .print_def_path( def_id, if let ty::InstanceDef::DropGlue(_, _) = instance.def { // Add the name of the dropped type to the symbol name &*instance.substs } else { &[] }, ) .unwrap(); if let ty::InstanceDef::VTableShim(..) = instance.def { let _ = printer.write_str("{{vtable-shim}}"); } if let ty::InstanceDef::ReifyShim(..) = instance.def { let _ = printer.write_str("{{reify-shim}}"); } printer.path.finish(hash) } fn get_symbol_hash<'tcx>( tcx: TyCtxt<'tcx>, // instance this name will be for instance: Instance<'tcx>, // type of the item, without any generic // parameters substituted; this is // included in the hash as a kind of // safeguard. item_type: Ty<'tcx>, instantiating_crate: Option, ) -> u64 { let def_id = instance.def_id(); let substs = instance.substs; debug!("get_symbol_hash(def_id={:?}, parameters={:?})", def_id, substs); tcx.with_stable_hashing_context(|mut hcx| { let mut hasher = StableHasher::new(); record_time(&tcx.sess.perf_stats.symbol_hash_time, || { // the main symbol name is not necessarily unique; hash in the // compiler's internal def-path, guaranteeing each symbol has a // truly unique path tcx.def_path_hash(def_id).hash_stable(&mut hcx, &mut hasher); // Include the main item-type. Note that, in this case, the // assertions about `needs_subst` may not hold, but this item-type // ought to be the same for every reference anyway. assert!(!item_type.has_erasable_regions()); hcx.while_hashing_spans(false, |hcx| { item_type.hash_stable(hcx, &mut hasher); // If this is a function, we hash the signature as well. // This is not *strictly* needed, but it may help in some // situations, see the `run-make/a-b-a-linker-guard` test. if let ty::FnDef(..) = item_type.kind() { item_type.fn_sig(tcx).hash_stable(hcx, &mut hasher); } // also include any type parameters (for generic items) substs.hash_stable(hcx, &mut hasher); if let Some(instantiating_crate) = instantiating_crate { tcx.def_path_hash(instantiating_crate.as_def_id()) .stable_crate_id() .hash_stable(hcx, &mut hasher); } // We want to avoid accidental collision between different types of instances. // Especially, `VTableShim`s and `ReifyShim`s may overlap with their original // instances without this. discriminant(&instance.def).hash_stable(hcx, &mut hasher); }); }); // 64 bits should be enough to avoid collisions. hasher.finish::() }) } // Follow C++ namespace-mangling style, see // https://en.wikipedia.org/wiki/Name_mangling for more info. // // It turns out that on macOS you can actually have arbitrary symbols in // function names (at least when given to LLVM), but this is not possible // when using unix's linker. Perhaps one day when we just use a linker from LLVM // we won't need to do this name mangling. The problem with name mangling is // that it seriously limits the available characters. For example we can't // have things like &T in symbol names when one would theoretically // want them for things like impls of traits on that type. // // To be able to work on all platforms and get *some* reasonable output, we // use C++ name-mangling. #[derive(Debug)] struct SymbolPath { result: String, temp_buf: String, } impl SymbolPath { fn new() -> Self { let mut result = SymbolPath { result: String::with_capacity(64), temp_buf: String::with_capacity(16) }; result.result.push_str("_ZN"); // _Z == Begin name-sequence, N == nested result } fn finalize_pending_component(&mut self) { if !self.temp_buf.is_empty() { let _ = write!(self.result, "{}{}", self.temp_buf.len(), self.temp_buf); self.temp_buf.clear(); } } fn finish(mut self, hash: u64) -> String { self.finalize_pending_component(); // E = end name-sequence let _ = write!(self.result, "17h{:016x}E", hash); self.result } } struct SymbolPrinter<'tcx> { tcx: TyCtxt<'tcx>, path: SymbolPath, // When `true`, `finalize_pending_component` isn't used. // This is needed when recursing into `path_qualified`, // or `path_generic_args`, as any nested paths are // logically within one component. keep_within_component: bool, } // HACK(eddyb) this relies on using the `fmt` interface to get // `PrettyPrinter` aka pretty printing of e.g. types in paths, // symbol names should have their own printing machinery. impl<'tcx> Printer<'tcx> for &mut SymbolPrinter<'tcx> { type Error = fmt::Error; type Path = Self; type Region = Self; type Type = Self; type DynExistential = Self; type Const = Self; fn tcx(&self) -> TyCtxt<'tcx> { self.tcx } fn print_region(self, _region: ty::Region<'_>) -> Result { Ok(self) } fn print_type(mut self, ty: Ty<'tcx>) -> Result { match *ty.kind() { // Print all nominal types as paths (unlike `pretty_print_type`). ty::FnDef(def_id, substs) | ty::Opaque(def_id, substs) | ty::Projection(ty::ProjectionTy { item_def_id: def_id, substs }) | ty::Closure(def_id, substs) | ty::Generator(def_id, substs, _) => self.print_def_path(def_id, substs), // The `pretty_print_type` formatting of array size depends on // -Zverbose flag, so we cannot reuse it here. ty::Array(ty, size) => { self.write_str("[")?; self = self.print_type(ty)?; self.write_str("; ")?; if let Some(size) = size.kind().try_to_bits(self.tcx().data_layout.pointer_size) { write!(self, "{}", size)? } else if let ty::ConstKind::Param(param) = size.kind() { self = param.print(self)? } else { self.write_str("_")? } self.write_str("]")?; Ok(self) } _ => self.pretty_print_type(ty), } } fn print_dyn_existential( mut self, predicates: &'tcx ty::List>, ) -> Result { let mut first = true; for p in predicates { if !first { write!(self, "+")?; } first = false; self = p.print(self)?; } Ok(self) } fn print_const(self, ct: ty::Const<'tcx>) -> Result { // only print integers match (ct.kind(), ct.ty().kind()) { (ty::ConstKind::Value(ty::ValTree::Leaf(scalar)), ty::Int(_) | ty::Uint(_)) => { // The `pretty_print_const` formatting depends on -Zverbose // flag, so we cannot reuse it here. let signed = matches!(ct.ty().kind(), ty::Int(_)); write!( self, "{:#?}", ty::ConstInt::new(scalar, signed, ct.ty().is_ptr_sized_integral()) )?; } _ => self.write_str("_")?, } Ok(self) } fn path_crate(self, cnum: CrateNum) -> Result { self.write_str(self.tcx.crate_name(cnum).as_str())?; Ok(self) } fn path_qualified( self, self_ty: Ty<'tcx>, trait_ref: Option>, ) -> Result { // Similar to `pretty_path_qualified`, but for the other // types that are printed as paths (see `print_type` above). match self_ty.kind() { ty::FnDef(..) | ty::Opaque(..) | ty::Projection(_) | ty::Closure(..) | ty::Generator(..) if trait_ref.is_none() => { self.print_type(self_ty) } _ => self.pretty_path_qualified(self_ty, trait_ref), } } fn path_append_impl( self, print_prefix: impl FnOnce(Self) -> Result, _disambiguated_data: &DisambiguatedDefPathData, self_ty: Ty<'tcx>, trait_ref: Option>, ) -> Result { self.pretty_path_append_impl( |mut cx| { cx = print_prefix(cx)?; if cx.keep_within_component { // HACK(eddyb) print the path similarly to how `FmtPrinter` prints it. cx.write_str("::")?; } else { cx.path.finalize_pending_component(); } Ok(cx) }, self_ty, trait_ref, ) } fn path_append( mut self, print_prefix: impl FnOnce(Self) -> Result, disambiguated_data: &DisambiguatedDefPathData, ) -> Result { self = print_prefix(self)?; // Skip `::{{extern}}` blocks and `::{{constructor}}` on tuple/unit structs. if let DefPathData::ForeignMod | DefPathData::Ctor = disambiguated_data.data { return Ok(self); } if self.keep_within_component { // HACK(eddyb) print the path similarly to how `FmtPrinter` prints it. self.write_str("::")?; } else { self.path.finalize_pending_component(); } write!(self, "{}", disambiguated_data.data)?; Ok(self) } fn path_generic_args( mut self, print_prefix: impl FnOnce(Self) -> Result, args: &[GenericArg<'tcx>], ) -> Result { self = print_prefix(self)?; let args = args.iter().cloned().filter(|arg| !matches!(arg.unpack(), GenericArgKind::Lifetime(_))); if args.clone().next().is_some() { self.generic_delimiters(|cx| cx.comma_sep(args)) } else { Ok(self) } } } impl<'tcx> PrettyPrinter<'tcx> for &mut SymbolPrinter<'tcx> { fn should_print_region(&self, _region: ty::Region<'_>) -> bool { false } fn comma_sep(mut self, mut elems: impl Iterator) -> Result where T: Print<'tcx, Self, Output = Self, Error = Self::Error>, { if let Some(first) = elems.next() { self = first.print(self)?; for elem in elems { self.write_str(",")?; self = elem.print(self)?; } } Ok(self) } fn generic_delimiters( mut self, f: impl FnOnce(Self) -> Result, ) -> Result { write!(self, "<")?; let kept_within_component = mem::replace(&mut self.keep_within_component, true); self = f(self)?; self.keep_within_component = kept_within_component; write!(self, ">")?; Ok(self) } } impl fmt::Write for SymbolPrinter<'_> { fn write_str(&mut self, s: &str) -> fmt::Result { // Name sanitation. LLVM will happily accept identifiers with weird names, but // gas doesn't! // gas accepts the following characters in symbols: a-z, A-Z, 0-9, ., _, $ // NVPTX assembly has more strict naming rules than gas, so additionally, dots // are replaced with '$' there. for c in s.chars() { if self.path.temp_buf.is_empty() { match c { 'a'..='z' | 'A'..='Z' | '_' => {} _ => { // Underscore-qualify anything that didn't start as an ident. self.path.temp_buf.push('_'); } } } match c { // Escape these with $ sequences '@' => self.path.temp_buf.push_str("$SP$"), '*' => self.path.temp_buf.push_str("$BP$"), '&' => self.path.temp_buf.push_str("$RF$"), '<' => self.path.temp_buf.push_str("$LT$"), '>' => self.path.temp_buf.push_str("$GT$"), '(' => self.path.temp_buf.push_str("$LP$"), ')' => self.path.temp_buf.push_str("$RP$"), ',' => self.path.temp_buf.push_str("$C$"), '-' | ':' | '.' if self.tcx.has_strict_asm_symbol_naming() => { // NVPTX doesn't support these characters in symbol names. self.path.temp_buf.push('$') } // '.' doesn't occur in types and functions, so reuse it // for ':' and '-' '-' | ':' => self.path.temp_buf.push('.'), // Avoid crashing LLVM in certain (LTO-related) situations, see #60925. 'm' if self.path.temp_buf.ends_with(".llv") => self.path.temp_buf.push_str("$u6d$"), // These are legal symbols 'a'..='z' | 'A'..='Z' | '0'..='9' | '_' | '.' | '$' => self.path.temp_buf.push(c), _ => { self.path.temp_buf.push('$'); for c in c.escape_unicode().skip(1) { match c { '{' => {} '}' => self.path.temp_buf.push('$'), c => self.path.temp_buf.push(c), } } } } } Ok(()) } }