diff options
Diffstat (limited to 'compiler/rustc_mir_transform/src/function_item_references.rs')
| -rw-r--r-- | compiler/rustc_mir_transform/src/function_item_references.rs | 205 |
1 files changed, 205 insertions, 0 deletions
diff --git a/compiler/rustc_mir_transform/src/function_item_references.rs b/compiler/rustc_mir_transform/src/function_item_references.rs new file mode 100644 index 000000000..2e4fe1e3e --- /dev/null +++ b/compiler/rustc_mir_transform/src/function_item_references.rs @@ -0,0 +1,205 @@ +use itertools::Itertools; +use rustc_errors::Applicability; +use rustc_hir::def_id::DefId; +use rustc_middle::mir::visit::Visitor; +use rustc_middle::mir::*; +use rustc_middle::ty::{ + self, + subst::{GenericArgKind, Subst, SubstsRef}, + EarlyBinder, PredicateKind, Ty, TyCtxt, +}; +use rustc_session::lint::builtin::FUNCTION_ITEM_REFERENCES; +use rustc_span::{symbol::sym, Span}; +use rustc_target::spec::abi::Abi; + +use crate::MirLint; + +pub struct FunctionItemReferences; + +impl<'tcx> MirLint<'tcx> for FunctionItemReferences { + fn run_lint(&self, tcx: TyCtxt<'tcx>, body: &Body<'tcx>) { + let mut checker = FunctionItemRefChecker { tcx, body }; + checker.visit_body(&body); + } +} + +struct FunctionItemRefChecker<'a, 'tcx> { + tcx: TyCtxt<'tcx>, + body: &'a Body<'tcx>, +} + +impl<'tcx> Visitor<'tcx> for FunctionItemRefChecker<'_, 'tcx> { + /// Emits a lint for function reference arguments bound by `fmt::Pointer` or passed to + /// `transmute`. This only handles arguments in calls outside macro expansions to avoid double + /// counting function references formatted as pointers by macros. + fn visit_terminator(&mut self, terminator: &Terminator<'tcx>, location: Location) { + if let TerminatorKind::Call { + func, + args, + destination: _, + target: _, + cleanup: _, + from_hir_call: _, + fn_span: _, + } = &terminator.kind + { + let source_info = *self.body.source_info(location); + let func_ty = func.ty(self.body, self.tcx); + if let ty::FnDef(def_id, substs_ref) = *func_ty.kind() { + // Handle calls to `transmute` + if self.tcx.is_diagnostic_item(sym::transmute, def_id) { + let arg_ty = args[0].ty(self.body, self.tcx); + for generic_inner_ty in arg_ty.walk() { + if let GenericArgKind::Type(inner_ty) = generic_inner_ty.unpack() { + if let Some((fn_id, fn_substs)) = + FunctionItemRefChecker::is_fn_ref(inner_ty) + { + let span = self.nth_arg_span(&args, 0); + self.emit_lint(fn_id, fn_substs, source_info, span); + } + } + } + } else { + self.check_bound_args(def_id, substs_ref, &args, source_info); + } + } + } + self.super_terminator(terminator, location); + } +} + +impl<'tcx> FunctionItemRefChecker<'_, 'tcx> { + /// Emits a lint for function reference arguments bound by `fmt::Pointer` in calls to the + /// function defined by `def_id` with the substitutions `substs_ref`. + fn check_bound_args( + &self, + def_id: DefId, + substs_ref: SubstsRef<'tcx>, + args: &[Operand<'tcx>], + source_info: SourceInfo, + ) { + let param_env = self.tcx.param_env(def_id); + let bounds = param_env.caller_bounds(); + for bound in bounds { + if let Some(bound_ty) = self.is_pointer_trait(&bound.kind().skip_binder()) { + // Get the argument types as they appear in the function signature. + let arg_defs = self.tcx.fn_sig(def_id).skip_binder().inputs(); + for (arg_num, arg_def) in arg_defs.iter().enumerate() { + // For all types reachable from the argument type in the fn sig + for generic_inner_ty in arg_def.walk() { + if let GenericArgKind::Type(inner_ty) = generic_inner_ty.unpack() { + // If the inner type matches the type bound by `Pointer` + if inner_ty == bound_ty { + // Do a substitution using the parameters from the callsite + let subst_ty = EarlyBinder(inner_ty).subst(self.tcx, substs_ref); + if let Some((fn_id, fn_substs)) = + FunctionItemRefChecker::is_fn_ref(subst_ty) + { + let mut span = self.nth_arg_span(args, arg_num); + if span.from_expansion() { + // The operand's ctxt wouldn't display the lint since it's inside a macro so + // we have to use the callsite's ctxt. + let callsite_ctxt = span.source_callsite().ctxt(); + span = span.with_ctxt(callsite_ctxt); + } + self.emit_lint(fn_id, fn_substs, source_info, span); + } + } + } + } + } + } + } + } + + /// If the given predicate is the trait `fmt::Pointer`, returns the bound parameter type. + fn is_pointer_trait(&self, bound: &PredicateKind<'tcx>) -> Option<Ty<'tcx>> { + if let ty::PredicateKind::Trait(predicate) = bound { + if self.tcx.is_diagnostic_item(sym::Pointer, predicate.def_id()) { + Some(predicate.trait_ref.self_ty()) + } else { + None + } + } else { + None + } + } + + /// If a type is a reference or raw pointer to the anonymous type of a function definition, + /// returns that function's `DefId` and `SubstsRef`. + fn is_fn_ref(ty: Ty<'tcx>) -> Option<(DefId, SubstsRef<'tcx>)> { + let referent_ty = match ty.kind() { + ty::Ref(_, referent_ty, _) => Some(referent_ty), + ty::RawPtr(ty_and_mut) => Some(&ty_and_mut.ty), + _ => None, + }; + referent_ty + .map(|ref_ty| { + if let ty::FnDef(def_id, substs_ref) = *ref_ty.kind() { + Some((def_id, substs_ref)) + } else { + None + } + }) + .unwrap_or(None) + } + + fn nth_arg_span(&self, args: &[Operand<'tcx>], n: usize) -> Span { + match &args[n] { + Operand::Copy(place) | Operand::Move(place) => { + self.body.local_decls[place.local].source_info.span + } + Operand::Constant(constant) => constant.span, + } + } + + fn emit_lint( + &self, + fn_id: DefId, + fn_substs: SubstsRef<'tcx>, + source_info: SourceInfo, + span: Span, + ) { + let lint_root = self.body.source_scopes[source_info.scope] + .local_data + .as_ref() + .assert_crate_local() + .lint_root; + let fn_sig = self.tcx.fn_sig(fn_id); + let unsafety = fn_sig.unsafety().prefix_str(); + let abi = match fn_sig.abi() { + Abi::Rust => String::from(""), + other_abi => { + let mut s = String::from("extern \""); + s.push_str(other_abi.name()); + s.push_str("\" "); + s + } + }; + let ident = self.tcx.item_name(fn_id).to_ident_string(); + let ty_params = fn_substs.types().map(|ty| format!("{}", ty)); + let const_params = fn_substs.consts().map(|c| format!("{}", c)); + let params = ty_params.chain(const_params).join(", "); + let num_args = fn_sig.inputs().map_bound(|inputs| inputs.len()).skip_binder(); + let variadic = if fn_sig.c_variadic() { ", ..." } else { "" }; + let ret = if fn_sig.output().skip_binder().is_unit() { "" } else { " -> _" }; + self.tcx.struct_span_lint_hir(FUNCTION_ITEM_REFERENCES, lint_root, span, |lint| { + lint.build("taking a reference to a function item does not give a function pointer") + .span_suggestion( + span, + &format!("cast `{}` to obtain a function pointer", ident), + format!( + "{} as {}{}fn({}{}){}", + if params.is_empty() { ident } else { format!("{}::<{}>", ident, params) }, + unsafety, + abi, + vec!["_"; num_args].join(", "), + variadic, + ret, + ), + Applicability::Unspecified, + ) + .emit(); + }); + } +} |