Added documentation for function_item_references lint
Added documentation for `function_item_references` lint to the rustc book and fixed comments in the lint checker itself.
This commit is contained in:
Ayrton
parent
d6fa7e15d6
commit
935fc3642a
@ -3,7 +3,7 @@ use rustc_middle::mir::visit::Visitor;
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use rustc_middle::mir::*;
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use rustc_middle::ty::{
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self,
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subst::{GenericArgKind, Subst},
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subst::{GenericArgKind, Subst, SubstsRef},
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PredicateAtom, Ty, TyCtxt, TyS,
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};
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use rustc_session::lint::builtin::FUNCTION_ITEM_REFERENCES;
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@ -27,6 +27,9 @@ struct FunctionItemRefChecker<'a, 'tcx> {
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}
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impl<'a, 'tcx> Visitor<'tcx> for FunctionItemRefChecker<'a, 'tcx> {
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/// Emits a lint for function reference arguments bound by `fmt::Pointer` or passed to
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/// `transmute`. This only handles arguments in calls outside macro expansions to avoid double
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/// counting function references formatted as pointers by macros.
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fn visit_terminator(&mut self, terminator: &Terminator<'tcx>, location: Location) {
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if let TerminatorKind::Call {
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func,
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@ -38,11 +41,11 @@ impl<'a, 'tcx> Visitor<'tcx> for FunctionItemRefChecker<'a, 'tcx> {
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} = &terminator.kind
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{
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let source_info = *self.body.source_info(location);
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//this handles all function calls outside macros
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// Only handle function calls outside macros
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if !source_info.span.from_expansion() {
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let func_ty = func.ty(self.body, self.tcx);
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if let ty::FnDef(def_id, substs_ref) = *func_ty.kind() {
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//handle `std::mem::transmute`
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// Handle calls to `transmute`
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if self.tcx.is_diagnostic_item(sym::transmute, def_id) {
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let arg_ty = args[0].ty(self.body, self.tcx);
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for generic_inner_ty in arg_ty.walk() {
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@ -55,48 +58,16 @@ impl<'a, 'tcx> Visitor<'tcx> for FunctionItemRefChecker<'a, 'tcx> {
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}
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}
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} else {
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//handle any function call with `std::fmt::Pointer` as a bound trait
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//this includes calls to `std::fmt::Pointer::fmt` outside of macros
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let param_env = self.tcx.param_env(def_id);
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let bounds = param_env.caller_bounds();
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for bound in bounds {
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if let Some(bound_ty) = self.is_pointer_trait(&bound.skip_binders()) {
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//get the argument types as they appear in the function signature
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let arg_defs = self.tcx.fn_sig(def_id).skip_binder().inputs();
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for (arg_num, arg_def) in arg_defs.iter().enumerate() {
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//for all types reachable from the argument type in the fn sig
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for generic_inner_ty in arg_def.walk() {
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if let GenericArgKind::Type(inner_ty) =
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generic_inner_ty.unpack()
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{
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//if the inner type matches the type bound by `Pointer`
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if TyS::same_type(inner_ty, bound_ty) {
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//do a substitution using the parameters from the callsite
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let subst_ty = inner_ty.subst(self.tcx, substs_ref);
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if let Some(fn_id) =
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FunctionItemRefChecker::is_fn_ref(subst_ty)
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{
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let ident =
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self.tcx.item_name(fn_id).to_ident_string();
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let span = self.nth_arg_span(&args, arg_num);
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self.emit_lint(ident, fn_id, source_info, span);
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}
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}
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}
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}
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}
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}
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}
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self.check_bound_args(def_id, substs_ref, &args, source_info);
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}
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}
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}
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}
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self.super_terminator(terminator, location);
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}
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//This handles `std::fmt::Pointer::fmt` when it's used in the formatting macros.
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//It's handled as an operand instead of a Call terminator so it won't depend on
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//whether the formatting macros call `fmt` directly, transmute it first or other
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//internal fmt details.
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/// Emits a lint for function references formatted with `fmt::Pointer::fmt` by macros. These
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/// cases are handled as operands instead of call terminators to avoid any dependence on
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/// unstable, internal formatting details like whether `fmt` is called directly or not.
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fn visit_operand(&mut self, operand: &Operand<'tcx>, location: Location) {
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let source_info = *self.body.source_info(location);
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if source_info.span.from_expansion() {
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@ -105,8 +76,8 @@ impl<'a, 'tcx> Visitor<'tcx> for FunctionItemRefChecker<'a, 'tcx> {
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if self.tcx.is_diagnostic_item(sym::pointer_trait_fmt, def_id) {
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let param_ty = substs_ref.type_at(0);
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if let Some(fn_id) = FunctionItemRefChecker::is_fn_ref(param_ty) {
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//the operand's ctxt wouldn't display the lint since it's inside a macro
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//so we have to use the callsite's ctxt
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// The operand's ctxt wouldn't display the lint since it's inside a macro so
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// we have to use the callsite's ctxt.
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let callsite_ctxt = source_info.span.source_callsite().ctxt();
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let span = source_info.span.with_ctxt(callsite_ctxt);
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let ident = self.tcx.item_name(fn_id).to_ident_string();
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@ -120,7 +91,42 @@ impl<'a, 'tcx> Visitor<'tcx> for FunctionItemRefChecker<'a, 'tcx> {
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}
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impl<'a, 'tcx> FunctionItemRefChecker<'a, 'tcx> {
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//return the bound parameter type if the trait is `std::fmt::Pointer`
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/// Emits a lint for function reference arguments bound by `fmt::Pointer` in calls to the
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/// function defined by `def_id` with the substitutions `substs_ref`.
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fn check_bound_args(
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&self,
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def_id: DefId,
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substs_ref: SubstsRef<'tcx>,
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args: &Vec<Operand<'tcx>>,
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source_info: SourceInfo,
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) {
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let param_env = self.tcx.param_env(def_id);
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let bounds = param_env.caller_bounds();
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for bound in bounds {
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if let Some(bound_ty) = self.is_pointer_trait(&bound.skip_binders()) {
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// Get the argument types as they appear in the function signature.
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let arg_defs = self.tcx.fn_sig(def_id).skip_binder().inputs();
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for (arg_num, arg_def) in arg_defs.iter().enumerate() {
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// For all types reachable from the argument type in the fn sig
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for generic_inner_ty in arg_def.walk() {
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if let GenericArgKind::Type(inner_ty) = generic_inner_ty.unpack() {
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// If the inner type matches the type bound by `Pointer`
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if TyS::same_type(inner_ty, bound_ty) {
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// Do a substitution using the parameters from the callsite
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let subst_ty = inner_ty.subst(self.tcx, substs_ref);
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if let Some(fn_id) = FunctionItemRefChecker::is_fn_ref(subst_ty) {
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let ident = self.tcx.item_name(fn_id).to_ident_string();
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let span = self.nth_arg_span(args, arg_num);
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self.emit_lint(ident, fn_id, source_info, span);
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}
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}
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}
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}
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}
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}
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}
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}
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/// If the given predicate is the trait `fmt::Pointer`, returns the bound parameter type.
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fn is_pointer_trait(&self, bound: &PredicateAtom<'tcx>) -> Option<Ty<'tcx>> {
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if let ty::PredicateAtom::Trait(predicate, _) = bound {
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if self.tcx.is_diagnostic_item(sym::pointer_trait, predicate.def_id()) {
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@ -132,6 +138,8 @@ impl<'a, 'tcx> FunctionItemRefChecker<'a, 'tcx> {
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None
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}
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}
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/// If a type is a reference or raw pointer to the anonymous type of a function definition,
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/// returns that function's `DefId`.
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fn is_fn_ref(ty: Ty<'tcx>) -> Option<DefId> {
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let referent_ty = match ty.kind() {
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ty::Ref(_, referent_ty, _) => Some(referent_ty),
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@ -27,7 +27,7 @@ pub mod dest_prop;
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pub mod dump_mir;
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pub mod early_otherwise_branch;
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pub mod elaborate_drops;
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pub mod function_references;
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pub mod function_item_references;
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pub mod generator;
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pub mod inline;
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pub mod instcombine;
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@ -267,7 +267,7 @@ fn mir_const<'tcx>(
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// MIR-level lints.
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&check_packed_ref::CheckPackedRef,
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&check_const_item_mutation::CheckConstItemMutation,
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&function_references::FunctionItemReferences,
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&function_item_references::FunctionItemReferences,
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// What we need to do constant evaluation.
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&simplify::SimplifyCfg::new("initial"),
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&rustc_peek::SanityCheck,
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@ -2648,6 +2648,30 @@ declare_lint! {
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}
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declare_lint! {
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/// The `function_item_references` lint detects function references that are
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/// formatted with [`fmt::Pointer`] or transmuted.
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///
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/// [`fmt::Pointer`]: https://doc.rust-lang.org/std/fmt/trait.Pointer.html
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///
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/// ### Example
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///
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/// ```rust
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/// fn foo() { }
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///
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/// fn main() {
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/// println!("{:p}", &foo);
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/// }
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/// ```
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///
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/// {{produces}}
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///
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/// ### Explanation
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///
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/// Taking a reference to a function may be mistaken as a way to obtain a
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/// pointer to that function. This can give unexpected results when
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/// formatting the reference as a pointer or transmuting it. This lint is
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/// issued when function references are formatted as pointers, passed as
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/// arguments bound by [`fmt::Pointer`] or transmuted.
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pub FUNCTION_ITEM_REFERENCES,
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Warn,
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"suggest casting functions to pointers when attempting to take references",
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@ -1,173 +1,173 @@
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warning: cast `foo` with `as fn() -> _` to obtain a function pointer
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--> $DIR/function-references.rs:40:18
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--> $DIR/function-item-references.rs:40:18
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LL | Pointer::fmt(&zst_ref, f)
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| ^^^^^^^^
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note: the lint level is defined here
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--> $DIR/function-references.rs:3:9
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--> $DIR/function-item-references.rs:3:9
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LL | #![warn(function_item_references)]
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| ^^^^^^^^^^^^^^^^^^^^^^^^
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warning: cast `foo` with `as fn() -> _` to obtain a function pointer
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--> $DIR/function-references.rs:77:22
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--> $DIR/function-item-references.rs:77:22
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LL | println!("{:p}", &foo);
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| ^^^^
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warning: cast `foo` with `as fn() -> _` to obtain a function pointer
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--> $DIR/function-references.rs:79:20
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--> $DIR/function-item-references.rs:79:20
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LL | print!("{:p}", &foo);
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| ^^^^
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warning: cast `foo` with `as fn() -> _` to obtain a function pointer
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--> $DIR/function-references.rs:81:21
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--> $DIR/function-item-references.rs:81:21
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LL | format!("{:p}", &foo);
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| ^^^^
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warning: cast `foo` with `as fn() -> _` to obtain a function pointer
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--> $DIR/function-references.rs:84:22
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--> $DIR/function-item-references.rs:84:22
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LL | println!("{:p}", &foo as *const _);
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| ^^^^^^^^^^^^^^^^
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warning: cast `foo` with `as fn() -> _` to obtain a function pointer
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--> $DIR/function-references.rs:86:22
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--> $DIR/function-item-references.rs:86:22
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LL | println!("{:p}", zst_ref);
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| ^^^^^^^
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warning: cast `foo` with `as fn() -> _` to obtain a function pointer
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--> $DIR/function-references.rs:88:22
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--> $DIR/function-item-references.rs:88:22
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LL | println!("{:p}", cast_zst_ptr);
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| ^^^^^^^^^^^^
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warning: cast `foo` with `as fn() -> _` to obtain a function pointer
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--> $DIR/function-references.rs:90:22
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--> $DIR/function-item-references.rs:90:22
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LL | println!("{:p}", coerced_zst_ptr);
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| ^^^^^^^^^^^^^^^
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warning: cast `foo` with `as fn() -> _` to obtain a function pointer
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--> $DIR/function-references.rs:93:22
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--> $DIR/function-item-references.rs:93:22
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LL | println!("{:p}", &fn_item);
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| ^^^^^^^^
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warning: cast `foo` with `as fn() -> _` to obtain a function pointer
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--> $DIR/function-references.rs:95:22
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--> $DIR/function-item-references.rs:95:22
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LL | println!("{:p}", indirect_ref);
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| ^^^^^^^^^^^^
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warning: cast `nop` with `as fn()` to obtain a function pointer
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--> $DIR/function-references.rs:98:22
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--> $DIR/function-item-references.rs:98:22
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LL | println!("{:p}", &nop);
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| ^^^^
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warning: cast `bar` with `as fn(_) -> _` to obtain a function pointer
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--> $DIR/function-references.rs:100:22
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--> $DIR/function-item-references.rs:100:22
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LL | println!("{:p}", &bar);
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| ^^^^
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warning: cast `baz` with `as fn(_, _) -> _` to obtain a function pointer
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--> $DIR/function-references.rs:102:22
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--> $DIR/function-item-references.rs:102:22
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LL | println!("{:p}", &baz);
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| ^^^^
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warning: cast `unsafe_fn` with `as unsafe fn()` to obtain a function pointer
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--> $DIR/function-references.rs:104:22
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--> $DIR/function-item-references.rs:104:22
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LL | println!("{:p}", &unsafe_fn);
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| ^^^^^^^^^^
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warning: cast `c_fn` with `as extern "C" fn()` to obtain a function pointer
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--> $DIR/function-references.rs:106:22
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--> $DIR/function-item-references.rs:106:22
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LL | println!("{:p}", &c_fn);
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| ^^^^^
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warning: cast `unsafe_c_fn` with `as unsafe extern "C" fn()` to obtain a function pointer
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--> $DIR/function-references.rs:108:22
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--> $DIR/function-item-references.rs:108:22
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LL | println!("{:p}", &unsafe_c_fn);
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| ^^^^^^^^^^^^
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warning: cast `variadic` with `as unsafe extern "C" fn(_, ...)` to obtain a function pointer
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--> $DIR/function-references.rs:110:22
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--> $DIR/function-item-references.rs:110:22
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LL | println!("{:p}", &variadic);
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| ^^^^^^^^^
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warning: cast `var` with `as fn(_) -> _` to obtain a function pointer
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--> $DIR/function-references.rs:112:22
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--> $DIR/function-item-references.rs:112:22
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LL | println!("{:p}", &std::env::var::<String>);
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| ^^^^^^^^^^^^^^^^^^^^^^^^
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warning: cast `nop` with `as fn()` to obtain a function pointer
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--> $DIR/function-references.rs:115:32
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--> $DIR/function-item-references.rs:115:32
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LL | println!("{:p} {:p} {:p}", &nop, &foo, &bar);
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| ^^^^
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warning: cast `foo` with `as fn() -> _` to obtain a function pointer
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--> $DIR/function-references.rs:115:38
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--> $DIR/function-item-references.rs:115:38
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LL | println!("{:p} {:p} {:p}", &nop, &foo, &bar);
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| ^^^^
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warning: cast `bar` with `as fn(_) -> _` to obtain a function pointer
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--> $DIR/function-references.rs:115:44
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--> $DIR/function-item-references.rs:115:44
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LL | println!("{:p} {:p} {:p}", &nop, &foo, &bar);
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| ^^^^
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warning: cast `foo` with `as fn() -> _` to obtain a function pointer
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--> $DIR/function-references.rs:130:41
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--> $DIR/function-item-references.rs:130:41
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LL | std::mem::transmute::<_, usize>(&foo);
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| ^^^^
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warning: cast `foo` with `as fn() -> _` to obtain a function pointer
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--> $DIR/function-references.rs:132:50
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--> $DIR/function-item-references.rs:132:50
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LL | std::mem::transmute::<_, (usize, usize)>((&foo, &bar));
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| ^^^^^^^^^^^^
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warning: cast `bar` with `as fn(_) -> _` to obtain a function pointer
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--> $DIR/function-references.rs:132:50
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--> $DIR/function-item-references.rs:132:50
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LL | std::mem::transmute::<_, (usize, usize)>((&foo, &bar));
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| ^^^^^^^^^^^^
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warning: cast `bar` with `as fn(_) -> _` to obtain a function pointer
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--> $DIR/function-references.rs:142:15
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--> $DIR/function-item-references.rs:142:15
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LL | print_ptr(&bar);
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| ^^^^
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warning: cast `bar` with `as fn(_) -> _` to obtain a function pointer
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--> $DIR/function-references.rs:144:24
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--> $DIR/function-item-references.rs:144:24
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LL | bound_by_ptr_trait(&bar);
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| ^^^^
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warning: cast `bar` with `as fn(_) -> _` to obtain a function pointer
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--> $DIR/function-references.rs:146:30
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--> $DIR/function-item-references.rs:146:30
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LL | bound_by_ptr_trait_tuple((&foo, &bar));
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| ^^^^^^^^^^^^
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warning: cast `foo` with `as fn() -> _` to obtain a function pointer
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--> $DIR/function-references.rs:146:30
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--> $DIR/function-item-references.rs:146:30
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LL | bound_by_ptr_trait_tuple((&foo, &bar));
|
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| ^^^^^^^^^^^^
|
||||
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