78599d83e7
To accurately reflect that RPITIT assoc items don't have a name. This avoids the use of `kw::Empty` to mean "no name", which is error prone. Helps with #137978.
77 lines
3.1 KiB
Rust
77 lines
3.1 KiB
Rust
use rustc_middle::mir::visit::Visitor;
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use rustc_middle::mir::{Body, Location, Operand, Terminator, TerminatorKind};
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use rustc_middle::ty::{AssocItem, AssocKind, TyCtxt};
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use rustc_session::lint::builtin::PTR_TO_INTEGER_TRANSMUTE_IN_CONSTS;
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use rustc_span::sym;
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use crate::errors;
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/// Check for transmutes that exhibit undefined behavior.
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/// For example, transmuting pointers to integers in a const context.
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pub(super) struct CheckUndefinedTransmutes;
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impl<'tcx> crate::MirLint<'tcx> for CheckUndefinedTransmutes {
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fn run_lint(&self, tcx: TyCtxt<'tcx>, body: &Body<'tcx>) {
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let mut checker = UndefinedTransmutesChecker { body, tcx };
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checker.visit_body(body);
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}
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}
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struct UndefinedTransmutesChecker<'a, 'tcx> {
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body: &'a Body<'tcx>,
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tcx: TyCtxt<'tcx>,
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}
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impl<'a, 'tcx> UndefinedTransmutesChecker<'a, 'tcx> {
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// This functions checks two things:
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// 1. `function` takes a raw pointer as input and returns an integer as output.
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// 2. `function` is called from a const function or an associated constant.
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//
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// Why do we consider const functions and associated constants only?
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//
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// Generally, undefined behavior in const items are handled by the evaluator.
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// But, const functions and associated constants are evaluated only when referenced.
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// This can result in undefined behavior in a library going unnoticed until
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// the function or constant is actually used.
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//
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// Therefore, we only consider const functions and associated constants here and leave
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// other const items to be handled by the evaluator.
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fn is_ptr_to_int_in_const(&self, function: &Operand<'tcx>) -> bool {
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let def_id = self.body.source.def_id();
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if self.tcx.is_const_fn(def_id)
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|| matches!(
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self.tcx.opt_associated_item(def_id),
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Some(AssocItem { kind: AssocKind::Const { .. }, .. })
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)
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{
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let fn_sig = function.ty(self.body, self.tcx).fn_sig(self.tcx).skip_binder();
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if let [input] = fn_sig.inputs() {
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return input.is_raw_ptr() && fn_sig.output().is_integral();
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}
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}
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false
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}
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}
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impl<'tcx> Visitor<'tcx> for UndefinedTransmutesChecker<'_, 'tcx> {
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// Check each block's terminator for calls to pointer to integer transmutes
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// in const functions or associated constants and emit a lint.
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fn visit_terminator(&mut self, terminator: &Terminator<'tcx>, location: Location) {
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if let TerminatorKind::Call { func, .. } = &terminator.kind
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&& let Some((func_def_id, _)) = func.const_fn_def()
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&& self.tcx.is_intrinsic(func_def_id, sym::transmute)
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&& self.is_ptr_to_int_in_const(func)
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&& let Some(call_id) = self.body.source.def_id().as_local()
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{
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let hir_id = self.tcx.local_def_id_to_hir_id(call_id);
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let span = self.body.source_info(location).span;
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self.tcx.emit_node_span_lint(
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PTR_TO_INTEGER_TRANSMUTE_IN_CONSTS,
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hir_id,
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span,
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errors::UndefinedTransmute,
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);
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}
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}
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}
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