compiler/rustc_mir/src/transform/check_packed_ref.rs

   1 use rustc_middle::mir::visit::{PlaceContext, Visitor};
   2 use rustc_middle::mir::*;
   3 use rustc_middle::ty::{self, TyCtxt};
   4 use rustc_session::lint::builtin::UNALIGNED_REFERENCES;
   5
   6 use crate::transform::MirPass;
   7 use crate::util;
   8
   9 pub struct CheckPackedRef;
  10
  11 impl<'tcx> MirPass<'tcx> for CheckPackedRef {
  12     fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
  13         let param_env = tcx.param_env(body.source.def_id());
  14         let source_info = SourceInfo::outermost(body.span);
  15         let mut checker = PackedRefChecker { body, tcx, param_env, source_info };
  16         checker.visit_body(&body);
  17     }
  18 }
  19
  20 struct PackedRefChecker<'a, 'tcx> {
  21     body: &'a Body<'tcx>,
  22     tcx: TyCtxt<'tcx>,
  23     param_env: ty::ParamEnv<'tcx>,
  24     source_info: SourceInfo,
  25 }
  26
  27 impl<'a, 'tcx> Visitor<'tcx> for PackedRefChecker<'a, 'tcx> {
  28     fn visit_terminator(&mut self, terminator: &Terminator<'tcx>, location: Location) {
  29         // Make sure we know where in the MIR we are.
  30         self.source_info = terminator.source_info;
  31         self.super_terminator(terminator, location);
  32     }
  33
  34     fn visit_statement(&mut self, statement: &Statement<'tcx>, location: Location) {
  35         // Make sure we know where in the MIR we are.
  36         self.source_info = statement.source_info;
  37         self.super_statement(statement, location);
  38     }
  39
  40     fn visit_place(&mut self, place: &Place<'tcx>, context: PlaceContext, _location: Location) {
  41         if context.is_borrow() {
  42             if util::is_disaligned(self.tcx, self.body, self.param_env, *place) {
  43                 let source_info = self.source_info;
  44                 let lint_root = self.body.source_scopes[source_info.scope]
  45                     .local_data
  46                     .as_ref()
  47                     .assert_crate_local()
  48                     .lint_root;
  49                 self.tcx.struct_span_lint_hir(
  50                     UNALIGNED_REFERENCES,
  51                     lint_root,
  52                     source_info.span,
  53                     |lint| {
  54                         lint.build("reference to packed field is unaligned")
  55                             .note(
  56                                 "fields of packed structs are not properly aligned, and creating \
  57                                 a misaligned reference is undefined behavior (even if that \
  58                                 reference is never dereferenced)",
  59                             )
  60                             .emit()
  61                     },
  62                 );
  63             }
  64         }
  65     }
  66 }