clippy_lints/src/invalid_ref.rs

   1 use rustc::lint::*;
   2 use rustc::ty;
   3 use rustc::hir::*;
   4 use utils::{match_def_path, opt_def_id, paths, span_help_and_lint};
   5
   6 /// **What it does:** Checks for creation of references to zeroed or uninitialized memory.
   7 ///
   8 /// **Why is this bad?** Creation of null references is undefined behavior.
   9 ///
  10 /// **Known problems:** None.
  11 ///
  12 /// **Example:**
  13 /// ```rust
  14 /// let bad_ref: &usize = std::mem::zeroed();
  15 /// ```
  16 declare_lint! {
  17     pub INVALID_REF,
  18     Warn,
  19     "creation of invalid reference"
  20 }
  21
  22 const ZERO_REF_SUMMARY: &str = "reference to zeroed memory";
  23 const UNINIT_REF_SUMMARY: &str = "reference to uninitialized memory";
  24 const HELP: &str = "Creation of a null reference is undefined behavior; \
  25                     see https://doc.rust-lang.org/reference/behavior-considered-undefined.html";
  26
  27 pub struct InvalidRef;
  28
  29 impl LintPass for InvalidRef {
  30     fn get_lints(&self) -> LintArray {
  31         lint_array!(INVALID_REF)
  32     }
  33 }
  34
  35 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for InvalidRef {
  36     fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
  37         if_chain! {
  38             if let ExprCall(ref path, ref args) = expr.node;
  39             if let ExprPath(ref qpath) = path.node;
  40             if args.len() == 0;
  41             if let ty::TyRef(..) = cx.tables.expr_ty(expr).sty;
  42             if let Some(def_id) = opt_def_id(cx.tables.qpath_def(qpath, path.hir_id));
  43             then {
  44                 let msg = if match_def_path(cx.tcx, def_id, &paths::MEM_ZEROED) |
  45                              match_def_path(cx.tcx, def_id, &paths::INIT)
  46                 {
  47                     ZERO_REF_SUMMARY
  48                 } else if match_def_path(cx.tcx, def_id, &paths::MEM_UNINIT) |
  49                           match_def_path(cx.tcx, def_id, &paths::UNINIT)
  50                 {
  51                     UNINIT_REF_SUMMARY
  52                 } else {
  53                     return;
  54                 };
  55                 span_help_and_lint(cx, INVALID_REF, expr.span, msg, HELP);
  56             }
  57         }
  58         return;
  59     }
  60 }