clippy_lints/src/invalid_ref.rs

   1 // Copyright 2014-2018 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution.
   3 //
   4 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   5 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   6 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   7 // option. This file may not be copied, modified, or distributed
   8 // except according to those terms.
   9
  10 use crate::utils::{match_def_path, opt_def_id, paths, span_help_and_lint};
  11 use if_chain::if_chain;
  12 use rustc::hir::*;
  13 use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
  14 use rustc::ty;
  15 use rustc::{declare_tool_lint, lint_array};
  16
  17 /// **What it does:** Checks for creation of references to zeroed or uninitialized memory.
  18 ///
  19 /// **Why is this bad?** Creation of null references is undefined behavior.
  20 ///
  21 /// **Known problems:** None.
  22 ///
  23 /// **Example:**
  24 /// ```rust
  25 /// let bad_ref: &usize = std::mem::zeroed();
  26 /// ```
  27 declare_clippy_lint! {
  28     pub INVALID_REF,
  29     correctness,
  30     "creation of invalid reference"
  31 }
  32
  33 const ZERO_REF_SUMMARY: &str = "reference to zeroed memory";
  34 const UNINIT_REF_SUMMARY: &str = "reference to uninitialized memory";
  35 const HELP: &str = "Creation of a null reference is undefined behavior; \
  36                     see https://doc.rust-lang.org/reference/behavior-considered-undefined.html";
  37
  38 pub struct InvalidRef;
  39
  40 impl LintPass for InvalidRef {
  41     fn get_lints(&self) -> LintArray {
  42         lint_array!(INVALID_REF)
  43     }
  44 }
  45
  46 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for InvalidRef {
  47     fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
  48         if_chain! {
  49             if let ExprKind::Call(ref path, ref args) = expr.node;
  50             if let ExprKind::Path(ref qpath) = path.node;
  51             if args.len() == 0;
  52             if let ty::Ref(..) = cx.tables.expr_ty(expr).sty;
  53             if let Some(def_id) = opt_def_id(cx.tables.qpath_def(qpath, path.hir_id));
  54             then {
  55                 let msg = if match_def_path(cx.tcx, def_id, &paths::MEM_ZEROED) |
  56                              match_def_path(cx.tcx, def_id, &paths::INIT)
  57                 {
  58                     ZERO_REF_SUMMARY
  59                 } else if match_def_path(cx.tcx, def_id, &paths::MEM_UNINIT) |
  60                           match_def_path(cx.tcx, def_id, &paths::UNINIT)
  61                 {
  62                     UNINIT_REF_SUMMARY
  63                 } else {
  64                     return;
  65                 };
  66                 span_help_and_lint(cx, INVALID_REF, expr.span, msg, HELP);
  67             }
  68         }
  69         return;
  70     }
  71 }