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
  11 use crate::rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
  12 use crate::rustc::{declare_tool_lint, lint_array};
  13 use if_chain::if_chain;
  14 use crate::rustc::ty;
  15 use crate::rustc::hir::*;
  16 use crate::utils::{match_def_path, opt_def_id, paths, span_help_and_lint};
  17
  18 /// **What it does:** Checks for creation of references to zeroed or uninitialized memory.
  19 ///
  20 /// **Why is this bad?** Creation of null references is undefined behavior.
  21 ///
  22 /// **Known problems:** None.
  23 ///
  24 /// **Example:**
  25 /// ```rust
  26 /// let bad_ref: &usize = std::mem::zeroed();
  27 /// ```
  28 declare_clippy_lint! {
  29     pub INVALID_REF,
  30     correctness,
  31     "creation of invalid reference"
  32 }
  33
  34 const ZERO_REF_SUMMARY: &str = "reference to zeroed memory";
  35 const UNINIT_REF_SUMMARY: &str = "reference to uninitialized memory";
  36 const HELP: &str = "Creation of a null reference is undefined behavior; \
  37                     see https://doc.rust-lang.org/reference/behavior-considered-undefined.html";
  38
  39 pub struct InvalidRef;
  40
  41 impl LintPass for InvalidRef {
  42     fn get_lints(&self) -> LintArray {
  43         lint_array!(INVALID_REF)
  44     }
  45 }
  46
  47 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for InvalidRef {
  48     fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
  49         if_chain! {
  50             if let ExprKind::Call(ref path, ref args) = expr.node;
  51             if let ExprKind::Path(ref qpath) = path.node;
  52             if args.len() == 0;
  53             if let ty::Ref(..) = cx.tables.expr_ty(expr).sty;
  54             if let Some(def_id) = opt_def_id(cx.tables.qpath_def(qpath, path.hir_id));
  55             then {
  56                 let msg = if match_def_path(cx.tcx, def_id, &paths::MEM_ZEROED) |
  57                              match_def_path(cx.tcx, def_id, &paths::INIT)
  58                 {
  59                     ZERO_REF_SUMMARY
  60                 } else if match_def_path(cx.tcx, def_id, &paths::MEM_UNINIT) |
  61                           match_def_path(cx.tcx, def_id, &paths::UNINIT)
  62                 {
  63                     UNINIT_REF_SUMMARY
  64                 } else {
  65                     return;
  66                 };
  67                 span_help_and_lint(cx, INVALID_REF, expr.span, msg, HELP);
  68             }
  69         }
  70         return;
  71     }
  72 }