2020-03-12 00:00:00 +00:00
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use crate::utils::{match_def_path, paths, span_lint, span_lint_and_help};
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use if_chain::if_chain;
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use rustc_hir::{BinOpKind, Expr, ExprKind};
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use rustc_lint::{LateContext, LateLintPass};
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use rustc_middle::ty;
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use rustc_session::{declare_lint_pass, declare_tool_lint};
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declare_clippy_lint! {
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/// **What it does:** Checks for comparisons with an address of a function item.
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///
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/// **Why is this bad?** Function item address is not guaranteed to be unique and could vary
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/// between different code generation units. Furthermore different function items could have
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/// the same address after being merged together.
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///
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/// **Known problems:** None.
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///
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/// **Example:**
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///
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/// ```rust
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/// type F = fn();
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/// fn a() {}
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/// let f: F = a;
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/// if f == a {
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/// // ...
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/// }
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/// ```
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pub FN_ADDRESS_COMPARISONS,
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correctness,
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"comparison with an address of a function item"
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}
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declare_clippy_lint! {
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/// **What it does:** Checks for comparisons with an address of a trait vtable.
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///
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/// **Why is this bad?** Comparing trait objects pointers compares an vtable addresses which
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/// are not guaranteed to be unique and could vary between different code generation units.
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/// Furthermore vtables for different types could have the same address after being merged
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/// together.
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///
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/// **Known problems:** None.
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///
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/// **Example:**
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///
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/// ```rust,ignore
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/// let a: Rc<dyn Trait> = ...
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/// let b: Rc<dyn Trait> = ...
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/// if Rc::ptr_eq(&a, &b) {
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/// ...
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/// }
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/// ```
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pub VTABLE_ADDRESS_COMPARISONS,
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correctness,
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"comparison with an address of a trait vtable"
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}
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declare_lint_pass!(UnnamedAddress => [FN_ADDRESS_COMPARISONS, VTABLE_ADDRESS_COMPARISONS]);
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2020-06-25 20:41:36 +00:00
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impl LateLintPass<'_> for UnnamedAddress {
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fn check_expr(&mut self, cx: &LateContext<'_>, expr: &Expr<'_>) {
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2020-03-12 00:00:00 +00:00
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fn is_comparison(binop: BinOpKind) -> bool {
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2020-07-14 12:59:59 +00:00
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matches!(
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binop,
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BinOpKind::Eq | BinOpKind::Lt | BinOpKind::Le | BinOpKind::Ne | BinOpKind::Ge | BinOpKind::Gt
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)
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2020-03-12 00:00:00 +00:00
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}
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2020-06-25 20:41:36 +00:00
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fn is_trait_ptr(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
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2020-07-17 08:47:04 +00:00
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match cx.typeck_results().expr_ty_adjusted(expr).kind {
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2020-03-12 00:00:00 +00:00
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ty::RawPtr(ty::TypeAndMut { ty, .. }) => ty.is_trait(),
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_ => false,
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}
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}
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2020-06-25 20:41:36 +00:00
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fn is_fn_def(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
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2020-07-17 08:47:04 +00:00
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matches!(cx.typeck_results().expr_ty(expr).kind, ty::FnDef(..))
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2020-03-12 00:00:00 +00:00
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}
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if_chain! {
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if let ExprKind::Binary(binop, ref left, ref right) = expr.kind;
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if is_comparison(binop.node);
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if is_trait_ptr(cx, left) && is_trait_ptr(cx, right);
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then {
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span_lint_and_help(
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cx,
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VTABLE_ADDRESS_COMPARISONS,
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expr.span,
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"comparing trait object pointers compares a non-unique vtable address",
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2020-04-18 10:28:29 +00:00
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None,
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2020-03-12 00:00:00 +00:00
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"consider extracting and comparing data pointers only",
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);
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}
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}
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if_chain! {
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if let ExprKind::Call(ref func, [ref _left, ref _right]) = expr.kind;
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if let ExprKind::Path(ref func_qpath) = func.kind;
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2020-06-26 02:55:23 +00:00
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if let Some(def_id) = cx.qpath_res(func_qpath, func.hir_id).opt_def_id();
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2020-03-12 00:00:00 +00:00
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if match_def_path(cx, def_id, &paths::PTR_EQ) ||
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match_def_path(cx, def_id, &paths::RC_PTR_EQ) ||
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match_def_path(cx, def_id, &paths::ARC_PTR_EQ);
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2020-07-17 08:47:04 +00:00
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let ty_param = cx.typeck_results().node_substs(func.hir_id).type_at(0);
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2020-03-12 00:00:00 +00:00
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if ty_param.is_trait();
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then {
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span_lint_and_help(
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cx,
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VTABLE_ADDRESS_COMPARISONS,
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expr.span,
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"comparing trait object pointers compares a non-unique vtable address",
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2020-04-18 10:28:29 +00:00
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None,
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2020-03-12 00:00:00 +00:00
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"consider extracting and comparing data pointers only",
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);
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}
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}
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if_chain! {
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if let ExprKind::Binary(binop, ref left, ref right) = expr.kind;
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if is_comparison(binop.node);
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2020-07-17 08:47:04 +00:00
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if cx.typeck_results().expr_ty_adjusted(left).is_fn_ptr() &&
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cx.typeck_results().expr_ty_adjusted(right).is_fn_ptr();
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2020-03-12 00:00:00 +00:00
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if is_fn_def(cx, left) || is_fn_def(cx, right);
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then {
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span_lint(
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cx,
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FN_ADDRESS_COMPARISONS,
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expr.span,
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"comparing with a non-unique address of a function item",
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);
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}
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}
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}
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}
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