| use crate::utils::{snippet_opt, span_lint, span_lint_and_sugg}; |
| use rustc_errors::Applicability; |
| use rustc_hir::{Expr, ExprKind}; |
| use rustc_lint::{LateContext, LateLintPass}; |
| use rustc_session::{declare_lint_pass, declare_tool_lint}; |
| use std::fmt; |
| |
| declare_clippy_lint! { |
| /// **What it does:** Checks for usage of the `offset` pointer method with a `usize` casted to an |
| /// `isize`. |
| /// |
| /// **Why is this bad?** If we’re always increasing the pointer address, we can avoid the numeric |
| /// cast by using the `add` method instead. |
| /// |
| /// **Known problems:** None |
| /// |
| /// **Example:** |
| /// ```rust |
| /// let vec = vec![b'a', b'b', b'c']; |
| /// let ptr = vec.as_ptr(); |
| /// let offset = 1_usize; |
| /// |
| /// unsafe { |
| /// ptr.offset(offset as isize); |
| /// } |
| /// ``` |
| /// |
| /// Could be written: |
| /// |
| /// ```rust |
| /// let vec = vec![b'a', b'b', b'c']; |
| /// let ptr = vec.as_ptr(); |
| /// let offset = 1_usize; |
| /// |
| /// unsafe { |
| /// ptr.add(offset); |
| /// } |
| /// ``` |
| pub PTR_OFFSET_WITH_CAST, |
| complexity, |
| "unneeded pointer offset cast" |
| } |
| |
| declare_lint_pass!(PtrOffsetWithCast => [PTR_OFFSET_WITH_CAST]); |
| |
| impl<'tcx> LateLintPass<'tcx> for PtrOffsetWithCast { |
| fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) { |
| // Check if the expressions is a ptr.offset or ptr.wrapping_offset method call |
| let (receiver_expr, arg_expr, method) = match expr_as_ptr_offset_call(cx, expr) { |
| Some(call_arg) => call_arg, |
| None => return, |
| }; |
| |
| // Check if the argument to the method call is a cast from usize |
| let cast_lhs_expr = match expr_as_cast_from_usize(cx, arg_expr) { |
| Some(cast_lhs_expr) => cast_lhs_expr, |
| None => return, |
| }; |
| |
| let msg = format!("use of `{}` with a `usize` casted to an `isize`", method); |
| if let Some(sugg) = build_suggestion(cx, method, receiver_expr, cast_lhs_expr) { |
| span_lint_and_sugg( |
| cx, |
| PTR_OFFSET_WITH_CAST, |
| expr.span, |
| &msg, |
| "try", |
| sugg, |
| Applicability::MachineApplicable, |
| ); |
| } else { |
| span_lint(cx, PTR_OFFSET_WITH_CAST, expr.span, &msg); |
| } |
| } |
| } |
| |
| // If the given expression is a cast from a usize, return the lhs of the cast |
| fn expr_as_cast_from_usize<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) -> Option<&'tcx Expr<'tcx>> { |
| if let ExprKind::Cast(ref cast_lhs_expr, _) = expr.kind { |
| if is_expr_ty_usize(cx, &cast_lhs_expr) { |
| return Some(cast_lhs_expr); |
| } |
| } |
| None |
| } |
| |
| // If the given expression is a ptr::offset or ptr::wrapping_offset method call, return the |
| // receiver, the arg of the method call, and the method. |
| fn expr_as_ptr_offset_call<'tcx>( |
| cx: &LateContext<'tcx>, |
| expr: &'tcx Expr<'_>, |
| ) -> Option<(&'tcx Expr<'tcx>, &'tcx Expr<'tcx>, Method)> { |
| if let ExprKind::MethodCall(ref path_segment, _, ref args, _) = expr.kind { |
| if is_expr_ty_raw_ptr(cx, &args[0]) { |
| if path_segment.ident.name == sym!(offset) { |
| return Some((&args[0], &args[1], Method::Offset)); |
| } |
| if path_segment.ident.name == sym!(wrapping_offset) { |
| return Some((&args[0], &args[1], Method::WrappingOffset)); |
| } |
| } |
| } |
| None |
| } |
| |
| // Is the type of the expression a usize? |
| fn is_expr_ty_usize<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'_>) -> bool { |
| cx.tables().expr_ty(expr) == cx.tcx.types.usize |
| } |
| |
| // Is the type of the expression a raw pointer? |
| fn is_expr_ty_raw_ptr<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'_>) -> bool { |
| cx.tables().expr_ty(expr).is_unsafe_ptr() |
| } |
| |
| fn build_suggestion<'tcx>( |
| cx: &LateContext<'tcx>, |
| method: Method, |
| receiver_expr: &Expr<'_>, |
| cast_lhs_expr: &Expr<'_>, |
| ) -> Option<String> { |
| let receiver = snippet_opt(cx, receiver_expr.span)?; |
| let cast_lhs = snippet_opt(cx, cast_lhs_expr.span)?; |
| Some(format!("{}.{}({})", receiver, method.suggestion(), cast_lhs)) |
| } |
| |
| #[derive(Copy, Clone)] |
| enum Method { |
| Offset, |
| WrappingOffset, |
| } |
| |
| impl Method { |
| #[must_use] |
| fn suggestion(self) -> &'static str { |
| match self { |
| Self::Offset => "add", |
| Self::WrappingOffset => "wrapping_add", |
| } |
| } |
| } |
| |
| impl fmt::Display for Method { |
| fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
| match self { |
| Self::Offset => write!(f, "offset"), |
| Self::WrappingOffset => write!(f, "wrapping_offset"), |
| } |
| } |
| } |