From d7b9e195c2df9e576abd2eba54f3fe6516619054 Mon Sep 17 00:00:00 2001 From: Lukas Lueg Date: Sat, 17 Dec 2022 14:16:45 +0100 Subject: [PATCH] Add size_of_ref lint Fixes #9995 --- CHANGELOG.md | 1 + clippy_lints/src/declared_lints.rs | 1 + clippy_lints/src/lib.rs | 2 + clippy_lints/src/size_of_ref.rs | 73 ++++++++++++++++++++++++++++++ tests/ui/size_of_ref.rs | 27 +++++++++++ tests/ui/size_of_ref.stderr | 27 +++++++++++ 6 files changed, 131 insertions(+) create mode 100644 clippy_lints/src/size_of_ref.rs create mode 100644 tests/ui/size_of_ref.rs create mode 100644 tests/ui/size_of_ref.stderr diff --git a/CHANGELOG.md b/CHANGELOG.md index 52efa8db4859..02f3188f8be0 100644 --- a/CHANGELOG.md +++ b/CHANGELOG.md @@ -4547,6 +4547,7 @@ Released 2018-09-13 [`single_match`]: https://rust-lang.github.io/rust-clippy/master/index.html#single_match [`single_match_else`]: https://rust-lang.github.io/rust-clippy/master/index.html#single_match_else [`size_of_in_element_count`]: https://rust-lang.github.io/rust-clippy/master/index.html#size_of_in_element_count +[`size_of_ref`]: https://rust-lang.github.io/rust-clippy/master/index.html#size_of_ref [`skip_while_next`]: https://rust-lang.github.io/rust-clippy/master/index.html#skip_while_next [`slow_vector_initialization`]: https://rust-lang.github.io/rust-clippy/master/index.html#slow_vector_initialization [`stable_sort_primitive`]: https://rust-lang.github.io/rust-clippy/master/index.html#stable_sort_primitive diff --git a/clippy_lints/src/declared_lints.rs b/clippy_lints/src/declared_lints.rs index 980e128cba41..2982460c9cfa 100644 --- a/clippy_lints/src/declared_lints.rs +++ b/clippy_lints/src/declared_lints.rs @@ -537,6 +537,7 @@ pub(crate) static LINTS: &[&crate::LintInfo] = &[ crate::single_char_lifetime_names::SINGLE_CHAR_LIFETIME_NAMES_INFO, crate::single_component_path_imports::SINGLE_COMPONENT_PATH_IMPORTS_INFO, crate::size_of_in_element_count::SIZE_OF_IN_ELEMENT_COUNT_INFO, + crate::size_of_ref::SIZE_OF_REF_INFO, crate::slow_vector_initialization::SLOW_VECTOR_INITIALIZATION_INFO, crate::std_instead_of_core::ALLOC_INSTEAD_OF_CORE_INFO, crate::std_instead_of_core::STD_INSTEAD_OF_ALLOC_INFO, diff --git a/clippy_lints/src/lib.rs b/clippy_lints/src/lib.rs index 676ef3946bf5..ccd89b778580 100644 --- a/clippy_lints/src/lib.rs +++ b/clippy_lints/src/lib.rs @@ -265,6 +265,7 @@ mod shadow; mod single_char_lifetime_names; mod single_component_path_imports; mod size_of_in_element_count; +mod size_of_ref; mod slow_vector_initialization; mod std_instead_of_core; mod strings; @@ -906,6 +907,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf: store.register_late_pass(|_| Box::new(semicolon_block::SemicolonBlock)); store.register_late_pass(|_| Box::new(fn_null_check::FnNullCheck)); store.register_late_pass(|_| Box::new(permissions_set_readonly_false::PermissionsSetReadonlyFalse)); + store.register_late_pass(|_| Box::new(size_of_ref::SizeOfRef)); // add lints here, do not remove this comment, it's used in `new_lint` } diff --git a/clippy_lints/src/size_of_ref.rs b/clippy_lints/src/size_of_ref.rs new file mode 100644 index 000000000000..3fcdb4288ce6 --- /dev/null +++ b/clippy_lints/src/size_of_ref.rs @@ -0,0 +1,73 @@ +use clippy_utils::{diagnostics::span_lint_and_help, path_def_id, ty::peel_mid_ty_refs}; +use rustc_hir::{Expr, ExprKind}; +use rustc_lint::{LateContext, LateLintPass}; +use rustc_session::{declare_lint_pass, declare_tool_lint}; +use rustc_span::sym; + +declare_clippy_lint! { + /// ### What it does + /// + /// Checks for calls to `std::mem::size_of_val()` where the argument is + /// a reference to a reference. + /// + /// ### Why is this bad? + /// + /// Calling `size_of_val()` with a reference to a reference as the argument + /// yields the size of the reference-type, not the size of the value behind + /// the reference. + /// + /// ### Example + /// ```rust + /// struct Foo { + /// buffer: [u8], + /// } + /// + /// impl Foo { + /// fn size(&self) -> usize { + /// // Note that `&self` as an argument is a `&&Foo`: Because `self` + /// // is already a reference, `&self` is a double-reference. + /// // The return value of `size_of_val()` therefor is the + /// // size of the reference-type, not the size of `self`. + /// std::mem::size_of_val(&self) + /// } + /// } + /// ``` + /// Use instead: + /// ```rust + /// struct Foo { + /// buffer: [u8], + /// } + /// + /// impl Foo { + /// fn size(&self) -> usize { + /// // Correct + /// std::mem::size_of_val(self) + /// } + /// } + /// ``` + #[clippy::version = "1.67.0"] + pub SIZE_OF_REF, + suspicious, + "Argument to `std::mem::size_of_val()` is a double-reference, which is almost certainly unintended" +} +declare_lint_pass!(SizeOfRef => [SIZE_OF_REF]); + +impl LateLintPass<'_> for SizeOfRef { + fn check_expr(&mut self, cx: &LateContext<'_>, expr: &'_ Expr<'_>) { + if let ExprKind::Call(path, [arg]) = expr.kind + && let Some(def_id) = path_def_id(cx, path) + && cx.tcx.is_diagnostic_item(sym::mem_size_of_val, def_id) + && let arg_ty = cx.typeck_results().expr_ty(arg) + && peel_mid_ty_refs(arg_ty).1 > 1 + { + span_lint_and_help( + cx, + SIZE_OF_REF, + expr.span, + "argument to `std::mem::size_of_val()` is a reference to a reference", + None, + "dereference the argument to `std::mem::size_of_val()` to get the size of the value instead of the size of the reference-type", + ); + } + } +} diff --git a/tests/ui/size_of_ref.rs b/tests/ui/size_of_ref.rs new file mode 100644 index 000000000000..1e83ab82907d --- /dev/null +++ b/tests/ui/size_of_ref.rs @@ -0,0 +1,27 @@ +#![allow(unused)] +#![warn(clippy::size_of_ref)] + +use std::mem::size_of_val; + +fn main() { + let x = 5; + let y = &x; + + size_of_val(&x); // no lint + size_of_val(y); // no lint + + size_of_val(&&x); + size_of_val(&y); +} + +struct S { + field: u32, + data: Vec, +} + +impl S { + /// Get size of object including `self`, in bytes. + pub fn size(&self) -> usize { + std::mem::size_of_val(&self) + (std::mem::size_of::() * self.data.capacity()) + } +} diff --git a/tests/ui/size_of_ref.stderr b/tests/ui/size_of_ref.stderr new file mode 100644 index 000000000000..d4c13ac3290b --- /dev/null +++ b/tests/ui/size_of_ref.stderr @@ -0,0 +1,27 @@ +error: argument to `std::mem::size_of_val()` is a reference to a reference + --> $DIR/size_of_ref.rs:13:5 + | +LL | size_of_val(&&x); + | ^^^^^^^^^^^^^^^^ + | + = help: dereference the argument to `std::mem::size_of_val()` to get the size of the value instead of the size of the reference-type + = note: `-D clippy::size-of-ref` implied by `-D warnings` + +error: argument to `std::mem::size_of_val()` is a reference to a reference + --> $DIR/size_of_ref.rs:14:5 + | +LL | size_of_val(&y); + | ^^^^^^^^^^^^^^^ + | + = help: dereference the argument to `std::mem::size_of_val()` to get the size of the value instead of the size of the reference-type + +error: argument to `std::mem::size_of_val()` is a reference to a reference + --> $DIR/size_of_ref.rs:25:9 + | +LL | std::mem::size_of_val(&self) + (std::mem::size_of::() * self.data.capacity()) + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | + = help: dereference the argument to `std::mem::size_of_val()` to get the size of the value instead of the size of the reference-type + +error: aborting due to 3 previous errors +