new lint ptr_to_temporary

Update mod.rs

Update mod.rs

Author: Centri3

CHANGELOG.md

@@ -5163,6 +5163,7 @@ Released 2018-09-13
 [`ptr_cast_constness`]: https://rust-lang.github.io/rust-clippy/master/index.html#ptr_cast_constness
 [`ptr_eq`]: https://rust-lang.github.io/rust-clippy/master/index.html#ptr_eq
 [`ptr_offset_with_cast`]: https://rust-lang.github.io/rust-clippy/master/index.html#ptr_offset_with_cast
+[`ptr_to_temporary`]: https://rust-lang.github.io/rust-clippy/master/index.html#ptr_to_temporary
 [`pub_enum_variant_names`]: https://rust-lang.github.io/rust-clippy/master/index.html#pub_enum_variant_names
 [`pub_use`]: https://rust-lang.github.io/rust-clippy/master/index.html#pub_use
 [`pub_with_shorthand`]: https://rust-lang.github.io/rust-clippy/master/index.html#pub_with_shorthand

clippy_lints/src/casts/mod.rs

@@ -18,6 +18,7 @@ mod fn_to_numeric_cast_any;
 mod fn_to_numeric_cast_with_truncation;
 mod ptr_as_ptr;
 mod ptr_cast_constness;
+mod ptr_to_temporary;
 mod unnecessary_cast;
 mod utils;
 
@@ -665,6 +666,33 @@ declare_clippy_lint! {
     "casting a known floating-point NaN into an integer"
 }
 
+declare_clippy_lint! {
+    /// ### What it does
+    /// Checks for raw pointers that point to temporary values.
+    ///
+    /// ### Why is this bad?
+    /// Usage of such a pointer can result in Undefined Behavior, as the pointer will stop pointing
+    /// to valid stack memory once the temporary is dropped.
+    ///
+    /// ### Example
+    /// ```rust,ignore
+    /// const PS: [usize; 3] = [2usize, 3usize, 11usize];
+    /// let mut ps = vec![];
+    ///
+    /// for p in PS {
+    ///     ps.push(&p as *const usize);
+    /// }
+    ///
+    /// for p in ps {
+    ///     unsafe { p.read() }; // ⚠️
+    /// }
+    /// ```
+    #[clippy::version = "1.72.0"]
+    pub PTR_TO_TEMPORARY,
+    correctness,
+    "disallows obtaining a raw pointer to a temporary value"
+}
+
 pub struct Casts {
     msrv: Msrv,
 }
@@ -699,6 +727,7 @@ impl_lint_pass!(Casts => [
     CAST_SLICE_FROM_RAW_PARTS,
     AS_PTR_CAST_MUT,
     CAST_NAN_TO_INT,
+    PTR_TO_TEMPORARY,
 ]);
 
 impl<'tcx> LateLintPass<'tcx> for Casts {
@@ -744,6 +773,7 @@ impl<'tcx> LateLintPass<'tcx> for Casts {
             }
 
             as_underscore::check(cx, expr, cast_to_hir);
+            ptr_to_temporary::check(cx, expr, cast_expr, cast_to_hir);
 
             if self.msrv.meets(msrvs::BORROW_AS_PTR) {
                 borrow_as_ptr::check(cx, expr, cast_expr, cast_to_hir);

clippy_lints/src/casts/ptr_to_temporary.rs

@@ -0,0 +1,34 @@
+use clippy_utils::diagnostics::span_lint_and_help;
+use rustc_hir::{BorrowKind, Expr, ExprKind, Ty, TyKind};
+use rustc_lint::LateContext;
+use rustc_middle::ty::adjustment::Adjust;
+
+use super::PTR_TO_TEMPORARY;
+
+pub(super) fn check<'tcx>(
+    cx: &LateContext<'tcx>,
+    expr: &'tcx Expr<'_>,
+    cast_expr: &'tcx Expr<'_>,
+    cast_to: &'tcx Ty<'_>,
+) {
+    if matches!(cast_to.kind, TyKind::Ptr(_))
+        && let ExprKind::AddrOf(BorrowKind::Ref, _, e) = cast_expr.kind
+    {
+        // rustc's criteria of a "temporary value", so this should be 100% accurate
+        if !e.is_place_expr(|base| {
+            cx.typeck_results()
+                .adjustments()
+                .get(base.hir_id)
+                .is_some_and(|x| x.iter().any(|adj| matches!(adj.kind, Adjust::Deref(_))))
+        }) {
+            span_lint_and_help(
+                cx,
+                PTR_TO_TEMPORARY,
+                expr.span,
+                "raw pointer to a temporary value",
+                None,
+                "usage of this pointer will cause Undefined Behavior; create a local binding to make it longer lived",
+            );
+        }
+    }
+}

clippy_lints/src/declared_lints.rs

@@ -94,6 +94,7 @@ pub(crate) static LINTS: &[&crate::LintInfo] = &[
     crate::casts::FN_TO_NUMERIC_CAST_WITH_TRUNCATION_INFO,
     crate::casts::PTR_AS_PTR_INFO,
     crate::casts::PTR_CAST_CONSTNESS_INFO,
+    crate::casts::PTR_TO_TEMPORARY_INFO,
     crate::casts::UNNECESSARY_CAST_INFO,
     crate::checked_conversions::CHECKED_CONVERSIONS_INFO,
     crate::cognitive_complexity::COGNITIVE_COMPLEXITY_INFO,

tests/ui/borrow_deref_ref.fixed

@@ -1,7 +1,7 @@
 //@run-rustfix
 //@aux-build: proc_macros.rs:proc-macro
 
-#![allow(dead_code, unused_variables)]
+#![allow(clippy::ptr_to_temporary, dead_code, unused_variables)]
 
 extern crate proc_macros;
 use proc_macros::with_span;

tests/ui/borrow_deref_ref.rs

@@ -1,7 +1,7 @@
 //@run-rustfix
 //@aux-build: proc_macros.rs:proc-macro
 
-#![allow(dead_code, unused_variables)]
+#![allow(clippy::ptr_to_temporary, dead_code, unused_variables)]
 
 extern crate proc_macros;
 use proc_macros::with_span;

tests/ui/cast_alignment.rs

@@ -9,7 +9,8 @@ extern crate libc;
     clippy::no_effect,
     clippy::unnecessary_operation,
     clippy::cast_lossless,
-    clippy::borrow_as_ptr
+    clippy::borrow_as_ptr,
+    clippy::ptr_to_temporary
 )]
 
 fn main() {

tests/ui/cast_alignment.stderr

@@ -1,25 +1,25 @@
 error: casting from `*const u8` to a more-strictly-aligned pointer (`*const u16`) (1 < 2 bytes)
-  --> $DIR/cast_alignment.rs:19:5
+  --> $DIR/cast_alignment.rs:20:5
    |
 LL |     (&1u8 as *const u8) as *const u16;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: `-D clippy::cast-ptr-alignment` implied by `-D warnings`
 
 error: casting from `*mut u8` to a more-strictly-aligned pointer (`*mut u16`) (1 < 2 bytes)
-  --> $DIR/cast_alignment.rs:20:5
+  --> $DIR/cast_alignment.rs:21:5
    |
 LL |     (&mut 1u8 as *mut u8) as *mut u16;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: casting from `*const u8` to a more-strictly-aligned pointer (`*const u16`) (1 < 2 bytes)
-  --> $DIR/cast_alignment.rs:23:5
+  --> $DIR/cast_alignment.rs:24:5
    |
 LL |     (&1u8 as *const u8).cast::<u16>();
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: casting from `*mut u8` to a more-strictly-aligned pointer (`*mut u16`) (1 < 2 bytes)
-  --> $DIR/cast_alignment.rs:24:5
+  --> $DIR/cast_alignment.rs:25:5
    |
 LL |     (&mut 1u8 as *mut u8).cast::<u16>();
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

tests/ui/ptr_to_temporary.rs

@@ -0,0 +1,34 @@
+#![allow(clippy::explicit_auto_deref, clippy::unnecessary_cast, clippy::useless_vec)]
+
+use std::ptr::addr_of;
+
+fn a() -> i32 {
+    0
+}
+
+struct Vec3 {
+    x: f32,
+    y: f32,
+    z: f32,
+}
+
+fn main() {
+    let _p = &0 as *const i32;
+    let _p = &a() as *const i32;
+    let vec = vec![1];
+    let _p = &vec.len() as *const usize;
+    let x = &(1 + 2) as *const i32;
+    let x = &(x as *const i32) as *const *const i32;
+
+    // Do not lint...
+    let ptr = &Vec3 { x: 1.0, y: 2.0, z: 3.0 };
+    let some_variable = 1i32;
+    let x = &(*ptr).x as *const f32;
+    let x = &(some_variable) as *const i32;
+
+    // ...As `addr_of!` does not report anything out of the ordinary
+    let ptr = &Vec3 { x: 1.0, y: 2.0, z: 3.0 };
+    let some_variable = 1i32;
+    let x = addr_of!((*ptr).x) as *const f32;
+    let x = addr_of!(some_variable);
+}

tests/ui/ptr_to_temporary.stderr

@@ -0,0 +1,43 @@
+error: raw pointer to a temporary value
+  --> $DIR/ptr_to_temporary.rs:16:14
+   |
+LL |     let _p = &0 as *const i32;
+   |              ^^^^^^^^^^^^^^^^
+   |
+   = help: usage of this pointer will cause Undefined Behavior; create a local binding to make it longer lived
+   = note: `#[deny(clippy::ptr_to_temporary)]` on by default
+
+error: raw pointer to a temporary value
+  --> $DIR/ptr_to_temporary.rs:17:14
+   |
+LL |     let _p = &a() as *const i32;
+   |              ^^^^^^^^^^^^^^^^^^
+   |
+   = help: usage of this pointer will cause Undefined Behavior; create a local binding to make it longer lived
+
+error: raw pointer to a temporary value
+  --> $DIR/ptr_to_temporary.rs:19:14
+   |
+LL |     let _p = &vec.len() as *const usize;
+   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = help: usage of this pointer will cause Undefined Behavior; create a local binding to make it longer lived
+
+error: raw pointer to a temporary value
+  --> $DIR/ptr_to_temporary.rs:20:13
+   |
+LL |     let x = &(1 + 2) as *const i32;
+   |             ^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = help: usage of this pointer will cause Undefined Behavior; create a local binding to make it longer lived
+
+error: raw pointer to a temporary value
+  --> $DIR/ptr_to_temporary.rs:21:13
+   |
+LL |     let x = &(x as *const i32) as *const *const i32;
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = help: usage of this pointer will cause Undefined Behavior; create a local binding to make it longer lived
+
+error: aborting due to 5 previous errors
+