Handle null pointer constness cast through methods

This covers two cases:

- `core::ptr::null::<T>().cast_mut()` -> `core::ptr::null_mut::<T>()`
- `core::ptr::null_mut::<T>().cast_const()` -> `core::ptr::null::<T>()`
This commit is contained in:
Samuel Tardieu 2024-09-07 21:57:29 +02:00
parent 9e9526c6ab
commit 30608732c2
5 changed files with 62 additions and 2 deletions

View file

@ -419,6 +419,8 @@ declare_clippy_lint! {
/// let ptr = mut_ptr as *const u32;
/// let ptr1 = std::ptr::null::<u32>() as *mut u32;
/// let ptr2 = std::ptr::null_mut::<u32>() as *const u32;
/// let ptr3 = std::ptr::null::<u32>().cast_mut();
/// let ptr4 = std::ptr::null_mut::<u32>().cast_const();
/// ```
/// Use instead:
/// ```no_run
@ -427,6 +429,8 @@ declare_clippy_lint! {
/// let ptr = mut_ptr.cast_const();
/// let ptr1 = std::ptr::null_mut::<u32>();
/// let ptr2 = std::ptr::null::<u32>();
/// let ptr3 = std::ptr::null_mut::<u32>();
/// let ptr4 = std::ptr::null::<u32>();
/// ```
#[clippy::version = "1.72.0"]
pub PTR_CAST_CONSTNESS,
@ -813,6 +817,7 @@ impl<'tcx> LateLintPass<'tcx> for Casts {
char_lit_as_u8::check(cx, expr);
ptr_as_ptr::check(cx, expr, &self.msrv);
cast_slice_different_sizes::check(cx, expr, &self.msrv);
ptr_cast_constness::check_null_ptr_cast_method(cx, expr);
}
extract_msrv_attr!(LateContext);

View file

@ -71,3 +71,30 @@ pub(super) fn check<'tcx>(
}
}
}
pub(super) fn check_null_ptr_cast_method(cx: &LateContext<'_>, expr: &Expr<'_>) {
if let ExprKind::MethodCall(method, cast_expr, [], _) = expr.kind
&& let ExprKind::Call(func, []) = cast_expr.kind
&& let ExprKind::Path(QPath::Resolved(None, path)) = func.kind
&& let Some(defid) = path.res.opt_def_id()
&& let method = match (cx.tcx.get_diagnostic_name(defid), method.ident.as_str()) {
(Some(sym::ptr_null), "cast_mut") => "null_mut",
(Some(sym::ptr_null_mut), "cast_const") => "null",
_ => return,
}
&& let Some(prefix) = std_or_core(cx)
&& let mut app = Applicability::MachineApplicable
&& let sugg = format!("{}", Sugg::hir_with_applicability(cx, cast_expr, "_", &mut app))
&& let Some((_, after_lt)) = sugg.split_once("::<")
{
span_lint_and_sugg(
cx,
PTR_CAST_CONSTNESS,
expr.span,
"changing constness of a null pointer",
format!("use `{method}()` directly instead"),
format!("{prefix}::ptr::{method}::<{after_lt}"),
app,
);
}
}

View file

@ -74,10 +74,14 @@ fn null_pointers() {
use std::ptr;
let _ = std::ptr::null_mut::<String>();
let _ = std::ptr::null::<u32>();
let _ = std::ptr::null_mut::<u32>();
let _ = std::ptr::null::<u32>();
// Make sure the lint is triggered inside a macro
let _ = inline!(std::ptr::null_mut::<u32>());
let _ = inline!(std::ptr::null_mut::<u32>());
// Do not lint inside macros from external crates
let _ = external!(ptr::null::<u32>() as *mut u32);
let _ = external!(ptr::null::<u32>().cast_mut());
}

View file

@ -74,10 +74,14 @@ fn null_pointers() {
use std::ptr;
let _ = ptr::null::<String>() as *mut String;
let _ = ptr::null_mut::<u32>() as *const u32;
let _ = ptr::null::<u32>().cast_mut();
let _ = ptr::null_mut::<u32>().cast_const();
// Make sure the lint is triggered inside a macro
let _ = inline!(ptr::null::<u32>() as *mut u32);
let _ = inline!(ptr::null::<u32>().cast_mut());
// Do not lint inside macros from external crates
let _ = external!(ptr::null::<u32>() as *mut u32);
let _ = external!(ptr::null::<u32>().cast_mut());
}

View file

@ -55,13 +55,33 @@ error: `as` casting to make a mutable null pointer into a const null pointer
LL | let _ = ptr::null_mut::<u32>() as *const u32;
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `null()` directly instead: `std::ptr::null::<u32>()`
error: changing constness of a null pointer
--> tests/ui/ptr_cast_constness.rs:77:13
|
LL | let _ = ptr::null::<u32>().cast_mut();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `null_mut()` directly instead: `std::ptr::null_mut::<u32>()`
error: changing constness of a null pointer
--> tests/ui/ptr_cast_constness.rs:78:13
|
LL | let _ = ptr::null_mut::<u32>().cast_const();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `null()` directly instead: `std::ptr::null::<u32>()`
error: `as` casting to make a const null pointer into a mutable null pointer
--> tests/ui/ptr_cast_constness.rs:79:21
--> tests/ui/ptr_cast_constness.rs:81:21
|
LL | let _ = inline!(ptr::null::<u32>() as *mut u32);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `null_mut()` directly instead: `std::ptr::null_mut::<u32>()`
|
= note: this error originates in the macro `__inline_mac_fn_null_pointers` (in Nightly builds, run with -Z macro-backtrace for more info)
error: aborting due to 10 previous errors
error: changing constness of a null pointer
--> tests/ui/ptr_cast_constness.rs:82:21
|
LL | let _ = inline!(ptr::null::<u32>().cast_mut());
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `null_mut()` directly instead: `std::ptr::null_mut::<u32>()`
|
= note: this error originates in the macro `__inline_mac_fn_null_pointers` (in Nightly builds, run with -Z macro-backtrace for more info)
error: aborting due to 13 previous errors