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https://github.com/rust-lang/rust-clippy
synced 2024-11-27 07:00:55 +00:00
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>()`
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9e9526c6ab
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5 changed files with 62 additions and 2 deletions
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@ -419,6 +419,8 @@ declare_clippy_lint! {
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/// let ptr = mut_ptr as *const u32;
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/// let ptr1 = std::ptr::null::<u32>() as *mut u32;
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/// let ptr2 = std::ptr::null_mut::<u32>() as *const u32;
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/// let ptr3 = std::ptr::null::<u32>().cast_mut();
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/// let ptr4 = std::ptr::null_mut::<u32>().cast_const();
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/// ```
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/// Use instead:
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/// ```no_run
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@ -427,6 +429,8 @@ declare_clippy_lint! {
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/// let ptr = mut_ptr.cast_const();
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/// let ptr1 = std::ptr::null_mut::<u32>();
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/// let ptr2 = std::ptr::null::<u32>();
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/// let ptr3 = std::ptr::null_mut::<u32>();
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/// let ptr4 = std::ptr::null::<u32>();
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/// ```
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#[clippy::version = "1.72.0"]
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pub PTR_CAST_CONSTNESS,
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@ -813,6 +817,7 @@ impl<'tcx> LateLintPass<'tcx> for Casts {
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char_lit_as_u8::check(cx, expr);
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ptr_as_ptr::check(cx, expr, &self.msrv);
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cast_slice_different_sizes::check(cx, expr, &self.msrv);
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ptr_cast_constness::check_null_ptr_cast_method(cx, expr);
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}
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extract_msrv_attr!(LateContext);
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@ -71,3 +71,30 @@ pub(super) fn check<'tcx>(
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}
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}
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}
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pub(super) fn check_null_ptr_cast_method(cx: &LateContext<'_>, expr: &Expr<'_>) {
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if let ExprKind::MethodCall(method, cast_expr, [], _) = expr.kind
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&& let ExprKind::Call(func, []) = cast_expr.kind
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&& let ExprKind::Path(QPath::Resolved(None, path)) = func.kind
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&& let Some(defid) = path.res.opt_def_id()
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&& let method = match (cx.tcx.get_diagnostic_name(defid), method.ident.as_str()) {
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(Some(sym::ptr_null), "cast_mut") => "null_mut",
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(Some(sym::ptr_null_mut), "cast_const") => "null",
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_ => return,
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}
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&& let Some(prefix) = std_or_core(cx)
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&& let mut app = Applicability::MachineApplicable
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&& let sugg = format!("{}", Sugg::hir_with_applicability(cx, cast_expr, "_", &mut app))
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&& let Some((_, after_lt)) = sugg.split_once("::<")
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{
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span_lint_and_sugg(
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cx,
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PTR_CAST_CONSTNESS,
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expr.span,
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"changing constness of a null pointer",
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format!("use `{method}()` directly instead"),
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format!("{prefix}::ptr::{method}::<{after_lt}"),
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app,
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);
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}
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}
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@ -74,10 +74,14 @@ fn null_pointers() {
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use std::ptr;
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let _ = std::ptr::null_mut::<String>();
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let _ = std::ptr::null::<u32>();
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let _ = std::ptr::null_mut::<u32>();
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let _ = std::ptr::null::<u32>();
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// Make sure the lint is triggered inside a macro
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let _ = inline!(std::ptr::null_mut::<u32>());
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let _ = inline!(std::ptr::null_mut::<u32>());
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// Do not lint inside macros from external crates
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let _ = external!(ptr::null::<u32>() as *mut u32);
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let _ = external!(ptr::null::<u32>().cast_mut());
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}
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@ -74,10 +74,14 @@ fn null_pointers() {
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use std::ptr;
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let _ = ptr::null::<String>() as *mut String;
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let _ = ptr::null_mut::<u32>() as *const u32;
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let _ = ptr::null::<u32>().cast_mut();
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let _ = ptr::null_mut::<u32>().cast_const();
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// Make sure the lint is triggered inside a macro
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let _ = inline!(ptr::null::<u32>() as *mut u32);
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let _ = inline!(ptr::null::<u32>().cast_mut());
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// Do not lint inside macros from external crates
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let _ = external!(ptr::null::<u32>() as *mut u32);
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let _ = external!(ptr::null::<u32>().cast_mut());
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}
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@ -55,13 +55,33 @@ error: `as` casting to make a mutable null pointer into a const null pointer
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LL | let _ = ptr::null_mut::<u32>() as *const u32;
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `null()` directly instead: `std::ptr::null::<u32>()`
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error: changing constness of a null pointer
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--> tests/ui/ptr_cast_constness.rs:77:13
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LL | let _ = ptr::null::<u32>().cast_mut();
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `null_mut()` directly instead: `std::ptr::null_mut::<u32>()`
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error: changing constness of a null pointer
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--> tests/ui/ptr_cast_constness.rs:78:13
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LL | let _ = ptr::null_mut::<u32>().cast_const();
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `null()` directly instead: `std::ptr::null::<u32>()`
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error: `as` casting to make a const null pointer into a mutable null pointer
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--> tests/ui/ptr_cast_constness.rs:79:21
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--> tests/ui/ptr_cast_constness.rs:81:21
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LL | let _ = inline!(ptr::null::<u32>() as *mut u32);
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `null_mut()` directly instead: `std::ptr::null_mut::<u32>()`
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= note: this error originates in the macro `__inline_mac_fn_null_pointers` (in Nightly builds, run with -Z macro-backtrace for more info)
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error: aborting due to 10 previous errors
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error: changing constness of a null pointer
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--> tests/ui/ptr_cast_constness.rs:82:21
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LL | let _ = inline!(ptr::null::<u32>().cast_mut());
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `null_mut()` directly instead: `std::ptr::null_mut::<u32>()`
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= note: this error originates in the macro `__inline_mac_fn_null_pointers` (in Nightly builds, run with -Z macro-backtrace for more info)
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error: aborting due to 13 previous errors
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