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Rollup merge of #132732 - gavincrawford:as_ptr_attribute, r=Urgau

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Use attributes for `dangling_pointers_from_temporaries` lint

Checking for dangling pointers by function name isn't ideal, and leaves out certain pointer-returning methods that don't follow the `as_ptr` naming convention. Using an attribute for this lint cleans things up and allows more thorough coverage of other methods, such as `UnsafeCell::get()`.
This commit is contained in:
Jacob Pratt 2024-11-20 01:54:24 -05:00 • committed by GitHub
commit 25dc4d0394
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13 changed files with 83 additions and 32 deletions
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27
compiler/rustc_lint/src/dangling.rs
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@ -43,13 +43,10 @@ declare_lint! {
}
/// FIXME: false negatives (i.e. the lint is not emitted when it should be)
/// 1. Method calls that are not checked for:
/// - [`temporary_unsafe_cell.get()`][`core::cell::UnsafeCell::get()`]
/// - [`temporary_sync_unsafe_cell.get()`][`core::cell::SyncUnsafeCell::get()`]
/// 2. Ways to get a temporary that are not recognized:
/// 1. Ways to get a temporary that are not recognized:
/// - `owning_temporary.field`
/// - `owning_temporary[index]`
/// 3. No checks for ref-to-ptr conversions:
/// 2. No checks for ref-to-ptr conversions:
/// - `&raw [mut] temporary`
/// - `&temporary as *(const|mut) _`
/// - `ptr::from_ref(&temporary)` and friends
@ -133,10 +130,11 @@ impl DanglingPointerSearcher<'_, '_> {
fn lint_expr(cx: &LateContext<'_>, expr: &Expr<'_>) {
if let ExprKind::MethodCall(method, receiver, _args, _span) = expr.kind
&& matches!(method.ident.name, sym::as_ptr | sym::as_mut_ptr)
&& let Some(fn_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id)
&& cx.tcx.has_attr(fn_id, sym::rustc_as_ptr)
&& is_temporary_rvalue(receiver)
&& let ty = cx.typeck_results().expr_ty(receiver)
&& is_interesting(cx.tcx, ty)
&& owns_allocation(cx.tcx, ty)
{
// FIXME: use `emit_node_lint` when `#[primary_span]` is added.
cx.tcx.emit_node_span_lint(
@ -199,24 +197,25 @@ fn is_temporary_rvalue(expr: &Expr<'_>) -> bool {
}
}
// Array, Vec, String, CString, MaybeUninit, Cell, Box<[_]>, Box<str>, Box<CStr>,
// or any of the above in arbitrary many nested Box'es.
fn is_interesting(tcx: TyCtxt<'_>, ty: Ty<'_>) -> bool {
// Array, Vec, String, CString, MaybeUninit, Cell, Box<[_]>, Box<str>, Box<CStr>, UnsafeCell,
// SyncUnsafeCell, or any of the above in arbitrary many nested Box'es.
fn owns_allocation(tcx: TyCtxt<'_>, ty: Ty<'_>) -> bool {
if ty.is_array() {
true
} else if let Some(inner) = ty.boxed_ty() {
inner.is_slice()
|| inner.is_str()
|| inner.ty_adt_def().is_some_and(|def| tcx.is_lang_item(def.did(), LangItem::CStr))
|| is_interesting(tcx, inner)
|| owns_allocation(tcx, inner)
} else if let Some(def) = ty.ty_adt_def() {
for lang_item in [LangItem::String, LangItem::MaybeUninit] {
for lang_item in [LangItem::String, LangItem::MaybeUninit, LangItem::UnsafeCell] {
if tcx.is_lang_item(def.did(), lang_item) {
return true;
}
}
tcx.get_diagnostic_name(def.did())
.is_some_and(|name| matches!(name, sym::cstring_type | sym::Vec | sym::Cell))
tcx.get_diagnostic_name(def.did()).is_some_and(|name| {
matches!(name, sym::cstring_type | sym::Vec | sym::Cell | sym::SyncUnsafeCell)
})
} else {
false
}