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Rollup merge of #113657 - Urgau:expand-incorrect_fn_null_check-lint, r=cjgillot

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Expand, rename and improve `incorrect_fn_null_checks` lint

This PR,

 - firstly, expand the lint by now linting on references
 - secondly, it renames the lint `incorrect_fn_null_checks` -> `useless_ptr_null_checks`
 - and thirdly it improves the lint by catching `ptr::from_mut`, `ptr::from_ref`, as well as `<*mut _>::cast` and `<*const _>::cast_mut`

Fixes https://github.com/rust-lang/rust/issues/113601
cc ```@est31```
This commit is contained in:
Matthias Krüger 2023-08-03 17:29:06 +02:00 • committed by GitHub
commit 7518ae566e
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17 changed files with 484 additions and 225 deletions
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112
compiler/rustc_lint/src/fn_null_check.rs
View file

@ -1,112 +0,0 @@
use crate::{lints::FnNullCheckDiag, LateContext, LateLintPass, LintContext};
use rustc_ast::LitKind;
use rustc_hir::{BinOpKind, Expr, ExprKind, TyKind};
use rustc_session::{declare_lint, declare_lint_pass};
use rustc_span::sym;
declare_lint! {
/// The `incorrect_fn_null_checks` lint checks for expression that checks if a
/// function pointer is null.
///
/// ### Example
///
/// ```rust
/// # fn test() {}
/// let fn_ptr: fn() = /* somehow obtained nullable function pointer */
/// # test;
///
/// if (fn_ptr as *const ()).is_null() { /* ... */ }
/// ```
///
/// {{produces}}
///
/// ### Explanation
///
/// Function pointers are assumed to be non-null, checking them for null will always
/// return false.
INCORRECT_FN_NULL_CHECKS,
Warn,
"incorrect checking of null function pointer"
}
declare_lint_pass!(IncorrectFnNullChecks => [INCORRECT_FN_NULL_CHECKS]);
fn is_fn_ptr_cast(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
let mut expr = expr.peel_blocks();
let mut had_at_least_one_cast = false;
while let ExprKind::Cast(cast_expr, cast_ty) = expr.kind
&& let TyKind::Ptr(_) = cast_ty.kind {
expr = cast_expr.peel_blocks();
had_at_least_one_cast = true;
}
had_at_least_one_cast && cx.typeck_results().expr_ty_adjusted(expr).is_fn()
}
impl<'tcx> LateLintPass<'tcx> for IncorrectFnNullChecks {
fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
match expr.kind {
// Catching:
// <*<const/mut> <ty>>::is_null(fn_ptr as *<const/mut> <ty>)
ExprKind::Call(path, [arg])
if let ExprKind::Path(ref qpath) = path.kind
&& let Some(def_id) = cx.qpath_res(qpath, path.hir_id).opt_def_id()
&& matches!(
cx.tcx.get_diagnostic_name(def_id),
Some(sym::ptr_const_is_null | sym::ptr_is_null)
)
&& is_fn_ptr_cast(cx, arg) =>
{
cx.emit_spanned_lint(INCORRECT_FN_NULL_CHECKS, expr.span, FnNullCheckDiag)
}
// Catching:
// (fn_ptr as *<const/mut> <ty>).is_null()
ExprKind::MethodCall(_, receiver, _, _)
if let Some(def_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id)
&& matches!(
cx.tcx.get_diagnostic_name(def_id),
Some(sym::ptr_const_is_null | sym::ptr_is_null)
)
&& is_fn_ptr_cast(cx, receiver) =>
{
cx.emit_spanned_lint(INCORRECT_FN_NULL_CHECKS, expr.span, FnNullCheckDiag)
}
ExprKind::Binary(op, left, right) if matches!(op.node, BinOpKind::Eq) => {
let to_check: &Expr<'_>;
if is_fn_ptr_cast(cx, left) {
to_check = right;
} else if is_fn_ptr_cast(cx, right) {
to_check = left;
} else {
return;
}
match to_check.kind {
// Catching:
// (fn_ptr as *<const/mut> <ty>) == (0 as <ty>)
ExprKind::Cast(cast_expr, _)
if let ExprKind::Lit(spanned) = cast_expr.kind
&& let LitKind::Int(v, _) = spanned.node && v == 0 =>
{
cx.emit_spanned_lint(INCORRECT_FN_NULL_CHECKS, expr.span, FnNullCheckDiag)
},
// Catching:
// (fn_ptr as *<const/mut> <ty>) == std::ptr::null()
ExprKind::Call(path, [])
if let ExprKind::Path(ref qpath) = path.kind
&& let Some(def_id) = cx.qpath_res(qpath, path.hir_id).opt_def_id()
&& let Some(diag_item) = cx.tcx.get_diagnostic_name(def_id)
&& (diag_item == sym::ptr_null || diag_item == sym::ptr_null_mut) =>
{
cx.emit_spanned_lint(INCORRECT_FN_NULL_CHECKS, expr.span, FnNullCheckDiag)
},
_ => {},
}
}
_ => {}
}
}
}

6
compiler/rustc_lint/src/lib.rs
View file

@ -57,7 +57,6 @@ mod early;
mod enum_intrinsics_non_enums;
mod errors;
mod expect;
mod fn_null_check;
mod for_loops_over_fallibles;
pub mod hidden_unicode_codepoints;
mod internal;
@ -76,6 +75,7 @@ mod noop_method_call;
mod opaque_hidden_inferred_bound;
mod pass_by_value;
mod passes;
mod ptr_nulls;
mod redundant_semicolon;
mod reference_casting;
mod traits;
@ -102,7 +102,6 @@ use builtin::*;
use deref_into_dyn_supertrait::*;
use drop_forget_useless::*;
use enum_intrinsics_non_enums::EnumIntrinsicsNonEnums;
use fn_null_check::*;
use for_loops_over_fallibles::*;
use hidden_unicode_codepoints::*;
use internal::*;
@ -117,6 +116,7 @@ use nonstandard_style::*;
use noop_method_call::*;
use opaque_hidden_inferred_bound::*;
use pass_by_value::*;
use ptr_nulls::*;
use redundant_semicolon::*;
use reference_casting::*;
use traits::*;
@ -227,7 +227,7 @@ late_lint_methods!(
// Depends on types used in type definitions
MissingCopyImplementations: MissingCopyImplementations,
// Depends on referenced function signatures in expressions
IncorrectFnNullChecks: IncorrectFnNullChecks,
PtrNullChecks: PtrNullChecks,
MutableTransmutes: MutableTransmutes,
TypeAliasBounds: TypeAliasBounds,
TrivialConstraints: TrivialConstraints,

20
compiler/rustc_lint/src/lints.rs
View file

@ -613,11 +613,23 @@ pub struct ExpectationNote {
pub rationale: Symbol,
}
// fn_null_check.rs
// ptr_nulls.rs
#[derive(LintDiagnostic)]
#[diag(lint_fn_null_check)]
#[help]
pub struct FnNullCheckDiag;
pub enum PtrNullChecksDiag<'a> {
#[diag(lint_ptr_null_checks_fn_ptr)]
#[help(lint_help)]
FnPtr {
orig_ty: Ty<'a>,
#[label]
label: Span,
},
#[diag(lint_ptr_null_checks_ref)]
Ref {
orig_ty: Ty<'a>,
#[label]
label: Span,
},
}
// for_loops_over_fallibles.rs
#[derive(LintDiagnostic)]

146
compiler/rustc_lint/src/ptr_nulls.rs Normal file
View file

@ -0,0 +1,146 @@
use crate::{lints::PtrNullChecksDiag, LateContext, LateLintPass, LintContext};
use rustc_ast::LitKind;
use rustc_hir::{BinOpKind, Expr, ExprKind, TyKind};
use rustc_session::{declare_lint, declare_lint_pass};
use rustc_span::sym;
declare_lint! {
/// The `useless_ptr_null_checks` lint checks for useless null checks against pointers
/// obtained from non-null types.
///
/// ### Example
///
/// ```rust
/// # fn test() {}
/// let fn_ptr: fn() = /* somehow obtained nullable function pointer */
/// # test;
///
/// if (fn_ptr as *const ()).is_null() { /* ... */ }
/// ```
///
/// {{produces}}
///
/// ### Explanation
///
/// Function pointers and references are assumed to be non-null, checking them for null
/// will always return false.
USELESS_PTR_NULL_CHECKS,
Warn,
"useless checking of non-null-typed pointer"
}
declare_lint_pass!(PtrNullChecks => [USELESS_PTR_NULL_CHECKS]);
/// This function detects and returns the original expression from a series of consecutive casts,
/// ie. `(my_fn as *const _ as *mut _).cast_mut()` would return the expression for `my_fn`.
fn ptr_cast_chain<'a>(cx: &'a LateContext<'_>, mut e: &'a Expr<'a>) -> Option<&'a Expr<'a>> {
let mut had_at_least_one_cast = false;
loop {
e = e.peel_blocks();
e = if let ExprKind::Cast(expr, t) = e.kind
&& let TyKind::Ptr(_) = t.kind {
had_at_least_one_cast = true;
expr
} else if let ExprKind::MethodCall(_, expr, [], _) = e.kind
&& let Some(def_id) = cx.typeck_results().type_dependent_def_id(e.hir_id)
&& matches!(cx.tcx.get_diagnostic_name(def_id), Some(sym::ptr_cast | sym::ptr_cast_mut)) {
had_at_least_one_cast = true;
expr
} else if let ExprKind::Call(path, [arg]) = e.kind
&& let ExprKind::Path(ref qpath) = path.kind
&& let Some(def_id) = cx.qpath_res(qpath, path.hir_id).opt_def_id()
&& matches!(cx.tcx.get_diagnostic_name(def_id), Some(sym::ptr_from_ref | sym::ptr_from_mut)) {
had_at_least_one_cast = true;
arg
} else if had_at_least_one_cast {
return Some(e);
} else {
return None;
};
}
}
fn incorrect_check<'a>(cx: &LateContext<'a>, expr: &Expr<'_>) -> Option<PtrNullChecksDiag<'a>> {
let expr = ptr_cast_chain(cx, expr)?;
let orig_ty = cx.typeck_results().expr_ty(expr);
if orig_ty.is_fn() {
Some(PtrNullChecksDiag::FnPtr { orig_ty, label: expr.span })
} else if orig_ty.is_ref() {
Some(PtrNullChecksDiag::Ref { orig_ty, label: expr.span })
} else {
None
}
}
impl<'tcx> LateLintPass<'tcx> for PtrNullChecks {
fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
match expr.kind {
// Catching:
// <*<const/mut> <ty>>::is_null(fn_ptr as *<const/mut> <ty>)
ExprKind::Call(path, [arg])
if let ExprKind::Path(ref qpath) = path.kind
&& let Some(def_id) = cx.qpath_res(qpath, path.hir_id).opt_def_id()
&& matches!(
cx.tcx.get_diagnostic_name(def_id),
Some(sym::ptr_const_is_null | sym::ptr_is_null)
)
&& let Some(diag) = incorrect_check(cx, arg) =>
{
cx.emit_spanned_lint(USELESS_PTR_NULL_CHECKS, expr.span, diag)
}
// Catching:
// (fn_ptr as *<const/mut> <ty>).is_null()
ExprKind::MethodCall(_, receiver, _, _)
if let Some(def_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id)
&& matches!(
cx.tcx.get_diagnostic_name(def_id),
Some(sym::ptr_const_is_null | sym::ptr_is_null)
)
&& let Some(diag) = incorrect_check(cx, receiver) =>
{
cx.emit_spanned_lint(USELESS_PTR_NULL_CHECKS, expr.span, diag)
}
ExprKind::Binary(op, left, right) if matches!(op.node, BinOpKind::Eq) => {
let to_check: &Expr<'_>;
let diag: PtrNullChecksDiag<'_>;
if let Some(ddiag) = incorrect_check(cx, left) {
to_check = right;
diag = ddiag;
} else if let Some(ddiag) = incorrect_check(cx, right) {
to_check = left;
diag = ddiag;
} else {
return;
}
match to_check.kind {
// Catching:
// (fn_ptr as *<const/mut> <ty>) == (0 as <ty>)
ExprKind::Cast(cast_expr, _)
if let ExprKind::Lit(spanned) = cast_expr.kind
&& let LitKind::Int(v, _) = spanned.node && v == 0 =>
{
cx.emit_spanned_lint(USELESS_PTR_NULL_CHECKS, expr.span, diag)
},
// Catching:
// (fn_ptr as *<const/mut> <ty>) == std::ptr::null()
ExprKind::Call(path, [])
if let ExprKind::Path(ref qpath) = path.kind
&& let Some(def_id) = cx.qpath_res(qpath, path.hir_id).opt_def_id()
&& let Some(diag_item) = cx.tcx.get_diagnostic_name(def_id)
&& (diag_item == sym::ptr_null || diag_item == sym::ptr_null_mut) =>
{
cx.emit_spanned_lint(USELESS_PTR_NULL_CHECKS, expr.span, diag)
},
_ => {},
}
}
_ => {}
}
}
}