Add lint fn_null_check

This commit is contained in:
Niki4tap 2022-12-18 02:16:04 +03:00
parent 3cc67d0856
commit 42106e0495
6 changed files with 196 additions and 1 deletions

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@ -4203,6 +4203,7 @@ Released 2018-09-13
[`float_cmp_const`]: https://rust-lang.github.io/rust-clippy/master/index.html#float_cmp_const
[`float_equality_without_abs`]: https://rust-lang.github.io/rust-clippy/master/index.html#float_equality_without_abs
[`fn_address_comparisons`]: https://rust-lang.github.io/rust-clippy/master/index.html#fn_address_comparisons
[`fn_null_check`]: https://rust-lang.github.io/rust-clippy/master/index.html#fn_null_check
[`fn_params_excessive_bools`]: https://rust-lang.github.io/rust-clippy/master/index.html#fn_params_excessive_bools
[`fn_to_numeric_cast`]: https://rust-lang.github.io/rust-clippy/master/index.html#fn_to_numeric_cast
[`fn_to_numeric_cast_any`]: https://rust-lang.github.io/rust-clippy/master/index.html#fn_to_numeric_cast_any

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@ -161,6 +161,7 @@ pub(crate) static LINTS: &[&crate::LintInfo] = &[
crate::float_literal::LOSSY_FLOAT_LITERAL_INFO,
crate::floating_point_arithmetic::IMPRECISE_FLOPS_INFO,
crate::floating_point_arithmetic::SUBOPTIMAL_FLOPS_INFO,
crate::fn_null_check::FN_NULL_CHECK_INFO,
crate::format::USELESS_FORMAT_INFO,
crate::format_args::FORMAT_IN_FORMAT_ARGS_INFO,
crate::format_args::TO_STRING_IN_FORMAT_ARGS_INFO,

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@ -0,0 +1,129 @@
use clippy_utils::consts::{constant, Constant};
use clippy_utils::diagnostics::span_lint_and_help;
use clippy_utils::{is_integer_literal, is_path_diagnostic_item};
use if_chain::if_chain;
use rustc_hir::{BinOpKind, Expr, ExprKind, TyKind};
use rustc_lint::{LateContext, LateLintPass};
use rustc_session::{declare_lint_pass, declare_tool_lint};
use rustc_span::sym;
declare_clippy_lint! {
/// ### What it does
/// Checks for comparing a function pointer to null.
///
/// ### Why is this bad?
/// Function pointers are assumed to not be null.
///
/// ### Example
/// ```rust,ignore
/// let fn_ptr: fn() = /* somehow obtained nullable function pointer */
///
/// if (fn_ptr as *const ()).is_null() { ... }
/// ```
/// Use instead:
/// ```rust
/// let fn_ptr: Option<fn()> = /* somehow obtained nullable function pointer */
///
/// if fn_ptr.is_none() { ... }
/// ```
#[clippy::version = "1.67.0"]
pub FN_NULL_CHECK,
correctness,
"`fn()` type assumed to be nullable"
}
declare_lint_pass!(FnNullCheck => [FN_NULL_CHECK]);
const LINT_MSG: &str = "function pointer assumed to be nullable, even though it isn't";
const HELP_MSG: &str = "try wrapping your function pointer type in `Option<T>` instead, and using `is_none` to check for null pointer value";
fn is_fn_ptr_cast(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
if_chain! {
if let ExprKind::Cast(cast_expr, cast_ty) = expr.kind;
if let TyKind::Ptr(_) = cast_ty.kind;
if cx.typeck_results().expr_ty_adjusted(cast_expr).is_fn();
then {
true
} else {
false
}
}
}
impl<'tcx> LateLintPass<'tcx> for FnNullCheck {
fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
// Catching:
// (fn_ptr as *<const/mut> <ty>).is_null()
if_chain! {
if let ExprKind::MethodCall(method_name, receiver, _, _) = expr.kind;
if method_name.ident.as_str() == "is_null";
if is_fn_ptr_cast(cx, receiver);
then {
span_lint_and_help(
cx,
FN_NULL_CHECK,
expr.span,
LINT_MSG,
None,
HELP_MSG
);
}
}
if let ExprKind::Binary(op, left, right) = expr.kind
&& let BinOpKind::Eq = op.node
{
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;
}
// Catching:
// (fn_ptr as *<const/mut> <ty>) == <const that evaluates to null_ptr>
let c = constant(cx, cx.typeck_results(), to_check);
if let Some((Constant::RawPtr(0), _)) = c {
span_lint_and_help(
cx,
FN_NULL_CHECK,
expr.span,
LINT_MSG,
None,
HELP_MSG
);
return;
}
// Catching:
// (fn_ptr as *<const/mut> <ty>) == (0 as <ty>)
if let ExprKind::Cast(cast_expr, _) = to_check.kind && is_integer_literal(cast_expr, 0) {
span_lint_and_help(
cx,
FN_NULL_CHECK,
expr.span,
LINT_MSG,
None,
HELP_MSG
);
return;
}
// Catching:
// (fn_ptr as *<const/mut> <ty>) == std::ptr::null()
if let ExprKind::Call(func, []) = to_check.kind &&
is_path_diagnostic_item(cx, func, sym::ptr_null)
{
span_lint_and_help(
cx,
FN_NULL_CHECK,
expr.span,
LINT_MSG,
None,
HELP_MSG
);
}
}
}
}

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@ -9,7 +9,7 @@ use rustc_span::symbol::sym;
use super::TRANSMUTE_NULL_TO_FN;
const LINT_MSG: &str = "transmuting a known null pointer into a function pointer";
const NOTE_MSG: &str = "this transmute results in a null function pointer";
const NOTE_MSG: &str = "this transmute results in undefined behavior";
const HELP_MSG: &str =
"try wrapping your function pointer type in `Option<T>` instead, and using `None` as a null pointer value";

21
tests/ui/fn_null_check.rs Normal file
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@ -0,0 +1,21 @@
#![allow(unused)]
#![warn(clippy::fn_null_check)]
#![allow(clippy::cmp_null)]
#![allow(clippy::ptr_eq)]
#![allow(clippy::zero_ptr)]
pub const ZPTR: *const () = 0 as *const _;
pub const NOT_ZPTR: *const () = 1 as *const _;
fn main() {
let fn_ptr = main;
if (fn_ptr as *mut ()).is_null() {}
if (fn_ptr as *const u8).is_null() {}
if (fn_ptr as *const ()) == std::ptr::null() {}
if (fn_ptr as *const ()) == (0 as *const ()) {}
if (fn_ptr as *const ()) == ZPTR {}
// no lint
if (fn_ptr as *const ()) == NOT_ZPTR {}
}

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@ -0,0 +1,43 @@
error: function pointer assumed to be nullable, even though it isn't
--> $DIR/fn_null_check.rs:13:8
|
LL | if (fn_ptr as *mut ()).is_null() {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= help: try wrapping your function pointer type in `Option<T>` instead, and using `is_none` to check for null pointer value
= note: `-D clippy::fn-null-check` implied by `-D warnings`
error: function pointer assumed to be nullable, even though it isn't
--> $DIR/fn_null_check.rs:14:8
|
LL | if (fn_ptr as *const u8).is_null() {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= help: try wrapping your function pointer type in `Option<T>` instead, and using `is_none` to check for null pointer value
error: function pointer assumed to be nullable, even though it isn't
--> $DIR/fn_null_check.rs:15:8
|
LL | if (fn_ptr as *const ()) == std::ptr::null() {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= help: try wrapping your function pointer type in `Option<T>` instead, and using `is_none` to check for null pointer value
error: function pointer assumed to be nullable, even though it isn't
--> $DIR/fn_null_check.rs:16:8
|
LL | if (fn_ptr as *const ()) == (0 as *const ()) {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= help: try wrapping your function pointer type in `Option<T>` instead, and using `is_none` to check for null pointer value
error: function pointer assumed to be nullable, even though it isn't
--> $DIR/fn_null_check.rs:17:8
|
LL | if (fn_ptr as *const ()) == ZPTR {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= help: try wrapping your function pointer type in `Option<T>` instead, and using `is_none` to check for null pointer value
error: aborting due to 5 previous errors