[`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
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,
--- /dev/null
+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
+ );
+ }
+ }
+ }
+}
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";
--- /dev/null
+#![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 {}
+}
--- /dev/null
+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
+
projects / rust.git / commitdiff