62 lines
2.0 KiB
Rust
62 lines
2.0 KiB
Rust
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use clippy_utils::consts::{constant_context, Constant};
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use clippy_utils::diagnostics::span_lint;
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use clippy_utils::is_path_diagnostic_item;
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use if_chain::if_chain;
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use rustc_ast::LitKind;
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use rustc_hir::{Expr, ExprKind};
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use rustc_lint::LateContext;
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use rustc_middle::ty::Ty;
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use rustc_span::symbol::sym;
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use super::TRANSMUTING_NULL;
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const LINT_MSG: &str = "transmuting a known null pointer into a reference";
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pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>, arg: &'tcx Expr<'_>, to_ty: Ty<'tcx>) -> bool {
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if !to_ty.is_ref() {
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return false;
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}
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// Catching transmute over constants that resolve to `null`.
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let mut const_eval_context = constant_context(cx, cx.typeck_results());
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if_chain! {
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if let ExprKind::Path(ref _qpath) = arg.kind;
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if let Some(Constant::RawPtr(x)) = const_eval_context.expr(arg);
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if x == 0;
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then {
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span_lint(cx, TRANSMUTING_NULL, expr.span, LINT_MSG);
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return true;
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}
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}
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// Catching:
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// `std::mem::transmute(0 as *const i32)`
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if_chain! {
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if let ExprKind::Cast(inner_expr, _cast_ty) = arg.kind;
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if let ExprKind::Lit(ref lit) = inner_expr.kind;
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if let LitKind::Int(0, _) = lit.node;
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then {
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span_lint(cx, TRANSMUTING_NULL, expr.span, LINT_MSG);
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return true;
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}
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}
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// Catching:
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// `std::mem::transmute(std::ptr::null::<i32>())`
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if_chain! {
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if let ExprKind::Call(func1, []) = arg.kind;
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if is_path_diagnostic_item(cx, func1, sym::ptr_null);
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then {
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span_lint(cx, TRANSMUTING_NULL, expr.span, LINT_MSG);
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return true;
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}
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}
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// FIXME:
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// Also catch transmutations of variables which are known nulls.
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// To do this, MIR const propagation seems to be the better tool.
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// Whenever MIR const prop routines are more developed, this will
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// become available. As of this writing (25/03/19) it is not yet.
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false
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}
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