diff options
Diffstat (limited to 'src/tools/clippy/clippy_lints/src/transmute/transmuting_null.rs')
-rw-r--r-- | src/tools/clippy/clippy_lints/src/transmute/transmuting_null.rs | 61 |
1 files changed, 61 insertions, 0 deletions
diff --git a/src/tools/clippy/clippy_lints/src/transmute/transmuting_null.rs b/src/tools/clippy/clippy_lints/src/transmute/transmuting_null.rs new file mode 100644 index 000000000..d8e349af7 --- /dev/null +++ b/src/tools/clippy/clippy_lints/src/transmute/transmuting_null.rs @@ -0,0 +1,61 @@ +use clippy_utils::consts::{constant_context, Constant}; +use clippy_utils::diagnostics::span_lint; +use clippy_utils::is_path_diagnostic_item; +use if_chain::if_chain; +use rustc_ast::LitKind; +use rustc_hir::{Expr, ExprKind}; +use rustc_lint::LateContext; +use rustc_middle::ty::Ty; +use rustc_span::symbol::sym; + +use super::TRANSMUTING_NULL; + +const LINT_MSG: &str = "transmuting a known null pointer into a reference"; + +pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>, arg: &'tcx Expr<'_>, to_ty: Ty<'tcx>) -> bool { + if !to_ty.is_ref() { + return false; + } + + // Catching transmute over constants that resolve to `null`. + let mut const_eval_context = constant_context(cx, cx.typeck_results()); + if_chain! { + if let ExprKind::Path(ref _qpath) = arg.kind; + if let Some(Constant::RawPtr(x)) = const_eval_context.expr(arg); + if x == 0; + then { + span_lint(cx, TRANSMUTING_NULL, expr.span, LINT_MSG); + return true; + } + } + + // Catching: + // `std::mem::transmute(0 as *const i32)` + if_chain! { + if let ExprKind::Cast(inner_expr, _cast_ty) = arg.kind; + if let ExprKind::Lit(ref lit) = inner_expr.kind; + if let LitKind::Int(0, _) = lit.node; + then { + span_lint(cx, TRANSMUTING_NULL, expr.span, LINT_MSG); + return true; + } + } + + // Catching: + // `std::mem::transmute(std::ptr::null::<i32>())` + if_chain! { + if let ExprKind::Call(func1, []) = arg.kind; + if is_path_diagnostic_item(cx, func1, sym::ptr_null); + then { + span_lint(cx, TRANSMUTING_NULL, expr.span, LINT_MSG); + return true; + } + } + + // FIXME: + // Also catch transmutations of variables which are known nulls. + // To do this, MIR const propagation seems to be the better tool. + // Whenever MIR const prop routines are more developed, this will + // become available. As of this writing (25/03/19) it is not yet. + false +} |