From 47080eacf83debe4cbd9bb8dbedaf2c29e084cbc Mon Sep 17 00:00:00 2001 From: Mara Bos Date: Wed, 25 May 2022 11:44:44 +0200 Subject: [PATCH] Improve invalid memory ordering diagnostics. --- compiler/rustc_lint/src/types.rs | 141 +++++++++++++------------------ 1 file changed, 60 insertions(+), 81 deletions(-) diff --git a/compiler/rustc_lint/src/types.rs b/compiler/rustc_lint/src/types.rs index 55b1ba9cd964..170d85f5cd50 100644 --- a/compiler/rustc_lint/src/types.rs +++ b/compiler/rustc_lint/src/types.rs @@ -4,7 +4,6 @@ use rustc_attr as attr; use rustc_data_structures::fx::FxHashSet; use rustc_errors::Applicability; use rustc_hir as hir; -use rustc_hir::def_id::DefId; use rustc_hir::{is_range_literal, Expr, ExprKind, Node}; use rustc_middle::ty::layout::{IntegerExt, LayoutOf, SizeSkeleton}; use rustc_middle::ty::subst::SubstsRef; @@ -1483,39 +1482,32 @@ impl InvalidAtomicOrdering { None } - fn matches_ordering(cx: &LateContext<'_>, did: DefId, orderings: &[Symbol]) -> bool { + fn match_ordering(cx: &LateContext<'_>, ord_arg: &Expr<'_>) -> Option { + let ExprKind::Path(ref ord_qpath) = ord_arg.kind else { return None }; + let did = cx.qpath_res(ord_qpath, ord_arg.hir_id).opt_def_id()?; let tcx = cx.tcx; let atomic_ordering = tcx.get_diagnostic_item(sym::Ordering); - orderings.iter().any(|ordering| { - tcx.item_name(did) == *ordering && { - let parent = tcx.parent(did); - Some(parent) == atomic_ordering - // needed in case this is a ctor, not a variant - || tcx.opt_parent(parent) == atomic_ordering - } - }) - } - - fn opt_ordering_defid(cx: &LateContext<'_>, ord_arg: &Expr<'_>) -> Option { - if let ExprKind::Path(ref ord_qpath) = ord_arg.kind { - cx.qpath_res(ord_qpath, ord_arg.hir_id).opt_def_id() - } else { - None - } + let name = tcx.item_name(did); + let parent = tcx.parent(did); + [sym::Relaxed, sym::Release, sym::Acquire, sym::AcqRel, sym::SeqCst].into_iter().find( + |&ordering| { + name == ordering + && (Some(parent) == atomic_ordering + // needed in case this is a ctor, not a variant + || tcx.opt_parent(parent) == atomic_ordering) + }, + ) } fn check_atomic_load_store(cx: &LateContext<'_>, expr: &Expr<'_>) { - use rustc_hir::def::{DefKind, Res}; - use rustc_hir::QPath; if let Some((method, args)) = Self::inherent_atomic_method_call(cx, expr, &[sym::load, sym::store]) && let Some((ordering_arg, invalid_ordering)) = match method { sym::load => Some((&args[1], sym::Release)), sym::store => Some((&args[2], sym::Acquire)), _ => None, } - && let ExprKind::Path(QPath::Resolved(_, path)) = ordering_arg.kind - && let Res::Def(DefKind::Ctor(..), ctor_id) = path.res - && Self::matches_ordering(cx, ctor_id, &[invalid_ordering, sym::AcqRel]) + && let Some(ordering) = Self::match_ordering(cx, ordering_arg) + && (ordering == invalid_ordering || ordering == sym::AcqRel) { cx.struct_span_lint(INVALID_ATOMIC_ORDERING, ordering_arg.span, |diag| { if method == sym::load { @@ -1537,9 +1529,7 @@ impl InvalidAtomicOrdering { && let ExprKind::Path(ref func_qpath) = func.kind && let Some(def_id) = cx.qpath_res(func_qpath, func.hir_id).opt_def_id() && matches!(cx.tcx.get_diagnostic_name(def_id), Some(sym::fence | sym::compiler_fence)) - && let ExprKind::Path(ref ordering_qpath) = &args[0].kind - && let Some(ordering_def_id) = cx.qpath_res(ordering_qpath, args[0].hir_id).opt_def_id() - && Self::matches_ordering(cx, ordering_def_id, &[sym::Relaxed]) + && Self::match_ordering(cx, &args[0]) == Some(sym::Relaxed) { cx.struct_span_lint(INVALID_ATOMIC_ORDERING, args[0].span, |diag| { diag.build("memory fences cannot have `Relaxed` ordering") @@ -1550,62 +1540,51 @@ impl InvalidAtomicOrdering { } fn check_atomic_compare_exchange(cx: &LateContext<'_>, expr: &Expr<'_>) { - if let Some((method, args)) = Self::inherent_atomic_method_call(cx, expr, &[sym::fetch_update, sym::compare_exchange, sym::compare_exchange_weak]) - && let Some((success_order_arg, failure_order_arg)) = match method { - sym::fetch_update => Some((&args[1], &args[2])), - sym::compare_exchange | sym::compare_exchange_weak => Some((&args[3], &args[4])), - _ => None, - } - && let Some(fail_ordering_def_id) = Self::opt_ordering_defid(cx, failure_order_arg) - { - // Helper type holding on to some checking and error reporting data. Has - // - (success ordering, - // - list of failure orderings forbidden by the success order, - // - suggestion message) - type OrdLintInfo = (Symbol, &'static [Symbol], &'static str); - const RELAXED: OrdLintInfo = (sym::Relaxed, &[sym::SeqCst, sym::Acquire], "ordering mode `Relaxed`"); - const ACQUIRE: OrdLintInfo = (sym::Acquire, &[sym::SeqCst], "ordering modes `Acquire` or `Relaxed`"); - const SEQ_CST: OrdLintInfo = (sym::SeqCst, &[], "ordering modes `Acquire`, `SeqCst` or `Relaxed`"); - const RELEASE: OrdLintInfo = (sym::Release, RELAXED.1, RELAXED.2); - const ACQREL: OrdLintInfo = (sym::AcqRel, ACQUIRE.1, ACQUIRE.2); - const SEARCH: [OrdLintInfo; 5] = [RELAXED, ACQUIRE, SEQ_CST, RELEASE, ACQREL]; + let Some((method, args)) = Self::inherent_atomic_method_call(cx, expr, &[sym::fetch_update, sym::compare_exchange, sym::compare_exchange_weak]) + else {return }; - let success_lint_info = Self::opt_ordering_defid(cx, success_order_arg) - .and_then(|success_ord_def_id| -> Option { - SEARCH - .iter() - .copied() - .find(|(ordering, ..)| { - Self::matches_ordering(cx, success_ord_def_id, &[*ordering]) - }) - }); - if Self::matches_ordering(cx, fail_ordering_def_id, &[sym::Release, sym::AcqRel]) { - // If we don't know the success order is, use what we'd suggest - // if it were maximally permissive. - let suggested = success_lint_info.unwrap_or(SEQ_CST).2; - cx.struct_span_lint(INVALID_ATOMIC_ORDERING, failure_order_arg.span, |diag| { - let msg = format!( - "{}'s failure ordering may not be `Release` or `AcqRel`", - method, - ); - diag.build(&msg) - .help(&format!("consider using {} instead", suggested)) - .emit(); - }); - } else if let Some((success_ord, bad_ords_given_success, suggested)) = success_lint_info { - if Self::matches_ordering(cx, fail_ordering_def_id, bad_ords_given_success) { - cx.struct_span_lint(INVALID_ATOMIC_ORDERING, failure_order_arg.span, |diag| { - let msg = format!( - "{}'s failure ordering may not be stronger than the success ordering of `{}`", - method, - success_ord, - ); - diag.build(&msg) - .help(&format!("consider using {} instead", suggested)) - .emit(); - }); - } - } + let (success_order_arg, fail_order_arg) = match method { + sym::fetch_update => (&args[1], &args[2]), + sym::compare_exchange | sym::compare_exchange_weak => (&args[3], &args[4]), + _ => return, + }; + + let Some(fail_ordering) = Self::match_ordering(cx, fail_order_arg) else { return }; + + if matches!(fail_ordering, sym::Release | sym::AcqRel) { + cx.struct_span_lint(INVALID_ATOMIC_ORDERING, fail_order_arg.span, |diag| { + diag.build(&format!( + "{method}'s failure ordering may not be `Release` or `AcqRel`, \ + since a failed {method} does not result in a write", + )) + .span_label(fail_order_arg.span, "invalid failure ordering") + .help("consider using Acquire or Relaxed failure ordering instead") + .emit(); + }); + } + + let Some(success_ordering) = Self::match_ordering(cx, success_order_arg) else { return }; + + if matches!( + (success_ordering, fail_ordering), + (sym::Relaxed | sym::Release, sym::Acquire) + | (sym::Relaxed | sym::Release | sym::Acquire | sym::AcqRel, sym::SeqCst) + ) { + let success_suggestion = + if success_ordering == sym::Release && fail_ordering == sym::Acquire { + sym::AcqRel + } else { + fail_ordering + }; + cx.struct_span_lint(INVALID_ATOMIC_ORDERING, success_order_arg.span, |diag| { + diag.build(&format!( + "{method}'s success ordering must be at least as strong as its failure ordering" + )) + .span_label(fail_order_arg.span, format!("{fail_ordering} failure ordering")) + .span_label(success_order_arg.span, format!("{success_ordering} success ordering")) + .help(format!("consider using {success_suggestion} success ordering instead")) + .emit(); + }); } } }