From 3826650c99b177364670dad9766ea499cab48dfc Mon Sep 17 00:00:00 2001 From: Cuong Manh Le Date: Wed, 21 Feb 2024 18:50:11 +0700 Subject: [release-branch.go1.22] cmd/compile: fix early deadcode with label statement CL 517775 moved early deadcode into unified writer. with new way to handle dead code with label statement involved: any statements after terminating statement will be considered dead until next label statement. However, this is not safe, because code after label statement may still refer to dead statements between terminating and label statement. It's only safe to remove statements after terminating *and* label one. Fixes #66134 Change-Id: Idb630165240931fad50789304a9e4535f51f56e2 Reviewed-on: https://go-review.googlesource.com/c/go/+/565596 LUCI-TryBot-Result: Go LUCI Reviewed-by: Keith Randall TryBot-Result: Gopher Robot Reviewed-by: Matthew Dempsky Run-TryBot: Cuong Manh Le Auto-Submit: Cuong Manh Le Reviewed-on: https://go-review.googlesource.com/c/go/+/569717 Reviewed-by: Michael Knyszek --- src/cmd/compile/internal/noder/writer.go | 15 +++++++++++---- test/fixedbugs/issue65593.go | 21 +++++++++++++++++++++ 2 files changed, 32 insertions(+), 4 deletions(-) create mode 100644 test/fixedbugs/issue65593.go diff --git a/src/cmd/compile/internal/noder/writer.go b/src/cmd/compile/internal/noder/writer.go index e5894c9505..c317f392c1 100644 --- a/src/cmd/compile/internal/noder/writer.go +++ b/src/cmd/compile/internal/noder/writer.go @@ -1209,10 +1209,17 @@ func (w *writer) stmt(stmt syntax.Stmt) { func (w *writer) stmts(stmts []syntax.Stmt) { dead := false w.Sync(pkgbits.SyncStmts) - for _, stmt := range stmts { - if dead { - // Any statements after a terminating statement are safe to - // omit, at least until the next labeled statement. + var lastLabel = -1 + for i, stmt := range stmts { + if _, ok := stmt.(*syntax.LabeledStmt); ok { + lastLabel = i + } + } + for i, stmt := range stmts { + if dead && i > lastLabel { + // Any statements after a terminating and last label statement are safe to omit. + // Otherwise, code after label statement may refer to dead stmts between terminating + // and label statement, see issue #65593. if _, ok := stmt.(*syntax.LabeledStmt); !ok { continue } diff --git a/test/fixedbugs/issue65593.go b/test/fixedbugs/issue65593.go new file mode 100644 index 0000000000..892a78122e --- /dev/null +++ b/test/fixedbugs/issue65593.go @@ -0,0 +1,21 @@ +// compile + +// Copyright 2024 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package p + +const run = false + +func f() { + if !run { + return + } + + messages := make(chan struct{}, 1) +main: + for range messages { + break main + } +} -- cgit v1.2.3-54-g00ecf