From c82304b7129d7e675ff010d54f58d039235e4802 Mon Sep 17 00:00:00 2001 From: Cuong Manh Le Date: Tue, 6 Sep 2022 12:54:54 +0700 Subject: cmd/compile: do not devirtualize defer/go calls For defer/go calls, the function/method value are evaluated immediately. So after devirtualizing, it may trigger a panic when implicitly deref a nil pointer receiver, causing the program behaves unexpectedly. It's safer to not devirtualizing defer/go calls at all. Fixes #52072 Change-Id: I562c2860e3e577b36387dc0a12ae5077bc0766bf Reviewed-on: https://go-review.googlesource.com/c/go/+/428495 Reviewed-by: Michael Knyszek Auto-Submit: Cuong Manh Le Reviewed-by: Matthew Dempsky TryBot-Result: Gopher Robot Run-TryBot: Cuong Manh Le --- .../compile/internal/devirtualize/devirtualize.go | 20 ++++++++++++++++++-- 1 file changed, 18 insertions(+), 2 deletions(-) (limited to 'src/cmd/compile/internal/devirtualize/devirtualize.go') diff --git a/src/cmd/compile/internal/devirtualize/devirtualize.go b/src/cmd/compile/internal/devirtualize/devirtualize.go index b620470b0e..7350a6f171 100644 --- a/src/cmd/compile/internal/devirtualize/devirtualize.go +++ b/src/cmd/compile/internal/devirtualize/devirtualize.go @@ -17,9 +17,25 @@ import ( // Func devirtualizes calls within fn where possible. func Func(fn *ir.Func) { ir.CurFunc = fn + + // For promoted methods (including value-receiver methods promoted to pointer-receivers), + // the interface method wrapper may contain expressions that can panic (e.g., ODEREF, ODOTPTR, ODOTINTER). + // Devirtualization involves inlining these expressions (and possible panics) to the call site. + // This normally isn't a problem, but for go/defer statements it can move the panic from when/where + // the call executes to the go/defer statement itself, which is a visible change in semantics (e.g., #52072). + // To prevent this, we skip devirtualizing calls within go/defer statements altogether. + goDeferCall := make(map[*ir.CallExpr]bool) ir.VisitList(fn.Body, func(n ir.Node) { - if call, ok := n.(*ir.CallExpr); ok { - Call(call) + switch n := n.(type) { + case *ir.GoDeferStmt: + if call, ok := n.Call.(*ir.CallExpr); ok { + goDeferCall[call] = true + } + return + case *ir.CallExpr: + if !goDeferCall[n] { + Call(n) + } } }) } -- cgit v1.3-5-g9baa