From 085529bd5fa3ab508784f6a3d42f15d2dafddc65 Mon Sep 17 00:00:00 2001 From: Cuong Manh Le Date: Mon, 30 May 2022 21:34:01 +0700 Subject: [PATCH] cmd/compile: fix wrong unsafe.Offsetof evaluation inside generic function For instantiated generic functions, all implicit dot operations are resolved. Thus unsafe.Offsetof may calculating the offset against the wrong base selector. To fix it, we must remove any implicit dot operations to find the first non-implicit one, which is the right base selector for calculating the offset. Fixes #53137 Change-Id: I38504067ce0f274615b306edc8f7d7933bdb631a Reviewed-on: https://go-review.googlesource.com/c/go/+/409355 Run-TryBot: Cuong Manh Le Reviewed-by: Dmitri Shuralyov Reviewed-by: Keith Randall TryBot-Result: Gopher Robot Reviewed-by: Keith Randall --- src/cmd/compile/internal/typecheck/const.go | 12 ++++++++ test/fixedbugs/issue53137.go | 32 +++++++++++++++++++++ 2 files changed, 44 insertions(+) create mode 100644 test/fixedbugs/issue53137.go diff --git a/src/cmd/compile/internal/typecheck/const.go b/src/cmd/compile/internal/typecheck/const.go index 22fa9e7d95..6109850c24 100644 --- a/src/cmd/compile/internal/typecheck/const.go +++ b/src/cmd/compile/internal/typecheck/const.go @@ -805,6 +805,18 @@ func evalunsafe(n ir.Node) int64 { sel.X = Expr(sel.X) sbase := sel.X + // Implicit dot may already be resolved for instantiating generic function. So we + // need to remove any implicit dot until we reach the first non-implicit one, it's + // the right base selector. See issue #53137. + var clobberBase func(n ir.Node) ir.Node + clobberBase = func(n ir.Node) ir.Node { + if sel, ok := n.(*ir.SelectorExpr); ok && sel.Implicit() { + return clobberBase(sel.X) + } + return n + } + sbase = clobberBase(sbase) + tsel := Expr(sel) n.X = tsel if tsel.Type() == nil { diff --git a/test/fixedbugs/issue53137.go b/test/fixedbugs/issue53137.go new file mode 100644 index 0000000000..a0e67211ce --- /dev/null +++ b/test/fixedbugs/issue53137.go @@ -0,0 +1,32 @@ +// run + +// Copyright 2022 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 main + +import ( + "unsafe" +) + +type Embedded struct { + B int +} + +type S[K any] struct { + A K + Embedded +} + +func showOffsets[K any](d *S[K]) { + o1 := unsafe.Offsetof(d.B) + o2 := unsafe.Offsetof(d.Embedded) + if o1 != o2 { + panic("offset mismatch") + } +} + +func main() { + showOffsets(new(S[int])) +}