From 49402bee36fd3d5cee9f4b2d2e1e8560ead0203b Mon Sep 17 00:00:00 2001 From: Than McIntosh Date: Thu, 15 Jul 2021 16:29:36 -0400 Subject: [PATCH] cmd/{compile,link}: fix bug in map.zero handling In CL 326211 a change was made to switch "go.map.zero" symbols from non-pkg DUPOK symbols to hashed symbols. The intent of this change was ensure that in cases where there are multiple competing go.map.zero symbols feeding into a link, the largest map.zero symbol is selected. The change was buggy, however, and resulted in duplicate symbols in the final binary (see bug cited below for details). This duplication was relatively benign for linux/ELF, but causes duplicate definition errors on Windows. This patch switches "go.map.zero" symbols back from hashed symbols to non-pkg DUPOK symbols, and updates the relevant code in the loader to ensure that we do the right thing when there are multiple competing DUPOK symbols with different sizes. Fixes #47185. Change-Id: I8aeb910c65827f5380144d07646006ba553c9251 Reviewed-on: https://go-review.googlesource.com/c/go/+/334930 Trust: Than McIntosh Run-TryBot: Than McIntosh TryBot-Result: Go Bot Reviewed-by: Cherry Mui --- src/cmd/compile/internal/gc/obj.go | 2 +- src/cmd/link/internal/loader/loader.go | 9 +++ test/fixedbugs/issue47185.dir/bad/bad.go | 72 ++++++++++++++++++++++++ test/fixedbugs/issue47185.dir/main.go | 28 +++++++++ test/fixedbugs/issue47185.go | 11 ++++ 5 files changed, 121 insertions(+), 1 deletion(-) create mode 100644 test/fixedbugs/issue47185.dir/bad/bad.go create mode 100644 test/fixedbugs/issue47185.dir/main.go create mode 100644 test/fixedbugs/issue47185.go diff --git a/src/cmd/compile/internal/gc/obj.go b/src/cmd/compile/internal/gc/obj.go index 55a0ab7da7..474d718525 100644 --- a/src/cmd/compile/internal/gc/obj.go +++ b/src/cmd/compile/internal/gc/obj.go @@ -148,7 +148,7 @@ func dumpdata() { if reflectdata.ZeroSize > 0 { zero := base.PkgLinksym("go.map", "zero", obj.ABI0) objw.Global(zero, int32(reflectdata.ZeroSize), obj.DUPOK|obj.RODATA) - zero.Set(obj.AttrContentAddressable, true) + zero.Set(obj.AttrStatic, true) } staticdata.WriteFuncSyms() diff --git a/src/cmd/link/internal/loader/loader.go b/src/cmd/link/internal/loader/loader.go index efca824d98..9d5319c312 100644 --- a/src/cmd/link/internal/loader/loader.go +++ b/src/cmd/link/internal/loader/loader.go @@ -459,6 +459,15 @@ func (st *loadState) addSym(name string, ver int, r *oReader, li uint32, kind in if l.flags&FlagStrictDups != 0 { l.checkdup(name, r, li, oldi) } + // Fix for issue #47185 -- given two dupok symbols with + // different sizes, favor symbol with larger size. See + // also issue #46653. + szdup := l.SymSize(oldi) + sz := int64(r.Sym(li).Siz()) + if szdup < sz { + // new symbol overwrites old symbol. + l.objSyms[oldi] = objSym{r.objidx, li} + } return oldi } oldr, oldli := l.toLocal(oldi) diff --git a/test/fixedbugs/issue47185.dir/bad/bad.go b/test/fixedbugs/issue47185.dir/bad/bad.go new file mode 100644 index 0000000000..1aa4fbb909 --- /dev/null +++ b/test/fixedbugs/issue47185.dir/bad/bad.go @@ -0,0 +1,72 @@ +// Copyright 2021 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 a + +// Note that the use of CGO here is solely to trigger external +// linking, since that is required to trigger that bad behavior +// in this bug. + +// #include +import "C" + +func Bad() { + m := make(map[int64]A) + a := m[0] + if len(a.B.C1.D2.E2.F1) != 0 || + len(a.B.C1.D2.E2.F2) != 0 || + len(a.B.C1.D2.E2.F3) != 0 || + len(a.B.C1.D2.E2.F4) != 0 || + len(a.B.C1.D2.E2.F5) != 0 || + len(a.B.C1.D2.E2.F6) != 0 || + len(a.B.C1.D2.E2.F7) != 0 || + len(a.B.C1.D2.E2.F8) != 0 || + len(a.B.C1.D2.E2.F9) != 0 || + len(a.B.C1.D2.E2.F10) != 0 || + len(a.B.C1.D2.E2.F11) != 0 || + len(a.B.C1.D2.E2.F16) != 0 { + panic("bad") + } + C.malloc(100) +} + +type A struct { + B +} + +type B struct { + C1 C + C2 C +} + +type C struct { + D1 D + D2 D +} + +type D struct { + E1 E + E2 E + E3 E + E4 E +} + +type E struct { + F1 string + F2 string + F3 string + F4 string + F5 string + F6 string + F7 string + F8 string + F9 string + F10 string + F11 string + F12 string + F13 string + F14 string + F15 string + F16 string +} diff --git a/test/fixedbugs/issue47185.dir/main.go b/test/fixedbugs/issue47185.dir/main.go new file mode 100644 index 0000000000..7b46e55d8b --- /dev/null +++ b/test/fixedbugs/issue47185.dir/main.go @@ -0,0 +1,28 @@ +// Copyright 2021 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 ( + bad "issue47185.dir/bad" +) + +func main() { + another() + bad.Bad() +} + +func another() L { + m := make(map[string]L) + return m[""] +} + +type L struct { + A Data + B Data +} + +type Data struct { + F1 [22][]string +} diff --git a/test/fixedbugs/issue47185.go b/test/fixedbugs/issue47185.go new file mode 100644 index 0000000000..9c921b8698 --- /dev/null +++ b/test/fixedbugs/issue47185.go @@ -0,0 +1,11 @@ +// +build cgo +// runindir + +// Copyright 2021 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. + +// Another test to verify compiler and linker handling of multiple +// competing map.zero symbol definitions. + +package ignored