[release-branch.go1.16] go1.16.6

Change-Id: Ic394096a2d9cc5927b812f3c457282b26901b2b7
Reviewed-on: https://go-review.googlesource.com/c/go/+/334089
Run-TryBot: Dmitri Shuralyov <dmitshur@golang.org>
Trust: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Filippo Valsorda <filippo@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>

README.md

@@ -3,7 +3,7 @@
 Go is an open source programming language that makes it easy to build simple,
 reliable, and efficient software.
 
-![Gopher image](doc/gopher/fiveyears.jpg)
+![Gopher image](https://golang.org/doc/gopher/fiveyears.jpg)
 *Gopher image by [Renee French][rf], licensed under [Creative Commons 3.0 Attributions license][cc3-by].*
 
 Our canonical Git repository is located at https://go.googlesource.com/go.

VERSION

@@ -0,0 +1 @@
+go1.16.6

misc/cgo/testplugin/plugin_test.go

@@ -201,12 +201,18 @@ func TestMethod(t *testing.T) {
 	// Exported symbol's method must be live.
 	goCmd(t, "build", "-buildmode=plugin", "-o", "plugin.so", "./method/plugin.go")
 	goCmd(t, "build", "-o", "method.exe", "./method/main.go")
-
-	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
-	defer cancel()
-	cmd := exec.CommandContext(ctx, "./method.exe")
-	out, err := cmd.CombinedOutput()
-	if err != nil {
-		t.Fatalf("%s: %v\n%s", strings.Join(cmd.Args, " "), err, out)
-	}
+	run(t, "./method.exe")
+}
+
+func TestMethod2(t *testing.T) {
+	goCmd(t, "build", "-buildmode=plugin", "-o", "method2.so", "./method2/plugin.go")
+	goCmd(t, "build", "-o", "method2.exe", "./method2/main.go")
+	run(t, "./method2.exe")
+}
+
+func TestIssue44956(t *testing.T) {
+	goCmd(t, "build", "-buildmode=plugin", "-o", "issue44956p1.so", "./issue44956/plugin1.go")
+	goCmd(t, "build", "-buildmode=plugin", "-o", "issue44956p2.so", "./issue44956/plugin2.go")
+	goCmd(t, "build", "-o", "issue44956.exe", "./issue44956/main.go")
+	run(t, "./issue44956.exe")
 }

misc/cgo/testplugin/testdata/issue44956/base/base.go

@@ -0,0 +1,7 @@
+// 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 base
+
+var X = &map[int]int{123: 456}

misc/cgo/testplugin/testdata/issue44956/main.go

@@ -0,0 +1,47 @@
+// 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.
+
+// Issue 44956: writable static temp is not exported correctly.
+// In the test below, package base is
+//
+//     X = &map{...}
+//
+// which compiles to
+//
+//     X = &stmp           // static
+//     stmp = makemap(...) // in init function
+//
+// plugin1 and plugin2 both import base. plugin1 doesn't use
+// base.X, so that symbol is deadcoded in plugin1.
+//
+// plugin1 is loaded first. base.init runs at that point, which
+// initialize base.stmp.
+//
+// plugin2 is then loaded. base.init already ran, so it doesn't run
+// again. When base.stmp is not exported, plugin2's base.X points to
+// its own private base.stmp, which is not initialized, fail.
+
+package main
+
+import "plugin"
+
+func main() {
+	_, err := plugin.Open("issue44956p1.so")
+	if err != nil {
+		panic("FAIL")
+	}
+
+	p2, err := plugin.Open("issue44956p2.so")
+	if err != nil {
+		panic("FAIL")
+	}
+	f, err := p2.Lookup("F")
+	if err != nil {
+		panic("FAIL")
+	}
+	x := f.(func() *map[int]int)()
+	if x == nil || (*x)[123] != 456 {
+		panic("FAIL")
+	}
+}

misc/cgo/testplugin/testdata/issue44956/plugin1.go

@@ -0,0 +1,9 @@
+// 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 _ "testplugin/issue44956/base"
+
+func main() {}

misc/cgo/testplugin/testdata/issue44956/plugin2.go

@@ -0,0 +1,11 @@
+// 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 "testplugin/issue44956/base"
+
+func F() *map[int]int { return base.X }
+
+func main() {}

misc/cgo/testplugin/testdata/method2/main.go

@@ -0,0 +1,32 @@
+// 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.
+
+// A type can be passed to a plugin and converted to interface
+// there. So its methods need to be live.
+
+package main
+
+import (
+	"plugin"
+
+	"testplugin/method2/p"
+)
+
+var t p.T
+
+type I interface { M() }
+
+func main() {
+	pl, err := plugin.Open("method2.so")
+	if err != nil {
+		panic(err)
+	}
+
+	f, err := pl.Lookup("F")
+	if err != nil {
+		panic(err)
+	}
+
+	f.(func(p.T) interface{})(t).(I).M()
+}

misc/cgo/testplugin/testdata/method2/p/p.go

@@ -0,0 +1,9 @@
+// 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 p
+
+type T int
+
+func (T) M() { println("M") }

misc/cgo/testplugin/testdata/method2/plugin.go

@@ -0,0 +1,11 @@
+// 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 "testplugin/method2/p"
+
+func main() {}
+
+func F(t p.T) interface{} { return t }

src/archive/zip/reader.go

@@ -99,7 +99,15 @@ func (z *Reader) init(r io.ReaderAt, size int64) error {
 		return err
 	}
 	z.r = r
-	z.File = make([]*File, 0, end.directoryRecords)
+	// Since the number of directory records is not validated, it is not
+	// safe to preallocate z.File without first checking that the specified
+	// number of files is reasonable, since a malformed archive may
+	// indicate it contains up to 1 << 128 - 1 files. Since each file has a
+	// header which will be _at least_ 30 bytes we can safely preallocate
+	// if (data size / 30) >= end.directoryRecords.
+	if (uint64(size)-end.directorySize)/30 >= end.directoryRecords {
+		z.File = make([]*File, 0, end.directoryRecords)
+	}
 	z.Comment = end.comment
 	rs := io.NewSectionReader(r, 0, size)
 	if _, err = rs.Seek(int64(end.directoryOffset), io.SeekStart); err != nil {
@@ -628,10 +636,11 @@ func (b *readBuf) sub(n int) readBuf {
 }
 
 // A fileListEntry is a File and its ename.
-// If file == nil, the fileListEntry describes a directory, without metadata.
+// If file == nil, the fileListEntry describes a directory without metadata.
 type fileListEntry struct {
-	name string
-	file *File // nil for directories
+	name  string
+	file  *File
+	isDir bool
 }
 
 type fileInfoDirEntry interface {
@@ -640,20 +649,26 @@ type fileInfoDirEntry interface {
 }
 
 func (e *fileListEntry) stat() fileInfoDirEntry {
-	if e.file != nil {
+	if !e.isDir {
 		return headerFileInfo{&e.file.FileHeader}
 	}
 	return e
 }
 
 // Only used for directories.
-func (f *fileListEntry) Name() string       { _, elem, _ := split(f.name); return elem }
-func (f *fileListEntry) Size() int64        { return 0 }
-func (f *fileListEntry) ModTime() time.Time { return time.Time{} }
-func (f *fileListEntry) Mode() fs.FileMode  { return fs.ModeDir | 0555 }
-func (f *fileListEntry) Type() fs.FileMode  { return fs.ModeDir }
-func (f *fileListEntry) IsDir() bool        { return true }
-func (f *fileListEntry) Sys() interface{}   { return nil }
+func (f *fileListEntry) Name() string      { _, elem, _ := split(f.name); return elem }
+func (f *fileListEntry) Size() int64       { return 0 }
+func (f *fileListEntry) Mode() fs.FileMode { return fs.ModeDir | 0555 }
+func (f *fileListEntry) Type() fs.FileMode { return fs.ModeDir }
+func (f *fileListEntry) IsDir() bool       { return true }
+func (f *fileListEntry) Sys() interface{}  { return nil }
+
+func (f *fileListEntry) ModTime() time.Time {
+	if f.file == nil {
+		return time.Time{}
+	}
+	return f.file.FileHeader.Modified.UTC()
+}
 
 func (f *fileListEntry) Info() (fs.FileInfo, error) { return f, nil }
 
@@ -664,7 +679,7 @@ func toValidName(name string) string {
 	if strings.HasPrefix(p, "/") {
 		p = p[len("/"):]
 	}
-	for strings.HasPrefix(name, "../") {
+	for strings.HasPrefix(p, "../") {
 		p = p[len("../"):]
 	}
 	return p
@@ -673,15 +688,32 @@ func toValidName(name string) string {
 func (r *Reader) initFileList() {
 	r.fileListOnce.Do(func() {
 		dirs := make(map[string]bool)
+		knownDirs := make(map[string]bool)
 		for _, file := range r.File {
+			isDir := len(file.Name) > 0 && file.Name[len(file.Name)-1] == '/'
 			name := toValidName(file.Name)
 			for dir := path.Dir(name); dir != "."; dir = path.Dir(dir) {
 				dirs[dir] = true
 			}
-			r.fileList = append(r.fileList, fileListEntry{name, file})
+			entry := fileListEntry{
+				name:  name,
+				file:  file,
+				isDir: isDir,
+			}
+			r.fileList = append(r.fileList, entry)
+			if isDir {
+				knownDirs[name] = true
+			}
 		}
 		for dir := range dirs {
-			r.fileList = append(r.fileList, fileListEntry{dir + "/", nil})
+			if !knownDirs[dir] {
+				entry := fileListEntry{
+					name:  dir,
+					file:  nil,
+					isDir: true,
+				}
+				r.fileList = append(r.fileList, entry)
+			}
 		}
 
 		sort.Slice(r.fileList, func(i, j int) bool { return fileEntryLess(r.fileList[i].name, r.fileList[j].name) })
@@ -705,7 +737,7 @@ func (r *Reader) Open(name string) (fs.File, error) {
 	if e == nil || !fs.ValidPath(name) {
 		return nil, &fs.PathError{Op: "open", Path: name, Err: fs.ErrNotExist}
 	}
-	if e.file == nil || strings.HasSuffix(e.file.Name, "/") {
+	if e.isDir {
 		return &openDir{e, r.openReadDir(name), 0}, nil
 	}
 	rc, err := e.file.Open()
@@ -730,7 +762,7 @@ func split(name string) (dir, elem string, isDir bool) {
 	return name[:i], name[i+1:], isDir
 }
 
-var dotFile = &fileListEntry{name: "./"}
+var dotFile = &fileListEntry{name: "./", isDir: true}
 
 func (r *Reader) openLookup(name string) *fileListEntry {
 	if name == "." {

src/archive/zip/reader_test.go

@@ -1073,11 +1073,155 @@ func TestIssue12449(t *testing.T) {
 }
 
 func TestFS(t *testing.T) {
-	z, err := OpenReader("testdata/unix.zip")
+	for _, test := range []struct {
+		file string
+		want []string
+	}{
+		{
+			"testdata/unix.zip",
+			[]string{"hello", "dir/bar", "readonly"},
+		},
+		{
+			"testdata/subdir.zip",
+			[]string{"a/b/c"},
+		},
+	} {
+		t.Run(test.file, func(t *testing.T) {
+			t.Parallel()
+			z, err := OpenReader(test.file)
+			if err != nil {
+				t.Fatal(err)
+			}
+			defer z.Close()
+			if err := fstest.TestFS(z, test.want...); err != nil {
+				t.Error(err)
+			}
+		})
+	}
+}
+
+func TestFSModTime(t *testing.T) {
+	t.Parallel()
+	z, err := OpenReader("testdata/subdir.zip")
 	if err != nil {
 		t.Fatal(err)
 	}
-	if err := fstest.TestFS(z, "hello", "dir/bar", "dir/empty", "readonly"); err != nil {
-		t.Fatal(err)
+	defer z.Close()
+
+	for _, test := range []struct {
+		name string
+		want time.Time
+	}{
+		{
+			"a",
+			time.Date(2021, 4, 19, 12, 29, 56, 0, timeZone(-7*time.Hour)).UTC(),
+		},
+		{
+			"a/b/c",
+			time.Date(2021, 4, 19, 12, 29, 59, 0, timeZone(-7*time.Hour)).UTC(),
+		},
+	} {
+		fi, err := fs.Stat(z, test.name)
+		if err != nil {
+			t.Errorf("%s: %v", test.name, err)
+			continue
+		}
+		if got := fi.ModTime(); !got.Equal(test.want) {
+			t.Errorf("%s: got modtime %v, want %v", test.name, got, test.want)
+		}
+	}
+}
+
+func TestCVE202127919(t *testing.T) {
+	// Archive containing only the file "../test.txt"
+	data := []byte{
+		0x50, 0x4b, 0x03, 0x04, 0x14, 0x00, 0x08, 0x00,
+		0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+		0x00, 0x00, 0x0b, 0x00, 0x00, 0x00, 0x2e, 0x2e,
+		0x2f, 0x74, 0x65, 0x73, 0x74, 0x2e, 0x74, 0x78,
+		0x74, 0x0a, 0xc9, 0xc8, 0x2c, 0x56, 0xc8, 0x2c,
+		0x56, 0x48, 0x54, 0x28, 0x49, 0x2d, 0x2e, 0x51,
+		0x28, 0x49, 0xad, 0x28, 0x51, 0x48, 0xcb, 0xcc,
+		0x49, 0xd5, 0xe3, 0x02, 0x04, 0x00, 0x00, 0xff,
+		0xff, 0x50, 0x4b, 0x07, 0x08, 0xc0, 0xd7, 0xed,
+		0xc3, 0x20, 0x00, 0x00, 0x00, 0x1a, 0x00, 0x00,
+		0x00, 0x50, 0x4b, 0x01, 0x02, 0x14, 0x00, 0x14,
+		0x00, 0x08, 0x00, 0x08, 0x00, 0x00, 0x00, 0x00,
+		0x00, 0xc0, 0xd7, 0xed, 0xc3, 0x20, 0x00, 0x00,
+		0x00, 0x1a, 0x00, 0x00, 0x00, 0x0b, 0x00, 0x00,
+		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x2e,
+		0x2e, 0x2f, 0x74, 0x65, 0x73, 0x74, 0x2e, 0x74,
+		0x78, 0x74, 0x50, 0x4b, 0x05, 0x06, 0x00, 0x00,
+		0x00, 0x00, 0x01, 0x00, 0x01, 0x00, 0x39, 0x00,
+		0x00, 0x00, 0x59, 0x00, 0x00, 0x00, 0x00, 0x00,
+	}
+	r, err := NewReader(bytes.NewReader([]byte(data)), int64(len(data)))
+	if err != nil {
+		t.Fatalf("Error reading the archive: %v", err)
+	}
+	_, err = r.Open("test.txt")
+	if err != nil {
+		t.Errorf("Error reading file: %v", err)
+	}
+}
+
+func TestCVE202133196(t *testing.T) {
+	// Archive that indicates it has 1 << 128 -1 files,
+	// this would previously cause a panic due to attempting
+	// to allocate a slice with 1 << 128 -1 elements.
+	data := []byte{
+		0x50, 0x4b, 0x03, 0x04, 0x14, 0x00, 0x08, 0x08,
+		0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+		0x00, 0x00, 0x03, 0x00, 0x00, 0x00, 0x01, 0x02,
+		0x03, 0x62, 0x61, 0x65, 0x03, 0x04, 0x00, 0x00,
+		0xff, 0xff, 0x50, 0x4b, 0x07, 0x08, 0xbe, 0x20,
+		0x5c, 0x6c, 0x09, 0x00, 0x00, 0x00, 0x03, 0x00,
+		0x00, 0x00, 0x50, 0x4b, 0x01, 0x02, 0x14, 0x00,
+		0x14, 0x00, 0x08, 0x08, 0x08, 0x00, 0x00, 0x00,
+		0x00, 0x00, 0xbe, 0x20, 0x5c, 0x6c, 0x09, 0x00,
+		0x00, 0x00, 0x03, 0x00, 0x00, 0x00, 0x03, 0x00,
+		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+		0x01, 0x02, 0x03, 0x50, 0x4b, 0x06, 0x06, 0x2c,
+		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x2d,
+		0x00, 0x2d, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+		0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00,
+		0x00, 0x00, 0x00, 0xff, 0xff, 0xff, 0xff, 0xff,
+		0xff, 0xff, 0xff, 0x31, 0x00, 0x00, 0x00, 0x00,
+		0x00, 0x00, 0x00, 0x3a, 0x00, 0x00, 0x00, 0x00,
+		0x00, 0x00, 0x00, 0x50, 0x4b, 0x06, 0x07, 0x00,
+		0x00, 0x00, 0x00, 0x6b, 0x00, 0x00, 0x00, 0x00,
+		0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x50,
+		0x4b, 0x05, 0x06, 0x00, 0x00, 0x00, 0x00, 0xff,
+		0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+		0xff, 0xff, 0xff, 0x00, 0x00,
+	}
+	_, err := NewReader(bytes.NewReader(data), int64(len(data)))
+	if err != ErrFormat {
+		t.Fatalf("unexpected error, got: %v, want: %v", err, ErrFormat)
+	}
+
+	// Also check that an archive containing a handful of empty
+	// files doesn't cause an issue
+	b := bytes.NewBuffer(nil)
+	w := NewWriter(b)
+	for i := 0; i < 5; i++ {
+		_, err := w.Create("")
+		if err != nil {
+			t.Fatalf("Writer.Create failed: %s", err)
+		}
+	}
+	if err := w.Close(); err != nil {
+		t.Fatalf("Writer.Close failed: %s", err)
+	}
+	r, err := NewReader(bytes.NewReader(b.Bytes()), int64(b.Len()))
+	if err != nil {
+		t.Fatalf("NewReader failed: %s", err)
+	}
+	if len(r.File) != 5 {
+		t.Errorf("Archive has unexpected number of files, got %d, want 5", len(r.File))
 	}
 }

src/cmd/compile/internal/gc/dwinl.go

@@ -243,7 +243,8 @@ func makePreinlineDclMap(fnsym *obj.LSym) map[varPos]int {
 			DeclCol:  pos.Col(),
 		}
 		if _, found := m[vp]; found {
-			Fatalf("child dcl collision on symbol %s within %v\n", n.Sym.Name, fnsym.Name)
+			// We can see collisions (variables with the same name/file/line/col) in obfuscated or machine-generated code -- see issue 44378 for an example. Skip duplicates in such cases, since it is unlikely that a human will be debugging such code.
+			continue
 		}
 		m[vp] = i
 	}

src/cmd/compile/internal/gc/escape.go

@@ -1376,9 +1376,10 @@ func containsClosure(f, c *Node) bool {
 
 // leak records that parameter l leaks to sink.
 func (l *EscLocation) leakTo(sink *EscLocation, derefs int) {
-	// If sink is a result parameter and we can fit return bits
-	// into the escape analysis tag, then record a return leak.
-	if sink.isName(PPARAMOUT) && sink.curfn == l.curfn {
+	// If sink is a result parameter that doesn't escape (#44614)
+	// and we can fit return bits into the escape analysis tag,
+	// then record as a result leak.
+	if !sink.escapes && sink.isName(PPARAMOUT) && sink.curfn == l.curfn {
 		// TODO(mdempsky): Eliminate dependency on Vargen here.
 		ri := int(sink.n.Name.Vargen) - 1
 		if ri < numEscResults {

src/cmd/compile/internal/gc/inl.go

@@ -1053,18 +1053,26 @@ func mkinlcall(n, fn *Node, maxCost int32, inlMap map[*Node]bool) *Node {
 		}
 	}
 
+	// We can delay declaring+initializing result parameters if:
+	// (1) there's exactly one "return" statement in the inlined function;
+	// (2) it's not an empty return statement (#44355); and
+	// (3) the result parameters aren't named.
+	delayretvars := true
+
 	nreturns := 0
 	inspectList(asNodes(fn.Func.Inl.Body), func(n *Node) bool {
 		if n != nil && n.Op == ORETURN {
 			nreturns++
+			if n.List.Len() == 0 {
+				delayretvars = false // empty return statement (case 2)
+			}
 		}
 		return true
 	})
 
-	// We can delay declaring+initializing result parameters if:
-	// (1) there's only one "return" statement in the inlined
-	// function, and (2) the result parameters aren't named.
-	delayretvars := nreturns == 1
+	if nreturns != 1 {
+		delayretvars = false // not exactly one return statement (case 1)
+	}
 
 	// temporaries for return values.
 	var retvars []*Node
@@ -1074,7 +1082,7 @@ func mkinlcall(n, fn *Node, maxCost int32, inlMap map[*Node]bool) *Node {
 			m = inlvar(n)
 			m = typecheck(m, ctxExpr)
 			inlvars[n] = m
-			delayretvars = false // found a named result parameter
+			delayretvars = false // found a named result parameter (case 3)
 		} else {
 			// anonymous return values, synthesize names for use in assignment that replaces return
 			m = retvar(t, i)

src/cmd/compile/internal/gc/obj.go

@@ -163,6 +163,7 @@ func dumpdata() {
 	if zerosize > 0 {
 		zero := mappkg.Lookup("zero")
 		ggloblsym(zero.Linksym(), int32(zerosize), obj.DUPOK|obj.RODATA)
+		zero.Linksym().Set(obj.AttrContentAddressable, true)
 	}
 
 	addGCLocals()

src/cmd/compile/internal/gc/sinit.go

@@ -363,15 +363,15 @@ func staticname(t *types.Type) *Node {
 	n := newname(lookup(fmt.Sprintf("%s%d", obj.StaticNamePref, statuniqgen)))
 	statuniqgen++
 	addvar(n, t, PEXTERN)
-	n.Sym.Linksym().Set(obj.AttrLocal, true)
 	return n
 }
 
-// readonlystaticname returns a name backed by a (writable) static data symbol.
+// readonlystaticname returns a name backed by a read-only static data symbol.
 func readonlystaticname(t *types.Type) *Node {
 	n := staticname(t)
 	n.MarkReadonly()
 	n.Sym.Linksym().Set(obj.AttrContentAddressable, true)
+	n.Sym.Linksym().Set(obj.AttrLocal, true)
 	return n
 }
 

src/cmd/compile/internal/gc/walk.go

@@ -3927,15 +3927,22 @@ func wrapCall(n *Node, init *Nodes) *Node {
 		}
 	}
 
+	wrapArgs := n.List.Slice()
+	// If there's a receiver argument, it needs to be passed through the wrapper too.
+	if n.Op == OCALLMETH || n.Op == OCALLINTER {
+		recv := n.Left.Left
+		wrapArgs = append([]*Node{recv}, wrapArgs...)
+	}
+
 	// origArgs keeps track of what argument is uintptr-unsafe/unsafe-uintptr conversion.
-	origArgs := make([]*Node, n.List.Len())
+	origArgs := make([]*Node, len(wrapArgs))
 	t := nod(OTFUNC, nil, nil)
-	for i, arg := range n.List.Slice() {
+	for i, arg := range wrapArgs {
 		s := lookupN("a", i)
 		if !isBuiltinCall && arg.Op == OCONVNOP && arg.Type.IsUintptr() && arg.Left.Type.IsUnsafePtr() {
 			origArgs[i] = arg
 			arg = arg.Left
-			n.List.SetIndex(i, arg)
+			wrapArgs[i] = arg
 		}
 		t.List.Append(symfield(s, arg.Type))
 	}
@@ -3953,6 +3960,12 @@ func wrapCall(n *Node, init *Nodes) *Node {
 		arg.Type = origArg.Type
 		args[i] = arg
 	}
+	if n.Op == OCALLMETH || n.Op == OCALLINTER {
+		// Move wrapped receiver argument back to its appropriate place.
+		recv := typecheck(args[0], ctxExpr)
+		n.Left.Left = recv
+		args = args[1:]
+	}
 	call := nod(n.Op, nil, nil)
 	if !isBuiltinCall {
 		call.Op = OCALL
@@ -3970,7 +3983,7 @@ func wrapCall(n *Node, init *Nodes) *Node {
 
 	call = nod(OCALL, nil, nil)
 	call.Left = fn.Func.Nname
-	call.List.Set(n.List.Slice())
+	call.List.Set(wrapArgs)
 	call = typecheck(call, ctxStmt)
 	call = walkexpr(call, init)
 	return call

src/cmd/compile/internal/ssa/gen/AMD64.rules

@@ -623,6 +623,14 @@
 // Recognize bit setting (a |= 1<<b) and toggling (a ^= 1<<b)
 (OR(Q|L) (SHL(Q|L) (MOV(Q|L)const [1]) y) x) => (BTS(Q|L) x y)
 (XOR(Q|L) (SHL(Q|L) (MOV(Q|L)const [1]) y) x) => (BTC(Q|L) x y)
+(ORLmodify [off] {sym} ptr s:(SHLL (MOVLconst [1]) <t> x) mem) =>
+	(BTSLmodify [off] {sym} ptr (ANDLconst <t> [31] x) mem)
+(ORQmodify [off] {sym} ptr s:(SHLQ (MOVQconst [1]) <t> x) mem) =>
+	(BTSQmodify [off] {sym} ptr (ANDQconst <t> [63] x) mem)
+(XORLmodify [off] {sym} ptr s:(SHLL (MOVLconst [1]) <t> x) mem) =>
+	(BTCLmodify [off] {sym} ptr (ANDLconst <t> [31] x) mem)
+(XORQmodify [off] {sym} ptr s:(SHLQ (MOVQconst [1]) <t> x) mem) =>
+	(BTCQmodify [off] {sym} ptr (ANDQconst <t> [63] x) mem)
 
 // Convert ORconst into BTS, if the code gets smaller, with boundary being
 // (ORL $40,AX is 3 bytes, ORL $80,AX is 6 bytes).
@@ -645,6 +653,10 @@
     => (BTRQconst [int8(log64(^c))] x)
 (ANDL (MOVLconst [c]) x) && isUint32PowerOfTwo(int64(^c)) && uint64(^c) >= 128
     => (BTRLconst [int8(log32(^c))] x)
+(ANDLmodify [off] {sym} ptr (NOTL s:(SHLL (MOVLconst [1]) <t> x)) mem) =>
+	(BTRLmodify [off] {sym} ptr (ANDLconst <t> [31] x) mem)
+(ANDQmodify [off] {sym} ptr (NOTQ s:(SHLQ (MOVQconst [1]) <t> x)) mem) =>
+	(BTRQmodify [off] {sym} ptr (ANDQconst <t> [63] x) mem)
 
 // Special-case bit patterns on first/last bit.
 // generic.rules changes ANDs of high-part/low-part masks into a couple of shifts,
@@ -2050,11 +2062,15 @@
 ((ADD|SUB|MUL|DIV)SD x l:(MOVSDload [off] {sym} ptr mem)) && canMergeLoadClobber(v, l, x) && clobber(l) => ((ADD|SUB|MUL|DIV)SDload x [off] {sym} ptr mem)
 ((ADD|SUB|MUL|DIV)SS x l:(MOVSSload [off] {sym} ptr mem)) && canMergeLoadClobber(v, l, x) && clobber(l) => ((ADD|SUB|MUL|DIV)SSload x [off] {sym} ptr mem)
 (MOVLstore {sym} [off] ptr y:((ADD|AND|OR|XOR)Lload x [off] {sym} ptr mem) mem) && y.Uses==1 && clobber(y) => ((ADD|AND|OR|XOR)Lmodify [off] {sym} ptr x mem)
-(MOVLstore {sym} [off] ptr y:((ADD|SUB|AND|OR|XOR|BTC|BTR|BTS)L l:(MOVLload [off] {sym} ptr mem) x) mem) && y.Uses==1 && l.Uses==1 && clobber(y, l) =>
-	((ADD|SUB|AND|OR|XOR|BTC|BTR|BTS)Lmodify [off] {sym} ptr x mem)
+(MOVLstore {sym} [off] ptr y:((ADD|SUB|AND|OR|XOR)L l:(MOVLload [off] {sym} ptr mem) x) mem) && y.Uses==1 && l.Uses==1 && clobber(y, l) =>
+	((ADD|SUB|AND|OR|XOR)Lmodify [off] {sym} ptr x mem)
+(MOVLstore {sym} [off] ptr y:((BTC|BTR|BTS)L l:(MOVLload [off] {sym} ptr mem) <t> x) mem) && y.Uses==1 && l.Uses==1 && clobber(y, l) =>
+	((BTC|BTR|BTS)Lmodify [off] {sym} ptr (ANDLconst <t> [31] x) mem)
 (MOVQstore {sym} [off] ptr y:((ADD|AND|OR|XOR)Qload x [off] {sym} ptr mem) mem) && y.Uses==1 && clobber(y) => ((ADD|AND|OR|XOR)Qmodify [off] {sym} ptr x mem)
-(MOVQstore {sym} [off] ptr y:((ADD|SUB|AND|OR|XOR|BTC|BTR|BTS)Q l:(MOVQload [off] {sym} ptr mem) x) mem) && y.Uses==1 && l.Uses==1 && clobber(y, l) =>
-	((ADD|SUB|AND|OR|XOR|BTC|BTR|BTS)Qmodify [off] {sym} ptr x mem)
+(MOVQstore {sym} [off] ptr y:((ADD|SUB|AND|OR|XOR)Q l:(MOVQload [off] {sym} ptr mem) x) mem) && y.Uses==1 && l.Uses==1 && clobber(y, l) =>
+	((ADD|SUB|AND|OR|XOR)Qmodify [off] {sym} ptr x mem)
+(MOVQstore {sym} [off] ptr y:((BTC|BTR|BTS)Q l:(MOVQload [off] {sym} ptr mem) <t> x) mem) && y.Uses==1 && l.Uses==1 && clobber(y, l) =>
+	((BTC|BTR|BTS)Qmodify [off] {sym} ptr (ANDQconst <t> [63] x) mem)
 
 // Merge ADDQconst and LEAQ into atomic loads.
 (MOV(Q|L|B)atomicload [off1] {sym} (ADDQconst [off2] ptr) mem) && is32Bit(int64(off1)+int64(off2)) =>

src/cmd/compile/internal/ssa/gen/AMD64Ops.go

@@ -358,6 +358,11 @@ func init() {
 		{name: "BTSQconst", argLength: 1, reg: gp11, asm: "BTSQ", resultInArg0: true, clobberFlags: true, aux: "Int8"}, // set bit auxint in arg0, 0 <= auxint < 64
 
 		// direct bit operation on memory operand
+		//
+		// Note that these operations do not mask the bit offset (arg1), and will write beyond their expected
+		// bounds if that argument is larger than 64/32 (for BT*Q and BT*L, respectively). If the compiler
+		// cannot prove that arg1 is in range, it must be explicitly masked (see e.g. the patterns that produce
+		// BT*modify from (MOVstore (BT* (MOVLload ptr mem) x) mem)).
 		{name: "BTCQmodify", argLength: 3, reg: gpstore, asm: "BTCQ", aux: "SymOff", typ: "Mem", clobberFlags: true, faultOnNilArg0: true, symEffect: "Read,Write"},     // complement bit arg1 in 64-bit arg0+auxint+aux, arg2=mem
 		{name: "BTCLmodify", argLength: 3, reg: gpstore, asm: "BTCL", aux: "SymOff", typ: "Mem", clobberFlags: true, faultOnNilArg0: true, symEffect: "Read,Write"},     // complement bit arg1 in 32-bit arg0+auxint+aux, arg2=mem
 		{name: "BTSQmodify", argLength: 3, reg: gpstore, asm: "BTSQ", aux: "SymOff", typ: "Mem", clobberFlags: true, faultOnNilArg0: true, symEffect: "Read,Write"},     // set bit arg1 in 64-bit arg0+auxint+aux, arg2=mem

src/cmd/compile/internal/ssa/rewrite.go

@@ -1469,7 +1469,7 @@ func mergePPC64AndSrwi(m, s int64) int64 {
 	if !isPPC64WordRotateMask(mask) {
 		return 0
 	}
-	return encodePPC64RotateMask(32-s, mask, 32)
+	return encodePPC64RotateMask((32-s)&31, mask, 32)
 }
 
 // Test if a shift right feeding into a CLRLSLDI can be merged into RLWINM.

src/cmd/compile/internal/ssa/rewriteAMD64.go

@@ -2998,6 +2998,36 @@ func rewriteValueAMD64_OpAMD64ANDLmodify(v *Value) bool {
 	v_2 := v.Args[2]
 	v_1 := v.Args[1]
 	v_0 := v.Args[0]
+	b := v.Block
+	// match: (ANDLmodify [off] {sym} ptr (NOTL s:(SHLL (MOVLconst [1]) <t> x)) mem)
+	// result: (BTRLmodify [off] {sym} ptr (ANDLconst <t> [31] x) mem)
+	for {
+		off := auxIntToInt32(v.AuxInt)
+		sym := auxToSym(v.Aux)
+		ptr := v_0
+		if v_1.Op != OpAMD64NOTL {
+			break
+		}
+		s := v_1.Args[0]
+		if s.Op != OpAMD64SHLL {
+			break
+		}
+		t := s.Type
+		x := s.Args[1]
+		s_0 := s.Args[0]
+		if s_0.Op != OpAMD64MOVLconst || auxIntToInt32(s_0.AuxInt) != 1 {
+			break
+		}
+		mem := v_2
+		v.reset(OpAMD64BTRLmodify)
+		v.AuxInt = int32ToAuxInt(off)
+		v.Aux = symToAux(sym)
+		v0 := b.NewValue0(v.Pos, OpAMD64ANDLconst, t)
+		v0.AuxInt = int32ToAuxInt(31)
+		v0.AddArg(x)
+		v.AddArg3(ptr, v0, mem)
+		return true
+	}
 	// match: (ANDLmodify [off1] {sym} (ADDQconst [off2] base) val mem)
 	// cond: is32Bit(int64(off1)+int64(off2))
 	// result: (ANDLmodify [off1+off2] {sym} base val mem)
@@ -3377,6 +3407,36 @@ func rewriteValueAMD64_OpAMD64ANDQmodify(v *Value) bool {
 	v_2 := v.Args[2]
 	v_1 := v.Args[1]
 	v_0 := v.Args[0]
+	b := v.Block
+	// match: (ANDQmodify [off] {sym} ptr (NOTQ s:(SHLQ (MOVQconst [1]) <t> x)) mem)
+	// result: (BTRQmodify [off] {sym} ptr (ANDQconst <t> [63] x) mem)
+	for {
+		off := auxIntToInt32(v.AuxInt)
+		sym := auxToSym(v.Aux)
+		ptr := v_0
+		if v_1.Op != OpAMD64NOTQ {
+			break
+		}
+		s := v_1.Args[0]
+		if s.Op != OpAMD64SHLQ {
+			break
+		}
+		t := s.Type
+		x := s.Args[1]
+		s_0 := s.Args[0]
+		if s_0.Op != OpAMD64MOVQconst || auxIntToInt64(s_0.AuxInt) != 1 {
+			break
+		}
+		mem := v_2
+		v.reset(OpAMD64BTRQmodify)
+		v.AuxInt = int32ToAuxInt(off)
+		v.Aux = symToAux(sym)
+		v0 := b.NewValue0(v.Pos, OpAMD64ANDQconst, t)
+		v0.AuxInt = int32ToAuxInt(63)
+		v0.AddArg(x)
+		v.AddArg3(ptr, v0, mem)
+		return true
+	}
 	// match: (ANDQmodify [off1] {sym} (ADDQconst [off2] base) val mem)
 	// cond: is32Bit(int64(off1)+int64(off2))
 	// result: (ANDQmodify [off1+off2] {sym} base val mem)
@@ -12709,9 +12769,9 @@ func rewriteValueAMD64_OpAMD64MOVLstore(v *Value) bool {
 		}
 		break
 	}
-	// match: (MOVLstore {sym} [off] ptr y:(BTCL l:(MOVLload [off] {sym} ptr mem) x) mem)
+	// match: (MOVLstore {sym} [off] ptr y:(BTCL l:(MOVLload [off] {sym} ptr mem) <t> x) mem)
 	// cond: y.Uses==1 && l.Uses==1 && clobber(y, l)
-	// result: (BTCLmodify [off] {sym} ptr x mem)
+	// result: (BTCLmodify [off] {sym} ptr (ANDLconst <t> [31] x) mem)
 	for {
 		off := auxIntToInt32(v.AuxInt)
 		sym := auxToSym(v.Aux)
@@ -12720,6 +12780,7 @@ func rewriteValueAMD64_OpAMD64MOVLstore(v *Value) bool {
 		if y.Op != OpAMD64BTCL {
 			break
 		}
+		t := y.Type
 		x := y.Args[1]
 		l := y.Args[0]
 		if l.Op != OpAMD64MOVLload || auxIntToInt32(l.AuxInt) != off || auxToSym(l.Aux) != sym {
@@ -12732,12 +12793,15 @@ func rewriteValueAMD64_OpAMD64MOVLstore(v *Value) bool {
 		v.reset(OpAMD64BTCLmodify)
 		v.AuxInt = int32ToAuxInt(off)
 		v.Aux = symToAux(sym)
-		v.AddArg3(ptr, x, mem)
+		v0 := b.NewValue0(l.Pos, OpAMD64ANDLconst, t)
+		v0.AuxInt = int32ToAuxInt(31)
+		v0.AddArg(x)
+		v.AddArg3(ptr, v0, mem)
 		return true
 	}
-	// match: (MOVLstore {sym} [off] ptr y:(BTRL l:(MOVLload [off] {sym} ptr mem) x) mem)
+	// match: (MOVLstore {sym} [off] ptr y:(BTRL l:(MOVLload [off] {sym} ptr mem) <t> x) mem)
 	// cond: y.Uses==1 && l.Uses==1 && clobber(y, l)
-	// result: (BTRLmodify [off] {sym} ptr x mem)
+	// result: (BTRLmodify [off] {sym} ptr (ANDLconst <t> [31] x) mem)
 	for {
 		off := auxIntToInt32(v.AuxInt)
 		sym := auxToSym(v.Aux)
@@ -12746,6 +12810,7 @@ func rewriteValueAMD64_OpAMD64MOVLstore(v *Value) bool {
 		if y.Op != OpAMD64BTRL {
 			break
 		}
+		t := y.Type
 		x := y.Args[1]
 		l := y.Args[0]
 		if l.Op != OpAMD64MOVLload || auxIntToInt32(l.AuxInt) != off || auxToSym(l.Aux) != sym {
@@ -12758,12 +12823,15 @@ func rewriteValueAMD64_OpAMD64MOVLstore(v *Value) bool {
 		v.reset(OpAMD64BTRLmodify)
 		v.AuxInt = int32ToAuxInt(off)
 		v.Aux = symToAux(sym)
-		v.AddArg3(ptr, x, mem)
+		v0 := b.NewValue0(l.Pos, OpAMD64ANDLconst, t)
+		v0.AuxInt = int32ToAuxInt(31)
+		v0.AddArg(x)
+		v.AddArg3(ptr, v0, mem)
 		return true
 	}
-	// match: (MOVLstore {sym} [off] ptr y:(BTSL l:(MOVLload [off] {sym} ptr mem) x) mem)
+	// match: (MOVLstore {sym} [off] ptr y:(BTSL l:(MOVLload [off] {sym} ptr mem) <t> x) mem)
 	// cond: y.Uses==1 && l.Uses==1 && clobber(y, l)
-	// result: (BTSLmodify [off] {sym} ptr x mem)
+	// result: (BTSLmodify [off] {sym} ptr (ANDLconst <t> [31] x) mem)
 	for {
 		off := auxIntToInt32(v.AuxInt)
 		sym := auxToSym(v.Aux)
@@ -12772,6 +12840,7 @@ func rewriteValueAMD64_OpAMD64MOVLstore(v *Value) bool {
 		if y.Op != OpAMD64BTSL {
 			break
 		}
+		t := y.Type
 		x := y.Args[1]
 		l := y.Args[0]
 		if l.Op != OpAMD64MOVLload || auxIntToInt32(l.AuxInt) != off || auxToSym(l.Aux) != sym {
@@ -12784,7 +12853,10 @@ func rewriteValueAMD64_OpAMD64MOVLstore(v *Value) bool {
 		v.reset(OpAMD64BTSLmodify)
 		v.AuxInt = int32ToAuxInt(off)
 		v.Aux = symToAux(sym)
-		v.AddArg3(ptr, x, mem)
+		v0 := b.NewValue0(l.Pos, OpAMD64ANDLconst, t)
+		v0.AuxInt = int32ToAuxInt(31)
+		v0.AddArg(x)
+		v.AddArg3(ptr, v0, mem)
 		return true
 	}
 	// match: (MOVLstore [off] {sym} ptr a:(ADDLconst [c] l:(MOVLload [off] {sym} ptr2 mem)) mem)
@@ -13525,6 +13597,7 @@ func rewriteValueAMD64_OpAMD64MOVQstore(v *Value) bool {
 	v_2 := v.Args[2]
 	v_1 := v.Args[1]
 	v_0 := v.Args[0]
+	b := v.Block
 	// match: (MOVQstore [off1] {sym} (ADDQconst [off2] ptr) val mem)
 	// cond: is32Bit(int64(off1)+int64(off2))
 	// result: (MOVQstore [off1+off2] {sym} ptr val mem)
@@ -13890,9 +13963,9 @@ func rewriteValueAMD64_OpAMD64MOVQstore(v *Value) bool {
 		}
 		break
 	}
-	// match: (MOVQstore {sym} [off] ptr y:(BTCQ l:(MOVQload [off] {sym} ptr mem) x) mem)
+	// match: (MOVQstore {sym} [off] ptr y:(BTCQ l:(MOVQload [off] {sym} ptr mem) <t> x) mem)
 	// cond: y.Uses==1 && l.Uses==1 && clobber(y, l)
-	// result: (BTCQmodify [off] {sym} ptr x mem)
+	// result: (BTCQmodify [off] {sym} ptr (ANDQconst <t> [63] x) mem)
 	for {
 		off := auxIntToInt32(v.AuxInt)
 		sym := auxToSym(v.Aux)
@@ -13901,6 +13974,7 @@ func rewriteValueAMD64_OpAMD64MOVQstore(v *Value) bool {
 		if y.Op != OpAMD64BTCQ {
 			break
 		}
+		t := y.Type
 		x := y.Args[1]
 		l := y.Args[0]
 		if l.Op != OpAMD64MOVQload || auxIntToInt32(l.AuxInt) != off || auxToSym(l.Aux) != sym {
@@ -13913,12 +13987,15 @@ func rewriteValueAMD64_OpAMD64MOVQstore(v *Value) bool {
 		v.reset(OpAMD64BTCQmodify)
 		v.AuxInt = int32ToAuxInt(off)
 		v.Aux = symToAux(sym)
-		v.AddArg3(ptr, x, mem)
+		v0 := b.NewValue0(l.Pos, OpAMD64ANDQconst, t)
+		v0.AuxInt = int32ToAuxInt(63)
+		v0.AddArg(x)
+		v.AddArg3(ptr, v0, mem)
 		return true
 	}
-	// match: (MOVQstore {sym} [off] ptr y:(BTRQ l:(MOVQload [off] {sym} ptr mem) x) mem)
+	// match: (MOVQstore {sym} [off] ptr y:(BTRQ l:(MOVQload [off] {sym} ptr mem) <t> x) mem)
 	// cond: y.Uses==1 && l.Uses==1 && clobber(y, l)
-	// result: (BTRQmodify [off] {sym} ptr x mem)
+	// result: (BTRQmodify [off] {sym} ptr (ANDQconst <t> [63] x) mem)
 	for {
 		off := auxIntToInt32(v.AuxInt)
 		sym := auxToSym(v.Aux)
@@ -13927,6 +14004,7 @@ func rewriteValueAMD64_OpAMD64MOVQstore(v *Value) bool {
 		if y.Op != OpAMD64BTRQ {
 			break
 		}
+		t := y.Type
 		x := y.Args[1]
 		l := y.Args[0]
 		if l.Op != OpAMD64MOVQload || auxIntToInt32(l.AuxInt) != off || auxToSym(l.Aux) != sym {
@@ -13939,12 +14017,15 @@ func rewriteValueAMD64_OpAMD64MOVQstore(v *Value) bool {
 		v.reset(OpAMD64BTRQmodify)
 		v.AuxInt = int32ToAuxInt(off)
 		v.Aux = symToAux(sym)
-		v.AddArg3(ptr, x, mem)
+		v0 := b.NewValue0(l.Pos, OpAMD64ANDQconst, t)
+		v0.AuxInt = int32ToAuxInt(63)
+		v0.AddArg(x)
+		v.AddArg3(ptr, v0, mem)
 		return true
 	}
-	// match: (MOVQstore {sym} [off] ptr y:(BTSQ l:(MOVQload [off] {sym} ptr mem) x) mem)
+	// match: (MOVQstore {sym} [off] ptr y:(BTSQ l:(MOVQload [off] {sym} ptr mem) <t> x) mem)
 	// cond: y.Uses==1 && l.Uses==1 && clobber(y, l)
-	// result: (BTSQmodify [off] {sym} ptr x mem)
+	// result: (BTSQmodify [off] {sym} ptr (ANDQconst <t> [63] x) mem)
 	for {
 		off := auxIntToInt32(v.AuxInt)
 		sym := auxToSym(v.Aux)
@@ -13953,6 +14034,7 @@ func rewriteValueAMD64_OpAMD64MOVQstore(v *Value) bool {
 		if y.Op != OpAMD64BTSQ {
 			break
 		}
+		t := y.Type
 		x := y.Args[1]
 		l := y.Args[0]
 		if l.Op != OpAMD64MOVQload || auxIntToInt32(l.AuxInt) != off || auxToSym(l.Aux) != sym {
@@ -13965,7 +14047,10 @@ func rewriteValueAMD64_OpAMD64MOVQstore(v *Value) bool {
 		v.reset(OpAMD64BTSQmodify)
 		v.AuxInt = int32ToAuxInt(off)
 		v.Aux = symToAux(sym)
-		v.AddArg3(ptr, x, mem)
+		v0 := b.NewValue0(l.Pos, OpAMD64ANDQconst, t)
+		v0.AuxInt = int32ToAuxInt(63)
+		v0.AddArg(x)
+		v.AddArg3(ptr, v0, mem)
 		return true
 	}
 	// match: (MOVQstore [off] {sym} ptr a:(ADDQconst [c] l:(MOVQload [off] {sym} ptr2 mem)) mem)
@@ -18352,6 +18437,33 @@ func rewriteValueAMD64_OpAMD64ORLmodify(v *Value) bool {
 	v_2 := v.Args[2]
 	v_1 := v.Args[1]
 	v_0 := v.Args[0]
+	b := v.Block
+	// match: (ORLmodify [off] {sym} ptr s:(SHLL (MOVLconst [1]) <t> x) mem)
+	// result: (BTSLmodify [off] {sym} ptr (ANDLconst <t> [31] x) mem)
+	for {
+		off := auxIntToInt32(v.AuxInt)
+		sym := auxToSym(v.Aux)
+		ptr := v_0
+		s := v_1
+		if s.Op != OpAMD64SHLL {
+			break
+		}
+		t := s.Type
+		x := s.Args[1]
+		s_0 := s.Args[0]
+		if s_0.Op != OpAMD64MOVLconst || auxIntToInt32(s_0.AuxInt) != 1 {
+			break
+		}
+		mem := v_2
+		v.reset(OpAMD64BTSLmodify)
+		v.AuxInt = int32ToAuxInt(off)
+		v.Aux = symToAux(sym)
+		v0 := b.NewValue0(v.Pos, OpAMD64ANDLconst, t)
+		v0.AuxInt = int32ToAuxInt(31)
+		v0.AddArg(x)
+		v.AddArg3(ptr, v0, mem)
+		return true
+	}
 	// match: (ORLmodify [off1] {sym} (ADDQconst [off2] base) val mem)
 	// cond: is32Bit(int64(off1)+int64(off2))
 	// result: (ORLmodify [off1+off2] {sym} base val mem)
@@ -19979,6 +20091,33 @@ func rewriteValueAMD64_OpAMD64ORQmodify(v *Value) bool {
 	v_2 := v.Args[2]
 	v_1 := v.Args[1]
 	v_0 := v.Args[0]
+	b := v.Block
+	// match: (ORQmodify [off] {sym} ptr s:(SHLQ (MOVQconst [1]) <t> x) mem)
+	// result: (BTSQmodify [off] {sym} ptr (ANDQconst <t> [63] x) mem)
+	for {
+		off := auxIntToInt32(v.AuxInt)
+		sym := auxToSym(v.Aux)
+		ptr := v_0
+		s := v_1
+		if s.Op != OpAMD64SHLQ {
+			break
+		}
+		t := s.Type
+		x := s.Args[1]
+		s_0 := s.Args[0]
+		if s_0.Op != OpAMD64MOVQconst || auxIntToInt64(s_0.AuxInt) != 1 {
+			break
+		}
+		mem := v_2
+		v.reset(OpAMD64BTSQmodify)
+		v.AuxInt = int32ToAuxInt(off)
+		v.Aux = symToAux(sym)
+		v0 := b.NewValue0(v.Pos, OpAMD64ANDQconst, t)
+		v0.AuxInt = int32ToAuxInt(63)
+		v0.AddArg(x)
+		v.AddArg3(ptr, v0, mem)
+		return true
+	}
 	// match: (ORQmodify [off1] {sym} (ADDQconst [off2] base) val mem)
 	// cond: is32Bit(int64(off1)+int64(off2))
 	// result: (ORQmodify [off1+off2] {sym} base val mem)
@@ -28014,6 +28153,33 @@ func rewriteValueAMD64_OpAMD64XORLmodify(v *Value) bool {
 	v_2 := v.Args[2]
 	v_1 := v.Args[1]
 	v_0 := v.Args[0]
+	b := v.Block
+	// match: (XORLmodify [off] {sym} ptr s:(SHLL (MOVLconst [1]) <t> x) mem)
+	// result: (BTCLmodify [off] {sym} ptr (ANDLconst <t> [31] x) mem)
+	for {
+		off := auxIntToInt32(v.AuxInt)
+		sym := auxToSym(v.Aux)
+		ptr := v_0
+		s := v_1
+		if s.Op != OpAMD64SHLL {
+			break
+		}
+		t := s.Type
+		x := s.Args[1]
+		s_0 := s.Args[0]
+		if s_0.Op != OpAMD64MOVLconst || auxIntToInt32(s_0.AuxInt) != 1 {
+			break
+		}
+		mem := v_2
+		v.reset(OpAMD64BTCLmodify)
+		v.AuxInt = int32ToAuxInt(off)
+		v.Aux = symToAux(sym)
+		v0 := b.NewValue0(v.Pos, OpAMD64ANDLconst, t)
+		v0.AuxInt = int32ToAuxInt(31)
+		v0.AddArg(x)
+		v.AddArg3(ptr, v0, mem)
+		return true
+	}
 	// match: (XORLmodify [off1] {sym} (ADDQconst [off2] base) val mem)
 	// cond: is32Bit(int64(off1)+int64(off2))
 	// result: (XORLmodify [off1+off2] {sym} base val mem)
@@ -28382,6 +28548,33 @@ func rewriteValueAMD64_OpAMD64XORQmodify(v *Value) bool {
 	v_2 := v.Args[2]
 	v_1 := v.Args[1]
 	v_0 := v.Args[0]
+	b := v.Block
+	// match: (XORQmodify [off] {sym} ptr s:(SHLQ (MOVQconst [1]) <t> x) mem)
+	// result: (BTCQmodify [off] {sym} ptr (ANDQconst <t> [63] x) mem)
+	for {
+		off := auxIntToInt32(v.AuxInt)
+		sym := auxToSym(v.Aux)
+		ptr := v_0
+		s := v_1
+		if s.Op != OpAMD64SHLQ {
+			break
+		}
+		t := s.Type
+		x := s.Args[1]
+		s_0 := s.Args[0]
+		if s_0.Op != OpAMD64MOVQconst || auxIntToInt64(s_0.AuxInt) != 1 {
+			break
+		}
+		mem := v_2
+		v.reset(OpAMD64BTCQmodify)
+		v.AuxInt = int32ToAuxInt(off)
+		v.Aux = symToAux(sym)
+		v0 := b.NewValue0(v.Pos, OpAMD64ANDQconst, t)
+		v0.AuxInt = int32ToAuxInt(63)
+		v0.AddArg(x)
+		v.AddArg3(ptr, v0, mem)
+		return true
+	}
 	// match: (XORQmodify [off1] {sym} (ADDQconst [off2] base) val mem)
 	// cond: is32Bit(int64(off1)+int64(off2))
 	// result: (XORQmodify [off1+off2] {sym} base val mem)

src/cmd/compile/internal/ssa/rewrite_test.go

@@ -205,6 +205,7 @@ func TestMergePPC64AndSrwi(t *testing.T) {
 		{0x00000000, 4, false, 0, 0},
 		{0xF0000000, 4, false, 0, 0},
 		{0xF0000000, 32, false, 0, 0},
+		{0xFFFFFFFF, 0, true, 0, 0xFFFFFFFF},
 	}
 	for i, v := range tests {
 		result := mergePPC64AndSrwi(v.and, v.srw)

src/cmd/compile/internal/ssa/shortcircuit.go

@@ -138,6 +138,24 @@ func shortcircuitBlock(b *Block) bool {
 	if len(b.Values) != nval+nOtherPhi {
 		return false
 	}
+	if nOtherPhi > 0 {
+		// Check for any phi which is the argument of another phi.
+		// These cases are tricky, as substitutions done by replaceUses
+		// are no longer trivial to do in any ordering. See issue 45175.
+		m := make(map[*Value]bool, 1+nOtherPhi)
+		for _, v := range b.Values {
+			if v.Op == OpPhi {
+				m[v] = true
+			}
+		}
+		for v := range m {
+			for _, a := range v.Args {
+				if a != v && m[a] {
+					return false
+				}
+			}
+		}
+	}
 
 	// Locate index of first const phi arg.
 	cidx := -1

src/cmd/go.mod

@@ -6,7 +6,7 @@ require (
 	github.com/google/pprof v0.0.0-20201203190320-1bf35d6f28c2
 	golang.org/x/arch v0.0.0-20201008161808-52c3e6f60cff
 	golang.org/x/crypto v0.0.0-20201016220609-9e8e0b390897
-	golang.org/x/mod v0.4.1
+	golang.org/x/mod v0.4.2-0.20210325185522-dbbbf8a3c6ea
 	golang.org/x/sys v0.0.0-20201204225414-ed752295db88 // indirect
 	golang.org/x/tools v0.0.0-20210107193943-4ed967dd8eff
 )

src/cmd/go.sum

@@ -14,8 +14,8 @@ golang.org/x/crypto v0.0.0-20200622213623-75b288015ac9/go.mod h1:LzIPMQfyMNhhGPh
 golang.org/x/crypto v0.0.0-20201016220609-9e8e0b390897 h1:pLI5jrR7OSLijeIDcmRxNmw2api+jEfxLoykJVice/E=
 golang.org/x/crypto v0.0.0-20201016220609-9e8e0b390897/go.mod h1:LzIPMQfyMNhhGPhUkYOs5KpL4U8rLKemX1yGLhDgUto=
 golang.org/x/mod v0.3.0/go.mod h1:s0Qsj1ACt9ePp/hMypM3fl4fZqREWJwdYDEqhRiZZUA=
-golang.org/x/mod v0.4.1 h1:Kvvh58BN8Y9/lBi7hTekvtMpm07eUZ0ck5pRHpsMWrY=
-golang.org/x/mod v0.4.1/go.mod h1:s0Qsj1ACt9ePp/hMypM3fl4fZqREWJwdYDEqhRiZZUA=
+golang.org/x/mod v0.4.2-0.20210325185522-dbbbf8a3c6ea h1:zAn46O7Vmm6KdLXx+635hPZSArrt/wNctv4Ab70Jw3k=
+golang.org/x/mod v0.4.2-0.20210325185522-dbbbf8a3c6ea/go.mod h1:s0Qsj1ACt9ePp/hMypM3fl4fZqREWJwdYDEqhRiZZUA=
 golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
 golang.org/x/net v0.0.0-20190620200207-3b0461eec859/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
 golang.org/x/net v0.0.0-20201021035429-f5854403a974/go.mod h1:sp8m0HH+o8qH0wwXwYZr8TS3Oi6o0r6Gce1SSxlDquU=

src/cmd/go/alldocs.go

@@ -692,18 +692,22 @@
 // arguments must satisfy the following constraints:
 //
 // - Arguments must be package paths or package patterns (with "..." wildcards).
-//   They must not be standard packages (like fmt), meta-patterns (std, cmd,
-//   all), or relative or absolute file paths.
+// They must not be standard packages (like fmt), meta-patterns (std, cmd,
+// all), or relative or absolute file paths.
+//
 // - All arguments must have the same version suffix. Different queries are not
-//   allowed, even if they refer to the same version.
+// allowed, even if they refer to the same version.
+//
 // - All arguments must refer to packages in the same module at the same version.
+//
 // - No module is considered the "main" module. If the module containing
-//   packages named on the command line has a go.mod file, it must not contain
-//   directives (replace and exclude) that would cause it to be interpreted
-//   differently than if it were the main module. The module must not require
-//   a higher version of itself.
+// packages named on the command line has a go.mod file, it must not contain
+// directives (replace and exclude) that would cause it to be interpreted
+// differently than if it were the main module. The module must not require
+// a higher version of itself.
+//
 // - Package path arguments must refer to main packages. Pattern arguments
-//   will only match main packages.
+// will only match main packages.
 //
 // If the arguments don't have version suffixes, "go install" may run in
 // module-aware mode or GOPATH mode, depending on the GO111MODULE environment

src/cmd/go/internal/get/get.go

@@ -431,7 +431,7 @@ func downloadPackage(p *load.Package) error {
 		}
 		importPrefix = importPrefix[:slash]
 	}
-	if err := module.CheckImportPath(importPrefix); err != nil {
+	if err := checkImportPath(importPrefix); err != nil {
 		return fmt.Errorf("%s: invalid import path: %v", p.ImportPath, err)
 	}
 	security := web.SecureOnly
@@ -591,3 +591,31 @@ func selectTag(goVersion string, tags []string) (match string) {
 	}
 	return ""
 }
+
+// checkImportPath is like module.CheckImportPath, but it forbids leading dots
+// in path elements. This can lead to 'go get' creating .git and other VCS
+// directories in places we might run VCS tools later.
+func checkImportPath(path string) error {
+	if err := module.CheckImportPath(path); err != nil {
+		return err
+	}
+	checkElem := func(elem string) error {
+		if elem[0] == '.' {
+			return fmt.Errorf("malformed import path %q: leading dot in path element", path)
+		}
+		return nil
+	}
+	elemStart := 0
+	for i, r := range path {
+		if r == '/' {
+			if err := checkElem(path[elemStart:]); err != nil {
+				return err
+			}
+			elemStart = i + 1
+		}
+	}
+	if err := checkElem(path[elemStart:]); err != nil {
+		return err
+	}
+	return nil
+}

src/cmd/go/internal/modcmd/download.go

@@ -86,9 +86,11 @@ func runDownload(ctx context.Context, cmd *base.Command, args []string) {
 	if !modload.HasModRoot() && len(args) == 0 {
 		base.Fatalf("go mod download: no modules specified (see 'go help mod download')")
 	}
-	if len(args) == 0 {
+	haveExplicitArgs := len(args) > 0
+	if !haveExplicitArgs {
 		args = []string{"all"}
-	} else if modload.HasModRoot() {
+	}
+	if modload.HasModRoot() {
 		modload.LoadModFile(ctx) // to fill Target
 		targetAtUpgrade := modload.Target.Path + "@upgrade"
 		targetAtPatch := modload.Target.Path + "@patch"
@@ -137,7 +139,20 @@ func runDownload(ctx context.Context, cmd *base.Command, args []string) {
 	listRetractions := false
 	type token struct{}
 	sem := make(chan token, runtime.GOMAXPROCS(0))
-	for _, info := range modload.ListModules(ctx, args, listU, listVersions, listRetractions) {
+	infos := modload.ListModules(ctx, args, listU, listVersions, listRetractions)
+	if !haveExplicitArgs {
+		// 'go mod download' is sometimes run without arguments to pre-populate
+		// the module cache. It may fetch modules that aren't needed to build
+		// packages in the main mdoule. This is usually not intended, so don't save
+		// sums for downloaded modules (golang.org/issue/45332).
+		// TODO(golang.org/issue/45551): For now, save sums needed to load the
+		// build list (same as 1.15 behavior). In the future, report an error if
+		// go.mod or go.sum need to be updated after loading the build list.
+		modload.WriteGoMod()
+		modload.DisallowWriteGoMod()
+	}
+
+	for _, info := range infos {
 		if info.Replace != nil {
 			info = info.Replace
 		}
@@ -187,6 +202,13 @@ func runDownload(ctx context.Context, cmd *base.Command, args []string) {
 		base.ExitIfErrors()
 	}
 
-	// Update go.mod and especially go.sum if needed.
-	modload.WriteGoMod()
+	// If there were explicit arguments, update go.mod and especially go.sum.
+	// 'go mod download mod@version' is a useful way to add a sum without using
+	// 'go get mod@version', which may have other side effects. We print this in
+	// some error message hints.
+	//
+	// Don't save sums for 'go mod download' without arguments; see comment above.
+	if haveExplicitArgs {
+		modload.WriteGoMod()
+	}
 }

src/cmd/go/internal/modcmd/tidy.go

@@ -61,11 +61,14 @@ func runTidy(ctx context.Context, cmd *base.Command, args []string) {
 	modload.ForceUseModules = true
 	modload.RootMode = modload.NeedRoot
 
+	modload.CheckTidyVersion(ctx, tidyE)
+
 	modload.LoadPackages(ctx, modload.PackageOpts{
-		Tags:                  imports.AnyTags(),
-		ResolveMissingImports: true,
-		LoadTests:             true,
-		AllowErrors:           tidyE,
+		Tags:                     imports.AnyTags(),
+		ResolveMissingImports:    true,
+		LoadTests:                true,
+		AllowErrors:              tidyE,
+		SilenceMissingStdImports: true,
 	}, "all")
 
 	modload.TidyBuildList()

src/cmd/go/internal/modcmd/vendor.go

@@ -64,10 +64,11 @@ func runVendor(ctx context.Context, cmd *base.Command, args []string) {
 	modload.RootMode = modload.NeedRoot
 
 	loadOpts := modload.PackageOpts{
-		Tags:                  imports.AnyTags(),
-		ResolveMissingImports: true,
-		UseVendorAll:          true,
-		AllowErrors:           vendorE,
+		Tags:                     imports.AnyTags(),
+		ResolveMissingImports:    true,
+		UseVendorAll:             true,
+		AllowErrors:              vendorE,
+		SilenceMissingStdImports: true,
 	}
 	_, pkgs := modload.LoadPackages(ctx, loadOpts, "all")
 

src/cmd/go/internal/modfetch/cache.go

@@ -84,6 +84,7 @@ func DownloadDir(m module.Version) (string, error) {
 		return "", err
 	}
 
+	// Check whether the directory itself exists.
 	dir := filepath.Join(cfg.GOMODCACHE, enc+"@"+encVer)
 	if fi, err := os.Stat(dir); os.IsNotExist(err) {
 		return dir, err
@@ -92,6 +93,9 @@ func DownloadDir(m module.Version) (string, error) {
 	} else if !fi.IsDir() {
 		return dir, &DownloadDirPartialError{dir, errors.New("not a directory")}
 	}
+
+	// Check if a .partial file exists. This is created at the beginning of
+	// a download and removed after the zip is extracted.
 	partialPath, err := CachePath(m, "partial")
 	if err != nil {
 		return dir, err
@@ -101,6 +105,19 @@ func DownloadDir(m module.Version) (string, error) {
 	} else if !os.IsNotExist(err) {
 		return dir, err
 	}
+
+	// Check if a .ziphash file exists. It should be created before the
+	// zip is extracted, but if it was deleted (by another program?), we need
+	// to re-calculate it.
+	ziphashPath, err := CachePath(m, "ziphash")
+	if err != nil {
+		return dir, err
+	}
+	if _, err := os.Stat(ziphashPath); os.IsNotExist(err) {
+		return dir, &DownloadDirPartialError{dir, errors.New("ziphash file is missing")}
+	} else if err != nil {
+		return dir, err
+	}
 	return dir, nil
 }
 

src/cmd/go/internal/modfetch/fetch.go

@@ -170,13 +170,16 @@ func DownloadZip(ctx context.Context, mod module.Version) (zipfile string, err e
 		if err != nil {
 			return cached{"", err}
 		}
+		ziphashfile := zipfile + "hash"
 
-		// Skip locking if the zipfile already exists.
+		// Return without locking if the zip and ziphash files exist.
 		if _, err := os.Stat(zipfile); err == nil {
-			return cached{zipfile, nil}
+			if _, err := os.Stat(ziphashfile); err == nil {
+				return cached{zipfile, nil}
+			}
 		}
 
-		// The zip file does not exist. Acquire the lock and create it.
+		// The zip or ziphash file does not exist. Acquire the lock and create them.
 		if cfg.CmdName != "mod download" {
 			fmt.Fprintf(os.Stderr, "go: downloading %s %s\n", mod.Path, mod.Version)
 		}
@@ -186,14 +189,6 @@ func DownloadZip(ctx context.Context, mod module.Version) (zipfile string, err e
 		}
 		defer unlock()
 
-		// Double-check that the zipfile was not created while we were waiting for
-		// the lock.
-		if _, err := os.Stat(zipfile); err == nil {
-			return cached{zipfile, nil}
-		}
-		if err := os.MkdirAll(filepath.Dir(zipfile), 0777); err != nil {
-			return cached{"", err}
-		}
 		if err := downloadZip(ctx, mod, zipfile); err != nil {
 			return cached{"", err}
 		}
@@ -206,6 +201,25 @@ func downloadZip(ctx context.Context, mod module.Version, zipfile string) (err e
 	ctx, span := trace.StartSpan(ctx, "modfetch.downloadZip "+zipfile)
 	defer span.Done()
 
+	// Double-check that the zipfile was not created while we were waiting for
+	// the lock in DownloadZip.
+	ziphashfile := zipfile + "hash"
+	var zipExists, ziphashExists bool
+	if _, err := os.Stat(zipfile); err == nil {
+		zipExists = true
+	}
+	if _, err := os.Stat(ziphashfile); err == nil {
+		ziphashExists = true
+	}
+	if zipExists && ziphashExists {
+		return nil
+	}
+
+	// Create parent directories.
+	if err := os.MkdirAll(filepath.Dir(zipfile), 0777); err != nil {
+		return err
+	}
+
 	// Clean up any remaining tempfiles from previous runs.
 	// This is only safe to do because the lock file ensures that their
 	// writers are no longer active.
@@ -217,6 +231,12 @@ func downloadZip(ctx context.Context, mod module.Version, zipfile string) (err e
 		}
 	}
 
+	// If the zip file exists, the ziphash file must have been deleted
+	// or lost after a file system crash. Re-hash the zip without downloading.
+	if zipExists {
+		return hashZip(mod, zipfile, ziphashfile)
+	}
+
 	// From here to the os.Rename call below is functionally almost equivalent to
 	// renameio.WriteToFile, with one key difference: we want to validate the
 	// contents of the file (by hashing it) before we commit it. Because the file
@@ -289,15 +309,7 @@ func downloadZip(ctx context.Context, mod module.Version, zipfile string) (err e
 	}
 
 	// Hash the zip file and check the sum before renaming to the final location.
-	hash, err := dirhash.HashZip(f.Name(), dirhash.DefaultHash)
-	if err != nil {
-		return err
-	}
-	if err := checkModSum(mod, hash); err != nil {
-		return err
-	}
-
-	if err := renameio.WriteFile(zipfile+"hash", []byte(hash), 0666); err != nil {
+	if err := hashZip(mod, f.Name(), ziphashfile); err != nil {
 		return err
 	}
 	if err := os.Rename(f.Name(), zipfile); err != nil {
@@ -309,6 +321,22 @@ func downloadZip(ctx context.Context, mod module.Version, zipfile string) (err e
 	return nil
 }
 
+// hashZip reads the zip file opened in f, then writes the hash to ziphashfile,
+// overwriting that file if it exists.
+//
+// If the hash does not match go.sum (or the sumdb if enabled), hashZip returns
+// an error and does not write ziphashfile.
+func hashZip(mod module.Version, zipfile, ziphashfile string) error {
+	hash, err := dirhash.HashZip(zipfile, dirhash.DefaultHash)
+	if err != nil {
+		return err
+	}
+	if err := checkModSum(mod, hash); err != nil {
+		return err
+	}
+	return renameio.WriteFile(ziphashfile, []byte(hash), 0666)
+}
+
 // makeDirsReadOnly makes a best-effort attempt to remove write permissions for dir
 // and its transitive contents.
 func makeDirsReadOnly(dir string) {
@@ -452,11 +480,6 @@ func HaveSum(mod module.Version) bool {
 
 // checkMod checks the given module's checksum.
 func checkMod(mod module.Version) {
-	if cfg.GOMODCACHE == "" {
-		// Do not use current directory.
-		return
-	}
-
 	// Do the file I/O before acquiring the go.sum lock.
 	ziphash, err := CachePath(mod, "ziphash")
 	if err != nil {
@@ -464,10 +487,6 @@ func checkMod(mod module.Version) {
 	}
 	data, err := renameio.ReadFile(ziphash)
 	if err != nil {
-		if errors.Is(err, fs.ErrNotExist) {
-			// This can happen if someone does rm -rf GOPATH/src/cache/download. So it goes.
-			return
-		}
 		base.Fatalf("verifying %v", module.VersionError(mod, err))
 	}
 	h := strings.TrimSpace(string(data))

src/cmd/go/internal/modget/get.go

@@ -1514,7 +1514,7 @@ func (r *resolver) checkPackagesAndRetractions(ctx context.Context, pkgPatterns
 		}
 	}
 	if retractPath != "" {
-		fmt.Fprintf(os.Stderr, "go: to switch to the latest unretracted version, run:\n\tgo get %s@latest", retractPath)
+		fmt.Fprintf(os.Stderr, "go: to switch to the latest unretracted version, run:\n\tgo get %s@latest\n", retractPath)
 	}
 }
 

src/cmd/go/internal/modget/query.go

@@ -186,7 +186,7 @@ func (q *query) validate() error {
 	if q.pattern == "all" {
 		// If there is no main module, "all" is not meaningful.
 		if !modload.HasModRoot() {
-			return fmt.Errorf(`cannot match "all": working directory is not part of a module`)
+			return fmt.Errorf(`cannot match "all": %v`, modload.ErrNoModRoot)
 		}
 		if !versionOkForMainModule(q.version) {
 			// TODO(bcmills): "all@none" seems like a totally reasonable way to

src/cmd/go/internal/modload/buildlist.go

@@ -11,10 +11,13 @@ import (
 	"cmd/go/internal/mvs"
 	"context"
 	"fmt"
+	"go/build"
 	"os"
 	"strings"
 
+	"golang.org/x/mod/modfile"
 	"golang.org/x/mod/module"
+	"golang.org/x/mod/semver"
 )
 
 // buildList is the list of modules to use for building packages.
@@ -226,6 +229,33 @@ func ReloadBuildList() []module.Version {
 	return capVersionSlice(buildList)
 }
 
+// CheckTidyVersion reports an error to stderr if the Go version indicated by
+// the go.mod file is not supported by this version of the 'go' command.
+//
+// If allowError is false, such an error terminates the program.
+func CheckTidyVersion(ctx context.Context, allowError bool) {
+	LoadModFile(ctx)
+	if index.goVersionV == "" {
+		return
+	}
+
+	tags := build.Default.ReleaseTags
+	maxGo := tags[len(tags)-1]
+	if !strings.HasPrefix(maxGo, "go") || !modfile.GoVersionRE.MatchString(maxGo[2:]) {
+		base.Fatalf("go: unrecognized go version %q", maxGo)
+	}
+	max := maxGo[2:]
+
+	if semver.Compare(index.goVersionV, "v"+max) > 0 {
+		have := index.goVersionV[1:]
+		if allowError {
+			fmt.Fprintf(os.Stderr, "go mod tidy: go.mod file indicates go %s, but maximum supported version is %s\n", have, max)
+		} else {
+			base.Fatalf("go mod tidy: go.mod file indicates go %s, but maximum supported version is %s\n", have, max)
+		}
+	}
+}
+
 // TidyBuildList trims the build list to the minimal requirements needed to
 // retain the same versions of all packages from the preceding call to
 // LoadPackages.

src/cmd/go/internal/modload/import.go

@@ -51,7 +51,7 @@ func (e *ImportMissingError) Error() string {
 		if e.isStd {
 			return fmt.Sprintf("package %s is not in GOROOT (%s)", e.Path, filepath.Join(cfg.GOROOT, "src", e.Path))
 		}
-		if e.QueryErr != nil {
+		if e.QueryErr != nil && e.QueryErr != ErrNoModRoot {
 			return fmt.Sprintf("cannot find module providing package %s: %v", e.Path, e.QueryErr)
 		}
 		if cfg.BuildMod == "mod" || (cfg.BuildMod == "readonly" && allowMissingModuleImports) {
@@ -66,13 +66,11 @@ func (e *ImportMissingError) Error() string {
 			return fmt.Sprintf("module %s provides package %s and is replaced but not required; to add it:\n\tgo get %s", e.replaced.Path, e.Path, suggestArg)
 		}
 
-		suggestion := ""
-		if !HasModRoot() {
-			suggestion = ": working directory is not part of a module"
-		} else {
-			suggestion = fmt.Sprintf("; to add it:\n\tgo get %s", e.Path)
+		message := fmt.Sprintf("no required module provides package %s", e.Path)
+		if e.QueryErr != nil {
+			return fmt.Sprintf("%s: %v", message, e.QueryErr)
 		}
-		return fmt.Sprintf("no required module provides package %s%s", e.Path, suggestion)
+		return fmt.Sprintf("%s; to add it:\n\tgo get %s", message, e.Path)
 	}
 
 	if e.newMissingVersion != "" {
@@ -318,7 +316,11 @@ func importFromBuildList(ctx context.Context, path string, buildList []module.Ve
 		return mods[0], dirs[0], nil
 	}
 
-	return module.Version{}, "", &ImportMissingError{Path: path, isStd: pathIsStd}
+	var queryErr error
+	if !HasModRoot() {
+		queryErr = ErrNoModRoot
+	}
+	return module.Version{}, "", &ImportMissingError{Path: path, QueryErr: queryErr, isStd: pathIsStd}
 }
 
 // queryImport attempts to locate a module that can be added to the current

src/cmd/go/internal/modload/init.go

@@ -177,7 +177,7 @@ func Init() {
 				base.Fatalf("go: cannot find main module, but -modfile was set.\n\t-modfile cannot be used to set the module root directory.")
 			}
 			if RootMode == NeedRoot {
-				base.Fatalf("go: cannot find main module; see 'go help modules'")
+				base.Fatalf("go: %v", ErrNoModRoot)
 			}
 			if !mustUseModules {
 				// GO111MODULE is 'auto', and we can't find a module root.
@@ -338,9 +338,11 @@ func die() {
 		}
 		base.Fatalf("go: cannot find main module, but found %s in %s\n\tto create a module there, run:\n\t%sgo mod init", name, dir, cdCmd)
 	}
-	base.Fatalf("go: cannot find main module; see 'go help modules'")
+	base.Fatalf("go: %v", ErrNoModRoot)
 }
 
+var ErrNoModRoot = errors.New("go.mod file not found in current directory or any parent directory; see 'go help modules'")
+
 // LoadModFile sets Target and, if there is a main module, parses the initial
 // build list from its go.mod file.
 //
@@ -539,9 +541,10 @@ func fixVersion(ctx context.Context, fixed *bool) modfile.VersionFixer {
 			}
 		}
 		if vers != "" && module.CanonicalVersion(vers) == vers {
-			if err := module.CheckPathMajor(vers, pathMajor); err == nil {
-				return vers, nil
+			if err := module.CheckPathMajor(vers, pathMajor); err != nil {
+				return "", module.VersionError(module.Version{Path: path, Version: vers}, err)
 			}
+			return vers, nil
 		}
 
 		info, err := Query(ctx, path, vers, "", nil)

src/cmd/go/internal/modload/list.go

@@ -73,7 +73,7 @@ func listModules(ctx context.Context, args []string, listVersions, listRetracted
 			base.Fatalf("go: cannot use relative path %s to specify module", arg)
 		}
 		if !HasModRoot() && (arg == "all" || strings.Contains(arg, "...")) {
-			base.Fatalf("go: cannot match %q: working directory is not part of a module", arg)
+			base.Fatalf("go: cannot match %q: %v", arg, ErrNoModRoot)
 		}
 		if i := strings.Index(arg, "@"); i >= 0 {
 			path := arg[:i]

src/cmd/go/internal/modload/load.go

@@ -170,6 +170,12 @@ type PackageOpts struct {
 	// that occur while loading packages. SilenceErrors implies AllowErrors.
 	SilenceErrors bool
 
+	// SilenceMissingStdImports indicates that LoadPackages should not print
+	// errors or terminate the process if an imported package is missing, and the
+	// import path looks like it might be in the standard library (perhaps in a
+	// future version).
+	SilenceMissingStdImports bool
+
 	// SilenceUnmatchedWarnings suppresses the warnings normally emitted for
 	// patterns that did not match any packages.
 	SilenceUnmatchedWarnings bool
@@ -287,8 +293,13 @@ func LoadPackages(ctx context.Context, opts PackageOpts, patterns ...string) (ma
 					sumErr.importerIsTest = importer.testOf != nil
 				}
 			}
+			silence := opts.SilenceErrors
+			if stdErr := (*ImportMissingError)(nil); errors.As(pkg.err, &stdErr) &&
+				stdErr.isStd && opts.SilenceMissingStdImports {
+				silence = true
+			}
 
-			if !opts.SilenceErrors {
+			if !silence {
 				if opts.AllowErrors {
 					fmt.Fprintf(os.Stderr, "%s: %v\n", pkg.stackText(), pkg.err)
 				} else {

src/cmd/go/internal/run/run.go

@@ -96,28 +96,12 @@ func runRun(ctx context.Context, cmd *base.Command, args []string) {
 		base.Fatalf("go run: no go files listed")
 	}
 	cmdArgs := args[i:]
-	if p.Error != nil {
-		base.Fatalf("%s", p.Error)
-	}
+	load.CheckPackageErrors([]*load.Package{p})
 
-	p.Internal.OmitDebug = true
-	if len(p.DepsErrors) > 0 {
-		// Since these are errors in dependencies,
-		// the same error might show up multiple times,
-		// once in each package that depends on it.
-		// Only print each once.
-		printed := map[*load.PackageError]bool{}
-		for _, err := range p.DepsErrors {
-			if !printed[err] {
-				printed[err] = true
-				base.Errorf("%s", err)
-			}
-		}
-	}
-	base.ExitIfErrors()
 	if p.Name != "main" {
 		base.Fatalf("go run: cannot run non-main package")
 	}
+	p.Internal.OmitDebug = true
 	p.Target = "" // must build - not up to date
 	if p.Internal.CmdlineFiles {
 		//set executable name if go file is given as cmd-argument

src/cmd/go/internal/work/build.go

@@ -482,18 +482,22 @@ To eliminate ambiguity about which module versions are used in the build, the
 arguments must satisfy the following constraints:
 
 - Arguments must be package paths or package patterns (with "..." wildcards).
-  They must not be standard packages (like fmt), meta-patterns (std, cmd,
-  all), or relative or absolute file paths.
+They must not be standard packages (like fmt), meta-patterns (std, cmd,
+all), or relative or absolute file paths.
+
 - All arguments must have the same version suffix. Different queries are not
-  allowed, even if they refer to the same version.
+allowed, even if they refer to the same version.
+
 - All arguments must refer to packages in the same module at the same version.
+
 - No module is considered the "main" module. If the module containing
-  packages named on the command line has a go.mod file, it must not contain
-  directives (replace and exclude) that would cause it to be interpreted
-  differently than if it were the main module. The module must not require
-  a higher version of itself.
+packages named on the command line has a go.mod file, it must not contain
+directives (replace and exclude) that would cause it to be interpreted
+differently than if it were the main module. The module must not require
+a higher version of itself.
+
 - Package path arguments must refer to main packages. Pattern arguments
-  will only match main packages.
+will only match main packages.
 
 If the arguments don't have version suffixes, "go install" may run in
 module-aware mode or GOPATH mode, depending on the GO111MODULE environment

src/cmd/go/testdata/mod/rsc.io_sampler_v1.2.1.txt

@@ -5,7 +5,7 @@ module "rsc.io/sampler"
 
 require "golang.org/x/text" v0.0.0-20170915032832-14c0d48ead0c
 -- .info --
-{"Version":"v1.2.1","Name":"cac3af4f8a0ab40054fa6f8d423108a63a1255bb","Short":"cac3af4f8a0a","Time":"2018-02-13T18:16:22Z"}EOF
+{"Version":"v1.2.1","Name":"cac3af4f8a0ab40054fa6f8d423108a63a1255bb","Short":"cac3af4f8a0a","Time":"2018-02-13T18:16:22Z"}
 -- hello.go --
 // Copyright 2018 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style

src/cmd/go/testdata/script/mod_convert_dep.txt

@@ -18,7 +18,7 @@ stdout '^m$'
 # Test that we ignore directories when trying to find alternate config files.
 cd $WORK/gopkgdir/x
 ! go list .
-stderr 'cannot find main module'
+stderr '^go: go.mod file not found in current directory or any parent directory; see ''go help modules''$'
 ! stderr 'Gopkg.lock'
 
 -- $WORK/test/Gopkg.lock --

src/cmd/go/testdata/script/mod_download.txt

@@ -107,13 +107,28 @@ stderr '^go mod download: skipping argument m that resolves to the main module\n
 ! go mod download m@latest
 stderr '^go mod download: m@latest: malformed module path "m": missing dot in first path element$'
 
-# download updates go.mod and populates go.sum
+# download without arguments updates go.mod and go.sum after loading the
+# build list, but does not save sums for downloaded zips.
 cd update
+cp go.mod.orig go.mod
 ! exists go.sum
 go mod download
+cmp go.mod.update go.mod
+cmp go.sum.update go.sum
+cp go.mod.orig go.mod
+rm go.sum
+
+# download with arguments (even "all") does update go.mod and go.sum.
+go mod download rsc.io/sampler
+cmp go.mod.update go.mod
 grep '^rsc.io/sampler v1.3.0 ' go.sum
-go list -m rsc.io/sampler
-stdout '^rsc.io/sampler v1.3.0$'
+cp go.mod.orig go.mod
+rm go.sum
+
+go mod download all
+cmp go.mod.update go.mod
+grep '^rsc.io/sampler v1.3.0 ' go.sum
+cd ..
 
 # allow go mod download without go.mod
 env GO111MODULE=auto
@@ -131,7 +146,7 @@ stderr 'get '$GOPROXY
 -- go.mod --
 module m
 
--- update/go.mod --
+-- update/go.mod.orig --
 module m
 
 go 1.16
@@ -140,3 +155,16 @@ require (
 	rsc.io/quote v1.5.2
 	rsc.io/sampler v1.2.1 // older version than in build list
 )
+-- update/go.mod.update --
+module m
+
+go 1.16
+
+require (
+	rsc.io/quote v1.5.2
+	rsc.io/sampler v1.3.0 // older version than in build list
+)
+-- update/go.sum.update --
+golang.org/x/text v0.0.0-20170915032832-14c0d48ead0c/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
+rsc.io/quote v1.5.2/go.mod h1:LzX7hefJvL54yjefDEDHNONDjII0t9xZLPXsUe+TKr0=
+rsc.io/sampler v1.3.0/go.mod h1:T1hPZKmBbMNahiBKFy5HrXp6adAjACjK9JXDnKaTXpA=

src/cmd/go/testdata/script/mod_edit.txt

@@ -16,9 +16,9 @@ cmpenv go.mod $WORK/go.mod.init
 cmpenv go.mod $WORK/go.mod.init
 
 # go mod edits
-go mod edit -droprequire=x.1 -require=x.1@v1.0.0 -require=x.2@v1.1.0 -droprequire=x.2 -exclude='x.1 @ v1.2.0' -exclude=x.1@v1.2.1 -replace=x.1@v1.3.0=y.1@v1.4.0 -replace='x.1@v1.4.0 = ../z' -retract=v1.6.0 -retract=[v1.1.0,v1.2.0] -retract=[v1.3.0,v1.4.0] -retract=v1.0.0
+go mod edit -droprequire=x.1 -require=x.1@v1.0.0 -require=x.2@v1.1.0 -droprequire=x.2 -exclude='x.1 @ v1.2.0' -exclude=x.1@v1.2.1 -exclude=x.1@v2.0.0+incompatible -replace=x.1@v1.3.0=y.1@v1.4.0 -replace='x.1@v1.4.0 = ../z' -retract=v1.6.0 -retract=[v1.1.0,v1.2.0] -retract=[v1.3.0,v1.4.0] -retract=v1.0.0
 cmpenv go.mod $WORK/go.mod.edit1
-go mod edit -droprequire=x.1 -dropexclude=x.1@v1.2.1 -dropreplace=x.1@v1.3.0 -require=x.3@v1.99.0 -dropretract=v1.0.0 -dropretract=[v1.1.0,v1.2.0]
+go mod edit -droprequire=x.1 -dropexclude=x.1@v1.2.1 -dropexclude=x.1@v2.0.0+incompatible -dropreplace=x.1@v1.3.0 -require=x.3@v1.99.0 -dropretract=v1.0.0 -dropretract=[v1.1.0,v1.2.0]
 cmpenv go.mod $WORK/go.mod.edit2
 
 # -exclude and -retract reject invalid versions.
@@ -27,6 +27,17 @@ stderr '^go mod: -exclude=example.com/m@bad: version "bad" invalid: must be of t
 ! go mod edit -retract=bad
 stderr '^go mod: -retract=bad: version "bad" invalid: must be of the form v1.2.3$'
 
+! go mod edit -exclude=example.com/m@v2.0.0
+stderr '^go mod: -exclude=example.com/m@v2\.0\.0: version "v2\.0\.0" invalid: should be v2\.0\.0\+incompatible \(or module example\.com/m/v2\)$'
+
+! go mod edit -exclude=example.com/m/v2@v1.0.0
+stderr '^go mod: -exclude=example.com/m/v2@v1\.0\.0: version "v1\.0\.0" invalid: should be v2, not v1$'
+
+! go mod edit -exclude=gopkg.in/example.v1@v2.0.0
+stderr '^go mod: -exclude=gopkg\.in/example\.v1@v2\.0\.0: version "v2\.0\.0" invalid: should be v1, not v2$'
+
+cmpenv go.mod $WORK/go.mod.edit2
+
 # go mod edit -json
 go mod edit -json
 cmpenv stdout $WORK/go.mod.json
@@ -88,6 +99,7 @@ require x.1 v1.0.0
 exclude (
 	x.1 v1.2.0
 	x.1 v1.2.1
+	x.1 v2.0.0+incompatible
 )
 
 replace (

src/cmd/go/testdata/script/mod_find.txt

@@ -49,7 +49,7 @@ rm go.mod
 # Test that we ignore directories when trying to find go.mod.
 cd $WORK/gomoddir
 ! go list .
-stderr 'cannot find main module'
+stderr '^go: go.mod file not found in current directory or any parent directory; see ''go help modules''$'
 
 [!symlink] stop
 

src/cmd/go/testdata/script/mod_get_missing_ziphash.txt

@@ -0,0 +1,55 @@
+# Test that if the module cache contains an extracted source directory but not
+# a ziphash, 'go build' complains about a missing sum, and 'go get' adds
+# the sum. Verifies #44749.
+
+# With a tidy go.sum, go build succeeds. This also populates the module cache.
+cp go.sum.tidy go.sum
+go build -n use
+env GOPROXY=off
+env GOSUMDB=off
+
+# Control case: if we delete the hash for rsc.io/quote v1.5.2,
+# 'go build' reports an error. 'go get' adds the sum.
+cp go.sum.bug go.sum
+! go build -n use
+stderr '^use.go:3:8: missing go.sum entry for module providing package rsc.io/quote \(imported by use\); to add:\n\tgo get use$'
+go get -d use
+cmp go.sum go.sum.tidy
+go build -n use
+
+# If we delete the hash *and* the ziphash file, we should see the same behavior.
+cp go.sum.bug go.sum
+rm $WORK/gopath/pkg/mod/cache/download/rsc.io/quote/@v/v1.5.2.ziphash
+! go build -n use
+stderr '^use.go:3:8: missing go.sum entry for module providing package rsc.io/quote \(imported by use\); to add:\n\tgo get use$'
+go get -d use
+cmp go.sum go.sum.tidy
+go build -n use
+
+-- go.mod --
+module use
+
+go 1.17
+
+require rsc.io/quote v1.5.2
+-- go.sum.tidy --
+golang.org/x/text v0.0.0-20170915032832-14c0d48ead0c h1:pvCbr/wm8HzDD3fVywevekufpn6tCGPY3spdHeZJEsw=
+golang.org/x/text v0.0.0-20170915032832-14c0d48ead0c/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
+rsc.io/quote v1.5.2 h1:3fEykkD9k7lYzXqCYrwGAf7iNhbk4yCjHmKBN9td4L0=
+rsc.io/quote v1.5.2/go.mod h1:LzX7hefJvL54yjefDEDHNONDjII0t9xZLPXsUe+TKr0=
+rsc.io/sampler v1.3.0 h1:HLGR/BgEtI3r0uymSP/nl2uPLsUnNJX8toRyhfpBTII=
+rsc.io/sampler v1.3.0/go.mod h1:T1hPZKmBbMNahiBKFy5HrXp6adAjACjK9JXDnKaTXpA=
+rsc.io/testonly v1.0.0 h1:K/VWHdO+Jv7woUXG0GzVNx1czBXUt3Ib1deaMn+xk64=
+rsc.io/testonly v1.0.0/go.mod h1:OqmGbIFOcF+XrFReLOGZ6BhMM7uMBiQwZsyNmh74SzY=
+-- go.sum.bug --
+golang.org/x/text v0.0.0-20170915032832-14c0d48ead0c h1:pvCbr/wm8HzDD3fVywevekufpn6tCGPY3spdHeZJEsw=
+golang.org/x/text v0.0.0-20170915032832-14c0d48ead0c/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
+rsc.io/quote v1.5.2/go.mod h1:LzX7hefJvL54yjefDEDHNONDjII0t9xZLPXsUe+TKr0=
+rsc.io/sampler v1.3.0 h1:HLGR/BgEtI3r0uymSP/nl2uPLsUnNJX8toRyhfpBTII=
+rsc.io/sampler v1.3.0/go.mod h1:T1hPZKmBbMNahiBKFy5HrXp6adAjACjK9JXDnKaTXpA=
+rsc.io/testonly v1.0.0 h1:K/VWHdO+Jv7woUXG0GzVNx1czBXUt3Ib1deaMn+xk64=
+rsc.io/testonly v1.0.0/go.mod h1:OqmGbIFOcF+XrFReLOGZ6BhMM7uMBiQwZsyNmh74SzY=
+-- use.go --
+package use
+
+import _ "rsc.io/quote"

src/cmd/go/testdata/script/mod_get_retract.txt

@@ -11,7 +11,7 @@ cp go.mod.orig go.mod
 go mod edit -require example.com/retract/self/prev@v1.9.0
 go get -d example.com/retract/self/prev
 stderr '^go: warning: example.com/retract/self/prev@v1.9.0: retracted by module author: self$'
-stderr '^go: to switch to the latest unretracted version, run:\n\tgo get example.com/retract/self/prev@latest$'
+stderr '^go: to switch to the latest unretracted version, run:\n\tgo get example.com/retract/self/prev@latest\n$'
 go list -m example.com/retract/self/prev
 stdout '^example.com/retract/self/prev v1.9.0$'
 

src/cmd/go/testdata/script/mod_get_trailing_slash.txt

@@ -1,6 +1,3 @@
-# Populate go.sum
-go mod download
-
 # go list should succeed to load a package ending with ".go" if the path does
 # not correspond to an existing local file. Listing a pattern ending with
 # ".go/" should try to list a package regardless of whether a file exists at the
@@ -31,3 +28,10 @@ module m
 go 1.13
 
 require example.com/dotgo.go v1.0.0
+-- go.sum --
+example.com/dotgo.go v1.0.0 h1:XKJfs0V8x2PvY2tX8bJBCEbCDLnt15ma2onwhVpew/I=
+example.com/dotgo.go v1.0.0/go.mod h1:Qi6z/X3AC5vHiuMt6HF2ICx3KhIBGrMdrA7YoPDKqR0=
+-- use.go --
+package use
+
+import _ "example.com/dotgo.go"

src/cmd/go/testdata/script/mod_install_pkg_version.txt

@@ -59,9 +59,9 @@ rm $GOPATH/bin
 env GO111MODULE=on
 go mod download rsc.io/fortune@v1.0.0
 ! go install $GOPATH/pkg/mod/rsc.io/fortune@v1.0.0
-stderr '^go: cannot find main module; see ''go help modules''$'
+stderr '^go: go\.mod file not found in current directory or any parent directory; see ''go help modules''$'
 ! go install ../pkg/mod/rsc.io/fortune@v1.0.0
-stderr '^go: cannot find main module; see ''go help modules''$'
+stderr '^go: go\.mod file not found in current directory or any parent directory; see ''go help modules''$'
 mkdir tmp
 cd tmp
 go mod init tmp

src/cmd/go/testdata/script/mod_invalid_path.txt

@@ -23,6 +23,20 @@ cd $WORK/gopath/src/badname
 ! go list .
 stderr 'invalid module path'
 
+# Test that an import path containing an element with a leading dot is valid,
+# but such a module path is not.
+# Verifies #43985.
+cd $WORK/gopath/src/dotname
+go list ./.dot
+stdout '^example.com/dotname/.dot$'
+go list ./use
+stdout '^example.com/dotname/use$'
+! go list -m example.com/dotname/.dot@latest
+stderr '^go list -m: example.com/dotname/.dot@latest: malformed module path "example.com/dotname/.dot": leading dot in path element$'
+go get -d example.com/dotname/.dot
+go get -d example.com/dotname/use
+go mod tidy
+
 -- mod/go.mod --
 
 -- mod/foo.go --
@@ -38,3 +52,13 @@ module .\.
 -- badname/foo.go --
 package badname
 
+-- dotname/go.mod --
+module example.com/dotname
+
+go 1.16
+-- dotname/.dot/dot.go --
+package dot
+-- dotname/use/use.go --
+package use
+
+import _ "example.com/dotname/.dot"

src/cmd/go/testdata/script/mod_invalid_path_plus.txt

@@ -0,0 +1,32 @@
+# https://golang.org/issue/44776
+# The '+' character should be disallowed in module paths, but allowed in package
+# paths within valid modules.
+
+go get -d example.net/cmd
+go list example.net/cmd/x++
+
+! go list -versions -m 'example.net/bad++'
+stderr '^go list -m: module example.net/bad\+\+: malformed module path "example.net/bad\+\+": invalid char ''\+''$'
+
+# TODO(bcmills): 'go get -d example.net/cmd/x++' should also work, but currently
+# it does not. This might be fixed by https://golang.org/cl/297891.
+! go get -d example.net/cmd/x++
+stderr '^go get: malformed module path "example.net/cmd/x\+\+": invalid char ''\+''$'
+
+-- go.mod --
+module example.com/m
+
+go 1.16
+
+replace (
+	example.net/cmd => ./cmd
+)
+
+-- cmd/go.mod --
+module example.net/cmd
+
+go 1.16
+-- cmd/x++/main.go --
+package main
+
+func main() {}

src/cmd/go/testdata/script/mod_outside.txt

@@ -12,13 +12,13 @@ stdout 'NUL|/dev/null'
 # 'go list' without arguments implicitly operates on the current directory,
 # which is not in a module.
 ! go list
-stderr 'cannot find main module'
+stderr '^go: go.mod file not found in current directory or any parent directory; see ''go help modules''$'
 go list -m
 stdout '^command-line-arguments$'
 # 'go list' in the working directory should fail even if there is a a 'package
 # main' present: without a main module, we do not know its package path.
 ! go list ./needmod
-stderr 'cannot find main module'
+stderr '^go: go.mod file not found in current directory or any parent directory; see ''go help modules''$'
 
 # 'go list all' lists the transitive import graph of the main module,
 # which is empty if there is no main module.
@@ -41,7 +41,7 @@ stdout 'command-line-arguments'
 
 # 'go list' on a package from a module should fail.
 ! go list example.com/printversion
-stderr '^no required module provides package example.com/printversion: working directory is not part of a module$'
+stderr '^no required module provides package example.com/printversion: go.mod file not found in current directory or any parent directory; see ''go help modules''$'
 
 
 # 'go list -m' with an explicit version should resolve that version.
@@ -54,19 +54,19 @@ stdout 'v1.0.0\s+v1.0.1\s+v1.1.0'
 
 # 'go list -m all' should fail. "all" is not meaningful outside of a module.
 ! go list -m all
-stderr 'go: cannot match "all": working directory is not part of a module'
+stderr 'go: cannot match "all": go.mod file not found in current directory or any parent directory; see ''go help modules''$'
 
 # 'go list -m <mods> all' should also fail.
 ! go list -m example.com/printversion@v1.0.0 all
-stderr 'go: cannot match "all": working directory is not part of a module'
+stderr 'go: cannot match "all": go.mod file not found in current directory or any parent directory; see ''go help modules''$'
 ! stdout 'example.com/version'
 
 # 'go list -m' with wildcards should fail. Wildcards match modules in the
 # build list, so they aren't meaningful outside a module.
 ! go list -m ...
-stderr 'go: cannot match "...": working directory is not part of a module'
+stderr 'go: cannot match "...": go.mod file not found in current directory or any parent directory; see ''go help modules''$'
 ! go list -m rsc.io/quote/...
-stderr 'go: cannot match "rsc.io/quote/...": working directory is not part of a module'
+stderr 'go: cannot match "rsc.io/quote/...": go.mod file not found in current directory or any parent directory; see ''go help modules''$'
 
 
 # 'go clean' should skip the current directory if it isn't in a module.
@@ -76,20 +76,20 @@ go clean -n
 
 # 'go mod graph' should fail, since there's no module graph.
 ! go mod graph
-stderr 'cannot find main module'
+stderr '^go: go.mod file not found in current directory or any parent directory; see ''go help modules''$'
 
 # 'go mod why' should fail, since there is no main module to depend on anything.
 ! go mod why -m example.com/version
-stderr 'cannot find main module'
+stderr '^go: go.mod file not found in current directory or any parent directory; see ''go help modules''$'
 
 # 'go mod edit', 'go mod tidy', and 'go mod fmt' should fail:
 # there is no go.mod file to edit.
 ! go mod tidy
-stderr 'cannot find main module'
+stderr '^go: go.mod file not found in current directory or any parent directory; see ''go help modules''$'
 ! go mod edit -fmt
-stderr 'cannot find main module'
+stderr '^go: go.mod file not found in current directory or any parent directory; see ''go help modules''$'
 ! go mod edit -require example.com/version@v1.0.0
-stderr 'cannot find main module'
+stderr '^go: go.mod file not found in current directory or any parent directory; see ''go help modules''$'
 
 
 # 'go mod download' without arguments should report an error.
@@ -104,33 +104,33 @@ exists $GOPATH/pkg/mod/cache/download/example.com/printversion/@v/v1.0.0.zip
 
 # 'go mod download all' should fail. "all" is not meaningful outside of a module.
 ! go mod download all
-stderr 'go: cannot match "all": working directory is not part of a module'
+stderr 'go: cannot match "all": go.mod file not found in current directory or any parent directory; see ''go help modules''$'
 
 
 # 'go mod vendor' should fail: it starts by clearing the existing vendor
 # directory, and we don't know where that is.
 ! go mod vendor
-stderr 'cannot find main module'
+stderr '^go: go.mod file not found in current directory or any parent directory; see ''go help modules''$'
 
 
 # 'go mod verify' should fail: we have no modules to verify.
 ! go mod verify
-stderr 'cannot find main module'
+stderr '^go: go.mod file not found in current directory or any parent directory; see ''go help modules''$'
 
 
 # 'go get' without arguments implicitly operates on the main module, and thus
 # should fail.
 ! go get
-stderr 'cannot find main module'
+stderr '^go: go.mod file not found in current directory or any parent directory; see ''go help modules''$'
 ! go get -u
-stderr 'cannot find main module'
+stderr '^go: go.mod file not found in current directory or any parent directory; see ''go help modules''$'
 ! go get -u ./needmod
-stderr 'cannot find main module'
+stderr '^go: go.mod file not found in current directory or any parent directory; see ''go help modules''$'
 
 # 'go get -u all' upgrades the transitive import graph of the main module,
 # which is empty.
 ! go get -u all
-stderr 'go get: cannot match "all": working directory is not part of a module'
+stderr '^go get: cannot match "all": go.mod file not found in current directory or any parent directory; see ''go help modules''$'
 
 # 'go get' should check the proposed module graph for consistency,
 # even though we won't write it anywhere.
@@ -147,16 +147,16 @@ exists $GOPATH/pkg/mod/example.com/version@v1.0.0
 # 'go build' without arguments implicitly operates on the current directory, and should fail.
 cd needmod
 ! go build
-stderr 'cannot find main module'
+stderr '^go: go.mod file not found in current directory or any parent directory; see ''go help modules''$'
 cd ..
 
 # 'go build' of a non-module directory should fail too.
 ! go build ./needmod
-stderr 'cannot find main module'
+stderr '^go: go.mod file not found in current directory or any parent directory; see ''go help modules''$'
 
 # 'go build' of source files should fail if they import anything outside std.
 ! go build -n ./needmod/needmod.go
-stderr '^needmod[/\\]needmod.go:10:2: no required module provides package example.com/version: working directory is not part of a module$'
+stderr '^needmod[/\\]needmod.go:10:2: no required module provides package example.com/version: go.mod file not found in current directory or any parent directory; see ''go help modules''$'
 
 # 'go build' of source files should succeed if they do not import anything outside std.
 go build -n -o ignore ./stdonly/stdonly.go
@@ -179,7 +179,7 @@ go doc fmt
 
 # 'go doc' should fail for a package path outside a module.
 ! go doc example.com/version
-stderr 'doc: no required module provides package example.com/version: working directory is not part of a module'
+stderr 'doc: no required module provides package example.com/version: go.mod file not found in current directory or any parent directory; see ''go help modules''$'
 
 # 'go install' with a version should succeed if all constraints are met.
 # See mod_install_pkg_version.
@@ -194,7 +194,7 @@ stderr '^go install: version is required when current directory is not in a modu
 # 'go install' should fail if a source file imports a package that must be
 # resolved to a module.
 ! go install ./needmod/needmod.go
-stderr 'needmod[/\\]needmod.go:10:2: no required module provides package example.com/version: working directory is not part of a module'
+stderr 'needmod[/\\]needmod.go:10:2: no required module provides package example.com/version: go.mod file not found in current directory or any parent directory; see ''go help modules''$'
 
 # 'go install' should succeed with a package in GOROOT.
 go install cmd/addr2line
@@ -206,12 +206,12 @@ stderr 'can only use path@version syntax with'
 
 # 'go run' should fail if a package argument must be resolved to a module.
 ! go run example.com/printversion
-stderr '^no required module provides package example.com/printversion: working directory is not part of a module$'
+stderr '^no required module provides package example.com/printversion: go.mod file not found in current directory or any parent directory; see ''go help modules''$'
 
 # 'go run' should fail if a source file imports a package that must be
 # resolved to a module.
 ! go run ./needmod/needmod.go
-stderr '^needmod[/\\]needmod.go:10:2: no required module provides package example.com/version: working directory is not part of a module$'
+stderr '^needmod[/\\]needmod.go:10:2: no required module provides package example.com/version: go.mod file not found in current directory or any parent directory; see ''go help modules''$'
 
 
 # 'go fmt' should be able to format files outside of a module.

src/cmd/go/testdata/script/mod_query.txt

@@ -1,9 +1,7 @@
 env GO111MODULE=on
 
-# Populate go.sum.
 # TODO(golang.org/issue/41297): we shouldn't need go.sum. None of the commands
 # below depend on the build list.
-go mod download
 
 go list -m -versions rsc.io/quote
 stdout '^rsc.io/quote v1.0.0 v1.1.0 v1.2.0 v1.2.1 v1.3.0 v1.4.0 v1.5.0 v1.5.1 v1.5.2 v1.5.3-pre1$'
@@ -36,6 +34,9 @@ stdout 'no matching versions for query ">v1.5.3"'
 module x
 require rsc.io/quote v1.0.0
 
+-- go.sum --
+rsc.io/quote v1.0.0 h1:kQ3IZQzPTiDJxSZI98YaWgxFEhlNdYASHvh+MplbViw=
+rsc.io/quote v1.0.0/go.mod h1:v83Ri/njykPcgJltBc/gEkJTmjTsNgtO1Y7vyIK1CQA=
 -- use.go --
 package use
 

src/cmd/go/testdata/script/mod_readonly.txt

@@ -89,7 +89,7 @@ stderr '^no required module provides package rsc.io/quote; to add it:\n\tgo get
 -- go.mod --
 module m
 
-go 1.20
+go 1.16
 
 -- x.go --
 package x
@@ -104,7 +104,7 @@ require (
 -- go.mod.redundant --
 module m
 
-go 1.20
+go 1.16
 
 require (
 	rsc.io/quote v1.5.2
@@ -114,7 +114,7 @@ require (
 -- go.mod.indirect --
 module m
 
-go 1.20
+go 1.16
 
 require (
 	rsc.io/quote v1.5.2 // indirect
@@ -124,7 +124,7 @@ require (
 -- go.mod.untidy --
 module m
 
-go 1.20
+go 1.16
 
 require (
 	rsc.io/sampler v1.3.0 // indirect

src/cmd/go/testdata/script/mod_retract.txt

@@ -1,8 +1,5 @@
 cp go.mod go.mod.orig
 
-# Populate go.sum.
-go mod download
-
 # 'go list pkg' does not report an error when a retracted version is used.
 go list -e -f '{{if .Error}}{{.Error}}{{end}}' ./use
 ! stdout .
@@ -32,6 +29,11 @@ go 1.15
 
 require example.com/retract v1.0.0-bad
 
+-- go.sum --
+example.com/retract v1.0.0-bad h1:liAW69rbtjY67x2CcNzat668L/w+YGgNX3lhJsWIJis=
+example.com/retract v1.0.0-bad/go.mod h1:0DvGGofJ9hr1q63cBrOY/jSY52OwhRGA0K47NE80I5Y=
+example.com/retract/self/prev v1.1.0 h1:0/8I/GTG+1eJTFeDQ/fUbgrMsVHHyKhh3Z8DSZp1fuA=
+example.com/retract/self/prev v1.1.0/go.mod h1:xl2EcklWuZZHVtHWcpzfSJQmnzAGpKZYpA/Wto7SZN4=
 -- use/use.go --
 package use
 

src/cmd/go/testdata/script/mod_retract_fix_version.txt

@@ -0,0 +1,48 @@
+# retract must not be used without a module directive.
+! go list -m all
+stderr 'go.mod:3: no module directive found, so retract cannot be used$'
+
+# Commands that update go.mod should fix non-canonical versions in
+# retract directives.
+# Verifies #44494.
+go mod edit -module=rsc.io/quote/v2
+! go list -m all
+stderr '^go: updates to go.mod needed; to update it:\n\tgo mod tidy$'
+go mod tidy
+go list -m all
+cmp go.mod go.mod.want
+
+# If a retracted version doesn't match the module's major version suffx,
+# an error should be reported.
+! go mod edit -retract=v3.0.1
+stderr '^go mod: -retract=v3.0.1: version "v3.0.1" invalid: should be v2, not v3$'
+cp go.mod.mismatch-v2 go.mod
+! go list -m all
+stderr 'go.mod:3: retract rsc.io/quote/v2: version "v3.0.1" invalid: should be v2, not v3$'
+
+cp go.mod.mismatch-v1 go.mod
+! go list -m all
+stderr 'go.mod:3: retract rsc.io/quote: version "v3.0.1" invalid: should be v0 or v1, not v3$'
+
+-- go.mod --
+go 1.16
+
+retract latest
+-- go.mod.want --
+go 1.16
+
+retract v2.0.1
+
+module rsc.io/quote/v2
+-- go.mod.mismatch-v2 --
+go 1.16
+
+retract v3.0.1
+
+module rsc.io/quote/v2
+-- go.mod.mismatch-v1 --
+go 1.16
+
+retract v3.0.1
+
+module rsc.io/quote

src/cmd/go/testdata/script/mod_tidy_error.txt

@@ -4,12 +4,12 @@ env GO111MODULE=on
 # 'go mod tidy' and 'go mod vendor' should not hide loading errors.
 
 ! go mod tidy
-stderr '^issue27063 imports\n\tnonexist: package nonexist is not in GOROOT \(.*\)'
+! stderr 'package nonexist is not in GOROOT'
 stderr '^issue27063 imports\n\tnonexist.example.com: cannot find module providing package nonexist.example.com'
 stderr '^issue27063 imports\n\tissue27063/other imports\n\tother.example.com/nonexist: cannot find module providing package other.example.com/nonexist'
 
 ! go mod vendor
-stderr '^issue27063 imports\n\tnonexist: package nonexist is not in GOROOT \(.*\)'
+! stderr 'package nonexist is not in GOROOT'
 stderr '^issue27063 imports\n\tnonexist.example.com: cannot find module providing package nonexist.example.com'
 stderr '^issue27063 imports\n\tissue27063/other imports\n\tother.example.com/nonexist: cannot find module providing package other.example.com/nonexist'
 

src/cmd/go/testdata/script/mod_tidy_too_new.txt

@@ -0,0 +1,48 @@
+# https://golang.org/issue/46142: 'go mod tidy' should error out if the version
+# in the go.mod file is newer than the most recent supported version.
+
+cp go.mod go.mod.orig
+
+
+# If the go.mod file specifies an unsupported Go version, 'go mod tidy' should
+# refuse to edit it: we don't know what a tidy go.mod file for that version
+# would look like.
+
+! go mod tidy
+stderr 'go mod tidy: go.mod file indicates go 2000.0, but maximum supported version is '$goversion'$'
+cmp go.mod go.mod.orig
+
+
+# The -e flag should push past the error and edit the file anyway,
+# but preserve the too-high version.
+
+cp go.mod.orig go.mod
+go mod tidy -e
+stderr 'go mod tidy: go.mod file indicates go 2000.0, but maximum supported version is '$goversion'$'
+cmp go.mod go.mod.tidy
+
+
+-- go.mod --
+module example.net/from/the/future
+
+go 2000.0
+
+replace example.net/m v0.0.0 => ./m
+-- go.mod.tidy --
+module example.net/from/the/future
+
+go 2000.0
+
+replace example.net/m v0.0.0 => ./m
+
+require example.net/m v0.0.0
+-- x.go --
+package x
+
+import "example.net/m"
+-- m/go.mod --
+module example.net/m
+
+go 1.17
+-- m/m.go --
+package m

src/cmd/go/testdata/script/mod_verify.txt

@@ -48,10 +48,13 @@ go mod tidy
 grep '^rsc.io/quote v1.1.0/go.mod ' go.sum
 grep '^rsc.io/quote v1.1.0 ' go.sum
 
-# sync should ignore missing ziphash; verify should not
+# verify should fail on a missing ziphash. tidy should restore it.
 rm $GOPATH/pkg/mod/cache/download/rsc.io/quote/@v/v1.1.0.ziphash
-go mod tidy
 ! go mod verify
+stderr '^rsc.io/quote v1.1.0: missing ziphash: open '$GOPATH'[/\\]pkg[/\\]mod[/\\]cache[/\\]download[/\\]rsc.io[/\\]quote[/\\]@v[/\\]v1.1.0.ziphash'
+go mod tidy
+exists $GOPATH/pkg/mod/cache/download/rsc.io/quote/@v/v1.1.0.ziphash
+go mod verify
 
 # Packages below module root should not be mentioned in go.sum.
 rm go.sum

src/cmd/link/internal/arm/asm.go

@@ -370,10 +370,16 @@ func trampoline(ctxt *ld.Link, ldr *loader.Loader, ri int, rs, s loader.Sym) {
 	r := relocs.At(ri)
 	switch r.Type() {
 	case objabi.R_CALLARM:
-		// r.Add is the instruction
-		// low 24-bit encodes the target address
-		t := (ldr.SymValue(rs) + int64(signext24(r.Add()&0xffffff)*4) - (ldr.SymValue(s) + int64(r.Off()))) / 4
-		if t > 0x7fffff || t < -0x800000 || (*ld.FlagDebugTramp > 1 && ldr.SymPkg(s) != ldr.SymPkg(rs)) {
+		var t int64
+		// ldr.SymValue(rs) == 0 indicates a cross-package jump to a function that is not yet
+		// laid out. Conservatively use a trampoline. This should be rare, as we lay out packages
+		// in dependency order.
+		if ldr.SymValue(rs) != 0 {
+			// r.Add is the instruction
+			// low 24-bit encodes the target address
+			t = (ldr.SymValue(rs) + int64(signext24(r.Add()&0xffffff)*4) - (ldr.SymValue(s) + int64(r.Off()))) / 4
+		}
+		if t > 0x7fffff || t < -0x800000 || ldr.SymValue(rs) == 0 || (*ld.FlagDebugTramp > 1 && ldr.SymPkg(s) != ldr.SymPkg(rs)) {
 			// direct call too far, need to insert trampoline.
 			// look up existing trampolines first. if we found one within the range
 			// of direct call, we can reuse it. otherwise create a new one.
@@ -445,7 +451,7 @@ func gentramp(arch *sys.Arch, linkmode ld.LinkMode, ldr *loader.Loader, tramp *l
 	arch.ByteOrder.PutUint32(P[8:], o3)
 	tramp.SetData(P)
 
-	if linkmode == ld.LinkExternal {
+	if linkmode == ld.LinkExternal || ldr.SymValue(target) == 0 {
 		r, _ := tramp.AddRel(objabi.R_ADDR)
 		r.SetOff(8)
 		r.SetSiz(4)

src/cmd/link/internal/ld/data.go

@@ -106,14 +106,12 @@ func trampoline(ctxt *Link, s loader.Sym) {
 		}
 		rs = ldr.ResolveABIAlias(rs)
 		if ldr.SymValue(rs) == 0 && (ldr.SymType(rs) != sym.SDYNIMPORT && ldr.SymType(rs) != sym.SUNDEFEXT) {
-			if ldr.SymPkg(rs) != ldr.SymPkg(s) {
-				if !isRuntimeDepPkg(ldr.SymPkg(s)) || !isRuntimeDepPkg(ldr.SymPkg(rs)) {
-					ctxt.Errorf(s, "unresolved inter-package jump to %s(%s) from %s", ldr.SymName(rs), ldr.SymPkg(rs), ldr.SymPkg(s))
-				}
-				// runtime and its dependent packages may call to each other.
-				// they are fine, as they will be laid down together.
+			if ldr.SymPkg(rs) == ldr.SymPkg(s) {
+				continue // symbols in the same package are laid out together
+			}
+			if isRuntimeDepPkg(ldr.SymPkg(s)) && isRuntimeDepPkg(ldr.SymPkg(rs)) {
+				continue // runtime packages are laid out together
 			}
-			continue
 		}
 
 		thearch.Trampoline(ctxt, ldr, ri, rs, s)

src/cmd/link/internal/ld/deadcode.go

@@ -24,6 +24,7 @@ type deadcodePass struct {
 	ifaceMethod     map[methodsig]bool // methods declared in reached interfaces
 	markableMethods []methodref        // methods of reached types
 	reflectSeen     bool               // whether we have seen a reflect method call
+	dynlink         bool
 
 	methodsigstmp []methodsig // scratch buffer for decoding method signatures
 }
@@ -34,6 +35,7 @@ func (d *deadcodePass) init() {
 	if objabi.Fieldtrack_enabled != 0 {
 		d.ldr.Reachparent = make([]loader.Sym, d.ldr.NSym())
 	}
+	d.dynlink = d.ctxt.DynlinkingGo()
 
 	if d.ctxt.BuildMode == BuildModeShared {
 		// Mark all symbols defined in this library as reachable when
@@ -111,6 +113,11 @@ func (d *deadcodePass) flood() {
 		var usedInIface bool
 
 		if isgotype {
+			if d.dynlink {
+				// When dynaamic linking, a type may be passed across DSO
+				// boundary and get converted to interface at the other side.
+				d.ldr.SetAttrUsedInIface(symIdx, true)
+			}
 			usedInIface = d.ldr.AttrUsedInIface(symIdx)
 		}
 

src/cmd/link/internal/ld/elf.go

@@ -1086,7 +1086,7 @@ func elfrelocsect(ctxt *Link, out *OutBuf, sect *sym.Section, syms []loader.Sym)
 		}
 	}
 
-	eaddr := int32(sect.Vaddr + sect.Length)
+	eaddr := sect.Vaddr + sect.Length
 	for _, s := range syms {
 		if !ldr.AttrReachable(s) {
 			continue

src/cmd/link/internal/ld/lib.go

@@ -533,7 +533,10 @@ func (ctxt *Link) loadlib() {
 	// up symbol by name may not get expected result.
 
 	iscgo = ctxt.LibraryByPkg["runtime/cgo"] != nil
-	ctxt.canUsePlugins = ctxt.LibraryByPkg["plugin"] != nil
+
+	// Plugins a require cgo support to function. Similarly, plugins may require additional
+	// internal linker support on some platforms which may not be implemented.
+	ctxt.canUsePlugins = ctxt.LibraryByPkg["plugin"] != nil && iscgo
 
 	// We now have enough information to determine the link mode.
 	determineLinkMode(ctxt)

src/cmd/link/internal/ld/macho.go

@@ -1168,7 +1168,7 @@ func machorelocsect(ctxt *Link, out *OutBuf, sect *sym.Section, syms []loader.Sy
 		}
 	}
 
-	eaddr := int32(sect.Vaddr + sect.Length)
+	eaddr := sect.Vaddr + sect.Length
 	for _, s := range syms {
 		if !ldr.AttrReachable(s) {
 			continue

src/cmd/link/internal/ld/symtab.go

@@ -31,6 +31,7 @@
 package ld
 
 import (
+	"cmd/internal/obj"
 	"cmd/internal/objabi"
 	"cmd/link/internal/loader"
 	"cmd/link/internal/sym"
@@ -102,10 +103,14 @@ func putelfsym(ctxt *Link, x loader.Sym, typ elf.SymType, curbind elf.SymBind) {
 		elfshnum = xosect.Elfsect.(*ElfShdr).shnum
 	}
 
+	sname := ldr.SymExtname(x)
+
 	// One pass for each binding: elf.STB_LOCAL, elf.STB_GLOBAL,
 	// maybe one day elf.STB_WEAK.
 	bind := elf.STB_GLOBAL
-	if ldr.IsFileLocal(x) || ldr.AttrVisibilityHidden(x) || ldr.AttrLocal(x) {
+	if ldr.IsFileLocal(x) && !isStaticTmp(sname) || ldr.AttrVisibilityHidden(x) || ldr.AttrLocal(x) {
+		// Static tmp is package local, but a package can be shared among multiple DSOs.
+		// They need to have a single view of the static tmp that are writable.
 		bind = elf.STB_LOCAL
 	}
 
@@ -140,8 +145,6 @@ func putelfsym(ctxt *Link, x loader.Sym, typ elf.SymType, curbind elf.SymBind) {
 		other |= 3 << 5
 	}
 
-	sname := ldr.SymExtname(x)
-
 	// When dynamically linking, we create Symbols by reading the names from
 	// the symbol tables of the shared libraries and so the names need to
 	// match exactly. Tools like DTrace will have to wait for now.
@@ -823,3 +826,7 @@ func setCarrierSize(typ sym.SymKind, sz int64) {
 	}
 	CarrierSymByType[typ].Size = sz
 }
+
+func isStaticTmp(name string) bool {
+	return strings.Contains(name, "."+obj.StaticNamePref)
+}

src/cmd/link/internal/ppc64/asm.go

@@ -642,6 +642,16 @@ func archrelocaddr(ldr *loader.Loader, target *ld.Target, syms *ld.ArchSyms, r l
 	return int64(o2)<<32 | int64(o1)
 }
 
+// Determine if the code was compiled so that the TOC register R2 is initialized and maintained
+func r2Valid(ctxt *ld.Link) bool {
+	switch ctxt.BuildMode {
+	case ld.BuildModeCArchive, ld.BuildModeCShared, ld.BuildModePIE, ld.BuildModeShared, ld.BuildModePlugin:
+		return true
+	}
+	// -linkshared option
+	return ctxt.IsSharedGoLink()
+}
+
 // resolve direct jump relocation r in s, and add trampoline if necessary
 func trampoline(ctxt *ld.Link, ldr *loader.Loader, ri int, rs, s loader.Sym) {
 
@@ -649,20 +659,26 @@ func trampoline(ctxt *ld.Link, ldr *loader.Loader, ri int, rs, s loader.Sym) {
 	// For internal linking, trampolines are always created for long calls.
 	// For external linking, the linker can insert a call stub to handle a long call, but depends on having the TOC address in
 	// r2.  For those build modes with external linking where the TOC address is not maintained in r2, trampolines must be created.
-	if ctxt.IsExternal() && (ctxt.DynlinkingGo() || ctxt.BuildMode == ld.BuildModeCArchive || ctxt.BuildMode == ld.BuildModeCShared || ctxt.BuildMode == ld.BuildModePIE) {
+	if ctxt.IsExternal() && r2Valid(ctxt) {
 		// No trampolines needed since r2 contains the TOC
 		return
 	}
 
 	relocs := ldr.Relocs(s)
 	r := relocs.At(ri)
-	t := ldr.SymValue(rs) + r.Add() - (ldr.SymValue(s) + int64(r.Off()))
+	var t int64
+	// ldr.SymValue(rs) == 0 indicates a cross-package jump to a function that is not yet
+	// laid out. Conservatively use a trampoline. This should be rare, as we lay out packages
+	// in dependency order.
+	if ldr.SymValue(rs) != 0 {
+		t = ldr.SymValue(rs) + r.Add() - (ldr.SymValue(s) + int64(r.Off()))
+	}
 	switch r.Type() {
 	case objabi.R_CALLPOWER:
 
 		// If branch offset is too far then create a trampoline.
 
-		if (ctxt.IsExternal() && ldr.SymSect(s) != ldr.SymSect(rs)) || (ctxt.IsInternal() && int64(int32(t<<6)>>6) != t) || (*ld.FlagDebugTramp > 1 && ldr.SymPkg(s) != ldr.SymPkg(rs)) {
+		if (ctxt.IsExternal() && ldr.SymSect(s) != ldr.SymSect(rs)) || (ctxt.IsInternal() && int64(int32(t<<6)>>6) != t) || ldr.SymValue(rs) == 0 || (*ld.FlagDebugTramp > 1 && ldr.SymPkg(s) != ldr.SymPkg(rs)) {
 			var tramp loader.Sym
 			for i := 0; ; i++ {
 
@@ -697,7 +713,7 @@ func trampoline(ctxt *ld.Link, ldr *loader.Loader, ri int, rs, s loader.Sym) {
 				}
 			}
 			if ldr.SymType(tramp) == 0 {
-				if ctxt.DynlinkingGo() || ctxt.BuildMode == ld.BuildModeCArchive || ctxt.BuildMode == ld.BuildModeCShared || ctxt.BuildMode == ld.BuildModePIE {
+				if r2Valid(ctxt) {
 					// Should have returned for above cases
 					ctxt.Errorf(s, "unexpected trampoline for shared or dynamic linking")
 				} else {
@@ -749,7 +765,7 @@ func gentramp(ctxt *ld.Link, ldr *loader.Loader, tramp *loader.SymbolBuilder, ta
 
 		// With external linking, the target address must be
 		// relocated using LO and HA
-		if ctxt.IsExternal() {
+		if ctxt.IsExternal() || ldr.SymValue(target) == 0 {
 			r, _ := tramp.AddRel(objabi.R_ADDRPOWER)
 			r.SetOff(0)
 			r.SetSiz(8) // generates 2 relocations: HA + LO

src/cmd/vendor/golang.org/x/mod/modfile/rule.go

@@ -125,6 +125,12 @@ func (f *File) AddComment(text string) {
 
 type VersionFixer func(path, version string) (string, error)
 
+// errDontFix is returned by a VersionFixer to indicate the version should be
+// left alone, even if it's not canonical.
+var dontFixRetract VersionFixer = func(_, vers string) (string, error) {
+	return vers, nil
+}
+
 // Parse parses the data, reported in errors as being from file,
 // into a File struct. It applies fix, if non-nil, to canonicalize all module versions found.
 func Parse(file string, data []byte, fix VersionFixer) (*File, error) {
@@ -142,7 +148,7 @@ func ParseLax(file string, data []byte, fix VersionFixer) (*File, error) {
 	return parseToFile(file, data, fix, false)
 }
 
-func parseToFile(file string, data []byte, fix VersionFixer, strict bool) (*File, error) {
+func parseToFile(file string, data []byte, fix VersionFixer, strict bool) (parsed *File, err error) {
 	fs, err := parse(file, data)
 	if err != nil {
 		return nil, err
@@ -150,8 +156,18 @@ func parseToFile(file string, data []byte, fix VersionFixer, strict bool) (*File
 	f := &File{
 		Syntax: fs,
 	}
-
 	var errs ErrorList
+
+	// fix versions in retract directives after the file is parsed.
+	// We need the module path to fix versions, and it might be at the end.
+	defer func() {
+		oldLen := len(errs)
+		f.fixRetract(fix, &errs)
+		if len(errs) > oldLen {
+			parsed, err = nil, errs
+		}
+	}()
+
 	for _, x := range fs.Stmt {
 		switch x := x.(type) {
 		case *Line:
@@ -370,7 +386,7 @@ func (f *File) add(errs *ErrorList, block *LineBlock, line *Line, verb string, a
 
 	case "retract":
 		rationale := parseRetractRationale(block, line)
-		vi, err := parseVersionInterval(verb, &args, fix)
+		vi, err := parseVersionInterval(verb, "", &args, dontFixRetract)
 		if err != nil {
 			if strict {
 				wrapError(err)
@@ -397,6 +413,47 @@ func (f *File) add(errs *ErrorList, block *LineBlock, line *Line, verb string, a
 	}
 }
 
+// fixRetract applies fix to each retract directive in f, appending any errors
+// to errs.
+//
+// Most versions are fixed as we parse the file, but for retract directives,
+// the relevant module path is the one specified with the module directive,
+// and that might appear at the end of the file (or not at all).
+func (f *File) fixRetract(fix VersionFixer, errs *ErrorList) {
+	if fix == nil {
+		return
+	}
+	path := ""
+	if f.Module != nil {
+		path = f.Module.Mod.Path
+	}
+	var r *Retract
+	wrapError := func(err error) {
+		*errs = append(*errs, Error{
+			Filename: f.Syntax.Name,
+			Pos:      r.Syntax.Start,
+			Err:      err,
+		})
+	}
+
+	for _, r = range f.Retract {
+		if path == "" {
+			wrapError(errors.New("no module directive found, so retract cannot be used"))
+			return // only print the first one of these
+		}
+
+		args := r.Syntax.Token
+		if args[0] == "retract" {
+			args = args[1:]
+		}
+		vi, err := parseVersionInterval("retract", path, &args, fix)
+		if err != nil {
+			wrapError(err)
+		}
+		r.VersionInterval = vi
+	}
+}
+
 // isIndirect reports whether line has a "// indirect" comment,
 // meaning it is in go.mod only for its effect on indirect dependencies,
 // so that it can be dropped entirely once the effective version of the
@@ -491,13 +548,13 @@ func AutoQuote(s string) string {
 	return s
 }
 
-func parseVersionInterval(verb string, args *[]string, fix VersionFixer) (VersionInterval, error) {
+func parseVersionInterval(verb string, path string, args *[]string, fix VersionFixer) (VersionInterval, error) {
 	toks := *args
 	if len(toks) == 0 || toks[0] == "(" {
 		return VersionInterval{}, fmt.Errorf("expected '[' or version")
 	}
 	if toks[0] != "[" {
-		v, err := parseVersion(verb, "", &toks[0], fix)
+		v, err := parseVersion(verb, path, &toks[0], fix)
 		if err != nil {
 			return VersionInterval{}, err
 		}
@@ -509,7 +566,7 @@ func parseVersionInterval(verb string, args *[]string, fix VersionFixer) (Versio
 	if len(toks) == 0 {
 		return VersionInterval{}, fmt.Errorf("expected version after '['")
 	}
-	low, err := parseVersion(verb, "", &toks[0], fix)
+	low, err := parseVersion(verb, path, &toks[0], fix)
 	if err != nil {
 		return VersionInterval{}, err
 	}
@@ -523,7 +580,7 @@ func parseVersionInterval(verb string, args *[]string, fix VersionFixer) (Versio
 	if len(toks) == 0 {
 		return VersionInterval{}, fmt.Errorf("expected version after ','")
 	}
-	high, err := parseVersion(verb, "", &toks[0], fix)
+	high, err := parseVersion(verb, path, &toks[0], fix)
 	if err != nil {
 		return VersionInterval{}, err
 	}
@@ -631,8 +688,7 @@ func parseVersion(verb string, path string, s *string, fix VersionFixer) (string
 		}
 	}
 	if fix != nil {
-		var err error
-		t, err = fix(path, t)
+		fixed, err := fix(path, t)
 		if err != nil {
 			if err, ok := err.(*module.ModuleError); ok {
 				return "", &Error{
@@ -643,19 +699,23 @@ func parseVersion(verb string, path string, s *string, fix VersionFixer) (string
 			}
 			return "", err
 		}
+		t = fixed
+	} else {
+		cv := module.CanonicalVersion(t)
+		if cv == "" {
+			return "", &Error{
+				Verb:    verb,
+				ModPath: path,
+				Err: &module.InvalidVersionError{
+					Version: t,
+					Err:     errors.New("must be of the form v1.2.3"),
+				},
+			}
+		}
+		t = cv
 	}
-	if v := module.CanonicalVersion(t); v != "" {
-		*s = v
-		return *s, nil
-	}
-	return "", &Error{
-		Verb:    verb,
-		ModPath: path,
-		Err: &module.InvalidVersionError{
-			Version: t,
-			Err:     errors.New("must be of the form v1.2.3"),
-		},
-	}
+	*s = t
+	return *s, nil
 }
 
 func modulePathMajor(path string) (string, error) {
@@ -835,11 +895,8 @@ func (f *File) DropRequire(path string) error {
 // AddExclude adds a exclude statement to the mod file. Errors if the provided
 // version is not a canonical version string
 func (f *File) AddExclude(path, vers string) error {
-	if !isCanonicalVersion(vers) {
-		return &module.InvalidVersionError{
-			Version: vers,
-			Err:     errors.New("must be of the form v1.2.3"),
-		}
+	if err := checkCanonicalVersion(path, vers); err != nil {
+		return err
 	}
 
 	var hint *Line
@@ -916,17 +973,15 @@ func (f *File) DropReplace(oldPath, oldVers string) error {
 // AddRetract adds a retract statement to the mod file. Errors if the provided
 // version interval does not consist of canonical version strings
 func (f *File) AddRetract(vi VersionInterval, rationale string) error {
-	if !isCanonicalVersion(vi.High) {
-		return &module.InvalidVersionError{
-			Version: vi.High,
-			Err:     errors.New("must be of the form v1.2.3"),
-		}
+	var path string
+	if f.Module != nil {
+		path = f.Module.Mod.Path
 	}
-	if !isCanonicalVersion(vi.Low) {
-		return &module.InvalidVersionError{
-			Version: vi.Low,
-			Err:     errors.New("must be of the form v1.2.3"),
-		}
+	if err := checkCanonicalVersion(path, vi.High); err != nil {
+		return err
+	}
+	if err := checkCanonicalVersion(path, vi.Low); err != nil {
+		return err
 	}
 
 	r := &Retract{
@@ -1086,8 +1141,40 @@ func lineRetractLess(li, lj *Line) bool {
 	return semver.Compare(vii.High, vij.High) > 0
 }
 
-// isCanonicalVersion tests if the provided version string represents a valid
-// canonical version.
-func isCanonicalVersion(vers string) bool {
-	return vers != "" && semver.Canonical(vers) == vers
+// checkCanonicalVersion returns a non-nil error if vers is not a canonical
+// version string or does not match the major version of path.
+//
+// If path is non-empty, the error text suggests a format with a major version
+// corresponding to the path.
+func checkCanonicalVersion(path, vers string) error {
+	_, pathMajor, pathMajorOk := module.SplitPathVersion(path)
+
+	if vers == "" || vers != module.CanonicalVersion(vers) {
+		if pathMajor == "" {
+			return &module.InvalidVersionError{
+				Version: vers,
+				Err:     fmt.Errorf("must be of the form v1.2.3"),
+			}
+		}
+		return &module.InvalidVersionError{
+			Version: vers,
+			Err:     fmt.Errorf("must be of the form %s.2.3", module.PathMajorPrefix(pathMajor)),
+		}
+	}
+
+	if pathMajorOk {
+		if err := module.CheckPathMajor(vers, pathMajor); err != nil {
+			if pathMajor == "" {
+				// In this context, the user probably wrote "v2.3.4" when they meant
+				// "v2.3.4+incompatible". Suggest that instead of "v0 or v1".
+				return &module.InvalidVersionError{
+					Version: vers,
+					Err:     fmt.Errorf("should be %s+incompatible (or module %s/%v)", vers, path, semver.Major(vers)),
+				}
+			}
+			return err
+		}
+	}
+
+	return nil
 }

src/cmd/vendor/golang.org/x/mod/module/module.go

@@ -224,12 +224,16 @@ func firstPathOK(r rune) bool {
 		'a' <= r && r <= 'z'
 }
 
-// pathOK reports whether r can appear in an import path element.
+// modPathOK reports whether r can appear in a module path element.
 // Paths can be ASCII letters, ASCII digits, and limited ASCII punctuation: - . _ and ~.
-// This matches what "go get" has historically recognized in import paths.
+//
+// This matches what "go get" has historically recognized in import paths,
+// and avoids confusing sequences like '%20' or '+' that would change meaning
+// if used in a URL.
+//
 // TODO(rsc): We would like to allow Unicode letters, but that requires additional
 // care in the safe encoding (see "escaped paths" above).
-func pathOK(r rune) bool {
+func modPathOK(r rune) bool {
 	if r < utf8.RuneSelf {
 		return r == '-' || r == '.' || r == '_' || r == '~' ||
 			'0' <= r && r <= '9' ||
@@ -239,6 +243,17 @@ func pathOK(r rune) bool {
 	return false
 }
 
+// modPathOK reports whether r can appear in a package import path element.
+//
+// Import paths are intermediate between module paths and file paths: we allow
+// disallow characters that would be confusing or ambiguous as arguments to
+// 'go get' (such as '@' and ' ' ), but allow certain characters that are
+// otherwise-unambiguous on the command line and historically used for some
+// binary names (such as '++' as a suffix for compiler binaries and wrappers).
+func importPathOK(r rune) bool {
+	return modPathOK(r) || r == '+'
+}
+
 // fileNameOK reports whether r can appear in a file name.
 // For now we allow all Unicode letters but otherwise limit to pathOK plus a few more punctuation characters.
 // If we expand the set of allowed characters here, we have to
@@ -270,7 +285,7 @@ func fileNameOK(r rune) bool {
 
 // CheckPath checks that a module path is valid.
 // A valid module path is a valid import path, as checked by CheckImportPath,
-// with two additional constraints.
+// with three additional constraints.
 // First, the leading path element (up to the first slash, if any),
 // by convention a domain name, must contain only lower-case ASCII letters,
 // ASCII digits, dots (U+002E), and dashes (U+002D);
@@ -280,8 +295,9 @@ func fileNameOK(r rune) bool {
 // and must not contain any dots. For paths beginning with "gopkg.in/",
 // this second requirement is replaced by a requirement that the path
 // follow the gopkg.in server's conventions.
+// Third, no path element may begin with a dot.
 func CheckPath(path string) error {
-	if err := checkPath(path, false); err != nil {
+	if err := checkPath(path, modulePath); err != nil {
 		return fmt.Errorf("malformed module path %q: %v", path, err)
 	}
 	i := strings.Index(path, "/")
@@ -315,7 +331,7 @@ func CheckPath(path string) error {
 //
 // A valid path element is a non-empty string made up of
 // ASCII letters, ASCII digits, and limited ASCII punctuation: - . _ and ~.
-// It must not begin or end with a dot (U+002E), nor contain two dots in a row.
+// It must not end with a dot (U+002E), nor contain two dots in a row.
 //
 // The element prefix up to the first dot must not be a reserved file name
 // on Windows, regardless of case (CON, com1, NuL, and so on). The element
@@ -326,19 +342,29 @@ func CheckPath(path string) error {
 // top-level package documentation for additional information about
 // subtleties of Unicode.
 func CheckImportPath(path string) error {
-	if err := checkPath(path, false); err != nil {
+	if err := checkPath(path, importPath); err != nil {
 		return fmt.Errorf("malformed import path %q: %v", path, err)
 	}
 	return nil
 }
 
+// pathKind indicates what kind of path we're checking. Module paths,
+// import paths, and file paths have different restrictions.
+type pathKind int
+
+const (
+	modulePath pathKind = iota
+	importPath
+	filePath
+)
+
 // checkPath checks that a general path is valid.
 // It returns an error describing why but not mentioning path.
 // Because these checks apply to both module paths and import paths,
 // the caller is expected to add the "malformed ___ path %q: " prefix.
 // fileName indicates whether the final element of the path is a file name
 // (as opposed to a directory name).
-func checkPath(path string, fileName bool) error {
+func checkPath(path string, kind pathKind) error {
 	if !utf8.ValidString(path) {
 		return fmt.Errorf("invalid UTF-8")
 	}
@@ -357,39 +383,45 @@ func checkPath(path string, fileName bool) error {
 	elemStart := 0
 	for i, r := range path {
 		if r == '/' {
-			if err := checkElem(path[elemStart:i], fileName); err != nil {
+			if err := checkElem(path[elemStart:i], kind); err != nil {
 				return err
 			}
 			elemStart = i + 1
 		}
 	}
-	if err := checkElem(path[elemStart:], fileName); err != nil {
+	if err := checkElem(path[elemStart:], kind); err != nil {
 		return err
 	}
 	return nil
 }
 
 // checkElem checks whether an individual path element is valid.
-// fileName indicates whether the element is a file name (not a directory name).
-func checkElem(elem string, fileName bool) error {
+func checkElem(elem string, kind pathKind) error {
 	if elem == "" {
 		return fmt.Errorf("empty path element")
 	}
 	if strings.Count(elem, ".") == len(elem) {
 		return fmt.Errorf("invalid path element %q", elem)
 	}
-	if elem[0] == '.' && !fileName {
+	if elem[0] == '.' && kind == modulePath {
 		return fmt.Errorf("leading dot in path element")
 	}
 	if elem[len(elem)-1] == '.' {
 		return fmt.Errorf("trailing dot in path element")
 	}
-	charOK := pathOK
-	if fileName {
-		charOK = fileNameOK
-	}
 	for _, r := range elem {
-		if !charOK(r) {
+		ok := false
+		switch kind {
+		case modulePath:
+			ok = modPathOK(r)
+		case importPath:
+			ok = importPathOK(r)
+		case filePath:
+			ok = fileNameOK(r)
+		default:
+			panic(fmt.Sprintf("internal error: invalid kind %v", kind))
+		}
+		if !ok {
 			return fmt.Errorf("invalid char %q", r)
 		}
 	}
@@ -406,7 +438,7 @@ func checkElem(elem string, fileName bool) error {
 		}
 	}
 
-	if fileName {
+	if kind == filePath {
 		// don't check for Windows short-names in file names. They're
 		// only an issue for import paths.
 		return nil
@@ -444,7 +476,7 @@ func checkElem(elem string, fileName bool) error {
 // top-level package documentation for additional information about
 // subtleties of Unicode.
 func CheckFilePath(path string) error {
-	if err := checkPath(path, true); err != nil {
+	if err := checkPath(path, filePath); err != nil {
 		return fmt.Errorf("malformed file path %q: %v", path, err)
 	}
 	return nil
@@ -647,7 +679,7 @@ func EscapePath(path string) (escaped string, err error) {
 // Versions are allowed to be in non-semver form but must be valid file names
 // and not contain exclamation marks.
 func EscapeVersion(v string) (escaped string, err error) {
-	if err := checkElem(v, true); err != nil || strings.Contains(v, "!") {
+	if err := checkElem(v, filePath); err != nil || strings.Contains(v, "!") {
 		return "", &InvalidVersionError{
 			Version: v,
 			Err:     fmt.Errorf("disallowed version string"),
@@ -706,7 +738,7 @@ func UnescapeVersion(escaped string) (v string, err error) {
 	if !ok {
 		return "", fmt.Errorf("invalid escaped version %q", escaped)
 	}
-	if err := checkElem(v, true); err != nil {
+	if err := checkElem(v, filePath); err != nil {
 		return "", fmt.Errorf("invalid escaped version %q: %v", v, err)
 	}
 	return v, nil

src/cmd/vendor/modules.txt

@@ -28,7 +28,7 @@ golang.org/x/arch/x86/x86asm
 golang.org/x/crypto/ed25519
 golang.org/x/crypto/ed25519/internal/edwards25519
 golang.org/x/crypto/ssh/terminal
-# golang.org/x/mod v0.4.1
+# golang.org/x/mod v0.4.2-0.20210325185522-dbbbf8a3c6ea
 ## explicit
 golang.org/x/mod/internal/lazyregexp
 golang.org/x/mod/modfile

src/crypto/tls/key_agreement.go

@@ -67,7 +67,11 @@ func (ka rsaKeyAgreement) generateClientKeyExchange(config *Config, clientHello
 		return nil, nil, err
 	}
 
-	encrypted, err := rsa.EncryptPKCS1v15(config.rand(), cert.PublicKey.(*rsa.PublicKey), preMasterSecret)
+	rsaKey, ok := cert.PublicKey.(*rsa.PublicKey)
+	if !ok {
+		return nil, nil, errors.New("tls: server certificate contains incorrect key type for selected ciphersuite")
+	}
+	encrypted, err := rsa.EncryptPKCS1v15(config.rand(), rsaKey, preMasterSecret)
 	if err != nil {
 		return nil, nil, err
 	}

src/encoding/xml/xml.go

@@ -271,7 +271,7 @@ func NewTokenDecoder(t TokenReader) *Decoder {
 // it will return an error.
 //
 // Token implements XML name spaces as described by
-// https://www.w3.org/TR/REC-xml-names/.  Each of the
+// https://www.w3.org/TR/REC-xml-names/. Each of the
 // Name structures contained in the Token has the Space
 // set to the URL identifying its name space when known.
 // If Token encounters an unrecognized name space prefix,
@@ -285,16 +285,17 @@ func (d *Decoder) Token() (Token, error) {
 	if d.nextToken != nil {
 		t = d.nextToken
 		d.nextToken = nil
-	} else if t, err = d.rawToken(); err != nil {
-		switch {
-		case err == io.EOF && d.t != nil:
-			err = nil
-		case err == io.EOF && d.stk != nil && d.stk.kind != stkEOF:
-			err = d.syntaxError("unexpected EOF")
+	} else {
+		if t, err = d.rawToken(); t == nil && err != nil {
+			if err == io.EOF && d.stk != nil && d.stk.kind != stkEOF {
+				err = d.syntaxError("unexpected EOF")
+			}
+			return nil, err
 		}
-		return t, err
+		// We still have a token to process, so clear any
+		// errors (e.g. EOF) and proceed.
+		err = nil
 	}
-
 	if !d.Strict {
 		if t1, ok := d.autoClose(t); ok {
 			d.nextToken = t

src/encoding/xml/xml_test.go

@@ -33,30 +33,90 @@ func (t *toks) Token() (Token, error) {
 
 func TestDecodeEOF(t *testing.T) {
 	start := StartElement{Name: Name{Local: "test"}}
-	t.Run("EarlyEOF", func(t *testing.T) {
-		d := NewTokenDecoder(&toks{earlyEOF: true, t: []Token{
-			start,
-			start.End(),
-		}})
-		err := d.Decode(&struct {
-			XMLName Name `xml:"test"`
-		}{})
-		if err != nil {
-			t.Error(err)
+	tests := []struct {
+		name   string
+		tokens []Token
+		ok     bool
+	}{
+		{
+			name: "OK",
+			tokens: []Token{
+				start,
+				start.End(),
+			},
+			ok: true,
+		},
+		{
+			name: "Malformed",
+			tokens: []Token{
+				start,
+				StartElement{Name: Name{Local: "bad"}},
+				start.End(),
+			},
+			ok: false,
+		},
+	}
+	for _, tc := range tests {
+		for _, eof := range []bool{true, false} {
+			name := fmt.Sprintf("%s/earlyEOF=%v", tc.name, eof)
+			t.Run(name, func(t *testing.T) {
+				d := NewTokenDecoder(&toks{
+					earlyEOF: eof,
+					t:        tc.tokens,
+				})
+				err := d.Decode(&struct {
+					XMLName Name `xml:"test"`
+				}{})
+				if tc.ok && err != nil {
+					t.Fatalf("d.Decode: expected nil error, got %v", err)
+				}
+				if _, ok := err.(*SyntaxError); !tc.ok && !ok {
+					t.Errorf("d.Decode: expected syntax error, got %v", err)
+				}
+			})
 		}
-	})
-	t.Run("LateEOF", func(t *testing.T) {
-		d := NewTokenDecoder(&toks{t: []Token{
-			start,
-			start.End(),
-		}})
-		err := d.Decode(&struct {
-			XMLName Name `xml:"test"`
-		}{})
-		if err != nil {
-			t.Error(err)
+	}
+}
+
+type toksNil struct {
+	returnEOF bool
+	t         []Token
+}
+
+func (t *toksNil) Token() (Token, error) {
+	if len(t.t) == 0 {
+		if !t.returnEOF {
+			// Return nil, nil before returning an EOF. It's legal, but
+			// discouraged.
+			t.returnEOF = true
+			return nil, nil
 		}
-	})
+		return nil, io.EOF
+	}
+	var tok Token
+	tok, t.t = t.t[0], t.t[1:]
+	return tok, nil
+}
+
+func TestDecodeNilToken(t *testing.T) {
+	for _, strict := range []bool{true, false} {
+		name := fmt.Sprintf("Strict=%v", strict)
+		t.Run(name, func(t *testing.T) {
+			start := StartElement{Name: Name{Local: "test"}}
+			bad := StartElement{Name: Name{Local: "bad"}}
+			d := NewTokenDecoder(&toksNil{
+				// Malformed
+				t: []Token{start, bad, start.End()},
+			})
+			d.Strict = strict
+			err := d.Decode(&struct {
+				XMLName Name `xml:"test"`
+			}{})
+			if _, ok := err.(*SyntaxError); !ok {
+				t.Errorf("d.Decode: expected syntax error, got %v", err)
+			}
+		})
+	}
 }
 
 const testInput = `

src/go.mod

@@ -4,7 +4,7 @@ go 1.16
 
 require (
 	golang.org/x/crypto v0.0.0-20201016220609-9e8e0b390897
-	golang.org/x/net v0.0.0-20201209123823-ac852fbbde11
+	golang.org/x/net v0.0.0-20210428183300-3f4a416c7d3b
 	golang.org/x/sys v0.0.0-20201204225414-ed752295db88 // indirect
 	golang.org/x/text v0.3.4 // indirect
 )

src/go.sum

@@ -2,8 +2,8 @@ golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACk
 golang.org/x/crypto v0.0.0-20201016220609-9e8e0b390897 h1:pLI5jrR7OSLijeIDcmRxNmw2api+jEfxLoykJVice/E=
 golang.org/x/crypto v0.0.0-20201016220609-9e8e0b390897/go.mod h1:LzIPMQfyMNhhGPhUkYOs5KpL4U8rLKemX1yGLhDgUto=
 golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
-golang.org/x/net v0.0.0-20201209123823-ac852fbbde11 h1:lwlPPsmjDKK0J6eG6xDWd5XPehI0R024zxjDnw3esPA=
-golang.org/x/net v0.0.0-20201209123823-ac852fbbde11/go.mod h1:m0MpNAwzfU5UDzcl9v0D8zg8gWTRqZa9RBIspLL5mdg=
+golang.org/x/net v0.0.0-20210428183300-3f4a416c7d3b h1:SQCMv1JDt7RN/Vp0bjtNMSufVVHgpFVzmDFdCLL31yY=
+golang.org/x/net v0.0.0-20210428183300-3f4a416c7d3b/go.mod h1:m0MpNAwzfU5UDzcl9v0D8zg8gWTRqZa9RBIspLL5mdg=
 golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20201119102817-f84b799fce68/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=

src/go/build/build_test.go

@@ -612,7 +612,7 @@ func TestImportPackageOutsideModule(t *testing.T) {
 	ctxt.GOPATH = gopath
 	ctxt.Dir = filepath.Join(gopath, "src/example.com/p")
 
-	want := "working directory is not part of a module"
+	want := "go.mod file not found in current directory or any parent directory"
 	if _, err := ctxt.Import("example.com/p", gopath, FindOnly); err == nil {
 		t.Fatal("importing package when no go.mod is present succeeded unexpectedly")
 	} else if errStr := err.Error(); !strings.Contains(errStr, want) {

src/math/big/ratconv.go

@@ -51,7 +51,8 @@ func (z *Rat) Scan(s fmt.ScanState, ch rune) error {
 // An optional base-10 ``e'' or base-2 ``p'' (or their upper-case variants)
 // exponent may be provided as well, except for hexadecimal floats which
 // only accept an (optional) ``p'' exponent (because an ``e'' or ``E'' cannot
-// be distinguished from a mantissa digit).
+// be distinguished from a mantissa digit). If the exponent's absolute value
+// is too large, the operation may fail.
 // The entire string, not just a prefix, must be valid for success. If the
 // operation failed, the value of z is undefined but the returned value is nil.
 func (z *Rat) SetString(s string) (*Rat, bool) {
@@ -169,6 +170,9 @@ func (z *Rat) SetString(s string) (*Rat, bool) {
 		if n < 0 {
 			n = -n
 		}
+		if n > 1e6 {
+			return nil, false // avoid excessively large exponents
+		}
 		pow5 := z.b.abs.expNN(natFive, nat(nil).setWord(Word(n)), nil) // use underlying array of z.b.abs
 		if exp5 > 0 {
 			z.a.abs = z.a.abs.mul(z.a.abs, pow5)
@@ -181,15 +185,12 @@ func (z *Rat) SetString(s string) (*Rat, bool) {
 	}
 
 	// apply exp2 contributions
+	if exp2 < -1e7 || exp2 > 1e7 {
+		return nil, false // avoid excessively large exponents
+	}
 	if exp2 > 0 {
-		if int64(uint(exp2)) != exp2 {
-			panic("exponent too large")
-		}
 		z.a.abs = z.a.abs.shl(z.a.abs, uint(exp2))
 	} else if exp2 < 0 {
-		if int64(uint(-exp2)) != -exp2 {
-			panic("exponent too large")
-		}
 		z.b.abs = z.b.abs.shl(z.b.abs, uint(-exp2))
 	}
 

src/math/big/ratconv_test.go

@@ -589,3 +589,28 @@ func TestIssue31184(t *testing.T) {
 		}
 	}
 }
+
+func TestIssue45910(t *testing.T) {
+	var x Rat
+	for _, test := range []struct {
+		input string
+		want  bool
+	}{
+		{"1e-1000001", false},
+		{"1e-1000000", true},
+		{"1e+1000000", true},
+		{"1e+1000001", false},
+
+		{"0p1000000000000", true},
+		{"1p-10000001", false},
+		{"1p-10000000", true},
+		{"1p+10000000", true},
+		{"1p+10000001", false},
+		{"1.770p02041010010011001001", false}, // test case from issue
+	} {
+		_, got := x.SetString(test.input)
+		if got != test.want {
+			t.Errorf("SetString(%s) got ok = %v; want %v", test.input, got, test.want)
+		}
+	}
+}

src/net/dnsclient_unix_test.go

@@ -1798,3 +1798,324 @@ func TestPTRandNonPTR(t *testing.T) {
 		t.Errorf("names = %q; want %q", names, want)
 	}
 }
+
+func TestCVE202133195(t *testing.T) {
+	fake := fakeDNSServer{
+		rh: func(n, _ string, q dnsmessage.Message, _ time.Time) (dnsmessage.Message, error) {
+			r := dnsmessage.Message{
+				Header: dnsmessage.Header{
+					ID:                 q.Header.ID,
+					Response:           true,
+					RCode:              dnsmessage.RCodeSuccess,
+					RecursionAvailable: true,
+				},
+				Questions: q.Questions,
+			}
+			switch q.Questions[0].Type {
+			case dnsmessage.TypeCNAME:
+				r.Answers = []dnsmessage.Resource{}
+			case dnsmessage.TypeA: // CNAME lookup uses a A/AAAA as a proxy
+				r.Answers = append(r.Answers,
+					dnsmessage.Resource{
+						Header: dnsmessage.ResourceHeader{
+							Name:   dnsmessage.MustNewName("<html>.golang.org."),
+							Type:   dnsmessage.TypeA,
+							Class:  dnsmessage.ClassINET,
+							Length: 4,
+						},
+						Body: &dnsmessage.AResource{
+							A: TestAddr,
+						},
+					},
+				)
+			case dnsmessage.TypeSRV:
+				n := q.Questions[0].Name
+				if n.String() == "_hdr._tcp.golang.org." {
+					n = dnsmessage.MustNewName("<html>.golang.org.")
+				}
+				r.Answers = append(r.Answers,
+					dnsmessage.Resource{
+						Header: dnsmessage.ResourceHeader{
+							Name:   n,
+							Type:   dnsmessage.TypeSRV,
+							Class:  dnsmessage.ClassINET,
+							Length: 4,
+						},
+						Body: &dnsmessage.SRVResource{
+							Target: dnsmessage.MustNewName("<html>.golang.org."),
+						},
+					},
+					dnsmessage.Resource{
+						Header: dnsmessage.ResourceHeader{
+							Name:   n,
+							Type:   dnsmessage.TypeSRV,
+							Class:  dnsmessage.ClassINET,
+							Length: 4,
+						},
+						Body: &dnsmessage.SRVResource{
+							Target: dnsmessage.MustNewName("good.golang.org."),
+						},
+					},
+				)
+			case dnsmessage.TypeMX:
+				r.Answers = append(r.Answers,
+					dnsmessage.Resource{
+						Header: dnsmessage.ResourceHeader{
+							Name:   dnsmessage.MustNewName("<html>.golang.org."),
+							Type:   dnsmessage.TypeMX,
+							Class:  dnsmessage.ClassINET,
+							Length: 4,
+						},
+						Body: &dnsmessage.MXResource{
+							MX: dnsmessage.MustNewName("<html>.golang.org."),
+						},
+					},
+					dnsmessage.Resource{
+						Header: dnsmessage.ResourceHeader{
+							Name:   dnsmessage.MustNewName("good.golang.org."),
+							Type:   dnsmessage.TypeMX,
+							Class:  dnsmessage.ClassINET,
+							Length: 4,
+						},
+						Body: &dnsmessage.MXResource{
+							MX: dnsmessage.MustNewName("good.golang.org."),
+						},
+					},
+				)
+			case dnsmessage.TypeNS:
+				r.Answers = append(r.Answers,
+					dnsmessage.Resource{
+						Header: dnsmessage.ResourceHeader{
+							Name:   dnsmessage.MustNewName("<html>.golang.org."),
+							Type:   dnsmessage.TypeNS,
+							Class:  dnsmessage.ClassINET,
+							Length: 4,
+						},
+						Body: &dnsmessage.NSResource{
+							NS: dnsmessage.MustNewName("<html>.golang.org."),
+						},
+					},
+					dnsmessage.Resource{
+						Header: dnsmessage.ResourceHeader{
+							Name:   dnsmessage.MustNewName("good.golang.org."),
+							Type:   dnsmessage.TypeNS,
+							Class:  dnsmessage.ClassINET,
+							Length: 4,
+						},
+						Body: &dnsmessage.NSResource{
+							NS: dnsmessage.MustNewName("good.golang.org."),
+						},
+					},
+				)
+			case dnsmessage.TypePTR:
+				r.Answers = append(r.Answers,
+					dnsmessage.Resource{
+						Header: dnsmessage.ResourceHeader{
+							Name:   dnsmessage.MustNewName("<html>.golang.org."),
+							Type:   dnsmessage.TypePTR,
+							Class:  dnsmessage.ClassINET,
+							Length: 4,
+						},
+						Body: &dnsmessage.PTRResource{
+							PTR: dnsmessage.MustNewName("<html>.golang.org."),
+						},
+					},
+					dnsmessage.Resource{
+						Header: dnsmessage.ResourceHeader{
+							Name:   dnsmessage.MustNewName("good.golang.org."),
+							Type:   dnsmessage.TypePTR,
+							Class:  dnsmessage.ClassINET,
+							Length: 4,
+						},
+						Body: &dnsmessage.PTRResource{
+							PTR: dnsmessage.MustNewName("good.golang.org."),
+						},
+					},
+				)
+			}
+			return r, nil
+		},
+	}
+
+	r := Resolver{PreferGo: true, Dial: fake.DialContext}
+	// Change the default resolver to match our manipulated resolver
+	originalDefault := DefaultResolver
+	DefaultResolver = &r
+	defer func() { DefaultResolver = originalDefault }()
+	// Redirect host file lookups.
+	defer func(orig string) { testHookHostsPath = orig }(testHookHostsPath)
+	testHookHostsPath = "testdata/hosts"
+
+	tests := []struct {
+		name string
+		f    func(*testing.T)
+	}{
+		{
+			name: "CNAME",
+			f: func(t *testing.T) {
+				expectedErr := &DNSError{Err: errMalformedDNSRecordsDetail, Name: "golang.org"}
+				_, err := r.LookupCNAME(context.Background(), "golang.org")
+				if err.Error() != expectedErr.Error() {
+					t.Fatalf("unexpected error: %s", err)
+				}
+				_, err = LookupCNAME("golang.org")
+				if err.Error() != expectedErr.Error() {
+					t.Fatalf("unexpected error: %s", err)
+				}
+			},
+		},
+		{
+			name: "SRV (bad record)",
+			f: func(t *testing.T) {
+				expected := []*SRV{
+					{
+						Target: "good.golang.org.",
+					},
+				}
+				expectedErr := &DNSError{Err: errMalformedDNSRecordsDetail, Name: "golang.org"}
+				_, records, err := r.LookupSRV(context.Background(), "target", "tcp", "golang.org")
+				if err.Error() != expectedErr.Error() {
+					t.Fatalf("unexpected error: %s", err)
+				}
+				if !reflect.DeepEqual(records, expected) {
+					t.Error("Unexpected record set")
+				}
+				_, records, err = LookupSRV("target", "tcp", "golang.org")
+				if err.Error() != expectedErr.Error() {
+					t.Errorf("unexpected error: %s", err)
+				}
+				if !reflect.DeepEqual(records, expected) {
+					t.Error("Unexpected record set")
+				}
+			},
+		},
+		{
+			name: "SRV (bad header)",
+			f: func(t *testing.T) {
+				_, _, err := r.LookupSRV(context.Background(), "hdr", "tcp", "golang.org.")
+				if expected := "lookup golang.org.: SRV header name is invalid"; err == nil || err.Error() != expected {
+					t.Errorf("Resolver.LookupSRV returned unexpected error, got %q, want %q", err, expected)
+				}
+				_, _, err = LookupSRV("hdr", "tcp", "golang.org.")
+				if expected := "lookup golang.org.: SRV header name is invalid"; err == nil || err.Error() != expected {
+					t.Errorf("LookupSRV returned unexpected error, got %q, want %q", err, expected)
+				}
+			},
+		},
+		{
+			name: "MX",
+			f: func(t *testing.T) {
+				expected := []*MX{
+					{
+						Host: "good.golang.org.",
+					},
+				}
+				expectedErr := &DNSError{Err: errMalformedDNSRecordsDetail, Name: "golang.org"}
+				records, err := r.LookupMX(context.Background(), "golang.org")
+				if err.Error() != expectedErr.Error() {
+					t.Fatalf("unexpected error: %s", err)
+				}
+				if !reflect.DeepEqual(records, expected) {
+					t.Error("Unexpected record set")
+				}
+				records, err = LookupMX("golang.org")
+				if err.Error() != expectedErr.Error() {
+					t.Fatalf("unexpected error: %s", err)
+				}
+				if !reflect.DeepEqual(records, expected) {
+					t.Error("Unexpected record set")
+				}
+			},
+		},
+		{
+			name: "NS",
+			f: func(t *testing.T) {
+				expected := []*NS{
+					{
+						Host: "good.golang.org.",
+					},
+				}
+				expectedErr := &DNSError{Err: errMalformedDNSRecordsDetail, Name: "golang.org"}
+				records, err := r.LookupNS(context.Background(), "golang.org")
+				if err.Error() != expectedErr.Error() {
+					t.Fatalf("unexpected error: %s", err)
+				}
+				if !reflect.DeepEqual(records, expected) {
+					t.Error("Unexpected record set")
+				}
+				records, err = LookupNS("golang.org")
+				if err.Error() != expectedErr.Error() {
+					t.Fatalf("unexpected error: %s", err)
+				}
+				if !reflect.DeepEqual(records, expected) {
+					t.Error("Unexpected record set")
+				}
+			},
+		},
+		{
+			name: "Addr",
+			f: func(t *testing.T) {
+				expected := []string{"good.golang.org."}
+				expectedErr := &DNSError{Err: errMalformedDNSRecordsDetail, Name: "192.0.2.42"}
+				records, err := r.LookupAddr(context.Background(), "192.0.2.42")
+				if err.Error() != expectedErr.Error() {
+					t.Fatalf("unexpected error: %s", err)
+				}
+				if !reflect.DeepEqual(records, expected) {
+					t.Error("Unexpected record set")
+				}
+				records, err = LookupAddr("192.0.2.42")
+				if err.Error() != expectedErr.Error() {
+					t.Fatalf("unexpected error: %s", err)
+				}
+				if !reflect.DeepEqual(records, expected) {
+					t.Error("Unexpected record set")
+				}
+			},
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, tc.f)
+	}
+}
+
+func TestNullMX(t *testing.T) {
+	fake := fakeDNSServer{
+		rh: func(n, _ string, q dnsmessage.Message, _ time.Time) (dnsmessage.Message, error) {
+			r := dnsmessage.Message{
+				Header: dnsmessage.Header{
+					ID:       q.Header.ID,
+					Response: true,
+					RCode:    dnsmessage.RCodeSuccess,
+				},
+				Questions: q.Questions,
+				Answers: []dnsmessage.Resource{
+					{
+						Header: dnsmessage.ResourceHeader{
+							Name:  q.Questions[0].Name,
+							Type:  dnsmessage.TypeMX,
+							Class: dnsmessage.ClassINET,
+						},
+						Body: &dnsmessage.MXResource{
+							MX: dnsmessage.MustNewName("."),
+						},
+					},
+				},
+			}
+			return r, nil
+		},
+	}
+	r := Resolver{PreferGo: true, Dial: fake.DialContext}
+	rrset, err := r.LookupMX(context.Background(), "golang.org")
+	if err != nil {
+		t.Fatalf("LookupMX: %v", err)
+	}
+	if want := []*MX{&MX{Host: "."}}; !reflect.DeepEqual(rrset, want) {
+		records := []string{}
+		for _, rr := range rrset {
+			records = append(records, fmt.Sprintf("%v", rr))
+		}
+		t.Errorf("records = [%v]; want [%v]", strings.Join(records, " "), want[0])
+	}
+}

src/net/http/httputil/reverseproxy.go

@@ -248,22 +248,18 @@ func (p *ReverseProxy) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
 	// important is "Connection" because we want a persistent
 	// connection, regardless of what the client sent to us.
 	for _, h := range hopHeaders {
-		hv := outreq.Header.Get(h)
-		if hv == "" {
-			continue
-		}
-		if h == "Te" && hv == "trailers" {
-			// Issue 21096: tell backend applications that
-			// care about trailer support that we support
-			// trailers. (We do, but we don't go out of
-			// our way to advertise that unless the
-			// incoming client request thought it was
-			// worth mentioning)
-			continue
-		}
 		outreq.Header.Del(h)
 	}
 
+	// Issue 21096: tell backend applications that care about trailer support
+	// that we support trailers. (We do, but we don't go out of our way to
+	// advertise that unless the incoming client request thought it was worth
+	// mentioning.) Note that we look at req.Header, not outreq.Header, since
+	// the latter has passed through removeConnectionHeaders.
+	if httpguts.HeaderValuesContainsToken(req.Header["Te"], "trailers") {
+		outreq.Header.Set("Te", "trailers")
+	}
+
 	// After stripping all the hop-by-hop connection headers above, add back any
 	// necessary for protocol upgrades, such as for websockets.
 	if reqUpType != "" {

src/net/http/httputil/reverseproxy_test.go

@@ -90,8 +90,9 @@ func TestReverseProxy(t *testing.T) {
 
 	getReq, _ := http.NewRequest("GET", frontend.URL, nil)
 	getReq.Host = "some-name"
-	getReq.Header.Set("Connection", "close")
-	getReq.Header.Set("Te", "trailers")
+	getReq.Header.Set("Connection", "close, TE")
+	getReq.Header.Add("Te", "foo")
+	getReq.Header.Add("Te", "bar, trailers")
 	getReq.Header.Set("Proxy-Connection", "should be deleted")
 	getReq.Header.Set("Upgrade", "foo")
 	getReq.Close = true
@@ -235,6 +236,64 @@ func TestReverseProxyStripHeadersPresentInConnection(t *testing.T) {
 	}
 }
 
+func TestReverseProxyStripEmptyConnection(t *testing.T) {
+	// See Issue 46313.
+	const backendResponse = "I am the backend"
+
+	// someConnHeader is some arbitrary header to be declared as a hop-by-hop header
+	// in the Request's Connection header.
+	const someConnHeader = "X-Some-Conn-Header"
+
+	backend := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if c := r.Header.Values("Connection"); len(c) != 0 {
+			t.Errorf("handler got header %q = %v; want empty", "Connection", c)
+		}
+		if c := r.Header.Get(someConnHeader); c != "" {
+			t.Errorf("handler got header %q = %q; want empty", someConnHeader, c)
+		}
+		w.Header().Add("Connection", "")
+		w.Header().Add("Connection", someConnHeader)
+		w.Header().Set(someConnHeader, "should be deleted")
+		io.WriteString(w, backendResponse)
+	}))
+	defer backend.Close()
+	backendURL, err := url.Parse(backend.URL)
+	if err != nil {
+		t.Fatal(err)
+	}
+	proxyHandler := NewSingleHostReverseProxy(backendURL)
+	frontend := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		proxyHandler.ServeHTTP(w, r)
+		if c := r.Header.Get(someConnHeader); c != "should be deleted" {
+			t.Errorf("handler modified header %q = %q; want %q", someConnHeader, c, "should be deleted")
+		}
+	}))
+	defer frontend.Close()
+
+	getReq, _ := http.NewRequest("GET", frontend.URL, nil)
+	getReq.Header.Add("Connection", "")
+	getReq.Header.Add("Connection", someConnHeader)
+	getReq.Header.Set(someConnHeader, "should be deleted")
+	res, err := frontend.Client().Do(getReq)
+	if err != nil {
+		t.Fatalf("Get: %v", err)
+	}
+	defer res.Body.Close()
+	bodyBytes, err := io.ReadAll(res.Body)
+	if err != nil {
+		t.Fatalf("reading body: %v", err)
+	}
+	if got, want := string(bodyBytes), backendResponse; got != want {
+		t.Errorf("got body %q; want %q", got, want)
+	}
+	if c := res.Header.Get("Connection"); c != "" {
+		t.Errorf("handler got header %q = %q; want empty", "Connection", c)
+	}
+	if c := res.Header.Get(someConnHeader); c != "" {
+		t.Errorf("handler got header %q = %q; want empty", someConnHeader, c)
+	}
+}
+
 func TestXForwardedFor(t *testing.T) {
 	const prevForwardedFor = "client ip"
 	const backendResponse = "I am the backend"

src/net/http/server.go

@@ -577,37 +577,17 @@ func (w *response) ReadFrom(src io.Reader) (n int64, err error) {
 		return io.CopyBuffer(writerOnly{w}, src, buf)
 	}
 
-	// sendfile path:
-
-	// Do not start actually writing response until src is readable.
-	// If body length is <= sniffLen, sendfile/splice path will do
-	// little anyway. This small read also satisfies sniffing the
-	// body in case Content-Type is missing.
-	nr, er := src.Read(buf[:sniffLen])
-	atEOF := errors.Is(er, io.EOF)
-	n += int64(nr)
-
-	if nr > 0 {
-		// Write the small amount read normally.
-		nw, ew := w.Write(buf[:nr])
-		if ew != nil {
-			err = ew
-		} else if nr != nw {
-			err = io.ErrShortWrite
+	// Copy the first sniffLen bytes before switching to ReadFrom.
+	// This ensures we don't start writing the response before the
+	// source is available (see golang.org/issue/5660) and provides
+	// enough bytes to perform Content-Type sniffing when required.
+	if !w.cw.wroteHeader {
+		n0, err := io.CopyBuffer(writerOnly{w}, io.LimitReader(src, sniffLen), buf)
+		n += n0
+		if err != nil || n0 < sniffLen {
+			return n, err
 		}
 	}
-	if err == nil && er != nil && !atEOF {
-		err = er
-	}
-
-	// Do not send StatusOK in the error case where nothing has been written.
-	if err == nil && !w.wroteHeader {
-		w.WriteHeader(StatusOK) // nr == 0, no error (or EOF)
-	}
-
-	if err != nil || atEOF {
-		return n, err
-	}
 
 	w.w.Flush()  // get rid of any previous writes
 	w.cw.flush() // make sure Header is written; flush data to rwc
@@ -620,7 +600,7 @@ func (w *response) ReadFrom(src io.Reader) (n int64, err error) {
 		return n, err
 	}
 
-	n0, err := io.Copy(writerOnly{w}, src)
+	n0, err := io.CopyBuffer(writerOnly{w}, src, buf)
 	n += n0
 	return n, err
 }

src/net/http/sniff_test.go

@@ -157,9 +157,25 @@ func testServerIssue5953(t *testing.T, h2 bool) {
 	resp.Body.Close()
 }
 
-func TestContentTypeWithCopy_h1(t *testing.T) { testContentTypeWithCopy(t, h1Mode) }
-func TestContentTypeWithCopy_h2(t *testing.T) { testContentTypeWithCopy(t, h2Mode) }
-func testContentTypeWithCopy(t *testing.T, h2 bool) {
+type byteAtATimeReader struct {
+	buf []byte
+}
+
+func (b *byteAtATimeReader) Read(p []byte) (n int, err error) {
+	if len(p) < 1 {
+		return 0, nil
+	}
+	if len(b.buf) == 0 {
+		return 0, io.EOF
+	}
+	p[0] = b.buf[0]
+	b.buf = b.buf[1:]
+	return 1, nil
+}
+
+func TestContentTypeWithVariousSources_h1(t *testing.T) { testContentTypeWithVariousSources(t, h1Mode) }
+func TestContentTypeWithVariousSources_h2(t *testing.T) { testContentTypeWithVariousSources(t, h2Mode) }
+func testContentTypeWithVariousSources(t *testing.T, h2 bool) {
 	defer afterTest(t)
 
 	const (
@@ -167,30 +183,86 @@ func testContentTypeWithCopy(t *testing.T, h2 bool) {
 		expected = "text/html; charset=utf-8"
 	)
 
-	cst := newClientServerTest(t, h2, HandlerFunc(func(w ResponseWriter, r *Request) {
-		// Use io.Copy from a bytes.Buffer to trigger ReadFrom.
-		buf := bytes.NewBuffer([]byte(input))
-		n, err := io.Copy(w, buf)
-		if int(n) != len(input) || err != nil {
-			t.Errorf("io.Copy(w, %q) = %v, %v want %d, nil", input, n, err, len(input))
-		}
-	}))
-	defer cst.close()
+	for _, test := range []struct {
+		name    string
+		handler func(ResponseWriter, *Request)
+	}{{
+		name: "write",
+		handler: func(w ResponseWriter, r *Request) {
+			// Write the whole input at once.
+			n, err := w.Write([]byte(input))
+			if int(n) != len(input) || err != nil {
+				t.Errorf("w.Write(%q) = %v, %v want %d, nil", input, n, err, len(input))
+			}
+		},
+	}, {
+		name: "write one byte at a time",
+		handler: func(w ResponseWriter, r *Request) {
+			// Write the input one byte at a time.
+			buf := []byte(input)
+			for i := range buf {
+				n, err := w.Write(buf[i : i+1])
+				if n != 1 || err != nil {
+					t.Errorf("w.Write(%q) = %v, %v want 1, nil", input, n, err)
+				}
+			}
+		},
+	}, {
+		name: "copy from Reader",
+		handler: func(w ResponseWriter, r *Request) {
+			// Use io.Copy from a plain Reader.
+			type readerOnly struct{ io.Reader }
+			buf := bytes.NewBuffer([]byte(input))
+			n, err := io.Copy(w, readerOnly{buf})
+			if int(n) != len(input) || err != nil {
+				t.Errorf("io.Copy(w, %q) = %v, %v want %d, nil", input, n, err, len(input))
+			}
+		},
+	}, {
+		name: "copy from bytes.Buffer",
+		handler: func(w ResponseWriter, r *Request) {
+			// Use io.Copy from a bytes.Buffer to trigger ReadFrom.
+			buf := bytes.NewBuffer([]byte(input))
+			n, err := io.Copy(w, buf)
+			if int(n) != len(input) || err != nil {
+				t.Errorf("io.Copy(w, %q) = %v, %v want %d, nil", input, n, err, len(input))
+			}
+		},
+	}, {
+		name: "copy one byte at a time",
+		handler: func(w ResponseWriter, r *Request) {
+			// Use io.Copy from a Reader that returns one byte at a time.
+			n, err := io.Copy(w, &byteAtATimeReader{[]byte(input)})
+			if int(n) != len(input) || err != nil {
+				t.Errorf("io.Copy(w, %q) = %v, %v want %d, nil", input, n, err, len(input))
+			}
+		},
+	}} {
+		t.Run(test.name, func(t *testing.T) {
+			cst := newClientServerTest(t, h2, HandlerFunc(test.handler))
+			defer cst.close()
+
+			resp, err := cst.c.Get(cst.ts.URL)
+			if err != nil {
+				t.Fatalf("Get: %v", err)
+			}
+			if ct := resp.Header.Get("Content-Type"); ct != expected {
+				t.Errorf("Content-Type = %q, want %q", ct, expected)
+			}
+			if want, got := resp.Header.Get("Content-Length"), fmt.Sprint(len(input)); want != got {
+				t.Errorf("Content-Length = %q, want %q", want, got)
+			}
+			data, err := io.ReadAll(resp.Body)
+			if err != nil {
+				t.Errorf("reading body: %v", err)
+			} else if !bytes.Equal(data, []byte(input)) {
+				t.Errorf("data is %q, want %q", data, input)
+			}
+			resp.Body.Close()
+
+		})
 
-	resp, err := cst.c.Get(cst.ts.URL)
-	if err != nil {
-		t.Fatalf("Get: %v", err)
 	}
-	if ct := resp.Header.Get("Content-Type"); ct != expected {
-		t.Errorf("Content-Type = %q, want %q", ct, expected)
-	}
-	data, err := io.ReadAll(resp.Body)
-	if err != nil {
-		t.Errorf("reading body: %v", err)
-	} else if !bytes.Equal(data, []byte(input)) {
-		t.Errorf("data is %q, want %q", data, input)
-	}
-	resp.Body.Close()
 }
 
 func TestSniffWriteSize_h1(t *testing.T) { testSniffWriteSize(t, h1Mode) }

src/net/http/transport_test.go

@@ -5314,7 +5314,6 @@ func TestMissingStatusNoPanic(t *testing.T) {
 
 	ln := newLocalListener(t)
 	addr := ln.Addr().String()
-	shutdown := make(chan bool, 1)
 	done := make(chan bool)
 	fullAddrURL := fmt.Sprintf("http://%s", addr)
 	raw := "HTTP/1.1 400\r\n" +
@@ -5326,10 +5325,7 @@ func TestMissingStatusNoPanic(t *testing.T) {
 		"Aloha Olaa"
 
 	go func() {
-		defer func() {
-			ln.Close()
-			close(done)
-		}()
+		defer close(done)
 
 		conn, _ := ln.Accept()
 		if conn != nil {
@@ -5360,7 +5356,7 @@ func TestMissingStatusNoPanic(t *testing.T) {
 		t.Errorf("got=%v want=%q", err, want)
 	}
 
-	close(shutdown)
+	ln.Close()
 	<-done
 }
 

src/net/lookup.go

@@ -389,8 +389,11 @@ func (r *Resolver) LookupPort(ctx context.Context, network, service string) (por
 // LookupCNAME does not return an error if host does not
 // contain DNS "CNAME" records, as long as host resolves to
 // address records.
+//
+// The returned canonical name is validated to be a properly
+// formatted presentation-format domain name.
 func LookupCNAME(host string) (cname string, err error) {
-	return DefaultResolver.lookupCNAME(context.Background(), host)
+	return DefaultResolver.LookupCNAME(context.Background(), host)
 }
 
 // LookupCNAME returns the canonical name for the given host.
@@ -403,8 +406,18 @@ func LookupCNAME(host string) (cname string, err error) {
 // LookupCNAME does not return an error if host does not
 // contain DNS "CNAME" records, as long as host resolves to
 // address records.
-func (r *Resolver) LookupCNAME(ctx context.Context, host string) (cname string, err error) {
-	return r.lookupCNAME(ctx, host)
+//
+// The returned canonical name is validated to be a properly
+// formatted presentation-format domain name.
+func (r *Resolver) LookupCNAME(ctx context.Context, host string) (string, error) {
+	cname, err := r.lookupCNAME(ctx, host)
+	if err != nil {
+		return "", err
+	}
+	if !isDomainName(cname) {
+		return "", &DNSError{Err: errMalformedDNSRecordsDetail, Name: host}
+	}
+	return cname, nil
 }
 
 // LookupSRV tries to resolve an SRV query of the given service,
@@ -416,8 +429,13 @@ func (r *Resolver) LookupCNAME(ctx context.Context, host string) (cname string,
 // That is, it looks up _service._proto.name. To accommodate services
 // publishing SRV records under non-standard names, if both service
 // and proto are empty strings, LookupSRV looks up name directly.
+//
+// The returned service names are validated to be properly
+// formatted presentation-format domain names. If the response contains
+// invalid names, those records are filtered out and an error
+// will be returned alongside the the remaining results, if any.
 func LookupSRV(service, proto, name string) (cname string, addrs []*SRV, err error) {
-	return DefaultResolver.lookupSRV(context.Background(), service, proto, name)
+	return DefaultResolver.LookupSRV(context.Background(), service, proto, name)
 }
 
 // LookupSRV tries to resolve an SRV query of the given service,
@@ -429,28 +447,115 @@ func LookupSRV(service, proto, name string) (cname string, addrs []*SRV, err err
 // That is, it looks up _service._proto.name. To accommodate services
 // publishing SRV records under non-standard names, if both service
 // and proto are empty strings, LookupSRV looks up name directly.
-func (r *Resolver) LookupSRV(ctx context.Context, service, proto, name string) (cname string, addrs []*SRV, err error) {
-	return r.lookupSRV(ctx, service, proto, name)
+//
+// The returned service names are validated to be properly
+// formatted presentation-format domain names. If the response contains
+// invalid names, those records are filtered out and an error
+// will be returned alongside the the remaining results, if any.
+func (r *Resolver) LookupSRV(ctx context.Context, service, proto, name string) (string, []*SRV, error) {
+	cname, addrs, err := r.lookupSRV(ctx, service, proto, name)
+	if err != nil {
+		return "", nil, err
+	}
+	if cname != "" && !isDomainName(cname) {
+		return "", nil, &DNSError{Err: "SRV header name is invalid", Name: name}
+	}
+	filteredAddrs := make([]*SRV, 0, len(addrs))
+	for _, addr := range addrs {
+		if addr == nil {
+			continue
+		}
+		if !isDomainName(addr.Target) {
+			continue
+		}
+		filteredAddrs = append(filteredAddrs, addr)
+	}
+	if len(addrs) != len(filteredAddrs) {
+		return cname, filteredAddrs, &DNSError{Err: errMalformedDNSRecordsDetail, Name: name}
+	}
+	return cname, filteredAddrs, nil
 }
 
 // LookupMX returns the DNS MX records for the given domain name sorted by preference.
+//
+// The returned mail server names are validated to be properly
+// formatted presentation-format domain names. If the response contains
+// invalid names, those records are filtered out and an error
+// will be returned alongside the the remaining results, if any.
+//
+// LookupMX uses context.Background internally; to specify the context, use
+// Resolver.LookupMX.
 func LookupMX(name string) ([]*MX, error) {
-	return DefaultResolver.lookupMX(context.Background(), name)
+	return DefaultResolver.LookupMX(context.Background(), name)
 }
 
 // LookupMX returns the DNS MX records for the given domain name sorted by preference.
+//
+// The returned mail server names are validated to be properly
+// formatted presentation-format domain names. If the response contains
+// invalid names, those records are filtered out and an error
+// will be returned alongside the the remaining results, if any.
 func (r *Resolver) LookupMX(ctx context.Context, name string) ([]*MX, error) {
-	return r.lookupMX(ctx, name)
+	records, err := r.lookupMX(ctx, name)
+	if err != nil {
+		return nil, err
+	}
+	filteredMX := make([]*MX, 0, len(records))
+	for _, mx := range records {
+		if mx == nil {
+			continue
+		}
+		// Bypass the hostname validity check for targets which contain only a dot,
+		// as this is used to represent a 'Null' MX record.
+		if mx.Host != "." && !isDomainName(mx.Host) {
+			continue
+		}
+		filteredMX = append(filteredMX, mx)
+	}
+	if len(records) != len(filteredMX) {
+		return filteredMX, &DNSError{Err: errMalformedDNSRecordsDetail, Name: name}
+	}
+	return filteredMX, nil
 }
 
 // LookupNS returns the DNS NS records for the given domain name.
+//
+// The returned name server names are validated to be properly
+// formatted presentation-format domain names. If the response contains
+// invalid names, those records are filtered out and an error
+// will be returned alongside the the remaining results, if any.
+//
+// LookupNS uses context.Background internally; to specify the context, use
+// Resolver.LookupNS.
 func LookupNS(name string) ([]*NS, error) {
-	return DefaultResolver.lookupNS(context.Background(), name)
+	return DefaultResolver.LookupNS(context.Background(), name)
 }
 
 // LookupNS returns the DNS NS records for the given domain name.
+//
+// The returned name server names are validated to be properly
+// formatted presentation-format domain names. If the response contains
+// invalid names, those records are filtered out and an error
+// will be returned alongside the the remaining results, if any.
 func (r *Resolver) LookupNS(ctx context.Context, name string) ([]*NS, error) {
-	return r.lookupNS(ctx, name)
+	records, err := r.lookupNS(ctx, name)
+	if err != nil {
+		return nil, err
+	}
+	filteredNS := make([]*NS, 0, len(records))
+	for _, ns := range records {
+		if ns == nil {
+			continue
+		}
+		if !isDomainName(ns.Host) {
+			continue
+		}
+		filteredNS = append(filteredNS, ns)
+	}
+	if len(records) != len(filteredNS) {
+		return filteredNS, &DNSError{Err: errMalformedDNSRecordsDetail, Name: name}
+	}
+	return filteredNS, nil
 }
 
 // LookupTXT returns the DNS TXT records for the given domain name.
@@ -466,14 +571,40 @@ func (r *Resolver) LookupTXT(ctx context.Context, name string) ([]string, error)
 // LookupAddr performs a reverse lookup for the given address, returning a list
 // of names mapping to that address.
 //
+// The returned names are validated to be properly formatted presentation-format
+// domain names. If the response contains invalid names, those records are filtered
+// out and an error will be returned alongside the the remaining results, if any.
+//
 // When using the host C library resolver, at most one result will be
 // returned. To bypass the host resolver, use a custom Resolver.
 func LookupAddr(addr string) (names []string, err error) {
-	return DefaultResolver.lookupAddr(context.Background(), addr)
+	return DefaultResolver.LookupAddr(context.Background(), addr)
 }
 
 // LookupAddr performs a reverse lookup for the given address, returning a list
 // of names mapping to that address.
-func (r *Resolver) LookupAddr(ctx context.Context, addr string) (names []string, err error) {
-	return r.lookupAddr(ctx, addr)
+//
+// The returned names are validated to be properly formatted presentation-format
+// domain names. If the response contains invalid names, those records are filtered
+// out and an error will be returned alongside the the remaining results, if any.
+func (r *Resolver) LookupAddr(ctx context.Context, addr string) ([]string, error) {
+	names, err := r.lookupAddr(ctx, addr)
+	if err != nil {
+		return nil, err
+	}
+	filteredNames := make([]string, 0, len(names))
+	for _, name := range names {
+		if isDomainName(name) {
+			filteredNames = append(filteredNames, name)
+		}
+	}
+	if len(names) != len(filteredNames) {
+		return filteredNames, &DNSError{Err: errMalformedDNSRecordsDetail, Name: addr}
+	}
+	return filteredNames, nil
 }
+
+// errMalformedDNSRecordsDetail is the DNSError detail which is returned when a Resolver.Lookup...
+// method recieves DNS records which contain invalid DNS names. This may be returned alongside
+// results which have had the malformed records filtered out.
+var errMalformedDNSRecordsDetail = "DNS response contained records which contain invalid names"

src/os/signal/signal_test.go

@@ -15,6 +15,7 @@ import (
 	"os"
 	"os/exec"
 	"runtime"
+	"runtime/trace"
 	"strconv"
 	"sync"
 	"syscall"
@@ -853,3 +854,44 @@ func TestNotifyContextStringer(t *testing.T) {
 		t.Errorf("c.String() = %q, want %q", got, want)
 	}
 }
+
+// #44193 test signal handling while stopping and starting the world.
+func TestSignalTrace(t *testing.T) {
+	done := make(chan struct{})
+	quit := make(chan struct{})
+	c := make(chan os.Signal, 1)
+	Notify(c, syscall.SIGHUP)
+
+	// Source and sink for signals busy loop unsynchronized with
+	// trace starts and stops. We are ultimately validating that
+	// signals and runtime.(stop|start)TheWorldGC are compatible.
+	go func() {
+		defer close(done)
+		defer Stop(c)
+		pid := syscall.Getpid()
+		for {
+			select {
+			case <-quit:
+				return
+			default:
+				syscall.Kill(pid, syscall.SIGHUP)
+			}
+			waitSig(t, c, syscall.SIGHUP)
+		}
+	}()
+
+	for i := 0; i < 100; i++ {
+		buf := new(bytes.Buffer)
+		if err := trace.Start(buf); err != nil {
+			t.Fatalf("[%d] failed to start tracing: %v", i, err)
+		}
+		time.After(1 * time.Microsecond)
+		trace.Stop()
+		size := buf.Len()
+		if size == 0 {
+			t.Fatalf("[%d] trace is empty", i)
+		}
+	}
+	close(quit)
+	<-done
+}

src/run.bash

@@ -23,15 +23,7 @@ fi
 
 eval $(../bin/go env)
 export GOROOT   # The api test requires GOROOT to be set, so set it to match ../bin/go.
-
-# We disallow local import for non-local packages, if $GOROOT happens
-# to be under $GOPATH, then some tests below will fail.  $GOPATH needs
-# to be set to a non-empty string, else Go will set a default value
-# that may also conflict with $GOROOT.  The $GOPATH value doesn't need
-# to point to an actual directory, it just needs to pass the semantic
-# checks performed by Go.  Use $GOROOT to define $GOPATH so that we
-# don't blunder into a user-defined symbolic link.
-export GOPATH=/dev/null
+export GOPATH=/nonexist-gopath
 
 unset CDPATH	# in case user has it set
 export GOBIN=$GOROOT/bin  # Issue 14340

src/run.bat

@@ -18,9 +18,7 @@ setlocal
 
 set GOBUILDFAIL=0
 
-:: we disallow local import for non-local packages, if %GOROOT% happens
-:: to be under %GOPATH%, then some tests below will fail
-set GOPATH=
+set GOPATH=c:\nonexist-gopath
 :: Issue 14340: ignore GOBIN during all.bat.
 set GOBIN=
 set GOFLAGS=

src/run.rc

@@ -12,10 +12,9 @@ if(! test -f ../bin/go){
 
 eval `{../bin/go env}
 
-GOPATH = () # we disallow local import for non-local packages, if $GOROOT happens
-            # to be under $GOPATH, then some tests below will fail
-GOBIN = () # Issue 14340
-GOFLAGS = ()
-GO111MODULE = ()
+GOPATH=/nonexist-gopath
+GOBIN=() # Issue 14340
+GOFLAGS=()
+GO111MODULE=()
 
 exec ../bin/go tool dist test -rebuild $*

src/runtime/cgo/linux_syscall.c

@@ -32,7 +32,7 @@ typedef struct {
 
 #define SET_RETVAL(fn) \
   uintptr_t ret = (uintptr_t) fn ; \
-  if (ret == -1) {                 \
+  if (ret == (uintptr_t) -1) {	   \
     x->retval = (uintptr_t) errno; \
   } else                           \
     x->retval = ret

src/runtime/pprof/pprof_test.go

@@ -279,7 +279,8 @@ func testCPUProfile(t *testing.T, matches matchFunc, need []string, avoid []stri
 
 	broken := false
 	switch runtime.GOOS {
-	case "darwin", "ios", "dragonfly", "netbsd", "illumos", "solaris":
+	// See https://golang.org/issue/45170 for AIX.
+	case "darwin", "ios", "dragonfly", "netbsd", "illumos", "solaris", "aix":
 		broken = true
 	case "openbsd":
 		if runtime.GOARCH == "arm" || runtime.GOARCH == "arm64" {

src/runtime/proc.go

@@ -1338,6 +1338,9 @@ func mPark() {
 	g := getg()
 	for {
 		notesleep(&g.m.park)
+		// Note, because of signal handling by this parked m,
+		// a preemptive mDoFixup() may actually occur via
+		// mDoFixupAndOSYield(). (See golang.org/issue/44193)
 		noteclear(&g.m.park)
 		if !mDoFixup() {
 			return
@@ -1571,6 +1574,22 @@ func syscall_runtime_doAllThreadsSyscall(fn func(bool) bool) {
 	for atomic.Load(&sched.sysmonStarting) != 0 {
 		osyield()
 	}
+
+	// We don't want this thread to handle signals for the
+	// duration of this critical section. The underlying issue
+	// being that this locked coordinating m is the one monitoring
+	// for fn() execution by all the other m's of the runtime,
+	// while no regular go code execution is permitted (the world
+	// is stopped). If this present m were to get distracted to
+	// run signal handling code, and find itself waiting for a
+	// second thread to execute go code before being able to
+	// return from that signal handling, a deadlock will result.
+	// (See golang.org/issue/44193.)
+	lockOSThread()
+	var sigmask sigset
+	sigsave(&sigmask)
+	sigblock(false)
+
 	stopTheWorldGC("doAllThreadsSyscall")
 	if atomic.Load(&newmHandoff.haveTemplateThread) != 0 {
 		// Ensure that there are no in-flight thread
@@ -1622,6 +1641,7 @@ func syscall_runtime_doAllThreadsSyscall(fn func(bool) bool) {
 			// the possibility of racing with mp.
 			lock(&mp.mFixup.lock)
 			mp.mFixup.fn = fn
+			atomic.Store(&mp.mFixup.used, 1)
 			if mp.doesPark {
 				// For non-service threads this will
 				// cause the wakeup to be short lived
@@ -1638,9 +1658,7 @@ func syscall_runtime_doAllThreadsSyscall(fn func(bool) bool) {
 				if mp.procid == tid {
 					continue
 				}
-				lock(&mp.mFixup.lock)
-				done = done && (mp.mFixup.fn == nil)
-				unlock(&mp.mFixup.lock)
+				done = atomic.Load(&mp.mFixup.used) == 0
 			}
 			if done {
 				break
@@ -1667,6 +1685,8 @@ func syscall_runtime_doAllThreadsSyscall(fn func(bool) bool) {
 		unlock(&mFixupRace.lock)
 	}
 	startTheWorldGC()
+	msigrestore(sigmask)
+	unlockOSThread()
 }
 
 // runSafePointFn runs the safe point function, if any, for this P.
@@ -2157,9 +2177,21 @@ var mFixupRace struct {
 // mDoFixup runs any outstanding fixup function for the running m.
 // Returns true if a fixup was outstanding and actually executed.
 //
+// Note: to avoid deadlocks, and the need for the fixup function
+// itself to be async safe, signals are blocked for the working m
+// while it holds the mFixup lock. (See golang.org/issue/44193)
+//
 //go:nosplit
 func mDoFixup() bool {
 	_g_ := getg()
+	if used := atomic.Load(&_g_.m.mFixup.used); used == 0 {
+		return false
+	}
+
+	// slow path - if fixup fn is used, block signals and lock.
+	var sigmask sigset
+	sigsave(&sigmask)
+	sigblock(false)
 	lock(&_g_.m.mFixup.lock)
 	fn := _g_.m.mFixup.fn
 	if fn != nil {
@@ -2176,7 +2208,6 @@ func mDoFixup() bool {
 			// is more obviously safe.
 			throw("GC must be disabled to protect validity of fn value")
 		}
-		*(*uintptr)(unsafe.Pointer(&_g_.m.mFixup.fn)) = 0
 		if _g_.racectx != 0 || !raceenabled {
 			fn(false)
 		} else {
@@ -2191,11 +2222,24 @@ func mDoFixup() bool {
 			_g_.racectx = 0
 			unlock(&mFixupRace.lock)
 		}
+		*(*uintptr)(unsafe.Pointer(&_g_.m.mFixup.fn)) = 0
+		atomic.Store(&_g_.m.mFixup.used, 0)
 	}
 	unlock(&_g_.m.mFixup.lock)
+	msigrestore(sigmask)
 	return fn != nil
 }
 
+// mDoFixupAndOSYield is called when an m is unable to send a signal
+// because the allThreadsSyscall mechanism is in progress. That is, an
+// mPark() has been interrupted with this signal handler so we need to
+// ensure the fixup is executed from this context.
+//go:nosplit
+func mDoFixupAndOSYield() {
+	mDoFixup()
+	osyield()
+}
+
 // templateThread is a thread in a known-good state that exists solely
 // to start new threads in known-good states when the calling thread
 // may not be in a good state.

src/runtime/runtime2.go

@@ -537,10 +537,13 @@ type m struct {
 	syscalltick   uint32
 	freelink      *m // on sched.freem
 
-	// mFixup is used to synchronize OS related m state (credentials etc)
-	// use mutex to access.
+	// mFixup is used to synchronize OS related m state
+	// (credentials etc) use mutex to access. To avoid deadlocks
+	// an atomic.Load() of used being zero in mDoFixupFn()
+	// guarantees fn is nil.
 	mFixup struct {
 		lock mutex
+		used uint32
 		fn   func(bool) bool
 	}
 

src/runtime/sigqueue.go

@@ -119,7 +119,7 @@ Send:
 			}
 		case sigFixup:
 			// nothing to do - we need to wait for sigIdle.
-			osyield()
+			mDoFixupAndOSYield()
 		}
 	}
 

src/runtime/symtab.go

@@ -102,7 +102,9 @@ func (ci *Frames) Next() (frame Frame, more bool) {
 		name := funcname(funcInfo)
 		if inldata := funcdata(funcInfo, _FUNCDATA_InlTree); inldata != nil {
 			inltree := (*[1 << 20]inlinedCall)(inldata)
-			ix := pcdatavalue(funcInfo, _PCDATA_InlTreeIndex, pc, nil)
+			// Non-strict as cgoTraceback may have added bogus PCs
+			// with a valid funcInfo but invalid PCDATA.
+			ix := pcdatavalue1(funcInfo, _PCDATA_InlTreeIndex, pc, nil, false)
 			if ix >= 0 {
 				// Note: entry is not modified. It always refers to a real frame, not an inlined one.
 				f = nil
@@ -183,7 +185,9 @@ func runtime_expandFinalInlineFrame(stk []uintptr) []uintptr {
 	var cache pcvalueCache
 	inltree := (*[1 << 20]inlinedCall)(inldata)
 	for {
-		ix := pcdatavalue(f, _PCDATA_InlTreeIndex, tracepc, &cache)
+		// Non-strict as cgoTraceback may have added bogus PCs
+		// with a valid funcInfo but invalid PCDATA.
+		ix := pcdatavalue1(f, _PCDATA_InlTreeIndex, tracepc, &cache, false)
 		if ix < 0 {
 			break
 		}

src/runtime/symtab_test.go

@@ -8,6 +8,7 @@ import (
 	"runtime"
 	"strings"
 	"testing"
+	"unsafe"
 )
 
 func TestCaller(t *testing.T) {
@@ -165,3 +166,87 @@ func TestNilName(t *testing.T) {
 		t.Errorf("Name() = %q, want %q", got, "")
 	}
 }
+
+var dummy int
+
+func inlined() {
+	// Side effect to prevent elimination of this entire function.
+	dummy = 42
+}
+
+// A function with an InlTree. Returns a PC within the function body.
+//
+// No inline to ensure this complete function appears in output.
+//
+//go:noinline
+func tracebackFunc(t *testing.T) uintptr {
+	// This body must be more complex than a single call to inlined to get
+	// an inline tree.
+	inlined()
+	inlined()
+
+	// Acquire a PC in this function.
+	pc, _, _, ok := runtime.Caller(0)
+	if !ok {
+		t.Fatalf("Caller(0) got ok false, want true")
+	}
+
+	return pc
+}
+
+// Test that CallersFrames handles PCs in the alignment region between
+// functions (int 3 on amd64) without crashing.
+//
+// Go will never generate a stack trace containing such an address, as it is
+// not a valid call site. However, the cgo traceback function passed to
+// runtime.SetCgoTraceback may not be completely accurate and may incorrect
+// provide PCs in Go code or the alignement region between functions.
+//
+// Go obviously doesn't easily expose the problematic PCs to running programs,
+// so this test is a bit fragile. Some details:
+//
+// * tracebackFunc is our target function. We want to get a PC in the
+//   alignment region following this function. This function also has other
+//   functions inlined into it to ensure it has an InlTree (this was the source
+//   of the bug in issue 44971).
+//
+// * We acquire a PC in tracebackFunc, walking forwards until FuncForPC says
+//   we're in a new function. The last PC of the function according to FuncForPC
+//   should be in the alignment region (assuming the function isn't already
+//   perfectly aligned).
+//
+// This is a regression test for issue 44971.
+func TestFunctionAlignmentTraceback(t *testing.T) {
+	pc := tracebackFunc(t)
+
+	// Double-check we got the right PC.
+	f := runtime.FuncForPC(pc)
+	if !strings.HasSuffix(f.Name(), "tracebackFunc") {
+		t.Fatalf("Caller(0) = %+v, want tracebackFunc", f)
+	}
+
+	// Iterate forward until we find a different function. Back up one
+	// instruction is (hopefully) an alignment instruction.
+	for runtime.FuncForPC(pc) == f {
+		pc++
+	}
+	pc--
+
+	// Is this an alignment region filler instruction? We only check this
+	// on amd64 for simplicity. If this function has no filler, then we may
+	// get a false negative, but will never get a false positive.
+	if runtime.GOARCH == "amd64" {
+		code := *(*uint8)(unsafe.Pointer(pc))
+		if code != 0xcc { // INT $3
+			t.Errorf("PC %v code got %#x want 0xcc", pc, code)
+		}
+	}
+
+	// Finally ensure that Frames.Next doesn't crash when processing this
+	// PC.
+	frames := runtime.CallersFrames([]uintptr{pc})
+	frame, _ := frames.Next()
+	if frame.Func != f {
+		t.Errorf("frames.Next() got %+v want %+v", frame.Func, f)
+	}
+}

src/runtime/time.go

@@ -263,6 +263,9 @@ func addtimer(t *timer) {
 
 	when := t.when
 
+	// Disable preemption while using pp to avoid changing another P's heap.
+	mp := acquirem()
+
 	pp := getg().m.p.ptr()
 	lock(&pp.timersLock)
 	cleantimers(pp)
@@ -270,6 +273,8 @@ func addtimer(t *timer) {
 	unlock(&pp.timersLock)
 
 	wakeNetPoller(when)
+
+	releasem(mp)
 }
 
 // doaddtimer adds t to the current P's heap.