cmd/dist: update to assume Go 1.17.13 as minimal Go bootstrap version

Replace explicit Go version names where possible with generic reference
to Go bootstrap version.

Updates #44505

Change-Id: I4a6439576efd40e72acd26fcc1472a1a8b0b06e7
Reviewed-on: https://go-review.googlesource.com/c/go/+/344330
Auto-Submit: Martin Möhrmann <martin@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
Run-TryBot: Martin Möhrmann <moehrmann@google.com>
Reviewed-by: Russ Cox <rsc@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>

src/cmd/dist/README

@@ -4,10 +4,10 @@ As of Go 1.5, dist and other parts of the compiler toolchain are written
 in Go, making bootstrapping a little more involved than in the past.
 The approach is to build the current release of Go with an earlier one.
 
-The process to install Go 1.x, for x ≥ 5, is:
+The process to install Go 1.x, for x ≥ 20, is:
 
-1. Build cmd/dist with Go 1.4.
-2. Using dist, build Go 1.x compiler toolchain with Go 1.4.
+1. Build cmd/dist with Go 1.17.13.
+2. Using dist, build Go 1.x compiler toolchain with Go 1.17.13.
 3. Using dist, rebuild Go 1.x compiler toolchain with itself.
 4. Using dist, build Go 1.x cmd/go (as go_bootstrap) with Go 1.x compiler toolchain.
 5. Using go_bootstrap, build the remaining Go 1.x standard library and commands.
@@ -16,8 +16,8 @@ NOTE: During the transition from the old C-based toolchain to the Go-based one,
 step 2 also builds the parts of the toolchain written in C, and step 3 does not
 recompile those.
 
-Because of backward compatibility, although the steps above say Go 1.4,
-in practice any release ≥ Go 1.4 but < Go 1.x will work as the bootstrap base.
+Because of backward compatibility, although the steps above say Go 1.17.13,
+in practice any release ≥ Go 1.17.13 but < Go 1.x will work as the bootstrap base.
 
 See golang.org/s/go15bootstrap for more details.
 

src/cmd/dist/build.go

@@ -386,7 +386,7 @@ func findgoversion() string {
 	// Note that we lightly parse internal/goversion/goversion.go to
 	// obtain the base version. We can't just import the package,
 	// because cmd/dist is built with a bootstrap GOROOT which could
-	// be an entirely different version of Go, like 1.4. We assume
+	// be an entirely different version of Go. We assume
 	// that the file contains "const Version = <Integer>".
 	goversionSource := readfile(pathf("%s/src/internal/goversion/goversion.go", goroot))
 	m := regexp.MustCompile(`(?m)^const Version = (\d+)`).FindStringSubmatch(goversionSource)
@@ -1253,18 +1253,10 @@ var toolchain = []string{"cmd/asm", "cmd/cgo", "cmd/compile", "cmd/link"}
 // The bootstrap command runs a build from scratch,
 // stopping at having installed the go_bootstrap command.
 //
-// WARNING: This command runs after cmd/dist is built with Go 1.4.
+// WARNING: This command runs after cmd/dist is built with the Go bootstrap toolchain.
 // It rebuilds and installs cmd/dist with the new toolchain, so other
 // commands (like "go tool dist test" in run.bash) can rely on bug fixes
-// made since Go 1.4, but this function cannot. In particular, the uses
-// of os/exec in this function cannot assume that
-//
-//	cmd.Env = append(os.Environ(), "X=Y")
-//
-// sets $X to Y in the command's environment. That guarantee was
-// added after Go 1.4, and in fact in Go 1.4 it was typically the opposite:
-// if $X was already present in os.Environ(), most systems preferred
-// that setting, not the new one.
+// made since the Go bootstrap version, but this function cannot.
 func cmdbootstrap() {
 	timelog("start", "dist bootstrap")
 	defer timelog("end", "dist bootstrap")
@@ -1361,11 +1353,11 @@ func cmdbootstrap() {
 
 	// To recap, so far we have built the new toolchain
 	// (cmd/asm, cmd/cgo, cmd/compile, cmd/link)
-	// using Go 1.4's toolchain and go command.
+	// using the Go bootstrap toolchain and go command.
 	// Then we built the new go command (as go_bootstrap)
 	// using the new toolchain and our own build logic (above).
 	//
-	//	toolchain1 = mk(new toolchain, go1.4 toolchain, go1.4 cmd/go)
+	//	toolchain1 = mk(new toolchain, go1.17 toolchain, go1.17 cmd/go)
 	//	go_bootstrap = mk(new cmd/go, toolchain1, cmd/dist)
 	//
 	// The toolchain1 we built earlier is built from the new sources,
@@ -1391,7 +1383,7 @@ func cmdbootstrap() {
 	}
 
 	// Toolchain2 should be semantically equivalent to toolchain1,
-	// but it was built using the new compilers instead of the Go 1.4 compilers,
+	// but it was built using the newly built compiler instead of the Go bootstrap compiler,
 	// so it should at the least run faster. Also, toolchain1 had no build IDs
 	// in the binaries, while toolchain2 does. In non-release builds, the
 	// toolchain's build IDs feed into constructing the build IDs of built targets,

src/cmd/dist/buildtool.go

@@ -2,11 +2,11 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// Build toolchain using Go 1.4.
+// Build toolchain using Go bootstrap version.
 //
 // The general strategy is to copy the source files we need into
 // a new GOPATH workspace, adjust import paths appropriately,
-// invoke the Go 1.4 go command to build those sources,
+// invoke the Go bootstrap toolchains go command to build those sources,
 // and then copy the binaries back.
 
 package main
@@ -20,13 +20,13 @@ import (
 )
 
 // bootstrapDirs is a list of directories holding code that must be
-// compiled with a Go 1.4 toolchain to produce the bootstrapTargets.
+// compiled with the Go bootstrap toolchain to produce the bootstrapTargets.
 // All directories in this list are relative to and must be below $GOROOT/src.
 //
 // The list has two kinds of entries: names beginning with cmd/ with
 // no other slashes, which are commands, and other paths, which are packages
 // supporting the commands. Packages in the standard library can be listed
-// if a newer copy needs to be substituted for the Go 1.4 copy when used
+// if a newer copy needs to be substituted for the Go bootstrap copy when used
 // by the command packages. Paths ending with /... automatically
 // include all packages within subdirectories as well.
 // These will be imported during bootstrap as bootstrap/name, like bootstrap/math/big.
@@ -87,18 +87,10 @@ var ignorePrefixes = []string{
 	"#",
 }
 
-// File suffixes that use build tags introduced since Go 1.4.
+// File suffixes that use build tags introduced since Go 1.17.
 // These must not be copied into the bootstrap build directory.
 // Also ignore test files.
 var ignoreSuffixes = []string{
-	"_arm64.s",
-	"_arm64.go",
-	"_loong64.s",
-	"_loong64.go",
-	"_riscv64.s",
-	"_riscv64.go",
-	"_wasm.s",
-	"_wasm.go",
 	"_test.s",
 	"_test.go",
 }
@@ -181,12 +173,12 @@ func bootstrapBuildTools() {
 		})
 	}
 
-	// Set up environment for invoking Go 1.4 go command.
-	// GOROOT points at Go 1.4 GOROOT,
+	// Set up environment for invoking Go bootstrap toolchains go command.
+	// GOROOT points at Go bootstrap GOROOT,
 	// GOPATH points at our bootstrap workspace,
 	// GOBIN is empty, so that binaries are installed to GOPATH/bin,
 	// and GOOS, GOHOSTOS, GOARCH, and GOHOSTOS are empty,
-	// so that Go 1.4 builds whatever kind of binary it knows how to build.
+	// so that Go bootstrap toolchain builds whatever kind of binary it knows how to build.
 	// Restore GOROOT, GOPATH, and GOBIN when done.
 	// Don't bother with GOOS, GOHOSTOS, GOARCH, and GOHOSTARCH,
 	// because setup will take care of those when bootstrapBuildTools returns.
@@ -205,20 +197,14 @@ func bootstrapBuildTools() {
 	os.Setenv("GOARCH", "")
 	os.Setenv("GOHOSTARCH", "")
 
-	// Run Go 1.4 to build binaries. Use -gcflags=-l to disable inlining to
-	// workaround bugs in Go 1.4's compiler. See discussion thread:
-	// https://groups.google.com/d/msg/golang-dev/Ss7mCKsvk8w/Gsq7VYI0AwAJ
+	// Run Go bootstrap to build binaries.
 	// Use the math_big_pure_go build tag to disable the assembly in math/big
 	// which may contain unsupported instructions.
 	// Use the purego build tag to disable other assembly code,
 	// such as in cmd/internal/notsha256.
-	// Note that if we are using Go 1.10 or later as bootstrap, the -gcflags=-l
-	// only applies to the final cmd/go binary, but that's OK: if this is Go 1.10
-	// or later we don't need to disable inlining to work around bugs in the Go 1.4 compiler.
 	cmd := []string{
 		pathf("%s/bin/go", goroot_bootstrap),
 		"install",
-		"-gcflags=-l",
 		"-tags=math_big_pure_go compiler_bootstrap purego",
 	}
 	if vflag > 0 {

src/cmd/dist/test.go

@@ -8,6 +8,7 @@ import (
 	"bytes"
 	"flag"
 	"fmt"
+	"io/fs"
 	"log"
 	"os"
 	"os/exec"
@@ -1709,8 +1710,7 @@ func (t *tester) makeGOROOTUnwritable() (undo func()) {
 	}
 	gocacheSubdir, _ := filepath.Rel(dir, gocache)
 
-	// Note: Can't use WalkDir here, because this has to compile with Go 1.4.
-	filepath.Walk(dir, func(path string, info os.FileInfo, err error) error {
+	filepath.WalkDir(dir, func(path string, d fs.DirEntry, err error) error {
 		if suffix := strings.TrimPrefix(path, dir+string(filepath.Separator)); suffix != "" {
 			if suffix == gocacheSubdir {
 				// Leave GOCACHE writable: we may need to write test binaries into it.
@@ -1723,11 +1723,18 @@ func (t *tester) makeGOROOTUnwritable() (undo func()) {
 				return filepath.SkipDir
 			}
 		}
-		if err == nil {
-			mode := info.Mode()
-			if mode&0222 != 0 && (mode.IsDir() || mode.IsRegular()) {
-				dirs = append(dirs, pathMode{path, mode})
-			}
+		if err != nil {
+			return nil
+		}
+
+		info, err := d.Info()
+		if err != nil {
+			return nil
+		}
+
+		mode := info.Mode()
+		if mode&0222 != 0 && (mode.IsDir() || mode.IsRegular()) {
+			dirs = append(dirs, pathMode{path, mode})
 		}
 		return nil
 	})
@@ -1747,7 +1754,7 @@ func (t *tester) makeGOROOTUnwritable() (undo func()) {
 
 // raceDetectorSupported is a copy of the function
 // internal/platform.RaceDetectorSupported, which can't be used here
-// because cmd/dist has to be buildable by Go 1.4.
+// because cmd/dist can not import internal packages during bootstrap.
 // The race detector only supports 48-bit VMA on arm64. But we don't have
 // a good solution to check VMA size(See https://golang.org/issue/29948)
 // raceDetectorSupported will always return true for arm64. But race

src/cmd/dist/util.go

@@ -85,7 +85,7 @@ func run(dir string, mode int, cmd ...string) string {
 	// as it runs without fear of mixing the output with some
 	// other command's output. Not buffering lets the output
 	// appear as it is printed instead of once the command exits.
-	// This is most important for the invocation of 'go1.4 build -v bootstrap/...'.
+	// This is most important for the invocation of 'go build -v bootstrap/...'.
 	if mode&(Background|ShowOutput) == ShowOutput {
 		xcmd.Stdout = os.Stdout
 		xcmd.Stderr = os.Stderr