blob: db0c9a7ea610b442129a556f5ac06f366aa6228d [file] [log] [blame]
// Copyright 2018 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 packagesdriver fetches type sizes for go/packages and go/analysis.
package packagesdriver
import (
var debug = false
// GetSizes returns the sizes used by the underlying driver with the given parameters.
func GetSizes(ctx context.Context, buildFlags, env []string, dir string, usesExportData bool) (types.Sizes, error) {
// TODO(matloob): Clean this up. This code is mostly a copy of packages.findExternalDriver.
const toolPrefix = "GOPACKAGESDRIVER="
tool := ""
for _, env := range env {
if val := strings.TrimPrefix(env, toolPrefix); val != env {
tool = val
if tool == "" {
var err error
tool, err = exec.LookPath("gopackagesdriver")
if err != nil {
// We did not find the driver, so use "go list".
tool = "off"
if tool == "off" {
return GetSizesGolist(ctx, buildFlags, env, dir, usesExportData)
req, err := json.Marshal(struct {
Command string `json:"command"`
Env []string `json:"env"`
BuildFlags []string `json:"build_flags"`
Command: "sizes",
Env: env,
BuildFlags: buildFlags,
if err != nil {
return nil, fmt.Errorf("failed to encode message to driver tool: %v", err)
buf := new(bytes.Buffer)
cmd := exec.CommandContext(ctx, tool)
cmd.Dir = dir
cmd.Env = env
cmd.Stdin = bytes.NewReader(req)
cmd.Stdout = buf
cmd.Stderr = new(bytes.Buffer)
if err := cmd.Run(); err != nil {
return nil, fmt.Errorf("%v: %v: %s", tool, err, cmd.Stderr)
var response struct {
// Sizes, if not nil, is the types.Sizes to use when type checking.
Sizes *types.StdSizes
if err := json.Unmarshal(buf.Bytes(), &response); err != nil {
return nil, err
return response.Sizes, nil
func GetSizesGolist(ctx context.Context, buildFlags, env []string, dir string, usesExportData bool) (types.Sizes, error) {
args := []string{"list", "-f", "{{context.GOARCH}} {{context.Compiler}}"}
args = append(args, buildFlags...)
args = append(args, "--", "unsafe")
stdout, stderr, err := invokeGo(ctx, env, dir, usesExportData, args...)
var goarch, compiler string
if err != nil {
if strings.Contains(err.Error(), "cannot find main module") {
// User's running outside of a module. All bets are off. Get GOARCH and guess compiler is gc.
// TODO(matloob): Is this a problem in practice?
envout, _, enverr := invokeGo(ctx, env, dir, usesExportData, "env", "GOARCH")
if enverr != nil {
return nil, err
goarch = strings.TrimSpace(envout.String())
compiler = "gc"
} else {
return nil, err
} else {
fields := strings.Fields(stdout.String())
if len(fields) < 2 {
return nil, fmt.Errorf("could not parse GOARCH and Go compiler in format \"<GOARCH> <compiler>\" from stdout of go command:\n%s\ndir: %s\nstdout: <<%s>>\nstderr: <<%s>>",
cmdDebugStr(env, args...), dir, stdout.String(), stderr.String())
goarch = fields[0]
compiler = fields[1]
return types.SizesFor(compiler, goarch), nil
// invokeGo returns the stdout and stderr of a go command invocation.
func invokeGo(ctx context.Context, env []string, dir string, usesExportData bool, args ...string) (*bytes.Buffer, *bytes.Buffer, error) {
if debug {
defer func(start time.Time) { log.Printf("%s for %v", time.Since(start), cmdDebugStr(env, args...)) }(time.Now())
stdout := new(bytes.Buffer)
stderr := new(bytes.Buffer)
cmd := exec.CommandContext(ctx, "go", args...)
// On darwin the cwd gets resolved to the real path, which breaks anything that
// expects the working directory to keep the original path, including the
// go command when dealing with modules.
// The Go stdlib has a special feature where if the cwd and the PWD are the
// same node then it trusts the PWD, so by setting it in the env for the child
// process we fix up all the paths returned by the go command.
cmd.Env = append(append([]string{}, env...), "PWD="+dir)
cmd.Dir = dir
cmd.Stdout = stdout
cmd.Stderr = stderr
if err := cmd.Run(); err != nil {
exitErr, ok := err.(*exec.ExitError)
if !ok {
// Catastrophic error:
// - executable not found
// - context cancellation
return nil, nil, fmt.Errorf("couldn't exec 'go %v': %s %T", args, err, err)
// Export mode entails a build.
// If that build fails, errors appear on stderr
// (despite the -e flag) and the Export field is blank.
// Do not fail in that case.
if !usesExportData {
return nil, nil, fmt.Errorf("go %v: %s: %s", args, exitErr, stderr)
// As of writing, go list -export prints some non-fatal compilation
// errors to stderr, even with -e set. We would prefer that it put
// them in the Package.Error JSON (see
// In the meantime, there's nowhere good to put them, but they can
// be useful for debugging. Print them if $GOPACKAGESPRINTGOLISTERRORS
// is set.
if len(stderr.Bytes()) != 0 && os.Getenv("GOPACKAGESPRINTGOLISTERRORS") != "" {
fmt.Fprintf(os.Stderr, "%s stderr: <<%s>>\n", cmdDebugStr(env, args...), stderr)
// debugging
if false {
fmt.Fprintf(os.Stderr, "%s stdout: <<%s>>\n", cmdDebugStr(env, args...), stdout)
return stdout, stderr, nil
func cmdDebugStr(envlist []string, args ...string) string {
env := make(map[string]string)
for _, kv := range envlist {
split := strings.Split(kv, "=")
k, v := split[0], split[1]
env[k] = v
return fmt.Sprintf("GOROOT=%v GOPATH=%v GO111MODULE=%v PWD=%v go %v", env["GOROOT"], env["GOPATH"], env["GO111MODULE"], env["PWD"], args)