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// Copyright 2020 The Fuchsia 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 build
import (
var (
// ErrBuildIDNotFound is a sometimes expected error that a build ID was not found.
ErrBuildIDNotFound = errors.New("build ID not found")
// Binary represents a binary produced by the build.
type Binary struct {
// CPU is the CPU architecture of the binary.
CPU string `json:"cpu"`
// OS is the operating system that the binary is for.
OS string `json:"os"`
// Environment is the toolchain environment name of what specific execution
// this was built for, e.g. "user", "host", "guest".
Environment string `json:"environment"`
// Label is the GN label of the binary target.
Label string `json:"label"`
// Type is the type of the binary.
Type string `json:"type"`
// Debug is the path to the unstripped or separate debug file is.
Debug string `json:"debug"`
// Dist is the path to the stripped binary for deployment/execution.
Dist string `json:"dist,omitempty"`
// BuildIDFile is the path to a file containing the lowercase ASCII
// hexadecimal representation of the ELF build ID.
BuildIDFile string `json:"elf_build_id,omitempty"`
// Breakpad is the path to the breakpad symbol file for the debug binary, if
// present.
Breakpad string `json:"breakpad,omitempty"`
// GSYM is the path to the GSYM symbol file for the debug binary, if
// present.
GSYM string `json:"gsym,omitempty"`
// ELFBuildID returns the build ID associated to a given binary. If no
// associated ID can be found - and no error unexpected error was experienced -
// ErrBuildIDNotFound is returned.
// build.GetBuildID() differs from elflib.GetBuildIDs() in that that former
// more statically determines the ID from build metadata, while the latter
// derives it directly from the ELF's notes section.
func (binary Binary) ELFBuildID(buildDir string) (string, error) {
// First, consider the case where the debug binary is already in a
// .build-id format, in which case may read the build ID out of the
// file path, being of the form
// `.../.build-id/<first two characters of buildID>/<remaining characters>.debug`.
tokens := strings.Split(binary.Debug, string(os.PathSeparator))
l := len(tokens)
if l >= 3 && tokens[l-3] == ".build-id" {
// First two characters + the rest.
return tokens[l-2] + trimExt(filepath.Base(tokens[l-1])), nil
if binary.BuildIDFile != "" {
p, err := filepath.Abs(filepath.Join(buildDir, binary.BuildIDFile))
if err != nil {
return "", err
f, err := os.Open(p)
if err == nil {
defer f.Close()
content, err := ioutil.ReadAll(f)
if err != nil {
return "", fmt.Errorf("failed to read binary's build ID file: %w", err)
trimmed := strings.TrimSpace(string(content))
if trimmed == "" {
return "", ErrBuildIDNotFound
return trimmed, nil
} else if !os.IsNotExist(err) {
// It is WAI that there are binary entries that don't correspond to
// anything that was actually built (i.e., was in the GN graph, but
// not in the Ninja graph or was not a prebuilt). In this case, we
// fall through.
return "", err
return "", ErrBuildIDNotFound
// LoadBinaries reads in the entries indexed in the given binary manifest.
func loadBinaries(manifest string) ([]Binary, error) {
f, err := os.Open(manifest)
if err != nil {
return nil, fmt.Errorf("failed to open %s: %w", manifest, err)
defer f.Close()
var bins []Binary
if err := json.NewDecoder(f).Decode(&bins); err != nil {
return nil, fmt.Errorf("failed to decode %s: %w", manifest, err)
return bins, nil
func trimExt(p string) string {
return p[:len(p)-len(filepath.Ext(p))]