Update symlinks in output directory when TOP dir changes
When TOP dir changes and we reuse the same output between the old and new checkouts, we need to rewrite all the symlinks used by Bazel and other tools in the out-directory to point to the new top directory. Otherwise, if the old source dir is deleted, the build will fail.
I used the OUT_DIR/soong/soong.environment.available file to find out the previous PWD.
Tested:
1. Create source dir 1, run build, create source dir 2, remote source dir 1, reuse out dir and rerun build => build succeeded with this change.
2. m libc after moving build TOP. Only the analysis phase was rerun, the actual build was not rerun.
Bug: b/300498226
Change-Id: I196625baa1f4efe7a4734accfa1f0be7c98a7920
diff --git a/ui/build/soong.go b/ui/build/soong.go
index 44c20a0..ac9bf3a 100644
--- a/ui/build/soong.go
+++ b/ui/build/soong.go
@@ -16,10 +16,13 @@
import (
"fmt"
+ "io/fs"
"os"
"path/filepath"
"strconv"
"strings"
+ "sync"
+ "sync/atomic"
"android/soong/bazel"
"android/soong/ui/metrics"
@@ -50,6 +53,13 @@
bootstrapEpoch = 1
)
+var (
+ // Used during parallel update of symlinks in out directory to reflect new
+ // TOP dir.
+ symlinkWg sync.WaitGroup
+ numFound, numUpdated uint32
+)
+
func writeEnvironmentFile(_ Context, envFile string, envDeps map[string]string) error {
data, err := shared.EnvFileContents(envDeps)
if err != nil {
@@ -465,10 +475,118 @@
}
}
+func updateSymlinks(ctx Context, dir, prevCWD, cwd string) error {
+ defer symlinkWg.Done()
+
+ visit := func(path string, d fs.DirEntry, err error) error {
+ if d.IsDir() && path != dir {
+ symlinkWg.Add(1)
+ go updateSymlinks(ctx, path, prevCWD, cwd)
+ return filepath.SkipDir
+ }
+ f, err := d.Info()
+ if err != nil {
+ return err
+ }
+ // If the file is not a symlink, we don't have to update it.
+ if f.Mode()&os.ModeSymlink != os.ModeSymlink {
+ return nil
+ }
+
+ atomic.AddUint32(&numFound, 1)
+ target, err := os.Readlink(path)
+ if err != nil {
+ return err
+ }
+ if strings.HasPrefix(target, prevCWD) &&
+ (len(target) == len(prevCWD) || target[len(prevCWD)] == '/') {
+ target = filepath.Join(cwd, target[len(prevCWD):])
+ if err := os.Remove(path); err != nil {
+ return err
+ }
+ if err := os.Symlink(target, path); err != nil {
+ return err
+ }
+ atomic.AddUint32(&numUpdated, 1)
+ }
+ return nil
+ }
+
+ if err := filepath.WalkDir(dir, visit); err != nil {
+ return err
+ }
+ return nil
+}
+
+func fixOutDirSymlinks(ctx Context, config Config, outDir string) error {
+ cwd, err := os.Getwd()
+ if err != nil {
+ return err
+ }
+
+ // Record the .top as the very last thing in the function.
+ tf := filepath.Join(outDir, ".top")
+ defer func() {
+ if err := os.WriteFile(tf, []byte(cwd), 0644); err != nil {
+ fmt.Fprintf(os.Stderr, fmt.Sprintf("Unable to log CWD: %v", err))
+ }
+ }()
+
+ // Find the previous working directory if it was recorded.
+ var prevCWD string
+ pcwd, err := os.ReadFile(tf)
+ if err != nil {
+ if os.IsNotExist(err) {
+ // No previous working directory recorded, nothing to do.
+ return nil
+ }
+ return err
+ }
+ prevCWD = strings.Trim(string(pcwd), "\n")
+
+ if prevCWD == cwd {
+ // We are in the same source dir, nothing to update.
+ return nil
+ }
+
+ symlinkWg.Add(1)
+ if err := updateSymlinks(ctx, outDir, prevCWD, cwd); err != nil {
+ return err
+ }
+ symlinkWg.Wait()
+ ctx.Println(fmt.Sprintf("Updated %d/%d symlinks in dir %v", numUpdated, numFound, outDir))
+ return nil
+}
+
+func migrateOutputSymlinks(ctx Context, config Config) error {
+ // Figure out the real out directory ("out" could be a symlink).
+ outDir := config.OutDir()
+ s, err := os.Lstat(outDir)
+ if err != nil {
+ if os.IsNotExist(err) {
+ // No out dir exists, no symlinks to migrate.
+ return nil
+ }
+ return err
+ }
+ if s.Mode()&os.ModeSymlink == os.ModeSymlink {
+ target, err := filepath.EvalSymlinks(outDir)
+ if err != nil {
+ return err
+ }
+ outDir = target
+ }
+ return fixOutDirSymlinks(ctx, config, outDir)
+}
+
func runSoong(ctx Context, config Config) {
ctx.BeginTrace(metrics.RunSoong, "soong")
defer ctx.EndTrace()
+ if err := migrateOutputSymlinks(ctx, config); err != nil {
+ ctx.Fatalf("failed to migrate output directory to current TOP dir: %v", err)
+ }
+
// We have two environment files: .available is the one with every variable,
// .used with the ones that were actually used. The latter is used to
// determine whether Soong needs to be re-run since why re-run it if only