* Move root finding from nix-collect-garbage' to nix-store --gc'.
This was necessary becase root finding must be done after acquisition of the global GC lock. This makes `nix-collect-garbage' obsolete; it is now just a wrapper around `nix-store --gc'. * Automatically remove stale GC roots (i.e., indirect GC roots that point to non-existent paths).
This commit is contained in:
Eelco Dolstra
parent
630ae0c9d7
commit
65b6c8ab4c
4 changed files with 75 additions and 111 deletions
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@ -1,83 +1,2 @@
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#! @perl@ -w
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use strict;
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use IPC::Open2;
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my $rootsDir = "@localstatedir@/nix/gcroots";
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my $storeDir = "@storedir@";
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my %alive;
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my $gcOper = "--delete";
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my $extraArgs = "";
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my @roots = ();
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# Parse the command line.
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for (my $i = 0; $i < scalar @ARGV; $i++) {
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my $arg = $ARGV[$i];
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if ($arg eq "--delete" || $arg eq "--print-live" || $arg eq "--print-dead") {
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$gcOper = $arg;
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}
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elsif ($arg =~ /^-v+$/) {
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$extraArgs = "$extraArgs $arg";
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}
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else { die "unknown argument `$arg'" };
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}
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# Recursively finds all symlinks to the store in the given directory.
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sub findRoots;
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sub findRoots {
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my $followSymlinks = shift;
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my $dir = shift;
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opendir(DIR, $dir) or die "cannot open directory `$dir': $!";
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my @names = readdir DIR or die "cannot read directory `$dir': $!";
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closedir DIR;
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foreach my $name (@names) {
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next if $name eq "." || $name eq "..";
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my $path = $dir . "/" . $name;
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if (-l $path) {
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my $target = readlink $path
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or die "cannot read symlink `$path': $!";
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if (substr($target, 0, length $storeDir) eq $storeDir) {
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# We're only interested in the store-level part.
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$target = substr($target, length $storeDir);
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$target = "$storeDir/$target";
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push @roots, $target;
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}
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elsif ($followSymlinks && -d $path) {
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findRoots 0, $path;
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}
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}
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elsif (-d $path) {
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findRoots $followSymlinks, $path;
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}
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}
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}
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# Find GC roots, starting at $rootsDir.
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findRoots 1, $rootsDir;
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# Run the collector with the roots we found.
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my $pid = open2(">&1", \*WRITE, "@bindir@/nix-store --gc $gcOper $extraArgs")
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or die "cannot run `nix-store --gc'";
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foreach my $root (@roots) {
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print WRITE "$root\n";
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}
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close WRITE;
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waitpid $pid, 0;
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$? == 0 or die "`nix-store --gc' failed";
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#! @shell@ -e
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exec @bindir@/nix-store --gc "$@"
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@ -26,7 +26,9 @@ static int openGCLock(LockType lockType)
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{
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Path fnGCLock = (format("%1%/%2%")
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% nixStateDir % gcLockName).str();
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debug(format("acquiring global GC lock `%1%'") % fnGCLock);
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AutoCloseFD fdGCLock = open(fnGCLock.c_str(), O_RDWR | O_CREAT, 0600);
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if (fdGCLock == -1)
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throw SysError(format("opening global GC lock `%1%'") % fnGCLock);
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@ -234,6 +236,46 @@ static void readTempRoots(PathSet & tempRoots, FDs & fds)
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}
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static void findRoots(const Path & path, bool recurseSymlinks,
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PathSet & roots)
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{
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struct stat st;
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if (lstat(path.c_str(), &st) == -1)
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throw SysError(format("statting `%1%'") % path);
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printMsg(lvlVomit, format("looking at `%1%'") % path);
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if (S_ISDIR(st.st_mode)) {
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Strings names = readDirectory(path);
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for (Strings::iterator i = names.begin(); i != names.end(); ++i)
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findRoots(path + "/" + *i, recurseSymlinks, roots);
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}
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else if (S_ISLNK(st.st_mode)) {
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string target = readLink(path);
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Path target2 = absPath(target, dirOf(path));
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if (isStorePath(target2)) {
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debug(format("found root `%1%' in `%2%'")
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% target2 % path);
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roots.insert(target2);
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}
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else if (recurseSymlinks) {
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if (pathExists(target2))
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findRoots(target2, false, roots);
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else {
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printMsg(lvlInfo, format("removing stale link from `%1%' to `%2%'") % path % target2);
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/* Note that we only delete when recursing, i.e., when
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we are still in the `gcroots' tree. We never
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delete stuff outside that tree. */
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unlink(path.c_str());
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}
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}
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}
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}
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static void dfsVisit(const PathSet & paths, const Path & path,
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PathSet & visited, Paths & sorted)
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{
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@ -265,8 +307,7 @@ static Paths topoSort(const PathSet & paths)
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}
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void collectGarbage(const PathSet & roots, GCAction action,
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PathSet & result)
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void collectGarbage(GCAction action, PathSet & result)
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{
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result.clear();
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@ -275,8 +316,16 @@ void collectGarbage(const PathSet & roots, GCAction action,
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b) Processes from creating new temporary root files. */
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AutoCloseFD fdGCLock = openGCLock(ltWrite);
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/* !!! Find the roots here, after we've grabbed the GC lock, since
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the set of permanent roots cannot increase now. */
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/* Find the roots. Since we've grabbed the GC lock, the set of
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permanent roots cannot increase now. */
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Path rootsDir = canonPath((format("%1%/%2%") % nixStateDir % gcRootsDir).str());
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PathSet roots;
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findRoots(rootsDir, true, roots);
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if (action == gcReturnRoots) {
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result = roots;
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return;
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}
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/* Determine the live paths which is just the closure of the
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roots under the `references' relation. */
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@ -5,15 +5,21 @@
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/* Garbage collector operation. */
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typedef enum { gcReturnLive, gcReturnDead, gcDeleteDead } GCAction;
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typedef enum {
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gcReturnRoots,
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gcReturnLive,
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gcReturnDead,
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gcDeleteDead,
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} GCAction;
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/* If `action' is set to `soReturnLive', return the set of paths
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reachable from (i.e. in the closure of) the specified roots. If
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`action' is `soReturnDead', return the set of paths not reachable
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from the roots. If `action' is `soDeleteDead', actually delete the
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latter set. */
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void collectGarbage(const PathSet & roots, GCAction action,
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PathSet & result);
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/* If `action' is set to `gcReturnRoots', find and return the set of
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roots for the garbage collector. These are the store paths
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symlinked to in the `gcroots' directory. If `action' is
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`gcReturnLive', return the set of paths reachable from (i.e. in the
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closure of) the roots. If `action' is `gcReturnDead', return the
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set of paths not reachable from the roots. If `action' is
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`gcDeleteDead', actually delete the latter set. */
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void collectGarbage(GCAction action, PathSet & result);
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/* Register a temporary GC root. This root will automatically
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disappear when this process exits. WARNING: this function should
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@ -38,9 +38,7 @@ static Path followSymlinks(Path & path)
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while (!isStorePath(path)) {
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if (!isLink(path)) return path;
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string target = readLink(path);
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path = canonPath(string(target, 0, 1) == "/"
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? target
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: path + "/" + target);
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path = absPath(target, dirOf(path));
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}
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return path;
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}
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@ -308,27 +306,19 @@ static void opIsValid(Strings opFlags, Strings opArgs)
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static void opGC(Strings opFlags, Strings opArgs)
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{
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GCAction action;
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GCAction action = gcDeleteDead;
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/* Do what? */
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for (Strings::iterator i = opFlags.begin();
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i != opFlags.end(); ++i)
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if (*i == "--print-live") action = gcReturnLive;
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if (*i == "--print-roots") action = gcReturnRoots;
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else if (*i == "--print-live") action = gcReturnLive;
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else if (*i == "--print-dead") action = gcReturnDead;
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else if (*i == "--delete") action = gcDeleteDead;
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else throw UsageError(format("bad sub-operation `%1%' in GC") % *i);
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/* Read the roots. */
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PathSet roots;
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while (1) {
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Path root;
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getline(cin, root);
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if (cin.eof()) break;
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roots.insert(root);
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}
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PathSet result;
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collectGarbage(roots, action, result);
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collectGarbage(action, result);
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if (action != gcDeleteDead) {
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for (PathSet::iterator i = result.begin(); i != result.end(); ++i)
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