* nix-build: use an indirection scheme to make it easier for users to
get rid of GC roots. Nix-build places a symlink `result' in the current directory. Previously, removing that symlink would not remove the store path being linked to as a GC root. Now, the GC root created by nix-build is actually a symlink in `/nix/var/nix/gcroots/auto' to `result'. So if that symlink is removed the GC root automatically becomes invalid (since it can no longer be resolved). The root itself is not automatically removed - the garbage collector should delete dangling roots.
This commit is contained in:
Eelco Dolstra
parent
dcc37c236c
commit
630ae0c9d7
7 changed files with 101 additions and 50 deletions
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@ -8,41 +8,52 @@ if test -z "$nixExpr"; then
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fi
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extraArgs=
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noLink=
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addDrvLink=0
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addOutLink=1
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userName=$USER
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if test -z "$username"; then userName="unknown"; fi
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trap 'rm -f ./.nix-build-tmp-*' EXIT
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# Process the arguments.
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for i in "$@"; do
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case "$i" in
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--no-link)
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noLink=1
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--add-drv-link)
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addDrvLink=1
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;;
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--no-link)
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addOutLink=0
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;;
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-*)
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extraArgs="$extraArgs $i"
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;;
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*)
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# Instantiate the Nix expression.
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prefix=
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if test "$addDrvLink" = 0; then prefix=.nix-build-tmp-; fi
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storeExprs=$(@bindir@/nix-instantiate \
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--add-root "@localstatedir@/nix/gcroots/nix-build/$userName-drv" \
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--add-root ./${prefix}derivation --indirect \
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"$i")
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for j in $storeExprs; do
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echo "store expression is $j" >&2
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echo "store expression is $j $(readlink "$j")" >&2
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done
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# Build the resulting store derivation.
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prefix=
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if test "$addOutLink" = 0; then prefix=.nix-build-tmp-; fi
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outPaths=$(@bindir@/nix-store \
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--add-root "@localstatedir@/nix/gcroots/nix-build/$userName-out" \
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--add-root ./${prefix}result --indirect \
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-rv $extraArgs $storeExprs)
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for j in $outPaths; do
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echo "$j"
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if test -z "$noLink"; then
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if test -L result; then
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rm result
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elif test -e result; then
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echo "cannot remove \`result' (not a symlink)"
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exit 1
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fi
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ln -s "$j" result
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fi
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echo "$j $(readlink "$j")"
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done
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;;
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esac
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done
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@ -13,6 +13,8 @@
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static string gcLockName = "gc.lock";
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static string tempRootsDir = "temproots";
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static string gcRootsDir = "gcroots";
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/* Acquire the global GC lock. This is used to prevent new Nix
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@ -49,40 +51,61 @@ static void createDirs(const Path & path)
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}
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Path addPermRoot(const Path & _storePath, const Path & _gcRoot)
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void createSymlink(const Path & link, const Path & target, bool careful)
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{
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/* Create directories up to `gcRoot'. */
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createDirs(dirOf(link));
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/* Remove the old symlink. */
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if (pathExists(link)) {
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if (careful && (!isLink(link) || !isStorePath(readLink(link))))
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throw Error(format("cannot create symlink `%1%'; already exists") % link);
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unlink(link.c_str());
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}
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/* And create the new own. */
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if (symlink(target.c_str(), link.c_str()) == -1)
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throw SysError(format("symlinking `%1%' to `%2%'")
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% link % target);
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}
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Path addPermRoot(const Path & _storePath, const Path & _gcRoot,
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bool indirect)
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{
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Path storePath(canonPath(_storePath));
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Path gcRoot(canonPath(_gcRoot));
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Path rootsDir = canonPath((format("%1%/%2%") % nixStateDir % "gcroots").str());
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if (string(gcRoot, 0, rootsDir.size() + 1) != rootsDir + "/")
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throw Error(format(
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"path `%1%' is not a valid garbage collector root; "
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"it's not in the `%1%' directory")
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% gcRoot % rootsDir);
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assertStorePath(storePath);
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/* Grab the global GC root. This prevents the set of permanent
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roots from increasing while a GC is in progress. */
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AutoCloseFD fdGCLock = openGCLock(ltRead);
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/* Create directories up to `gcRoot'. */
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createDirs(dirOf(gcRoot));
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if (indirect) {
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string hash = printHash32(hashString(htSHA1, gcRoot));
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Path realRoot = canonPath((format("%1%/%2%/auto/%3%")
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% nixStateDir % gcRootsDir % hash).str());
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/* Remove the old symlink. */
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unlink(gcRoot.c_str());
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createSymlink(gcRoot, storePath, true);
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createSymlink(realRoot, gcRoot, false);
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}
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/* And create the new own. */
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if (symlink(storePath.c_str(), gcRoot.c_str()) == -1)
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throw SysError(format("symlinking `%1%' to `%2%'")
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% gcRoot % storePath);
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else {
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Path rootsDir = canonPath((format("%1%/%2%") % nixStateDir % gcRootsDir).str());
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if (string(gcRoot, 0, rootsDir.size() + 1) != rootsDir + "/")
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throw Error(format(
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"path `%1%' is not a valid garbage collector root; "
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"it's not in the directory `%2%'")
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% gcRoot % rootsDir);
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createSymlink(gcRoot, storePath, false);
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}
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return gcRoot;
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}
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static string tempRootsDir = "temproots";
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/* The file to which we write our temporary roots. */
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static Path fnTempRoots;
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static AutoCloseFD fdTempRoots;
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@ -27,7 +27,8 @@ void addTempRoot(const Path & path);
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void removeTempRoots();
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/* Register a permanent GC root. */
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Path addPermRoot(const Path & storePath, const Path & gcRoot);
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Path addPermRoot(const Path & storePath, const Path & gcRoot,
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bool indirect);
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#endif /* !__GC_H */
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@ -135,6 +135,15 @@ Path readLink(const Path & path)
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}
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bool isLink(const Path & path)
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{
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struct stat st;
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if (lstat(path.c_str(), &st))
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throw SysError(format("getting status of `%1%'") % path);
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return S_ISLNK(st.st_mode);
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}
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Strings readDirectory(const Path & path)
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{
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Strings names;
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@ -84,6 +84,8 @@ bool pathExists(const Path & path);
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in any way canonicalised. */
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Path readLink(const Path & path);
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bool isLink(const Path & path);
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/* Read the contents of a directory. The entries `.' and `..' are
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removed. */
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Strings readDirectory(const Path & path);
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@ -29,6 +29,7 @@ static Expr evalStdin(EvalState & state, bool parseOnly)
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static Path gcRoot;
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static int rootNr = 0;
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static bool indirectRoot = false;
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/* Print out the paths of the resulting derivation(s). If the user
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@ -51,7 +52,8 @@ static void printDrvPaths(EvalState & state, Expr e)
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printGCWarning();
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else
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drvPath = addPermRoot(drvPath,
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makeRootName(gcRoot, rootNr));
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makeRootName(gcRoot, rootNr),
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indirectRoot);
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cout << format("%1%\n") % drvPath;
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return;
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}
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@ -110,8 +112,10 @@ void run(Strings args)
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else if (arg == "--add-root") {
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if (i == args.end())
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throw UsageError("`--add-root requires an argument");
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gcRoot = *i++;
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gcRoot = absPath(*i++);
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}
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else if (arg == "--indirect")
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indirectRoot = true;
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else if (arg[0] == '-')
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throw UsageError(format("unknown flag `%1%`") % arg);
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else
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@ -1,9 +1,5 @@
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#include <iostream>
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <unistd.h>
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#include "globals.hh"
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#include "build.hh"
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#include "gc.hh"
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@ -24,6 +20,7 @@ void printHelp()
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static Path gcRoot;
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static int rootNr = 0;
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static bool indirectRoot = false;
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static Path findOutput(const Derivation & drv, string id)
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@ -37,11 +34,9 @@ static Path findOutput(const Derivation & drv, string id)
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static Path followSymlinks(Path & path)
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{
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path = absPath(path);
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while (!isStorePath(path)) {
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struct stat st;
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if (lstat(path.c_str(), &st))
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throw SysError(format("getting status of `%1%'") % path);
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if (!S_ISLNK(st.st_mode)) return 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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if (gcRoot == "")
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printGCWarning();
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else
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outPath = addPermRoot(outPath, makeRootName(gcRoot, rootNr));
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outPath = addPermRoot(outPath,
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makeRootName(gcRoot, rootNr),
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indirectRoot);
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return outPath;
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} else {
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@ -191,6 +188,7 @@ static void opQuery(Strings opFlags, Strings opArgs)
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for (Strings::iterator i = opArgs.begin();
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i != opArgs.end(); i++)
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{
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*i = followSymlinks(*i);
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if (forceRealise) realisePath(*i);
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Derivation drv = derivationFromPath(*i);
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cout << format("%1%\n") % findOutput(drv, "out");
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@ -206,6 +204,7 @@ static void opQuery(Strings opFlags, Strings opArgs)
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for (Strings::iterator i = opArgs.begin();
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i != opArgs.end(); i++)
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{
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*i = followSymlinks(*i);
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Path path = maybeUseOutput(*i, useOutput, forceRealise);
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if (query == qRequisites)
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storePathRequisites(path, includeOutputs, paths);
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@ -441,8 +440,10 @@ void run(Strings args)
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else if (arg == "--add-root") {
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if (i == args.end())
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throw UsageError("`--add-root requires an argument");
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gcRoot = *i++;
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gcRoot = absPath(*i++);
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}
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else if (arg == "--indirect")
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indirectRoot = true;
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else if (arg[0] == '-')
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opFlags.push_back(arg);
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else
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