daemon: Invoke 'guix gc --list-busy' instead of 'list-runtime-roots'.

* nix/scripts/list-runtime-roots.in: Remove.
* guix/store/roots.scm (%proc-directory): New variable.
(proc-file-roots, proc-exe-roots, proc-cwd-roots)
(proc-fd-roots, proc-maps-roots, proc-environ-roots)
(referenced-files, canonicalize-store-item, busy-store-items): New
procedures, taken from 'list-runtime-roots.in'.
* nix/libstore/globals.hh (Settings)[guixProgram]: New field.
* nix/libstore/globals.cc (Settings::processEnvironment): Initialize
'guixProgram'.
* nix/libstore/gc.cc (addAdditionalRoots): Drop code related to
'NIX_ROOT_FINDER'.  Run "guix gc --list-busy".
* nix/local.mk (nodist_pkglibexec_SCRIPTS): Remove
'scripts/list-runtime-roots'.
* config-daemon.ac: Don't output nix/scripts/list-runtime-roots.
* build-aux/pre-inst-env.in: Don't set 'NIX_ROOT_FINDER'.
Set 'GUIX'.
* doc/guix.texi (Invoking guix gc): Document '--list-busy'.
* guix/scripts/gc.scm (show-help, %options): Add "--list-busy".
(guix-gc)[list-busy]: New procedure.
Handle the 'list-busy' action.

3 files changed, 8 insertions, 7 deletions

diff --git a/nix/libstore/gc.cc b/nix/libstore/gc.cc
index 46171e116c..c466996668 100644
--- a/nix/libstore/gc.cc
+++ b/nix/libstore/gc.cc
@@ -339,14 +339,11 @@ Roots LocalStore::findRoots()
 
 static void addAdditionalRoots(StoreAPI & store, PathSet & roots)
 {
-    Path rootFinder = getEnv("NIX_ROOT_FINDER",
-        settings.nixLibexecDir + "/list-runtime-roots");
+    debug(format("executing `%1% gc --list-busy' to find additional roots")
+	  % settings.guixProgram);
 
-    if (rootFinder.empty()) return;
-
-    debug(format("executing `%1%' to find additional roots") % rootFinder);
-
-    string result = runProgram(rootFinder);
+    const Strings args = { "gc", "--list-busy" };
+    string result = runProgram(settings.guixProgram, false, args);
 
     StringSet paths = tokenizeString<StringSet>(result, "\n");
 
diff --git a/nix/libstore/globals.cc b/nix/libstore/globals.cc
index 6df20e7a52..8f7c976fcb 100644
--- a/nix/libstore/globals.cc
+++ b/nix/libstore/globals.cc
@@ -73,6 +73,7 @@ void Settings::processEnvironment()
     nixLibexecDir = canonPath(getEnv("NIX_LIBEXEC_DIR", NIX_LIBEXEC_DIR));
     nixBinDir = canonPath(getEnv("NIX_BIN_DIR", NIX_BIN_DIR));
     nixDaemonSocketFile = canonPath(nixStateDir + DEFAULT_SOCKET_PATH);
+    guixProgram = canonPath(getEnv("GUIX", nixBinDir + "/guix"));
 }
 
 
diff --git a/nix/libstore/globals.hh b/nix/libstore/globals.hh
index b073f724b6..0d9315a41a 100644
--- a/nix/libstore/globals.hh
+++ b/nix/libstore/globals.hh
@@ -66,6 +66,9 @@ struct Settings {
     /* File name of the socket the daemon listens to.  */
     Path nixDaemonSocketFile;
 
+    /* Absolute file name of the 'guix' program.  */
+    Path guixProgram;
+
     /* Whether to keep temporary directories of failed builds. */
     bool keepFailed;