* Call find-runtime-roots.pl from the garbage collector to prevent

  running applications etc. from being garbage collected.

2 files changed, 36 insertions, 16 deletions

diff --git a/src/libstore/build.cc b/src/libstore/build.cc
index 99828a55d..c80b3dfe9 100644
--- a/src/libstore/build.cc
+++ b/src/libstore/build.cc
@@ -12,10 +12,6 @@
 #include <unistd.h>
 #include <errno.h>
 
-#ifdef __CYGWIN__
-#include <windows.h>
-#endif
-
 #include <pwd.h>
 #include <grp.h>
 
@@ -321,13 +317,6 @@ const char * * strings2CharPtrs(const Strings & ss)
 }
 
 
-/* Hack for Cygwin: _exit() doesn't seem to work quite right, since
-   some Berkeley DB code appears to be called when a child exits
-   through _exit() (e.g., because execve() failed).  So call the
-   Windows API directly. */
-#ifdef __CYGWIN__
-#define _exit(n) ExitProcess(n)
-#endif
 
 
 //////////////////////////////////////////////////////////////////////
@@ -460,9 +449,9 @@ static void killUser(uid_t uid)
         
         } catch (exception & e) {
             cerr << format("build error: %1%\n") % e.what();
-            _exit(1);
+            quickExit(1);
         }
-        _exit(0);
+        quickExit(0);
     }
     
     /* parent */
@@ -944,7 +933,7 @@ DerivationGoal::HookReply DerivationGoal::tryBuildHook()
         } catch (exception & e) {
             cerr << format("build error: %1%\n") % e.what();
         }
-        _exit(1);
+        quickExit(1);
     }
     
     /* parent */
@@ -1340,7 +1329,7 @@ void DerivationGoal::startBuilder()
         } catch (exception & e) {
             cerr << format("build error: %1%\n") % e.what();
         }
-        _exit(1);
+        quickExit(1);
     }
 
     
@@ -1779,7 +1768,7 @@ void SubstitutionGoal::tryToRun()
         } catch (exception & e) {
             cerr << format("substitute error: %1%\n") % e.what();
         }
-        _exit(1);
+        quickExit(1);
     }
     
     /* parent */
diff --git a/src/libstore/gc.cc b/src/libstore/gc.cc
index 484a5f2be..3831de440 100644
--- a/src/libstore/gc.cc
+++ b/src/libstore/gc.cc
@@ -316,6 +316,31 @@ static void findRoots(const Path & path, bool recurseSymlinks,
 }
 
 
+static void addAdditionalRoots(PathSet & roots)
+{
+    Path rootFinder = getEnv("NIX_ROOT_FINDER",
+        "/nix/libexec/nix/find-runtime-roots.pl"); /* !!! */
+
+    if (rootFinder.empty()) return;
+    
+    printMsg(lvlDebug, format("executing `%1%' to find additional roots") % rootFinder);
+
+    string result = runProgram(rootFinder);
+
+    Strings paths = tokenizeString(result, "\n");
+    
+    for (Strings::iterator i = paths.begin(); i != paths.end(); ++i) {
+        if (isInStore(*i)) {
+            Path path = toStorePath(*i);
+            if (roots.find(path) == roots.end()) {
+                debug(format("found additional root `%1%'") % path);
+                roots.insert(path);
+            }
+        }
+    }
+}
+
+
 static void dfsVisit(const PathSet & paths, const Path & path,
     PathSet & visited, Paths & sorted)
 {
@@ -370,6 +395,12 @@ void collectGarbage(GCAction action, const PathSet & pathsToDelete,
     if (!ignoreLiveness)
         findRoots(rootsDir, true, roots);
 
+    /* Add additional roots returned by the program specified by the
+       NIX_ROOT_FINDER environment variable.  This is typically used
+       to add running programs to the set of roots (to prevent them
+       from being garbage collected). */
+    addAdditionalRoots(roots);
+
     if (action == gcReturnRoots) {
         result = roots;
         return;