* A GC setting `gc-keep-outputs' to specify whether output paths of

derivations should be kept.

src/libstore/gc.cc

@@ -213,14 +213,9 @@ static void readTempRoots(PathSet & tempRoots, FDs & fds)
         lockFile(*fd, ltRead, true);
 
         /* Read the entire file. */
-        struct stat st;
-        if (fstat(*fd, &st) == -1)
-            throw SysError(format("statting `%1%'") % path);
-        unsigned char buf[st.st_size]; /* !!! stack space */
-        readFull(*fd, buf, st.st_size);
+        string contents = readFile(*fd);
 
         /* Extract the roots. */
-        string contents((char *) buf, st.st_size);
         unsigned int pos = 0, end;
 
         while ((end = contents.find((char) 0, pos)) != string::npos) {
@@ -310,7 +305,9 @@ static Paths topoSort(const PathSet & paths)
 void collectGarbage(GCAction action, PathSet & result)
 {
     result.clear();
-    
+
+    string gcKeepOutputs = querySetting("gc-keep-outputs", "false");
+
     /* Acquire the global GC root.  This prevents
        a) New roots from being added.
        b) Processes from creating new temporary root files. */
@@ -333,6 +330,19 @@ void collectGarbage(GCAction action, PathSet & result)
     for (PathSet::const_iterator i = roots.begin(); i != roots.end(); ++i)
         computeFSClosure(canonPath(*i), livePaths);
 
+    if (gcKeepOutputs == "true") {
+        /* Hmz, identical to storePathRequisites in nix-store. */
+        for (PathSet::iterator i = livePaths.begin();
+             i != livePaths.end(); ++i)
+            if (isDerivation(*i)) {
+                Derivation drv = derivationFromPath(*i);
+                for (DerivationOutputs::iterator j = drv.outputs.begin();
+                     j != drv.outputs.end(); ++j)
+                    if (isValidPath(j->second.path))
+                        computeFSClosure(j->second.path, livePaths);
+            }
+    }
+
     if (action == gcReturnLive) {
         result = livePaths;
         return;

src/libstore/globals.cc

@@ -1,10 +1,14 @@
 #include "globals.hh"
 
+#include <map>
+
+
 string nixStore = "/UNINIT";
 string nixDataDir = "/UNINIT";
 string nixLogDir = "/UNINIT";
 string nixStateDir = "/UNINIT";
 string nixDBPath = "/UNINIT";
+string nixConfDir = "/UNINIT";
 
 bool keepFailed = false;
 
@@ -17,3 +21,49 @@ Verbosity buildVerbosity = lvlInfo;
 unsigned int maxBuildJobs = 1;
 
 bool readOnlyMode = false;
+
+
+static bool settingsRead = false;
+
+static map<string, string> settings;
+
+
+static void readSettings()
+{
+    Path settingsFile = (format("%1%/%2%") % nixConfDir % "nix.conf").str();
+    if (!pathExists(settingsFile)) return;
+    string contents = readFile(settingsFile);
+
+    unsigned int pos = 0;
+
+    while (pos < contents.size()) {
+        string line;
+        while (pos < contents.size() && contents[pos] != '\n')
+            line += contents[pos++];
+        pos++;
+
+        unsigned int hash = line.find('#');
+        if (hash != string::npos)
+            line = string(line, 0, hash);
+
+        if (line.find_first_not_of(" ") == string::npos) continue;
+
+        istringstream is(line);
+        string name, sep, value;
+        is >> name >> sep >> value;
+        if (sep != "=" || !is)
+            throw Error(format("illegal configuration line `%1%'") % line);
+        
+        settings[name] = value;
+    };
+    
+    settingsRead = true;
+}
+
+
+string querySetting(const string & name, const string & def)
+{
+    if (!settingsRead) readSettings();
+    map<string, string>::iterator i = settings.find(name);
+    return i == settings.end() ? def : i->second;
+}

src/libstore/globals.hh

@@ -23,6 +23,11 @@ extern string nixStateDir;
 /* nixDBPath is the path name of our Berkeley DB environment. */
 extern string nixDBPath;
 
+/* nixConfDir is the directory where configuration files are
+   stored. */
+extern string nixConfDir;
+
+
 
 /* Misc. global flags. */
 
@@ -48,4 +53,7 @@ extern unsigned int maxBuildJobs;
 extern bool readOnlyMode;
 
 
+string querySetting(const string & name, const string & def);
+
+
 #endif /* !__GLOBALS_H */