* Started removing closure store expressions, i.e., the explicit

representation of closures as ATerms in the Nix store.  Instead, the
  file system pointer graph is now stored in the Nix database.  This
  has many advantages:

  - It greatly simplifies the implementation (we can drop the notion
    of `successors', and so on).

  - It makes registering roots for the garbage collector much easier.
    Instead of specifying the closure expression as a root, you can
    simply specify the store path that must be retained as a root.
    This could not be done previously, since there was no way to find
    the closure store expression containing a given store path.
    
  - Better traceability: it is now possible to query what paths are
    referenced by a path, and what paths refer to a path.

src/libexpr/primops.cc

@@ -16,6 +16,7 @@ static Expr primImport(EvalState & state, const ATermVector & args)
 }
 
 
+#if 0
 static PathSet storeExprRootsCached(EvalState & state, const Path & nePath)
 {
     DrvRoots::iterator i = state.drvRoots.find(nePath);
@@ -27,6 +28,7 @@ static PathSet storeExprRootsCached(EvalState & state, const Path & nePath)
         return paths;
     }
 }
+#endif
 
 
 /* Returns the hash of a derivation modulo fixed-output
@@ -49,13 +51,11 @@ static PathSet storeExprRootsCached(EvalState & state, const Path & nePath)
    paths have been replaced by the result of a recursive call to this
    function, and that for fixed-output derivations we return
    (basically) its outputHash. */
-static Hash hashDerivationModulo(EvalState & state, StoreExpr ne)
+static Hash hashDerivationModulo(EvalState & state, Derivation drv)
 {
-    if (ne.type == StoreExpr::neDerivation) {
-
     /* Return a fixed hash for fixed-output derivations. */
-        if (ne.derivation.outputs.size() == 1) {
+    if (drv.outputs.size() == 1) {
-            DerivationOutputs::iterator i = ne.derivation.outputs.begin();
+        DerivationOutputs::const_iterator i = drv.outputs.begin();
         if (i->first == "out" &&
             i->second.hash != "")
         {
@@ -66,66 +66,27 @@ static Hash hashDerivationModulo(EvalState & state, StoreExpr ne)
         }
     }
 
-        /* For other derivations, replace the inputs paths with
+    /* For other derivations, replace the inputs paths with recursive
-           recursive calls to this function.*/
+       calls to this function.*/
     PathSet inputs2;
-        for (PathSet::iterator i = ne.derivation.inputs.begin();
+    for (PathSet::iterator i = drv.inputDrvs.begin();
-             i != ne.derivation.inputs.end(); ++i)
+         i != drv.inputDrvs.end(); ++i)
     {
         Hash h = state.drvHashes[*i];
         if (h.type == htUnknown) {
-                StoreExpr ne2 = storeExprFromPath(*i);
+            Derivation drv2 = derivationFromPath(*i);
-                h = hashDerivationModulo(state, ne2);
+            h = hashDerivationModulo(state, drv2);
             state.drvHashes[*i] = h;
         }
         inputs2.insert(printHash(h));
     }
-	ne.derivation.inputs = inputs2;
+    drv.inputDrvs = inputs2;
-    }
     
-    return hashTerm(unparseStoreExpr(ne));
+    return hashTerm(unparseDerivation(drv));
 }
 
 
-static Path copyAtom(EvalState & state, const Path & srcPath)
+static void processBinding(EvalState & state, Expr e, Derivation & drv,
-{
-    /* !!! should be cached */
-    Path dstPath(addToStore(srcPath));
-
-    ClosureElem elem;
-    StoreExpr ne;
-    ne.type = StoreExpr::neClosure;
-    ne.closure.roots.insert(dstPath);
-    ne.closure.elems[dstPath] = elem;
-
-    Path drvPath = writeTerm(unparseStoreExpr(ne), "c");
-
-    /* !!! can we get rid of drvRoots? */
-    state.drvRoots[drvPath] = ne.closure.roots;
-
-    /* Optimisation, but required in read-only mode! because in that
-       case we don't actually write store expressions, so we can't
-       read them later. */
-    state.drvHashes[drvPath] = hashDerivationModulo(state, ne);
-
-    printMsg(lvlChatty, format("copied `%1%' -> closure `%2%'")
-        % srcPath % drvPath);
-    return drvPath;
-}
-
-
-static string addInput(EvalState & state, 
-    Path & nePath, StoreExpr & ne)
-{
-    PathSet paths = storeExprRootsCached(state, nePath);
-    if (paths.size() != 1) abort();
-    Path path = *(paths.begin());
-    ne.derivation.inputs.insert(nePath);
-    return path;
-}
-
-
-static void processBinding(EvalState & state, Expr e, StoreExpr & ne,
     Strings & ss)
 {
     e = evalExpr(state, e);
@@ -155,25 +116,28 @@ static void processBinding(EvalState & state, Expr e, StoreExpr & ne,
 
             a = queryAttr(e, "outPath");
             if (!a) throw Error("output path missing");
-            PathSet drvRoots;
+            /* !!! supports only single output path */
-            drvRoots.insert(evalPath(state, a));
+            Path outPath = evalPath(state, a);
 
-            state.drvRoots[drvPath] = drvRoots;
+            drv.inputDrvs.insert(drvPath);
-
+            ss.push_back(outPath);
-            ss.push_back(addInput(state, drvPath, ne));
         } else
             throw Error("invalid derivation attribute");
     }
 
     else if (matchPath(e, s)) {
-        Path drvPath = copyAtom(state, aterm2String(s));
+        Path srcPath(aterm2String(s));
-        ss.push_back(addInput(state, drvPath, ne));
+        Path dstPath(addToStore(srcPath));
+        printMsg(lvlChatty, format("copied source `%1%' -> `%2%'")
+            % srcPath % dstPath);
+        drv.inputSrcs.insert(dstPath);
+        ss.push_back(dstPath);
     }
     
     else if (matchList(e, es)) {
         for (ATermIterator i(es); i; ++i) {
             startNest(nest, lvlVomit, format("processing list element"));
-	    processBinding(state, evalExpr(state, *i), ne, ss);
+	    processBinding(state, evalExpr(state, *i), drv, ss);
         }
     }
 
@@ -181,7 +145,7 @@ static void processBinding(EvalState & state, Expr e, StoreExpr & ne,
 
     else if (matchSubPath(e, e1, e2)) {
         Strings ss2;
-        processBinding(state, evalExpr(state, e1), ne, ss2);
+        processBinding(state, evalExpr(state, e1), drv, ss2);
         if (ss2.size() != 1)
             throw Error("left-hand side of `~' operator cannot be a list");
         e2 = evalExpr(state, e2);
@@ -223,8 +187,7 @@ static Expr primDerivation(EvalState & state, const ATermVector & _args)
     queryAllAttrs(args, attrs, true);
 
     /* Build the derivation expression by processing the attributes. */
-    StoreExpr ne;
+    Derivation drv;
-    ne.type = StoreExpr::neDerivation;
 
     string drvName;
     
@@ -241,7 +204,7 @@ static Expr primDerivation(EvalState & state, const ATermVector & _args)
 
         Strings ss;
         try {
-            processBinding(state, value, ne, ss);
+            processBinding(state, value, drv, ss);
         } catch (Error & e) {
             throw Error(format("while processing the derivation attribute `%1%' at %2%:\n%3%")
                 % key % showPos(pos) % e.msg());
@@ -251,16 +214,16 @@ static Expr primDerivation(EvalState & state, const ATermVector & _args)
            command-line arguments to the builder. */
         if (key == "args") {
             for (Strings::iterator i = ss.begin(); i != ss.end(); ++i)
-                ne.derivation.args.push_back(*i);
+                drv.args.push_back(*i);
         }
 
         /* All other attributes are passed to the builder through the
            environment. */
         else {
             string s = concatStrings(ss);
-            ne.derivation.env[key] = s;
+            drv.env[key] = s;
-            if (key == "builder") ne.derivation.builder = s;
+            if (key == "builder") drv.builder = s;
-            else if (key == "system") ne.derivation.platform = s;
+            else if (key == "system") drv.platform = s;
             else if (key == "name") drvName = s;
             else if (key == "outputHash") outputHash = s;
             else if (key == "outputHashAlgo") outputHashAlgo = s;
@@ -268,9 +231,9 @@ static Expr primDerivation(EvalState & state, const ATermVector & _args)
     }
     
     /* Do we have all required attributes? */
-    if (ne.derivation.builder == "")
+    if (drv.builder == "")
         throw Error("required attribute `builder' missing");
-    if (ne.derivation.platform == "")
+    if (drv.platform == "")
         throw Error("required attribute `system' missing");
     if (drvName == "")
         throw Error("required attribute `name' missing");
@@ -312,22 +275,22 @@ static Expr primDerivation(EvalState & state, const ATermVector & _args)
        paths are empty, and the corresponding environment variables
        have an empty value.  This ensures that changes in the set of
        output names do get reflected in the hash. */
-    ne.derivation.env["out"] = "";
+    drv.env["out"] = "";
-    ne.derivation.outputs["out"] =
+    drv.outputs["out"] =
         DerivationOutput("", outputHashAlgo, outputHash);
         
     /* Use the masked derivation expression to compute the output
        path. */
     Path outPath = makeStorePath("output:out",
-        hashDerivationModulo(state, ne), drvName);
+        hashDerivationModulo(state, drv), drvName);
 
     /* Construct the final derivation store expression. */
-    ne.derivation.env["out"] = outPath;
+    drv.env["out"] = outPath;
-    ne.derivation.outputs["out"] =
+    drv.outputs["out"] =
         DerivationOutput(outPath, outputHashAlgo, outputHash);
 
     /* Write the resulting term into the Nix store directory. */
-    Path drvPath = writeTerm(unparseStoreExpr(ne), "d-" + drvName);
+    Path drvPath = writeTerm(unparseDerivation(drv), "d-" + drvName);
 
     printMsg(lvlChatty, format("instantiated `%1%' -> `%2%'")
         % drvName % drvPath);
@@ -335,7 +298,7 @@ static Expr primDerivation(EvalState & state, const ATermVector & _args)
     /* Optimisation, but required in read-only mode! because in that
        case we don't actually write store expressions, so we can't
        read them later. */
-    state.drvHashes[drvPath] = hashDerivationModulo(state, ne);
+    state.drvHashes[drvPath] = hashDerivationModulo(state, drv);
 
     /* !!! assumes a single output */
     attrs.set("outPath", makeAttrRHS(makePath(toATerm(outPath)), makeNoPos()));

src/libstore/gc.cc

@@ -7,6 +7,7 @@
 #include <unistd.h>
 
 
+#if 0
 void followLivePaths(Path nePath, PathSet & live)
 {
     /* Just to be sure, canonicalise the path.  It is important to do
@@ -96,3 +97,4 @@ PathSet findDeadPaths(const PathSet & live, time_t minAge)
     
     return dead;
 }
+#endif

src/libstore/misc.cc

@@ -1,16 +1,32 @@
 #include "normalise.hh"
 
 
-StoreExpr storeExprFromPath(const Path & path)
+Derivation derivationFromPath(const Path & drvPath)
 {
-    assertStorePath(path);
+    assertStorePath(drvPath);
-    ensurePath(path);
+    ensurePath(drvPath);
-    ATerm t = ATreadFromNamedFile(path.c_str());
+    ATerm t = ATreadFromNamedFile(drvPath.c_str());
-    if (!t) throw Error(format("cannot read aterm from `%1%'") % path);
+    if (!t) throw Error(format("cannot read aterm from `%1%'") % drvPath);
-    return parseStoreExpr(t);
+    return parseDerivation(t);
 }
 
 
+void computeFSClosure(const Path & storePath,
+    PathSet & paths)
+{
+    if (paths.find(storePath) != paths.end()) return;
+    paths.insert(storePath);
+
+    PathSet references;
+    queryReferences(storePath, references);
+
+    for (PathSet::iterator i = references.begin();
+         i != references.end(); ++i)
+        computeFSClosure(*i, paths);
+}
+
+
+#if 0
 PathSet storeExprRoots(const Path & nePath)
 {
     PathSet paths;
@@ -71,3 +87,4 @@ PathSet storeExprRequisites(const Path & nePath,
         paths, doneSet);
     return paths;
 }
+#endif

src/libstore/normalise.hh

@@ -4,28 +4,31 @@
 #include "storeexpr.hh"
 
 
-/* Normalise a store expression.  That is, if the expression is a
+/* Perform the specified derivation, if necessary.  That is, do
-   derivation, a path containing an equivalent closure expression is
+   whatever is necessary to create the output paths of the
-   returned.  This requires that the derivation is performed, unless a
+   derivation.  If the output paths already exists, we're done.  If
-   successor is known. */
+   they have substitutes, we can use those instead.  Otherwise, the
-Path normaliseStoreExpr(const Path & nePath);
+   build action described by the derivation is performed, after
-
+   recursively building any sub-derivations. */
-/* Realise a store expression.  If the expression is a derivation, it
+void buildDerivation(const Path & drvPath);
-   is first normalised into a closure.  The closure is then realised
-   in the file system (i.e., it is ensured that each path in the
-   closure exists in the file system, if necessary by using the
-   substitute mechanism).  Returns the normal form of the expression
-   (i.e., its closure expression). */
-Path realiseStoreExpr(const Path & nePath);
 
 /* Ensure that a path exists, possibly by instantiating it by
    realising a substitute. */
-void ensurePath(const Path & path);
+void ensurePath(const Path & storePath);
 
-/* Read a store expression, after ensuring its existence through
+/* Read a derivation store expression, after ensuring its existence
-   ensurePath(). */
+   through ensurePath(). */
-StoreExpr storeExprFromPath(const Path & path);
+Derivation derivationFromPath(const Path & drvPath);
 
+
+/* Places in `paths' the set of all store paths in the file system
+   closure of `storePath'; that is, all paths than can be directly or
+   indirectly reached from it.  `paths' is not cleared. */
+void computeFSClosure(const Path & storePath,
+    PathSet & paths);
+
+
+#if 0
 /* Get the list of root (output) paths of the given store
    expression. */
 PathSet storeExprRoots(const Path & nePath);
@@ -39,6 +42,7 @@ PathSet storeExprRoots(const Path & nePath);
    successors. */
 PathSet storeExprRequisites(const Path & nePath,
     bool includeExprs, bool includeSuccessors);
+#endif
 
 
 #endif /* !__NORMALISE_H */

src/libstore/store.cc

@@ -23,23 +23,18 @@ static Database nixDB;
    is, produced by a succesful build). */
 static TableId dbValidPaths = 0;
 
-/* dbSuccessors :: Path -> Path
+/* dbReferences :: Path -> [Path]
 
-   Each pair $(p_1, p_2)$ in this mapping records the fact that the
+   This table lists the outgoing file system references for each
-   Nix expression stored at path $p_1$ has a successor expression
+   output path that has been built by a Nix derivation.  These are
-   stored at path $p_2$.
+   found by scanning the path for the hash components of input
+   paths. */
+static TableId dbReferences = 0;
 
-   Note that a term $y$ is a successor of $x$ iff there exists a
+/* dbReferers :: Path -> [Path]
-   sequence of rewrite steps that rewrites $x$ into $y$.
-*/
-static TableId dbSuccessors = 0;
 
-/* dbSuccessorsRev :: Path -> [Path]
+   This table is just the reverse mapping of dbReferences. */
-
+static TableId dbReferers = 0;
-   The reverse mapping of dbSuccessors (i.e., it stores the
-   predecessors of a Nix expression).
-*/
-static TableId dbSuccessorsRev = 0;
 
 /* dbSubstitutes :: Path -> [[Path]]
 
@@ -76,8 +71,8 @@ void openDB()
         return;
     }
     dbValidPaths = nixDB.openTable("validpaths");
-    dbSuccessors = nixDB.openTable("successors");
+    dbReferences = nixDB.openTable("references");
-    dbSuccessorsRev = nixDB.openTable("successors-rev");
+    dbReferers = nixDB.openTable("referers");
     dbSubstitutes = nixDB.openTable("substitutes");
 }
 
@@ -199,81 +194,31 @@ bool isValidPath(const Path & path)
 }
 
 
-static bool isUsablePathTxn(const Path & path, const Transaction & txn)
+void setReferences(const Transaction & txn, const Path & storePath,
+    const PathSet & references)
 {
-    if (isValidPathTxn(path, txn)) return true;
+    nixDB.setStrings(txn, dbReferences, storePath,
-    Paths subs;
+        Paths(references.begin(), references.end()));
-    nixDB.queryStrings(txn, dbSubstitutes, path, subs);
+
-    return subs.size() > 0;
+    /* Update the referers mappings of all referenced paths. */
+    for (PathSet::const_iterator i = references.begin();
+         i != references.end(); ++i)
+    {
+        Paths referers;
+        nixDB.queryStrings(txn, dbReferers, *i, referers);
+        PathSet referers2(referers.begin(), referers.end());
+        referers2.insert(storePath);
+        nixDB.setStrings(txn, dbReferers, *i,
+            Paths(referers2.begin(), referers2.end()));
+    }
 }
 
 
-void registerSuccessor(const Transaction & txn,
+void queryReferences(const Path & storePath, PathSet & references)
-    const Path & srcPath, const Path & sucPath)
 {
-    assertStorePath(srcPath);
+    Paths references2;
-    assertStorePath(sucPath);
+    nixDB.queryStrings(noTxn, dbReferences, storePath, references2);
-    
+    references.insert(references2.begin(), references2.end());
-    if (!isUsablePathTxn(sucPath, txn))	throw Error(
-	format("path `%1%' cannot be a successor, since it is not usable")
-	% sucPath);
-
-    Path known;
-    if (nixDB.queryString(txn, dbSuccessors, srcPath, known) &&
-        known != sucPath)
-    {
-        throw Error(format(
-            "the `impossible' happened: expression in path "
-            "`%1%' appears to have multiple successors "
-            "(known `%2%', new `%3%'")
-            % srcPath % known % sucPath);
-    }
-
-    Paths revs;
-    nixDB.queryStrings(txn, dbSuccessorsRev, sucPath, revs);
-    if (find(revs.begin(), revs.end(), srcPath) == revs.end())
-        revs.push_back(srcPath);
-
-    nixDB.setString(txn, dbSuccessors, srcPath, sucPath);
-    nixDB.setStrings(txn, dbSuccessorsRev, sucPath, revs);
-}
-
-
-void unregisterSuccessor(const Path & srcPath)
-{
-    assertStorePath(srcPath);
-
-    Transaction txn(nixDB);
-
-    Path sucPath;
-    if (!nixDB.queryString(txn, dbSuccessors, srcPath, sucPath)) {
-        txn.abort();
-        return;
-    }
-    nixDB.delPair(txn, dbSuccessors, srcPath);
-
-    Paths revs;
-    nixDB.queryStrings(txn, dbSuccessorsRev, sucPath, revs);
-    Paths::iterator i = find(revs.begin(), revs.end(), srcPath);
-    assert(i != revs.end());
-    revs.erase(i);
-    nixDB.setStrings(txn, dbSuccessorsRev, sucPath, revs);
-
-    txn.commit();
-}
-
-
-bool querySuccessor(const Path & srcPath, Path & sucPath)
-{
-    return nixDB.queryString(noTxn, dbSuccessors, srcPath, sucPath);
-}
-
-
-Paths queryPredecessors(const Path & sucPath)
-{
-    Paths revs;
-    nixDB.queryStrings(noTxn, dbSuccessorsRev, sucPath, revs);
-    return revs;
 }
 
 
@@ -355,18 +300,6 @@ Substitutes querySubstitutes(const Path & srcPath)
 }
 
 
-static void unregisterPredecessors(const Path & path, Transaction & txn)
-{
-    /* Remove any successor mappings to this path (but not *from*
-       it). */
-    Paths revs;
-    nixDB.queryStrings(txn, dbSuccessorsRev, path, revs);
-    for (Paths::iterator i = revs.begin(); i != revs.end(); ++i)
-        nixDB.delPair(txn, dbSuccessors, *i);
-    nixDB.delPair(txn, dbSuccessorsRev, path);
-}
- 
-
 void clearSubstitutes()
 {
     Transaction txn(nixDB);
@@ -375,16 +308,6 @@ void clearSubstitutes()
     Paths subKeys;
     nixDB.enumTable(txn, dbSubstitutes, subKeys);
     for (Paths::iterator i = subKeys.begin(); i != subKeys.end(); ++i) {
-
-        /* If this path has not become valid in the mean-while, delete
-           any successor mappings *to* it.  This is to preserve the
-           invariant the all successors are `usable' as opposed to
-           `valid' (i.e., the successor must be valid *or* have at
-           least one substitute). */
-        if (!isValidPath(*i)) {
-            unregisterPredecessors(*i, txn);
-        }
-        
         /* Delete all substitutes for path *i. */
         nixDB.delPair(txn, dbSubstitutes, *i);
     }
@@ -407,7 +330,6 @@ static void invalidatePath(const Path & path, Transaction & txn)
     debug(format("unregistering path `%1%'") % path);
 
     nixDB.delPair(txn, dbValidPaths, path);
-    unregisterPredecessors(path, txn);
 }
 
 
@@ -562,34 +484,5 @@ void verifyStore()
             nixDB.delPair(txn, dbSubstitutes, *i);
     }
 
-    /* Check that the values of the successor mappings are usable
-       paths. */ 
-    Paths sucKeys;
-    nixDB.enumTable(txn, dbSuccessors, sucKeys);
-    for (Paths::iterator i = sucKeys.begin(); i != sucKeys.end(); ++i) {
-        /* Note that *i itself does not have to be valid, just its
-           successor. */
-        Path sucPath;
-        if (nixDB.queryString(txn, dbSuccessors, *i, sucPath) &&
-            usablePaths.find(sucPath) == usablePaths.end())
-        {
-            printMsg(lvlError,
-                format("found successor mapping to non-existent path `%1%'") % sucPath);
-            nixDB.delPair(txn, dbSuccessors, *i);
-        }
-    }
-
-    /* Check that the keys of the reverse successor mappings are valid
-       paths. */ 
-    Paths rsucKeys;
-    nixDB.enumTable(txn, dbSuccessorsRev, rsucKeys);
-    for (Paths::iterator i = rsucKeys.begin(); i != rsucKeys.end(); ++i) {
-        if (usablePaths.find(*i) == usablePaths.end()) {
-            printMsg(lvlError,
-                format("found reverse successor mapping for non-existent path `%1%'") % *i);
-            nixDB.delPair(txn, dbSuccessorsRev, *i);
-        }
-    }
-
     txn.commit();
 }

src/libstore/store.hh

@@ -40,27 +40,6 @@ void createStoreTransaction(Transaction & txn);
 /* Copy a path recursively. */
 void copyPath(const Path & src, const Path & dst);
 
-/* Register a successor.  This function accepts a transaction handle
-   so that it can be enclosed in an atomic operation with calls to
-   registerValidPath().  This must be atomic, since if we register a
-   successor for a derivation without registering the paths built in
-   the derivation, we have a successor with dangling pointers, and if
-   we do it in reverse order, we can get an obstructed build (since to
-   rebuild the successor, the outputs paths must not exist). */
-void registerSuccessor(const Transaction & txn,
-    const Path & srcPath, const Path & sucPath);
-
-/* Remove a successor mapping. */
-void unregisterSuccessor(const Path & srcPath);
-
-/* Return the predecessors of the Nix expression stored at the given
-   path. */
-bool querySuccessor(const Path & srcPath, Path & sucPath);
-
-/* Return the predecessors of the Nix expression stored at the given
-   path. */
-Paths queryPredecessors(const Path & sucPath);
-
 /* Register a substitute. */
 typedef list<pair<Path, Substitute> > SubstitutePairs;
 void registerSubstitutes(const Transaction & txn,
@@ -81,6 +60,14 @@ void assertStorePath(const Path & path);
 /* Checks whether a path is valid. */ 
 bool isValidPath(const Path & path);
 
+/* Sets the set of outgoing FS references for a store path. */
+void setReferences(const Transaction & txn, const Path & storePath,
+    const PathSet & references);
+
+/* Queries the set of outgoing FS references for a store path.  The
+   result is not cleared. */
+void queryReferences(const Path & storePath, PathSet & references);
+
 /* Constructs a unique store path name. */
 Path makeStorePath(const string & type,
     const Hash & hash, const string & suffix);

src/libstore/storeexpr-ast.def

@@ -1,8 +1,6 @@
 init initStoreExprHelpers
 
-Closure | ATermList ATermList | ATerm |
+Derive | ATermList ATermList ATermList string string ATermList ATermList | ATerm |
-Derive | ATermList ATermList string string ATermList ATermList | ATerm |
 
 | string string | ATerm | EnvBinding |
-| string ATermList | ATerm | ClosureElem |
 | string string string string | ATerm | DerivationOutput |

src/libstore/storeexpr.cc

@@ -20,7 +20,7 @@ Path writeTerm(ATerm t, const string & suffix)
 }
 
 
-void checkPath(const string & s)
+static void checkPath(const string & s)
 {
     if (s.size() == 0 || s[0] != '/')
         throw Error(format("bad path `%1%' in store expression") % s);
@@ -39,108 +39,53 @@ static void parsePaths(ATermList paths, PathSet & out)
 }
 
 
-static void checkClosure(const Closure & closure)
+void throwBadDrv(ATerm t)
 {
-    if (closure.elems.size() == 0)
+    throw badTerm("not a valid derivation", t);
-        throw Error("empty closure");
-
-    PathSet decl;
-    for (ClosureElems::const_iterator i = closure.elems.begin();
-         i != closure.elems.end(); i++)
-        decl.insert(i->first);
-    
-    for (PathSet::const_iterator i = closure.roots.begin();
-         i != closure.roots.end(); i++)
-        if (decl.find(*i) == decl.end())
-            throw Error(format("undefined root path `%1%'") % *i);
-    
-    for (ClosureElems::const_iterator i = closure.elems.begin();
-         i != closure.elems.end(); i++)
-        for (PathSet::const_iterator j = i->second.refs.begin();
-             j != i->second.refs.end(); j++)
-            if (decl.find(*j) == decl.end())
-                throw Error(
-		    format("undefined path `%1%' referenced by `%2%'")
-		    % *j % i->first);
 }
 
 
-/* Parse a closure. */
+Derivation parseDerivation(ATerm t)
-static bool parseClosure(ATerm t, Closure & closure)
 {
-    ATermList roots, elems;
+    Derivation drv;
-
+    ATermList outs, inDrvs, inSrcs, args, bnds;
-    if (!matchClosure(t, roots, elems))
-        return false;
-
-    parsePaths(roots, closure.roots);
-
-    for (ATermIterator i(elems); i; ++i) {
-        ATerm path;
-        ATermList refs;
-        if (!matchClosureElem(*i, path, refs))
-            throw badTerm("not a closure element", *i);
-        ClosureElem elem;
-        parsePaths(refs, elem.refs);
-        closure.elems[aterm2String(path)] = elem;
-    }
-
-    checkClosure(closure);
-    return true;
-}
-
-
-static bool parseDerivation(ATerm t, Derivation & derivation)
-{
-    ATermList outs, ins, args, bnds;
     ATerm builder, platform;
 
-    if (!matchDerive(t, outs, ins, platform, builder, args, bnds))
+    if (!matchDerive(t, outs, inDrvs, inSrcs, platform, builder, args, bnds))
-        return false;
+        throwBadDrv(t);
 
     for (ATermIterator i(outs); i; ++i) {
         ATerm id, path, hashAlgo, hash;
         if (!matchDerivationOutput(*i, id, path, hashAlgo, hash))
-            return false;
+            throwBadDrv(t);
         DerivationOutput out;
         out.path = aterm2String(path);
         checkPath(out.path);
         out.hashAlgo = aterm2String(hashAlgo);
         out.hash = aterm2String(hash);
-        derivation.outputs[aterm2String(id)] = out;
+        drv.outputs[aterm2String(id)] = out;
     }
 
-    parsePaths(ins, derivation.inputs);
+    parsePaths(inDrvs, drv.inputDrvs);
+    parsePaths(inSrcs, drv.inputSrcs);
 
-    derivation.builder = aterm2String(builder);
+    drv.builder = aterm2String(builder);
-    derivation.platform = aterm2String(platform);
+    drv.platform = aterm2String(platform);
     
     for (ATermIterator i(args); i; ++i) {
         if (ATgetType(*i) != AT_APPL)
             throw badTerm("string expected", *i);
-        derivation.args.push_back(aterm2String(*i));
+        drv.args.push_back(aterm2String(*i));
     }
 
     for (ATermIterator i(bnds); i; ++i) {
         ATerm s1, s2;
         if (!matchEnvBinding(*i, s1, s2))
             throw badTerm("tuple of strings expected", *i);
-        derivation.env[aterm2String(s1)] = aterm2String(s2);
+        drv.env[aterm2String(s1)] = aterm2String(s2);
     }
 
-    return true;
+    return drv;
-}
-
-
-StoreExpr parseStoreExpr(ATerm t)
-{
-    StoreExpr ne;
-    if (parseClosure(t, ne.closure))
-        ne.type = StoreExpr::neClosure;
-    else if (parseDerivation(t, ne.derivation))
-        ne.type = StoreExpr::neDerivation;
-    else throw badTerm("not a store expression", t);
-    return ne;
 }
 
 
@@ -154,27 +99,11 @@ static ATermList unparsePaths(const PathSet & paths)
 }
 
 
-static ATerm unparseClosure(const Closure & closure)
+ATerm unparseDerivation(const Derivation & drv)
-{
-    ATermList roots = unparsePaths(closure.roots);
-    
-    ATermList elems = ATempty;
-    for (ClosureElems::const_iterator i = closure.elems.begin();
-         i != closure.elems.end(); i++)
-        elems = ATinsert(elems,
-            makeClosureElem(
-                toATerm(i->first),
-                unparsePaths(i->second.refs)));
-
-    return makeClosure(roots, elems);
-}
-
-
-static ATerm unparseDerivation(const Derivation & derivation)
 {
     ATermList outputs = ATempty;
-    for (DerivationOutputs::const_iterator i = derivation.outputs.begin();
+    for (DerivationOutputs::const_iterator i = drv.outputs.begin();
-         i != derivation.outputs.end(); i++)
+         i != drv.outputs.end(); i++)
         outputs = ATinsert(outputs,
             makeDerivationOutput(
                 toATerm(i->first),
@@ -183,13 +112,13 @@ static ATerm unparseDerivation(const Derivation & derivation)
                 toATerm(i->second.hash)));
 
     ATermList args = ATempty;
-    for (Strings::const_iterator i = derivation.args.begin();
+    for (Strings::const_iterator i = drv.args.begin();
-         i != derivation.args.end(); i++)
+         i != drv.args.end(); i++)
         args = ATinsert(args, toATerm(*i));
 
     ATermList env = ATempty;
-    for (StringPairs::const_iterator i = derivation.env.begin();
+    for (StringPairs::const_iterator i = drv.env.begin();
-         i != derivation.env.end(); i++)
+         i != drv.env.end(); i++)
         env = ATinsert(env,
             makeEnvBinding(
                 toATerm(i->first),
@@ -197,19 +126,10 @@ static ATerm unparseDerivation(const Derivation & derivation)
 
     return makeDerive(
         ATreverse(outputs),
-        unparsePaths(derivation.inputs),
+        unparsePaths(drv.inputDrvs),
-        toATerm(derivation.platform),
+        unparsePaths(drv.inputSrcs),
-        toATerm(derivation.builder),
+        toATerm(drv.platform),
+        toATerm(drv.builder),
         ATreverse(args),
         ATreverse(env));
 }
-
-
-ATerm unparseStoreExpr(const StoreExpr & ne)
-{
-    if (ne.type == StoreExpr::neClosure)
-        return unparseClosure(ne.closure);
-    else if (ne.type == StoreExpr::neDerivation)
-        return unparseDerivation(ne.derivation);
-    else abort();
-}

src/libstore/storeexpr.hh

@@ -14,11 +14,13 @@ struct ClosureElem
 
 typedef map<Path, ClosureElem> ClosureElems;
 
+/*
 struct Closure
 {
     PathSet roots;
     ClosureElems elems;
 };
+*/
 
 
 struct DerivationOutput
@@ -43,20 +45,14 @@ typedef map<string, string> StringPairs;
 struct Derivation
 {
     DerivationOutputs outputs; /* keyed on symbolic IDs */
-    PathSet inputs; /* store expressions, not actual inputs */
+    PathSet inputDrvs; /* inputs that are sub-derivations */
+    PathSet inputSrcs; /* inputs that are sources */
     string platform;
     Path builder;
     Strings args;
     StringPairs env;
 };
 
-struct StoreExpr
-{
-    enum { neClosure, neDerivation } type;
-    Closure closure;
-    Derivation derivation;
-};
-
 
 /* Hash an aterm. */
 Hash hashTerm(ATerm t);
@@ -65,10 +61,10 @@ Hash hashTerm(ATerm t);
 Path writeTerm(ATerm t, const string & suffix);
 
 /* Parse a store expression. */
-StoreExpr parseStoreExpr(ATerm t);
+Derivation parseDerivation(ATerm t);
 
 /* Parse a store expression. */
-ATerm unparseStoreExpr(const StoreExpr & ne);
+ATerm unparseDerivation(const Derivation & drv);
 
 
 #endif /* !__STOREEXPR_H */

src/nix-env/main.cc

@@ -222,13 +222,13 @@ void createUserEnv(EvalState & state, const DrvInfos & drvs,
         abort();
     
     /* Realise the resulting store expression. */
-    debug(format("realising user environment"));
+    debug(format("building user environment"));
-    Path nfPath = realiseStoreExpr(topLevelDrv.drvPath);
+    buildDerivation(topLevelDrv.drvPath);
 
     /* Switch the current user environment to the output path. */
     debug(format("switching to new user environment"));
     Path generation = createGeneration(profile,
-        topLevelDrv.outPath, topLevelDrv.drvPath, nfPath);
+        topLevelDrv.outPath, topLevelDrv.drvPath);
     switchLink(profile, generation);
 }
 

src/nix-env/profiles.cc

@@ -18,7 +18,7 @@ static int parseName(const string & profileName, const string & name)
 {
     if (string(name, 0, profileName.size() + 1) != profileName + "-") return -1;
     string s = string(name, profileName.size() + 1);
-    int p = s.find("-link");
+    unsigned int p = s.find("-link");
     if (p == string::npos) return -1;
     int n;
     if (string2Int(string(s, 0, p), n) && n >= 0)
@@ -62,17 +62,15 @@ Generations findGenerations(Path profile, int & curGen)
 
 
 static void makeNames(const Path & profile, unsigned int num,
-    Path & generation, Path & gcrootDrv, Path & gcrootClr)
+    Path & generation, Path & gcrootDrv)
 {
     Path prefix = (format("%1%-%2%") % profile % num).str();
     generation = prefix + "-link";
     gcrootDrv = prefix + "-drv.gcroot";
-    gcrootClr = prefix + "-clr.gcroot";
 }
 
 
-Path createGeneration(Path profile, Path outPath,
+Path createGeneration(Path profile, Path outPath, Path drvPath)
-    Path drvPath, Path clrPath)
 {
     /* The new generation number should be higher than old the
        previous ones. */
@@ -81,10 +79,10 @@ Path createGeneration(Path profile, Path outPath,
     unsigned int num = gens.size() > 0 ? gens.front().number : 0;
         
     /* Create the new generation. */
-    Path generation, gcrootDrv, gcrootClr;
+    Path generation, gcrootDrv;
 
     while (1) {
-        makeNames(profile, num, generation, gcrootDrv, gcrootClr);
+        makeNames(profile, num, generation, gcrootDrv);
         if (symlink(outPath.c_str(), generation.c_str()) == 0) break;
         if (errno != EEXIST)
             throw SysError(format("creating symlink `%1%'") % generation);
@@ -93,7 +91,6 @@ Path createGeneration(Path profile, Path outPath,
     }
 
     writeStringToFile(gcrootDrv, drvPath);
-    writeStringToFile(gcrootClr, clrPath);
 
     return generation;
 }
@@ -108,10 +105,9 @@ static void removeFile(const Path & path)
 
 void deleteGeneration(const Path & profile, unsigned int gen)
 {
-    Path generation, gcrootDrv, gcrootClr;
+    Path generation, gcrootDrv;
-    makeNames(profile, gen, generation, gcrootDrv, gcrootClr);
+    makeNames(profile, gen, generation, gcrootDrv);
     removeFile(generation);
-    if (pathExists(gcrootClr)) removeFile(gcrootClr);
     if (pathExists(gcrootDrv)) removeFile(gcrootDrv);
 }
 

src/nix-env/profiles.hh

@@ -28,8 +28,7 @@ typedef list<Generation> Generations;
    profile, sorted by generation number. */
 Generations findGenerations(Path profile, int & curGen);
     
-Path createGeneration(Path profile, Path outPath,
+Path createGeneration(Path profile, Path outPath, Path drvPath);
-    Path drvPath, Path clrPath);
 
 void deleteGeneration(const Path & profile, unsigned int gen);
 

src/nix-store/dotgraph.cc

@@ -2,6 +2,7 @@
 #include "normalise.hh"
 
 
+#if 0
 static string dotQuote(const string & s)
 {
     return "\"" + s + "\"";
@@ -133,3 +134,4 @@ void printDotGraph(const PathSet & roots)
 
     cout << "}\n";
 }
+#endif

src/nix-store/main.cc

@@ -18,21 +18,18 @@ void printHelp()
 }
 
 
-/* Realise paths from the given store expressions. */
+/* Build the given derivations. */
-static void opRealise(Strings opFlags, Strings opArgs)
+static void opBuild(Strings opFlags, Strings opArgs)
 {
     if (!opFlags.empty()) throw UsageError("unknown flag");
 
     for (Strings::iterator i = opArgs.begin();
          i != opArgs.end(); i++)
-    {
+        buildDerivation(*i);
-        Path nfPath = realiseStoreExpr(*i);
-        cout << format("%1%\n") % (string) nfPath;
-    }
 }
 
 
-/* Add paths to the Nix values directory and print the hashes of those
+/* Add files to the Nix values directory and print the resulting
    paths. */
 static void opAdd(Strings opFlags, Strings opArgs)
 {
@@ -43,6 +40,7 @@ static void opAdd(Strings opFlags, Strings opArgs)
 }
 
 
+#if 0
 Path maybeNormalise(const Path & ne, bool normalise, bool realise)
 {
     if (realise) {
@@ -131,24 +129,7 @@ static void opQuery(Strings opFlags, Strings opArgs)
             abort();
     }
 }
-
+#endif
-
-static void opSuccessor(Strings opFlags, Strings opArgs)
-{
-    if (!opFlags.empty()) throw UsageError("unknown flag");
-    if (opArgs.size() % 2) throw UsageError("expecting even number of arguments");
-
-    Transaction txn;
-    createStoreTransaction(txn);
-    for (Strings::iterator i = opArgs.begin();
-         i != opArgs.end(); )
-    {
-        Path path1 = *i++;
-        Path path2 = *i++;
-        registerSuccessor(txn, path1, path2);
-    }
-    txn.commit();
-}
 
 
 static void opSubstitute(Strings opFlags, Strings opArgs)
@@ -195,7 +176,6 @@ static void opClearSubstitutes(Strings opFlags, Strings opArgs)
 }
 
 
-
 static void opValidPath(Strings opFlags, Strings opArgs)
 {
     if (!opFlags.empty()) throw UsageError("unknown flag");
@@ -222,6 +202,7 @@ static void opIsValid(Strings opFlags, Strings opArgs)
 
 static void opGC(Strings opFlags, Strings opArgs)
 {
+#if 0
     /* Do what? */
     enum { soPrintLive, soPrintDead, soDelete } subOp;
     time_t minAge = 0;
@@ -275,6 +256,7 @@ static void opGC(Strings opFlags, Strings opArgs)
             deleteFromStore(*i);
         }
     }
+#endif
 }
 
 
@@ -354,14 +336,12 @@ void run(Strings args)
 
         Operation oldOp = op;
 
-        if (arg == "--realise" || arg == "-r")
+        if (arg == "--build" || arg == "-b")
-            op = opRealise;
+            op = opBuild;
         else if (arg == "--add" || arg == "-A")
             op = opAdd;
-        else if (arg == "--query" || arg == "-q")
+        //        else if (arg == "--query" || arg == "-q")
-            op = opQuery;
+        //            op = opQuery;
-        else if (arg == "--successor")
-            op = opSuccessor;
         else if (arg == "--substitute")
             op = opSubstitute;
         else if (arg == "--clear-substitutes")