More work on the scheduler for windows

- Get a rump derivation goal: hook instance will come later, local
  derivation goal will come after that.

- Start cleaning up the channel / waiting code with an abstraction.

src/libstore/build/derivation-goal.hh

@@ -0,0 +1,352 @@
+#pragma once
+///@file
+
+#include "parsed-derivations.hh"
+#ifndef _WIN32
+#  include "user-lock.hh"
+#endif
+#include "outputs-spec.hh"
+#include "store-api.hh"
+#include "pathlocks.hh"
+#include "goal.hh"
+
+namespace nix {
+
+using std::map;
+
+#ifndef _WIN32 // TODO enable build hook on Windows
+struct HookInstance;
+#endif
+
+typedef enum {rpAccept, rpDecline, rpPostpone} HookReply;
+
+/**
+ * Unless we are repairing, we don't both to test validity and just assume it,
+ * so the choices are `Absent` or `Valid`.
+ */
+enum struct PathStatus {
+    Corrupt,
+    Absent,
+    Valid,
+};
+
+struct InitialOutputStatus {
+    StorePath path;
+    PathStatus status;
+    /**
+     * Valid in the store, and additionally non-corrupt if we are repairing
+     */
+    bool isValid() const {
+        return status == PathStatus::Valid;
+    }
+    /**
+     * Merely present, allowed to be corrupt
+     */
+    bool isPresent() const {
+        return status == PathStatus::Corrupt
+            || status == PathStatus::Valid;
+    }
+};
+
+struct InitialOutput {
+    bool wanted;
+    Hash outputHash;
+    std::optional<InitialOutputStatus> known;
+};
+
+/**
+ * A goal for building some or all of the outputs of a derivation.
+ */
+struct DerivationGoal : public Goal
+{
+    /**
+     * Whether to use an on-disk .drv file.
+     */
+    bool useDerivation;
+
+    /** The path of the derivation. */
+    StorePath drvPath;
+
+    /**
+     * The goal for the corresponding resolved derivation
+     */
+    std::shared_ptr<DerivationGoal> resolvedDrvGoal;
+
+    /**
+     * The specific outputs that we need to build.
+     */
+    OutputsSpec wantedOutputs;
+
+    /**
+     * Mapping from input derivations + output names to actual store
+     * paths. This is filled in by waiteeDone() as each dependency
+     * finishes, before inputsRealised() is reached.
+     */
+    std::map<std::pair<StorePath, std::string>, StorePath> inputDrvOutputs;
+
+    /**
+     * See `needRestart`; just for that field.
+     */
+    enum struct NeedRestartForMoreOutputs {
+        /**
+         * The goal state machine is progressing based on the current value of
+         * `wantedOutputs. No actions are needed.
+         */
+        OutputsUnmodifedDontNeed,
+        /**
+         * `wantedOutputs` has been extended, but the state machine is
+         * proceeding according to its old value, so we need to restart.
+         */
+        OutputsAddedDoNeed,
+        /**
+         * The goal state machine has progressed to the point of doing a build,
+         * in which case all outputs will be produced, so extensions to
+         * `wantedOutputs` no longer require a restart.
+         */
+        BuildInProgressWillNotNeed,
+    };
+
+    /**
+     * Whether additional wanted outputs have been added.
+     */
+    NeedRestartForMoreOutputs needRestart = NeedRestartForMoreOutputs::OutputsUnmodifedDontNeed;
+
+    /**
+     * See `retrySubstitution`; just for that field.
+     */
+    enum RetrySubstitution {
+        /**
+         * No issues have yet arose, no need to restart.
+         */
+        NoNeed,
+        /**
+         * Something failed and there is an incomplete closure. Let's retry
+         * substituting.
+         */
+        YesNeed,
+        /**
+         * We are current or have already retried substitution, and whether or
+         * not something goes wrong we will not retry again.
+         */
+        AlreadyRetried,
+    };
+
+    /**
+     * Whether to retry substituting the outputs after building the
+     * inputs. This is done in case of an incomplete closure.
+     */
+    RetrySubstitution retrySubstitution = RetrySubstitution::NoNeed;
+
+    /**
+     * The derivation stored at drvPath.
+     */
+    std::unique_ptr<Derivation> drv;
+
+    std::unique_ptr<ParsedDerivation> parsedDrv;
+
+    /**
+     * The remainder is state held during the build.
+     */
+
+    /**
+     * Locks on (fixed) output paths.
+     */
+    PathLocks outputLocks;
+
+    /**
+     * All input paths (that is, the union of FS closures of the
+     * immediate input paths).
+     */
+    StorePathSet inputPaths;
+
+    std::map<std::string, InitialOutput> initialOutputs;
+
+    /**
+     * File descriptor for the log file.
+     */
+    AutoCloseFD fdLogFile;
+    std::shared_ptr<BufferedSink> logFileSink, logSink;
+
+    /**
+     * Number of bytes received from the builder's stdout/stderr.
+     */
+    unsigned long logSize;
+
+    /**
+     * The most recent log lines.
+     */
+    std::list<std::string> logTail;
+
+    std::string currentLogLine;
+    size_t currentLogLinePos = 0; // to handle carriage return
+
+    std::string currentHookLine;
+
+#ifndef _WIN32 // TODO enable build hook on Windows
+    /**
+     * The build hook.
+     */
+    std::unique_ptr<HookInstance> hook;
+#endif
+
+    /**
+     * The sort of derivation we are building.
+     */
+    std::optional<DerivationType> derivationType;
+
+    typedef void (DerivationGoal::*GoalState)();
+    GoalState state;
+
+    BuildMode buildMode;
+
+    std::unique_ptr<MaintainCount<uint64_t>> mcExpectedBuilds, mcRunningBuilds;
+
+    std::unique_ptr<Activity> act;
+
+    /**
+     * Activity that denotes waiting for a lock.
+     */
+    std::unique_ptr<Activity> actLock;
+
+    std::map<ActivityId, Activity> builderActivities;
+
+    /**
+     * The remote machine on which we're building.
+     */
+    std::string machineName;
+
+    DerivationGoal(const StorePath & drvPath,
+        const OutputsSpec & wantedOutputs, Worker & worker,
+        BuildMode buildMode = bmNormal);
+    DerivationGoal(const StorePath & drvPath, const BasicDerivation & drv,
+        const OutputsSpec & wantedOutputs, Worker & worker,
+        BuildMode buildMode = bmNormal);
+    virtual ~DerivationGoal();
+
+    void timedOut(Error && ex) override;
+
+    std::string key() override;
+
+    void work() override;
+
+    /**
+     * Add wanted outputs to an already existing derivation goal.
+     */
+    void addWantedOutputs(const OutputsSpec & outputs);
+
+    /**
+     * The states.
+     */
+    void getDerivation();
+    void loadDerivation();
+    void haveDerivation();
+    void outputsSubstitutionTried();
+    void gaveUpOnSubstitution();
+    void closureRepaired();
+    void inputsRealised();
+    void tryToBuild();
+    virtual void tryLocalBuild();
+    void buildDone();
+
+    void resolvedFinished();
+
+    /**
+     * Is the build hook willing to perform the build?
+     */
+    HookReply tryBuildHook();
+
+    virtual int getChildStatus();
+
+    /**
+     * Check that the derivation outputs all exist and register them
+     * as valid.
+     */
+    virtual SingleDrvOutputs registerOutputs();
+
+    /**
+     * Open a log file and a pipe to it.
+     */
+    Path openLogFile();
+
+    /**
+     * Sign the newly built realisation if the store allows it
+     */
+    virtual void signRealisation(Realisation&) {}
+
+    /**
+     * Close the log file.
+     */
+    void closeLogFile();
+
+    /**
+     * Close the read side of the logger pipe.
+     */
+    virtual void closeReadPipes();
+
+    /**
+     * Cleanup hooks for buildDone()
+     */
+    virtual void cleanupHookFinally();
+    virtual void cleanupPreChildKill();
+    virtual void cleanupPostChildKill();
+    virtual bool cleanupDecideWhetherDiskFull();
+    virtual void cleanupPostOutputsRegisteredModeCheck();
+    virtual void cleanupPostOutputsRegisteredModeNonCheck();
+
+    virtual bool isReadDesc(Descriptor fd);
+
+    /**
+     * Callback used by the worker to write to the log.
+     */
+    void handleChildOutput(Descriptor fd, std::string_view data) override;
+    void handleEOF(Descriptor fd) override;
+    void flushLine();
+
+    /**
+     * Wrappers around the corresponding Store methods that first consult the
+     * derivation.  This is currently needed because when there is no drv file
+     * there also is no DB entry.
+     */
+    std::map<std::string, std::optional<StorePath>> queryPartialDerivationOutputMap();
+    OutputPathMap queryDerivationOutputMap();
+
+    /**
+     * Update 'initialOutputs' to determine the current status of the
+     * outputs of the derivation. Also returns a Boolean denoting
+     * whether all outputs are valid and non-corrupt, and a
+     * 'SingleDrvOutputs' structure containing the valid outputs.
+     */
+    std::pair<bool, SingleDrvOutputs> checkPathValidity();
+
+    /**
+     * Aborts if any output is not valid or corrupt, and otherwise
+     * returns a 'SingleDrvOutputs' structure containing all outputs.
+     */
+    SingleDrvOutputs assertPathValidity();
+
+    /**
+     * Forcibly kill the child process, if any.
+     */
+    virtual void killChild();
+
+    void repairClosure();
+
+    void started();
+
+    void done(
+        BuildResult::Status status,
+        SingleDrvOutputs builtOutputs = {},
+        std::optional<Error> ex = {});
+
+    void waiteeDone(GoalPtr waitee, ExitCode result) override;
+
+    StorePathSet exportReferences(const StorePathSet & storePaths);
+
+    JobCategory jobCategory() const override {
+        return JobCategory::Build;
+    };
+};
+
+MakeError(NotDeterministic, BuildError);
+
+}

src/libstore/build/drv-output-substitution-goal.hh

@@ -7,10 +7,7 @@
 #include "store-api.hh"
 #include "goal.hh"
 #include "realisation.hh"
-
-#ifdef _WIN32
-#  include "windows-async-pipe.hh"
-#endif
+#include "muxable-pipe.hh"
 
 namespace nix {
 
@@ -48,11 +45,7 @@ class DrvOutputSubstitutionGoal : public Goal {
 
     struct DownloadState
     {
-#ifndef _WIN32
-        Pipe outPipe;
-#else
-        windows::AsyncPipe outPipe;
-#endif
+        MuxablePipe outPipe;
         std::promise<std::shared_ptr<const Realisation>> promise;
     };
 

src/libstore/build/substitution-goal.hh

@@ -3,10 +3,7 @@
 
 #include "store-api.hh"
 #include "goal.hh"
-
-#ifdef _WIN32
-#  include "windows-async-pipe.hh"
-#endif
+#include "muxable-pipe.hh"
 
 namespace nix {
 
@@ -48,11 +45,7 @@ struct PathSubstitutionGoal : public Goal
     /**
      * Pipe for the substituter's standard output.
      */
-#ifndef _WIN32
-    Pipe outPipe;
-#else
-    windows::AsyncPipe outPipe;
-#endif
+    MuxablePipe outPipe;
 
     /**
      * The substituter thread.

src/libstore/build/worker.cc

@@ -3,19 +3,13 @@
 #include "worker.hh"
 #include "substitution-goal.hh"
 #include "drv-output-substitution-goal.hh"
+#include "derivation-goal.hh"
 #ifndef _WIN32 // TODO Enable building on Windows
 #  include "local-derivation-goal.hh"
 #  include "hook-instance.hh"
 #endif
 #include "signals.hh"
 
-#ifndef _WIN32
-#  include <poll.h>
-#else
-#  include <ioapiset.h>
-#  include "windows-error.hh"
-#endif
-
 namespace nix {
 
 Worker::Worker(Store & store, Store & evalStore)
@@ -49,7 +43,6 @@ Worker::~Worker()
     assert(expectedNarSize == 0);
 }
 
-#ifndef _WIN32 // TODO Enable building on Windows
 
 std::shared_ptr<DerivationGoal> Worker::makeDerivationGoalCommon(
     const StorePath & drvPath,
@@ -73,9 +66,13 @@ std::shared_ptr<DerivationGoal> Worker::makeDerivationGoal(const StorePath & drv
     const OutputsSpec & wantedOutputs, BuildMode buildMode)
 {
     return makeDerivationGoalCommon(drvPath, wantedOutputs, [&]() -> std::shared_ptr<DerivationGoal> {
-        return !dynamic_cast<LocalStore *>(&store)
-            ? std::make_shared</* */DerivationGoal>(drvPath, wantedOutputs, *this, buildMode)
-            : std::make_shared<LocalDerivationGoal>(drvPath, wantedOutputs, *this, buildMode);
+        return
+#ifndef _WIN32 // TODO Enable building on Windows
+            dynamic_cast<LocalStore *>(&store)
+            ? std::make_shared<LocalDerivationGoal>(drvPath, wantedOutputs, *this, buildMode)
+            :
+#endif
+            std::make_shared</* */DerivationGoal>(drvPath, wantedOutputs, *this, buildMode);
     });
 }
 
@@ -83,14 +80,16 @@ std::shared_ptr<DerivationGoal> Worker::makeBasicDerivationGoal(const StorePath
     const BasicDerivation & drv, const OutputsSpec & wantedOutputs, BuildMode buildMode)
 {
     return makeDerivationGoalCommon(drvPath, wantedOutputs, [&]() -> std::shared_ptr<DerivationGoal> {
-        return !dynamic_cast<LocalStore *>(&store)
-            ? std::make_shared</* */DerivationGoal>(drvPath, drv, wantedOutputs, *this, buildMode)
-            : std::make_shared<LocalDerivationGoal>(drvPath, drv, wantedOutputs, *this, buildMode);
+        return
+#ifndef _WIN32 // TODO Enable building on Windows
+            dynamic_cast<LocalStore *>(&store)
+            ? std::make_shared<LocalDerivationGoal>(drvPath, drv, wantedOutputs, *this, buildMode)
+            :
+#endif
+            std::make_shared</* */DerivationGoal>(drvPath, drv, wantedOutputs, *this, buildMode);
     });
 }
 
-#endif
-
 
 std::shared_ptr<PathSubstitutionGoal> Worker::makePathSubstitutionGoal(const StorePath & path, RepairFlag repair, std::optional<ContentAddress> ca)
 {
@@ -122,14 +121,10 @@ GoalPtr Worker::makeGoal(const DerivedPath & req, BuildMode buildMode)
 {
     return std::visit(overloaded {
         [&](const DerivedPath::Built & bfd) -> GoalPtr {
-#ifndef _WIN32 // TODO Enable building on Windows
             if (auto bop = std::get_if<DerivedPath::Opaque>(&*bfd.drvPath))
                 return makeDerivationGoal(bop->path, bfd.outputs, buildMode);
             else
                 throw UnimplementedError("Building dynamic derivations in one shot is not yet implemented.");
-#else
-            throw UnimplementedError("Building derivations not yet implemented on Windows");
-#endif
         },
         [&](const DerivedPath::Opaque & bo) -> GoalPtr {
             return makePathSubstitutionGoal(bo.path, buildMode == bmRepair ? Repair : NoRepair);
@@ -155,11 +150,9 @@ static void removeGoal(std::shared_ptr<G> goal, std::map<K, std::weak_ptr<G>> &
 
 void Worker::removeGoal(GoalPtr goal)
 {
-#ifndef _WIN32 // TODO Enable building on Windows
     if (auto drvGoal = std::dynamic_pointer_cast<DerivationGoal>(goal))
         nix::removeGoal(drvGoal, derivationGoals);
     else
-#endif
     if (auto subGoal = std::dynamic_pointer_cast<PathSubstitutionGoal>(goal))
         nix::removeGoal(subGoal, substitutionGoals);
     else if (auto subGoal = std::dynamic_pointer_cast<DrvOutputSubstitutionGoal>(goal))
@@ -204,7 +197,7 @@ unsigned Worker::getNrSubstitutions()
 }
 
 
-void Worker::childStarted(GoalPtr goal, const std::set<Child::CommChannel> & channels,
+void Worker::childStarted(GoalPtr goal, const std::set<MuxablePipePollState::CommChannel> & channels,
     bool inBuildSlot, bool respectTimeouts)
 {
     Child child;
@@ -298,14 +291,12 @@ void Worker::run(const Goals & _topGoals)
 
     for (auto & i : _topGoals) {
         topGoals.insert(i);
-#ifndef _WIN32 // TODO Enable building on Windows
         if (auto goal = dynamic_cast<DerivationGoal *>(i.get())) {
             topPaths.push_back(DerivedPath::Built {
                 .drvPath = makeConstantStorePathRef(goal->drvPath),
                 .outputs = goal->wantedOutputs,
             });
         } else
-#endif
         if (auto goal = dynamic_cast<PathSubstitutionGoal *>(i.get())) {
             topPaths.push_back(DerivedPath::Opaque{goal->storePath});
         }
@@ -428,47 +419,26 @@ void Worker::waitForInput()
     if (useTimeout)
         vomit("sleeping %d seconds", timeout);
 
+    MuxablePipePollState state;
+
 #ifndef _WIN32
     /* Use select() to wait for the input side of any logger pipe to
        become `available'.  Note that `available' (i.e., non-blocking)
        includes EOF. */
-    std::vector<struct pollfd> pollStatus;
-    std::map<int, size_t> fdToPollStatus;
     for (auto & i : children) {
         for (auto & j : i.channels) {
-            pollStatus.push_back((struct pollfd) { .fd = j, .events = POLLIN });
-            fdToPollStatus[j] = pollStatus.size() - 1;
+            state.pollStatus.push_back((struct pollfd) { .fd = j, .events = POLLIN });
+            state.fdToPollStatus[j] = state.pollStatus.size() - 1;
         }
     }
-
-    if (poll(pollStatus.data(), pollStatus.size(),
-            useTimeout ? timeout * 1000 : -1) == -1) {
-        if (errno == EINTR) return;
-        throw SysError("waiting for input");
-    }
-#else
-    OVERLAPPED_ENTRY oentries[0x20] = {0};
-    ULONG removed;
-    bool gotEOF = false;
-
-    // we are on at least Windows Vista / Server 2008 and can get many (countof(oentries)) statuses in one API call
-    if (!GetQueuedCompletionStatusEx(
-        ioport.get(),
-        oentries,
-        sizeof(oentries) / sizeof(*oentries),
-        &removed,
-        useTimeout ? timeout * 1000 : INFINITE,
-        false))
-    {
-        windows::WinError winError("GetQueuedCompletionStatusEx");
-        if (winError.lastError != WAIT_TIMEOUT)
-            throw winError;
-        assert(removed == 0);
-    } else {
-        assert(0 < removed && removed <= sizeof(oentries)/sizeof(*oentries));
-    }
 #endif
 
+    state.poll(
+#ifdef _WIN32
+        ioport.get(),
+#endif
+        useTimeout ? (std::optional { timeout * 1000 }) : std::nullopt);
+
     auto after = steady_time_point::clock::now();
 
     /* Process all available file descriptors. FIXME: this is
@@ -482,75 +452,18 @@ void Worker::waitForInput()
         GoalPtr goal = j->goal.lock();
         assert(goal);
 
-#ifndef _WIN32
-        std::set<Descriptor> fds2(j->channels);
-        std::vector<unsigned char> buffer(4096);
-        for (auto & k : fds2) {
-            const auto fdPollStatusId = get(fdToPollStatus, k);
-            assert(fdPollStatusId);
-            assert(*fdPollStatusId < pollStatus.size());
-            if (pollStatus.at(*fdPollStatusId).revents) {
-                ssize_t rd = ::read(fromDescriptorReadOnly(k), buffer.data(), buffer.size());
-                // FIXME: is there a cleaner way to handle pt close
-                // than EIO? Is this even standard?
-                if (rd == 0 || (rd == -1 && errno == EIO)) {
-                    debug("%1%: got EOF", goal->getName());
-                    goal->handleEOF(k);
-                    j->channels.erase(k);
-                } else if (rd == -1) {
-                    if (errno != EINTR)
-                        throw SysError("%s: read failed", goal->getName());
-                } else {
-                    printMsg(lvlVomit, "%1%: read %2% bytes",
-                        goal->getName(), rd);
-                    std::string_view data((char *) buffer.data(), rd);
-                    j->lastOutput = after;
-                    goal->handleChildOutput(k, data);
-                }
-            }
-        }
-#else
-        decltype(j->channels)::iterator p = j->channels.begin();
-        while (p != j->channels.end()) {
-            decltype(p) nextp = p;
-            ++nextp;
-            for (ULONG i = 0; i < removed; i++) {
-                if (oentries[i].lpCompletionKey == ((ULONG_PTR)((*p)->readSide.get()) ^ 0x5555)) {
-                    printMsg(lvlVomit, "%s: read %s bytes", goal->getName(), oentries[i].dwNumberOfBytesTransferred);
-                    if (oentries[i].dwNumberOfBytesTransferred > 0) {
-                        std::string data {
-                            (char *) (*p)->buffer.data(),
-                            oentries[i].dwNumberOfBytesTransferred,
-                        };
-                        //std::cerr << "read  [" << data << "]" << std::endl;
-                        j->lastOutput = after;
-                        goal->handleChildOutput((*p)->readSide.get(), data);
-                    }
-
-                    if (gotEOF) {
-                        debug("%s: got EOF", goal->getName());
-                        goal->handleEOF((*p)->readSide.get());
-                        nextp = j->channels.erase(p); // no need to maintain `j->channels` ?
-                    } else {
-                        BOOL rc = ReadFile((*p)->readSide.get(), (*p)->buffer.data(), (*p)->buffer.size(), &(*p)->got, &(*p)->overlapped);
-                        if (rc) {
-                            // here is possible (but not obligatory) to call `goal->handleChildOutput` and repeat ReadFile immediately
-                        } else {
-                            windows::WinError winError("ReadFile(%s, ..)", (*p)->readSide.get());
-                            if (winError.lastError == ERROR_BROKEN_PIPE) {
-                                debug("%s: got EOF", goal->getName());
-                                goal->handleEOF((*p)->readSide.get());
-                                nextp = j->channels.erase(p); // no need to maintain `j->channels` ?
-                            } else if (winError.lastError != ERROR_IO_PENDING)
-                                throw winError;
-                        }
-                    }
-                    break;
-                }
-            }
-            p = nextp;
-        }
-#endif
+        state.iterate(
+            j->channels,
+            [&](Descriptor k, std::string_view data) {
+                printMsg(lvlVomit, "%1%: read %2% bytes",
+                    goal->getName(), data.size());
+                j->lastOutput = after;
+                goal->handleChildOutput(k, data);
+            },
+            [&](Descriptor k) {
+                debug("%1%: got EOF", goal->getName());
+                goal->handleEOF(k);
+            });
 
         if (goal->exitCode == Goal::ecBusy &&
             0 != settings.maxSilentTime &&

src/libstore/build/worker.hh

@@ -5,10 +5,7 @@
 #include "store-api.hh"
 #include "goal.hh"
 #include "realisation.hh"
-
-#ifdef _WIN32
-#  include "windows-async-pipe.hh"
-#endif
+#include "muxable-pipe.hh"
 
 #include <future>
 #include <thread>
@@ -16,9 +13,7 @@
 namespace nix {
 
 /* Forward definition. */
-#ifndef _WIN32 // TODO Enable building on Windows
 struct DerivationGoal;
-#endif
 struct PathSubstitutionGoal;
 class DrvOutputSubstitutionGoal;
 
@@ -46,17 +41,9 @@ typedef std::chrono::time_point<std::chrono::steady_clock> steady_time_point;
  */
 struct Child
 {
-    using CommChannel =
-#ifndef _WIN32
-        Descriptor
-#else
-        windows::AsyncPipe *
-#endif
-        ;
-
     WeakGoalPtr goal;
     Goal * goal2; // ugly hackery
-    std::set<CommChannel> channels;
+    std::set<MuxablePipePollState::CommChannel> channels;
     bool respectTimeouts;
     bool inBuildSlot;
     /**
@@ -116,9 +103,7 @@ private:
      * Maps used to prevent multiple instantiations of a goal for the
      * same derivation / path.
      */
-#ifndef _WIN32 // TODO Enable building on Windows
     std::map<StorePath, std::weak_ptr<DerivationGoal>> derivationGoals;
-#endif
     std::map<StorePath, std::weak_ptr<PathSubstitutionGoal>> substitutionGoals;
     std::map<DrvOutput, std::weak_ptr<DrvOutputSubstitutionGoal>> drvOutputSubstitutionGoals;
 
@@ -207,7 +192,6 @@ public:
      * Make a goal (with caching).
      */
 
-#ifndef _WIN32 // TODO Enable building on Windows
     /**
      * @ref DerivationGoal "derivation goal"
      */
@@ -222,7 +206,6 @@ public:
     std::shared_ptr<DerivationGoal> makeBasicDerivationGoal(
         const StorePath & drvPath, const BasicDerivation & drv,
         const OutputsSpec & wantedOutputs, BuildMode buildMode = bmNormal);
-#endif
 
     /**
      * @ref SubstitutionGoal "substitution goal"
@@ -263,7 +246,7 @@ public:
      * Registers a running child process.  `inBuildSlot` means that
      * the process counts towards the jobs limit.
      */
-    void childStarted(GoalPtr goal, const std::set<Child::CommChannel> & channels,
+    void childStarted(GoalPtr goal, const std::set<MuxablePipePollState::CommChannel> & channels,
         bool inBuildSlot, bool respectTimeouts);
 
     /**