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-rw-r--r--INSTALL229
-rw-r--r--README.md5
-rw-r--r--doc/manual/advanced-topics/distributed-builds.xml3
-rw-r--r--doc/manual/installation/prerequisites-source.xml4
-rw-r--r--misc/docker/Dockerfile3
-rw-r--r--nix.spec.in23
-rw-r--r--scripts/local.mk9
-rw-r--r--src/libstore/build.cc6
-rw-r--r--src/libstore/download.cc2
-rw-r--r--src/libstore/misc.cc266
-rw-r--r--src/libstore/nar-info.cc4
-rw-r--r--src/libutil/hash.cc1
-rw-r--r--src/libutil/thread-pool.cc6
-rw-r--r--src/libutil/thread-pool.hh2
-rw-r--r--tests/common.sh.in1
15 files changed, 201 insertions, 363 deletions
diff --git a/INSTALL b/INSTALL
deleted file mode 100644
index a4b34144dcff..000000000000
--- a/INSTALL
+++ /dev/null
@@ -1,229 +0,0 @@
-Copyright 1994, 1995, 1996, 1999, 2000, 2001, 2002 Free Software
-Foundation, Inc.
-
-   This file is free documentation; the Free Software Foundation gives
-unlimited permission to copy, distribute and modify it.
-
-Basic Installation
-==================
-
-   These are generic installation instructions.
-
-   The `configure' shell script attempts to guess correct values for
-various system-dependent variables used during compilation.  It uses
-those values to create a `Makefile' in each directory of the package.
-It may also create one or more `.h' files containing system-dependent
-definitions.  Finally, it creates a shell script `config.status' that
-you can run in the future to recreate the current configuration, and a
-file `config.log' containing compiler output (useful mainly for
-debugging `configure').
-
-   It can also use an optional file (typically called `config.cache'
-and enabled with `--cache-file=config.cache' or simply `-C') that saves
-the results of its tests to speed up reconfiguring.  (Caching is
-disabled by default to prevent problems with accidental use of stale
-cache files.)
-
-   If you need to do unusual things to compile the package, please try
-to figure out how `configure' could check whether to do them, and mail
-diffs or instructions to the address given in the `README' so they can
-be considered for the next release.  If you are using the cache, and at
-some point `config.cache' contains results you don't want to keep, you
-may remove or edit it.
-
-   The file `configure.ac' (or `configure.in') is used to create
-`configure' by a program called `autoconf'.  You only need
-`configure.ac' if you want to change it or regenerate `configure' using
-a newer version of `autoconf'.
-
-The simplest way to compile this package is:
-
-  1. `cd' to the directory containing the package's source code and type
-     `./configure' to configure the package for your system.  If you're
-     using `csh' on an old version of System V, you might need to type
-     `sh ./configure' instead to prevent `csh' from trying to execute
-     `configure' itself.
-
-     Running `configure' takes awhile.  While running, it prints some
-     messages telling which features it is checking for.
-
-  2. Type `make' to compile the package.
-
-  3. Optionally, type `make check' to run any self-tests that come with
-     the package.
-
-  4. Type `make install' to install the programs and any data files and
-     documentation.
-
-  5. You can remove the program binaries and object files from the
-     source code directory by typing `make clean'.  To also remove the
-     files that `configure' created (so you can compile the package for
-     a different kind of computer), type `make distclean'.  There is
-     also a `make maintainer-clean' target, but that is intended mainly
-     for the package's developers.  If you use it, you may have to get
-     all sorts of other programs in order to regenerate files that came
-     with the distribution.
-
-Compilers and Options
-=====================
-
-   Some systems require unusual options for compilation or linking that
-the `configure' script does not know about.  Run `./configure --help'
-for details on some of the pertinent environment variables.
-
-   You can give `configure' initial values for configuration parameters
-by setting variables in the command line or in the environment.  Here
-is an example:
-
-     ./configure CC=c89 CFLAGS=-O2 LIBS=-lposix
-
-   *Note Defining Variables::, for more details.
-
-Compiling For Multiple Architectures
-====================================
-
-   You can compile the package for more than one kind of computer at the
-same time, by placing the object files for each architecture in their
-own directory.  To do this, you must use a version of `make' that
-supports the `VPATH' variable, such as GNU `make'.  `cd' to the
-directory where you want the object files and executables to go and run
-the `configure' script.  `configure' automatically checks for the
-source code in the directory that `configure' is in and in `..'.
-
-   If you have to use a `make' that does not support the `VPATH'
-variable, you have to compile the package for one architecture at a
-time in the source code directory.  After you have installed the
-package for one architecture, use `make distclean' before reconfiguring
-for another architecture.
-
-Installation Names
-==================
-
-   By default, `make install' will install the package's files in
-`/usr/local/bin', `/usr/local/man', etc.  You can specify an
-installation prefix other than `/usr/local' by giving `configure' the
-option `--prefix=PATH'.
-
-   You can specify separate installation prefixes for
-architecture-specific files and architecture-independent files.  If you
-give `configure' the option `--exec-prefix=PATH', the package will use
-PATH as the prefix for installing programs and libraries.
-Documentation and other data files will still use the regular prefix.
-
-   In addition, if you use an unusual directory layout you can give
-options like `--bindir=PATH' to specify different values for particular
-kinds of files.  Run `configure --help' for a list of the directories
-you can set and what kinds of files go in them.
-
-   If the package supports it, you can cause programs to be installed
-with an extra prefix or suffix on their names by giving `configure' the
-option `--program-prefix=PREFIX' or `--program-suffix=SUFFIX'.
-
-Optional Features
-=================
-
-   Some packages pay attention to `--enable-FEATURE' options to
-`configure', where FEATURE indicates an optional part of the package.
-They may also pay attention to `--with-PACKAGE' options, where PACKAGE
-is something like `gnu-as' or `x' (for the X Window System).  The
-`README' should mention any `--enable-' and `--with-' options that the
-package recognizes.
-
-   For packages that use the X Window System, `configure' can usually
-find the X include and library files automatically, but if it doesn't,
-you can use the `configure' options `--x-includes=DIR' and
-`--x-libraries=DIR' to specify their locations.
-
-Specifying the System Type
-==========================
-
-   There may be some features `configure' cannot figure out
-automatically, but needs to determine by the type of machine the package
-will run on.  Usually, assuming the package is built to be run on the
-_same_ architectures, `configure' can figure that out, but if it prints
-a message saying it cannot guess the machine type, give it the
-`--build=TYPE' option.  TYPE can either be a short name for the system
-type, such as `sun4', or a canonical name which has the form:
-
-     CPU-COMPANY-SYSTEM
-
-where SYSTEM can have one of these forms:
-
-     OS KERNEL-OS
-
-   See the file `config.sub' for the possible values of each field.  If
-`config.sub' isn't included in this package, then this package doesn't
-need to know the machine type.
-
-   If you are _building_ compiler tools for cross-compiling, you should
-use the `--target=TYPE' option to select the type of system they will
-produce code for.
-
-   If you want to _use_ a cross compiler, that generates code for a
-platform different from the build platform, you should specify the
-"host" platform (i.e., that on which the generated programs will
-eventually be run) with `--host=TYPE'.
-
-Sharing Defaults
-================
-
-   If you want to set default values for `configure' scripts to share,
-you can create a site shell script called `config.site' that gives
-default values for variables like `CC', `cache_file', and `prefix'.
-`configure' looks for `PREFIX/share/config.site' if it exists, then
-`PREFIX/etc/config.site' if it exists.  Or, you can set the
-`CONFIG_SITE' environment variable to the location of the site script.
-A warning: not all `configure' scripts look for a site script.
-
-Defining Variables
-==================
-
-   Variables not defined in a site shell script can be set in the
-environment passed to `configure'.  However, some packages may run
-configure again during the build, and the customized values of these
-variables may be lost.  In order to avoid this problem, you should set
-them in the `configure' command line, using `VAR=value'.  For example:
-
-     ./configure CC=/usr/local2/bin/gcc
-
-will cause the specified gcc to be used as the C compiler (unless it is
-overridden in the site shell script).
-
-`configure' Invocation
-======================
-
-   `configure' recognizes the following options to control how it
-operates.
-
-`--help'
-`-h'
-     Print a summary of the options to `configure', and exit.
-
-`--version'
-`-V'
-     Print the version of Autoconf used to generate the `configure'
-     script, and exit.
-
-`--cache-file=FILE'
-     Enable the cache: use and save the results of the tests in FILE,
-     traditionally `config.cache'.  FILE defaults to `/dev/null' to
-     disable caching.
-
-`--config-cache'
-`-C'
-     Alias for `--cache-file=config.cache'.
-
-`--quiet'
-`--silent'
-`-q'
-     Do not print messages saying which checks are being made.  To
-     suppress all normal output, redirect it to `/dev/null' (any error
-     messages will still be shown).
-
-`--srcdir=DIR'
-     Look for the package's source code in directory DIR.  Usually
-     `configure' can determine that directory automatically.
-
-`configure' also accepts some other, not widely useful, options.  Run
-`configure --help' for more details.
-
diff --git a/README.md b/README.md
index e77ce302f193..6d1b3243f5dd 100644
--- a/README.md
+++ b/README.md
@@ -9,6 +9,11 @@ To find out more about the tool, usage and installation instructions, please
 read the manual, which is available on the Nix website at
 <http://nixos.org/nix/manual>.
 
+## Contributing
+
+Take a look at the [Hacking Section](http://nixos.org/nix/manual/#chap-hacking)
+of the manual. It helps you to get started with building Nix from source.
+
 ## License
 
 Nix is released under the LGPL v2.1
diff --git a/doc/manual/advanced-topics/distributed-builds.xml b/doc/manual/advanced-topics/distributed-builds.xml
index 70f396f81cdb..1f8d98f5d8fe 100644
--- a/doc/manual/advanced-topics/distributed-builds.xml
+++ b/doc/manual/advanced-topics/distributed-builds.xml
@@ -44,7 +44,8 @@ outputs and perform the remote build.  To use it, you should set
 <envar>NIX_BUILD_HOOK</envar> to
 <filename><replaceable>prefix</replaceable>/libexec/nix/build-remote.pl</filename>.
 You should also define a list of available build machines and point
-the environment variable <envar>NIX_REMOTE_SYSTEMS</envar> to it.  An
+the environment variable <envar>NIX_REMOTE_SYSTEMS</envar> to
+it. <envar>NIX_REMOTE_SYSTEMS</envar> must be an absolute path. An
 example configuration is shown in <xref linkend='ex-remote-systems'
 />.  Each line in the file specifies a machine, with the following
 bits of information:
diff --git a/doc/manual/installation/prerequisites-source.xml b/doc/manual/installation/prerequisites-source.xml
index 49036d940bd4..c0065f133700 100644
--- a/doc/manual/installation/prerequisites-source.xml
+++ b/doc/manual/installation/prerequisites-source.xml
@@ -19,6 +19,10 @@
   it from <link
   xlink:href="http://www.freedesktop.org/wiki/Software/pkg-config"
   />.</para></listitem>
+  
+  <listitem><para>The OpenSSL library to calculate cryptographic hashes.
+  If your distribution does not provide it, you can get it from <link
+  xlink:href="https://www.openssl.org"/>.</para></listitem>
 
   <listitem><para>The bzip2 compressor program and the
   <literal>libbz2</literal> library.  Thus you must have bzip2
diff --git a/misc/docker/Dockerfile b/misc/docker/Dockerfile
index bfa0c34d0947..098633fc3c86 100644
--- a/misc/docker/Dockerfile
+++ b/misc/docker/Dockerfile
@@ -17,4 +17,5 @@ ENV \
     ENV=/etc/profile \
     PATH=/root/.nix-profile/bin:/root/.nix-profile/sbin:/bin:/sbin:/usr/bin:/usr/sbin \
     GIT_SSL_CAINFO=/root/.nix-profile/etc/ssl/certs/ca-bundle.crt \
-    SSL_CERT_FILE=/root/.nix-profile/etc/ssl/certs/ca-bundle.crt
+    SSL_CERT_FILE=/root/.nix-profile/etc/ssl/certs/ca-bundle.crt \
+    NIX_PATH=/nix/var/nix/profiles/per-user/root/channels/
diff --git a/nix.spec.in b/nix.spec.in
index dff8efbdcbed..61da404a3844 100644
--- a/nix.spec.in
+++ b/nix.spec.in
@@ -1,16 +1,16 @@
 %global nixbld_user "nix-builder-"
-%global nixbld_group "nix-builders"
+%global nixbld_group "nixbld"
 
 Summary: The Nix software deployment system
 Name: nix
 Version: @PACKAGE_VERSION@
 Release: 2%{?dist}
 License: LGPLv2+
-%if 0%{?rhel}
+%if 0%{?rhel} && 0%{?rhel} < 7
 Group: Applications/System
 %endif
 URL: http://nixos.org/
-Source0: %{name}-%{version}.tar.bz2
+Source0: %{name}-%{version}.tar.xz
 %if 0%{?el5}
 BuildRoot: %(mktemp -ud %{_tmppath}/%{name}-%{version}-%{release}-XXXXXX)
 %endif
@@ -41,7 +41,7 @@ it can be used equally well under other Unix systems.
 
 %package        devel
 Summary:        Development files for %{name}
-%if 0%{?rhel}
+%if 0%{?rhel} && 0%{?rhel} < 7
 Group:          Development/Libraries
 %endif
 Requires:       %{name}%{?_isa} = %{version}-%{release}
@@ -53,7 +53,7 @@ developing applications that use %{name}.
 
 %package doc
 Summary:        Documentation files for %{name}
-%if 0%{?rhel}
+%if 0%{?rhel} && 0%{?rhel} < 7
 Group:          Documentation
 %endif
 BuildArch:      noarch
@@ -65,7 +65,7 @@ The %{name}-doc package contains documentation files for %{name}.
 
 %package -n emacs-%{name}
 Summary:        Nix mode for Emacs
-%if 0%{?rhel}
+%if 0%{?rhel} && 0%{?rhel} < 7
 Group:          Applications/Editors
 %endif
 BuildArch:      noarch
@@ -77,7 +77,7 @@ This package provides a major mode for editing Nix expressions.
 
 %package -n emacs-%{name}-el
 Summary:        Elisp source files for emacs-%{name}
-%if 0%{?rhel}
+%if 0%{?rhel} && 0%{?rhel} < 7
 Group:          Applications/Editors
 %endif
 BuildArch:      noarch
@@ -118,6 +118,10 @@ make DESTDIR=$RPM_BUILD_ROOT install
 
 find $RPM_BUILD_ROOT -name '*.la' -exec rm -f {} ';'
 
+# make the store
+mkdir -p $RPM_BUILD_ROOT/nix/store
+chmod 1775 $RPM_BUILD_ROOT/nix/store
+
 # make per-user directories
 for d in profiles gcroots;
 do
@@ -155,8 +159,7 @@ done
 
 %post
 chgrp %{nixbld_group} /nix/store
-chmod 1775 /nix/store
-%if ! 0%{?rhel}
+%if ! 0%{?rhel} || 0%{?rhel} >= 7
 # Enable and start Nix worker
 systemctl enable nix-daemon.socket nix-daemon.service
 systemctl start  nix-daemon.socket
@@ -168,7 +171,7 @@ systemctl start  nix-daemon.socket
 %{perl_vendorarch}/*
 %exclude %dir %{perl_vendorarch}/auto/
 %{_prefix}/libexec/*
-%if ! 0%{?rhel}
+%if ! 0%{?rhel} || 0%{?rhel} >= 7
 %{_prefix}/lib/systemd/system/nix-daemon.socket
 %{_prefix}/lib/systemd/system/nix-daemon.service
 %endif
diff --git a/scripts/local.mk b/scripts/local.mk
index 86b6d08500aa..edaf44cc492d 100644
--- a/scripts/local.mk
+++ b/scripts/local.mk
@@ -9,18 +9,23 @@ bin-scripts += $(nix_bin_scripts)
 
 nix_noinst_scripts := \
   $(d)/build-remote.pl \
-  $(d)/resolve-system-dependencies.pl \
   $(d)/nix-http-export.cgi \
   $(d)/nix-profile.sh \
   $(d)/nix-reduce-build
 
+ifeq ($(OS), Darwin)
+  nix_noinst_scripts += $(d)/resolve-system-dependencies.pl
+endif
+
 noinst-scripts += $(nix_noinst_scripts)
 
 profiledir = $(sysconfdir)/profile.d
 
 $(eval $(call install-file-as, $(d)/nix-profile.sh, $(profiledir)/nix.sh, 0644))
 $(eval $(call install-program-in, $(d)/build-remote.pl, $(libexecdir)/nix))
-$(eval $(call install-program-in, $(d)/resolve-system-dependencies.pl, $(libexecdir)/nix))
+ifeq ($(OS), Darwin)
+  $(eval $(call install-program-in, $(d)/resolve-system-dependencies.pl, $(libexecdir)/nix))
+endif
 $(eval $(call install-symlink, nix-build, $(bindir)/nix-shell))
 
 clean-files += $(nix_bin_scripts) $(nix_noinst_scripts)
diff --git a/src/libstore/build.cc b/src/libstore/build.cc
index 0a4df8ca7af4..af2c908c30db 100644
--- a/src/libstore/build.cc
+++ b/src/libstore/build.cc
@@ -1075,8 +1075,10 @@ void DerivationGoal::outputsSubstituted()
 {
     trace("all outputs substituted (maybe)");
 
-    if (nrFailed > 0 && nrFailed > nrNoSubstituters + nrIncompleteClosure && !settings.tryFallback)
-        throw Error(format("some substitutes for the outputs of derivation ‘%1%’ failed (usually happens due to networking issues); try ‘--fallback’ to build derivation from source ") % drvPath);
+    if (nrFailed > 0 && nrFailed > nrNoSubstituters + nrIncompleteClosure && !settings.tryFallback) {
+        done(BuildResult::TransientFailure, (format("some substitutes for the outputs of derivation ‘%1%’ failed (usually happens due to networking issues); try ‘--fallback’ to build derivation from source ") % drvPath).str());
+        return;
+    }
 
     /*  If the substitutes form an incomplete closure, then we should
         build the dependencies of this derivation, but after that, we
diff --git a/src/libstore/download.cc b/src/libstore/download.cc
index 6e39330e40d9..04a2b325c651 100644
--- a/src/libstore/download.cc
+++ b/src/libstore/download.cc
@@ -157,7 +157,7 @@ struct CurlDownloader : public Downloader
             curl_easy_setopt(curl, CURLOPT_SSL_VERIFYHOST, 0);
         }
 
-        data->clear();
+        data = make_ref<std::string>();
 
         if (requestHeaders) {
             curl_slist_free_all(requestHeaders);
diff --git a/src/libstore/misc.cc b/src/libstore/misc.cc
index 4bb043aaf17e..da654ba0d2c3 100644
--- a/src/libstore/misc.cc
+++ b/src/libstore/misc.cc
@@ -2,6 +2,7 @@
 #include "globals.hh"
 #include "local-store.hh"
 #include "store-api.hh"
+#include "thread-pool.hh"
 
 
 namespace nix {
@@ -10,157 +11,196 @@ namespace nix {
 void Store::computeFSClosure(const Path & path,
     PathSet & paths, bool flipDirection, bool includeOutputs, bool includeDerivers)
 {
-    if (paths.find(path) != paths.end()) return;
-    paths.insert(path);
+    ThreadPool pool;
 
-    PathSet edges;
+    Sync<bool> state_;
 
-    if (flipDirection) {
-        queryReferrers(path, edges);
+    std::function<void(Path)> doPath;
 
-        if (includeOutputs) {
-            PathSet derivers = queryValidDerivers(path);
-            for (auto & i : derivers)
-                edges.insert(i);
+    doPath = [&](const Path & path) {
+        {
+            auto state(state_.lock());
+            if (paths.count(path)) return;
+            paths.insert(path);
         }
 
-        if (includeDerivers && isDerivation(path)) {
-            PathSet outputs = queryDerivationOutputs(path);
-            for (auto & i : outputs)
-                if (isValidPath(i) && queryPathInfo(i)->deriver == path)
-                    edges.insert(i);
-        }
-
-    } else {
         auto info = queryPathInfo(path);
-        edges = info->references;
 
-        if (includeOutputs && isDerivation(path)) {
-            PathSet outputs = queryDerivationOutputs(path);
-            for (auto & i : outputs)
-                if (isValidPath(i)) edges.insert(i);
+        if (flipDirection) {
+
+            PathSet referrers;
+            queryReferrers(path, referrers);
+            for (auto & ref : referrers)
+                if (ref != path)
+                    pool.enqueue(std::bind(doPath, ref));
+
+            if (includeOutputs) {
+                PathSet derivers = queryValidDerivers(path);
+                for (auto & i : derivers)
+                    pool.enqueue(std::bind(doPath, i));
+            }
+
+            if (includeDerivers && isDerivation(path)) {
+                PathSet outputs = queryDerivationOutputs(path);
+                for (auto & i : outputs)
+                    if (isValidPath(i) && queryPathInfo(i)->deriver == path)
+                        pool.enqueue(std::bind(doPath, i));
+            }
+
+        } else {
+
+            for (auto & ref : info->references)
+                if (ref != path)
+                    pool.enqueue(std::bind(doPath, ref));
+
+            if (includeOutputs && isDerivation(path)) {
+                PathSet outputs = queryDerivationOutputs(path);
+                for (auto & i : outputs)
+                    if (isValidPath(i)) pool.enqueue(std::bind(doPath, i));
+            }
+
+            if (includeDerivers && isValidPath(info->deriver))
+                pool.enqueue(std::bind(doPath, info->deriver));
+
         }
+    };
 
-        if (includeDerivers && isValidPath(info->deriver))
-            edges.insert(info->deriver);
-    }
+    pool.enqueue(std::bind(doPath, path));
 
-    for (auto & i : edges)
-        computeFSClosure(i, paths, flipDirection, includeOutputs, includeDerivers);
+    pool.process();
 }
 
 
 void Store::queryMissing(const PathSet & targets,
-    PathSet & willBuild, PathSet & willSubstitute, PathSet & unknown,
-    unsigned long long & downloadSize, unsigned long long & narSize)
+    PathSet & willBuild_, PathSet & willSubstitute_, PathSet & unknown_,
+    unsigned long long & downloadSize_, unsigned long long & narSize_)
 {
-    downloadSize = narSize = 0;
+    downloadSize_ = narSize_ = 0;
 
-    PathSet todo(targets.begin(), targets.end()), done;
+    ThreadPool pool;
 
-    /* Getting substitute info has high latency when using the binary
-       cache substituter.  Thus it's essential to do substitute
-       queries in parallel as much as possible.  To accomplish this
-       we do the following:
-
-       - For all paths still to be processed (‘todo’), we add all
-         paths for which we need info to the set ‘query’.  For an
-         unbuilt derivation this is the output paths; otherwise, it's
-         the path itself.
-
-       - We get info about all paths in ‘query’ in parallel.
+    struct State
+    {
+        PathSet done;
+        PathSet & unknown, & willSubstitute, & willBuild;
+        unsigned long long & downloadSize;
+        unsigned long long & narSize;
+    };
 
-       - We process the results and add new items to ‘todo’ if
-         necessary.  E.g. if a path is substitutable, then we need to
-         get info on its references.
+    struct DrvState
+    {
+        size_t left;
+        bool done = false;
+        PathSet outPaths;
+        DrvState(size_t left) : left(left) { }
+    };
 
-       - Repeat until ‘todo’ is empty.
-    */
+    Sync<State> state_(State{PathSet(), unknown_, willSubstitute_, willBuild_, downloadSize_, narSize_});
 
-    while (!todo.empty()) {
+    std::function<void(Path)> doPath;
 
-        PathSet query, todoDrv, todoNonDrv;
+    auto mustBuildDrv = [&](const Path & drvPath, const Derivation & drv) {
+        {
+            auto state(state_.lock());
+            state->willBuild.insert(drvPath);
+        }
 
-        for (auto & i : todo) {
-            if (done.find(i) != done.end()) continue;
-            done.insert(i);
+        for (auto & i : drv.inputDrvs)
+            pool.enqueue(std::bind(doPath, makeDrvPathWithOutputs(i.first, i.second)));
+    };
 
-            DrvPathWithOutputs i2 = parseDrvPathWithOutputs(i);
+    auto checkOutput = [&](
+        const Path & drvPath, ref<Derivation> drv, const Path & outPath, ref<Sync<DrvState>> drvState_)
+    {
+        if (drvState_->lock()->done) return;
 
-            if (isDerivation(i2.first)) {
-                if (!isValidPath(i2.first)) {
-                    // FIXME: we could try to substitute p.
-                    unknown.insert(i);
-                    continue;
+        SubstitutablePathInfos infos;
+        querySubstitutablePathInfos({outPath}, infos);
+
+        if (infos.empty()) {
+            drvState_->lock()->done = true;
+            mustBuildDrv(drvPath, *drv);
+        } else {
+            {
+                auto drvState(drvState_->lock());
+                if (drvState->done) return;
+                assert(drvState->left);
+                drvState->left--;
+                drvState->outPaths.insert(outPath);
+                if (!drvState->left) {
+                    for (auto & path : drvState->outPaths)
+                        pool.enqueue(std::bind(doPath, path));
                 }
-                Derivation drv = derivationFromPath(i2.first);
-
-                PathSet invalid;
-                for (auto & j : drv.outputs)
-                    if (wantOutput(j.first, i2.second)
-                        && !isValidPath(j.second.path))
-                        invalid.insert(j.second.path);
-                if (invalid.empty()) continue;
-
-                todoDrv.insert(i);
-                if (settings.useSubstitutes && drv.substitutesAllowed())
-                    query.insert(invalid.begin(), invalid.end());
-            }
-
-            else {
-                if (isValidPath(i)) continue;
-                query.insert(i);
-                todoNonDrv.insert(i);
             }
         }
+    };
 
-        todo.clear();
+    doPath = [&](const Path & path) {
 
-        SubstitutablePathInfos infos;
-        querySubstitutablePathInfos(query, infos);
+        {
+            auto state(state_.lock());
+            if (state->done.count(path)) return;
+            state->done.insert(path);
+        }
+
+        DrvPathWithOutputs i2 = parseDrvPathWithOutputs(path);
 
-        for (auto & i : todoDrv) {
-            DrvPathWithOutputs i2 = parseDrvPathWithOutputs(i);
+        if (isDerivation(i2.first)) {
+            if (!isValidPath(i2.first)) {
+                // FIXME: we could try to substitute the derivation.
+                auto state(state_.lock());
+                state->unknown.insert(path);
+                return;
+            }
 
-            // FIXME: cache this
             Derivation drv = derivationFromPath(i2.first);
 
-            PathSet outputs;
-            bool mustBuild = false;
+            PathSet invalid;
+            for (auto & j : drv.outputs)
+                if (wantOutput(j.first, i2.second)
+                    && !isValidPath(j.second.path))
+                    invalid.insert(j.second.path);
+            if (invalid.empty()) return;
+
             if (settings.useSubstitutes && drv.substitutesAllowed()) {
-                for (auto & j : drv.outputs) {
-                    if (!wantOutput(j.first, i2.second)) continue;
-                    if (!isValidPath(j.second.path)) {
-                        if (infos.find(j.second.path) == infos.end())
-                            mustBuild = true;
-                        else
-                            outputs.insert(j.second.path);
-                    }
-                }
+                auto drvState = make_ref<Sync<DrvState>>(DrvState(invalid.size()));
+                for (auto & output : invalid)
+                    pool.enqueue(std::bind(checkOutput, i2.first, make_ref<Derivation>(drv), output, drvState));
             } else
-                mustBuild = true;
+                mustBuildDrv(i2.first, drv);
 
-            if (mustBuild) {
-                willBuild.insert(i2.first);
-                todo.insert(drv.inputSrcs.begin(), drv.inputSrcs.end());
-                for (auto & j : drv.inputDrvs)
-                    todo.insert(makeDrvPathWithOutputs(j.first, j.second));
-            } else
-                todoNonDrv.insert(outputs.begin(), outputs.end());
-        }
+        } else {
 
-        for (auto & i : todoNonDrv) {
-            done.insert(i);
-            SubstitutablePathInfos::iterator info = infos.find(i);
-            if (info != infos.end()) {
-                willSubstitute.insert(i);
-                downloadSize += info->second.downloadSize;
-                narSize += info->second.narSize;
-                todo.insert(info->second.references.begin(), info->second.references.end());
-            } else
-                unknown.insert(i);
+            if (isValidPath(path)) return;
+
+            SubstitutablePathInfos infos;
+            querySubstitutablePathInfos({path}, infos);
+
+            if (infos.empty()) {
+                auto state(state_.lock());
+                state->unknown.insert(path);
+                return;
+            }
+
+            auto info = infos.find(path);
+            assert(info != infos.end());
+
+            {
+                auto state(state_.lock());
+                state->willSubstitute.insert(path);
+                state->downloadSize += info->second.downloadSize;
+                state->narSize += info->second.narSize;
+            }
+
+            for (auto & ref : info->second.references)
+                pool.enqueue(std::bind(doPath, ref));
         }
-    }
+    };
+
+    for (auto & path : targets)
+        pool.enqueue(std::bind(doPath, path));
+
+    pool.process();
 }
 
 
diff --git a/src/libstore/nar-info.cc b/src/libstore/nar-info.cc
index 1aacca84b800..b0a8d77c2fba 100644
--- a/src/libstore/nar-info.cc
+++ b/src/libstore/nar-info.cc
@@ -6,7 +6,7 @@ namespace nix {
 NarInfo::NarInfo(const Store & store, const std::string & s, const std::string & whence)
 {
     auto corrupt = [&]() {
-        throw Error("NAR info file ‘%1%’ is corrupt");
+        throw Error(format("NAR info file ‘%1%’ is corrupt") % whence);
     };
 
     auto parseHashField = [&](const string & s) {
@@ -73,7 +73,7 @@ NarInfo::NarInfo(const Store & store, const std::string & s, const std::string &
 
     if (compression == "") compression = "bzip2";
 
-    if (path.empty() || url.empty()) corrupt();
+    if (path.empty() || url.empty() || narSize == 0 || !narHash) corrupt();
 }
 
 std::string NarInfo::to_string() const
diff --git a/src/libutil/hash.cc b/src/libutil/hash.cc
index fa42587777cd..81aced0fde16 100644
--- a/src/libutil/hash.cc
+++ b/src/libutil/hash.cc
@@ -121,6 +121,7 @@ const string base32Chars = "0123456789abcdfghijklmnpqrsvwxyz";
 
 string printHash32(const Hash & hash)
 {
+    assert(hash.hashSize);
     size_t len = hash.base32Len();
     assert(len);
 
diff --git a/src/libutil/thread-pool.cc b/src/libutil/thread-pool.cc
index 32363ecf0098..696ecd6c38c8 100644
--- a/src/libutil/thread-pool.cc
+++ b/src/libutil/thread-pool.cc
@@ -36,7 +36,8 @@ ThreadPool::~ThreadPool()
 void ThreadPool::enqueue(const work_t & t)
 {
     auto state(state_.lock());
-    assert(!state->quit);
+    if (state->quit)
+        throw ThreadPoolShutDown("cannot enqueue a work item while the thread pool is shutting down");
     state->left.push(t);
     if (state->left.size() > state->workers.size() && state->workers.size() < maxThreads)
         state->workers.emplace_back(&ThreadPool::workerEntry, this);
@@ -84,7 +85,8 @@ void ThreadPool::workerEntry()
         } catch (std::exception & e) {
             auto state(state_.lock());
             if (state->exception) {
-                if (!dynamic_cast<Interrupted*>(&e))
+                if (!dynamic_cast<Interrupted*>(&e) &&
+                    !dynamic_cast<ThreadPoolShutDown*>(&e))
                     printMsg(lvlError, format("error: %s") % e.what());
             } else {
                 state->exception = std::current_exception();
diff --git a/src/libutil/thread-pool.hh b/src/libutil/thread-pool.hh
index 78b63467d62e..b64dc52d473e 100644
--- a/src/libutil/thread-pool.hh
+++ b/src/libutil/thread-pool.hh
@@ -10,6 +10,8 @@
 
 namespace nix {
 
+MakeError(ThreadPoolShutDown, Error)
+
 /* A simple thread pool that executes a queue of work items
    (lambdas). */
 class ThreadPool
diff --git a/tests/common.sh.in b/tests/common.sh.in
index e721c36967b9..097d94bb1eea 100644
--- a/tests/common.sh.in
+++ b/tests/common.sh.in
@@ -17,6 +17,7 @@ export NIX_CONF_DIR=$TEST_ROOT/etc
 export NIX_MANIFESTS_DIR=$TEST_ROOT/var/nix/manifests
 export _NIX_TEST_SHARED=$TEST_ROOT/shared
 export NIX_REMOTE=$NIX_REMOTE_
+unset NIX_PATH
 export TEST_HOME=$TEST_ROOT/test-home
 export HOME=$TEST_HOME
 mkdir -p $TEST_HOME