ASR_BASE

Change-Id: Icf3719cc0afe3eeb3edc7fa80a2eb5199ca9dda1
diff --git a/tools/ninja/patches/001-backport-gtest.patch b/tools/ninja/patches/001-backport-gtest.patch
new file mode 100644
index 0000000..1440f29
--- /dev/null
+++ b/tools/ninja/patches/001-backport-gtest.patch
@@ -0,0 +1,153 @@
+From afcd4a146fb82843f6ff695f89504ce4ca65ddfd Mon Sep 17 00:00:00 2001
+From: David 'Digit' Turner <digit+github@google.com>
+Date: Sun, 12 May 2024 23:45:28 +0200
+Subject: [PATCH] configure.py: Support --gtest-source-dir to build tests.
+
+Allow the Ninja build plan generated by configure.py to
+build `ninja_test` by compiling GoogleTest from source if
+the path to the library if passed through the new option
+`--gtest-source-dir` or the GTEST_SOURCE_DIR environment
+variable.
+
+For simplicity, probing for an installed version of the
+library, and linking to it, is not supported (use the
+CMake build for this).
+
+This also removes the obsolete `--gtest-dir` option.
+
++ Update README.md
+
+Fixes #2447
+---
+ README.md    | 13 ++++++++
+ configure.py | 83 +++++++++++++++++++++++++++++++++++++++++++++++++++-
+ 2 files changed, 95 insertions(+), 1 deletion(-)
+
+--- a/README.md
++++ b/README.md
+@@ -34,6 +34,19 @@ via CMake. For more details see
+ This will generate the `ninja` binary and a `build.ninja` file you can now use
+ to build Ninja with itself.
+ 
++If you have a GoogleTest source directory, you can build the tests
++by passing its path with `--gtest-source-dir=PATH` option, or the
++`GTEST_SOURCE_DIR` environment variable, e.g.:
++
++```
++./configure.py --bootstrap --gtest-source-dir=/path/to/googletest
++./ninja all     # build ninja_test and other auxiliary binaries
++./ninja_test`   # run the unit-test suite.
++```
++
++Use the CMake build below if you want to use a preinstalled binary
++version of the library.
++
+ ### CMake
+ 
+ ```
+--- a/configure.py
++++ b/configure.py
+@@ -213,7 +213,10 @@ parser.add_option('--debug', action='sto
+ parser.add_option('--profile', metavar='TYPE',
+                   choices=profilers,
+                   help='enable profiling (' + '/'.join(profilers) + ')',)
+-parser.add_option('--with-gtest', metavar='PATH', help='ignored')
++parser.add_option('--gtest-source-dir', metavar='PATH',
++                  help='Path to GoogleTest source directory. If not provided ' +
++                       'GTEST_SOURCE_DIR will be probed in the environment. ' +
++                       'Tests will not be built without a value.')
+ parser.add_option('--with-python', metavar='EXE',
+                   help='use EXE as the Python interpreter',
+                   default=os.path.basename(sys.executable))
+@@ -425,6 +428,7 @@ n.variable('cflags', ' '.join(shell_esca
+ if 'LDFLAGS' in configure_env:
+     ldflags.append(configure_env['LDFLAGS'])
+ n.variable('ldflags', ' '.join(shell_escape(flag) for flag in ldflags))
++
+ n.newline()
+ 
+ if platform.is_msvc():
+@@ -582,6 +586,83 @@ if options.bootstrap:
+     # build.ninja file.
+     n = ninja_writer
+ 
++# Build the ninja_test executable only if the GTest source directory
++# is provided explicitly. Either from the environment with GTEST_SOURCE_DIR
++# or with the --gtest-source-dir command-line option.
++#
++# Do not try to look for an installed binary version, and link against it
++# because doing so properly is platform-specific (use the CMake build for
++# this).
++if options.gtest_source_dir:
++    gtest_src_dir = options.gtest_source_dir
++else:
++    gtest_src_dir = os.environ.get('GTEST_SOURCE_DIR')
++
++if gtest_src_dir:
++    # Verify GoogleTest source directory, and add its include directory
++    # to the global include search path (even for non-test sources) to
++    # keep the build plan generation simple.
++    gtest_all_cc = os.path.join(gtest_src_dir, 'googletest', 'src', 'gtest-all.cc')
++    if not os.path.exists(gtest_all_cc):
++        print('ERROR: Missing GoogleTest source file: %s' % gtest_all_cc)
++        sys.exit(1)
++
++    n.comment('Tests all build into ninja_test executable.')
++
++    # Test-specific version of cflags, must include the GoogleTest
++    # include directory. Also GoogleTest can only build with a C++14 compiler.
++    test_cflags = [f.replace('std=c++11', 'std=c++14') for f in cflags]
++    test_cflags.append('-I' + os.path.join(gtest_src_dir, 'googletest', 'include'))
++
++    test_variables = [('cflags', test_cflags)]
++    if platform.is_msvc():
++        test_variables += [('pdb', 'ninja_test.pdb')]
++
++    test_names = [
++        'build_log_test',
++        'build_test',
++        'clean_test',
++        'clparser_test',
++        'depfile_parser_test',
++        'deps_log_test',
++        'disk_interface_test',
++        'dyndep_parser_test',
++        'edit_distance_test',
++        'graph_test',
++        'json_test',
++        'lexer_test',
++        'manifest_parser_test',
++        'ninja_test',
++        'state_test',
++        'string_piece_util_test',
++        'subprocess_test',
++        'test',
++        'util_test',
++    ]
++    if platform.is_windows():
++        test_names += [
++            'includes_normalize_test',
++            'msvc_helper_test',
++        ]
++
++    objs = []
++    for name in test_names:
++        objs += cxx(name, variables=test_variables)
++
++    # Build GTest as a monolithic source file.
++    # This requires one extra include search path, so replace the
++    # value of 'cflags' in our list.
++    gtest_all_variables = test_variables[1:] + [
++      ('cflags', test_cflags + ['-I' + os.path.join(gtest_src_dir, 'googletest') ]),
++    ]
++    # Do not use cxx() directly to ensure the object file is under $builddir.
++    objs += n.build(built('gtest_all' + objext), 'cxx', gtest_all_cc, variables=gtest_all_variables)
++
++    ninja_test = n.build(binary('ninja_test'), 'link', objs, implicit=ninja_lib,
++                         variables=[('libs', libs)])
++    n.newline()
++    all_targets += ninja_test
++
+ n.comment('Ancillary executables.')
+ 
+ if platform.is_aix() and '-maix64' not in ldflags:
diff --git a/tools/ninja/patches/010-bootstrap-configure-only.patch b/tools/ninja/patches/010-bootstrap-configure-only.patch
new file mode 100644
index 0000000..4785ac6
--- /dev/null
+++ b/tools/ninja/patches/010-bootstrap-configure-only.patch
@@ -0,0 +1,24 @@
+--- a/configure.py
++++ b/configure.py
+@@ -198,6 +198,8 @@ parser = OptionParser()
+ profilers = ['gmon', 'pprof']
+ parser.add_option('--bootstrap', action='store_true',
+                   help='bootstrap a ninja binary from nothing')
++parser.add_option('--no-rebuild', action='store_true',
++                  help='let user execute ninja after build.ninja generation')
+ parser.add_option('--verbose', action='store_true',
+                   help='enable verbose build')
+ parser.add_option('--platform',
+@@ -756,7 +758,11 @@ n.build('all', 'phony', all_targets)
+ n.close()
+ print('wrote %s.' % BUILD_FILENAME)
+ 
+-if options.bootstrap:
++if options.bootstrap and options.no_rebuild:
++    print('bootstrap complete. execute ninja in this directory...')
++    print(os.getcwd())
++
++elif options.bootstrap:
+     print('bootstrap complete.  rebuilding...')
+ 
+     rebuild_args = []
diff --git a/tools/ninja/patches/100-make_jobserver_support.patch b/tools/ninja/patches/100-make_jobserver_support.patch
new file mode 100644
index 0000000..82ecf02
--- /dev/null
+++ b/tools/ninja/patches/100-make_jobserver_support.patch
@@ -0,0 +1,2143 @@
+From afec30f5caf4b051827ffdd822ebd27c58219fee Mon Sep 17 00:00:00 2001
+From: Stefan Becker <stefanb@gpartner-nvidia.com>
+Date: Tue, 22 Mar 2016 13:48:07 +0200
+Subject: [PATCH 01/11] Add GNU make jobserver client support
+
+- add new TokenPool interface
+- GNU make implementation for TokenPool parses and verifies the magic
+  information from the MAKEFLAGS environment variable
+- RealCommandRunner tries to acquire TokenPool
+  * if no token pool is available then there is no change in behaviour
+- When a token pool is available then RealCommandRunner behaviour
+  changes as follows
+  * CanRunMore() only returns true if TokenPool::Acquire() returns true
+  * StartCommand() calls TokenPool::Reserve()
+  * WaitForCommand() calls TokenPool::Release()
+
+Documentation for GNU make jobserver
+
+  http://make.mad-scientist.net/papers/jobserver-implementation/
+
+--- a/configure.py
++++ b/configure.py
+@@ -543,11 +543,13 @@ for name in ['build',
+              'state',
+              'status',
+              'string_piece_util',
++             'tokenpool-gnu-make',
+              'util',
+              'version']:
+     objs += cxx(name, variables=cxxvariables)
+ if platform.is_windows():
+     for name in ['subprocess-win32',
++                 'tokenpool-gnu-make-win32',
+                  'includes_normalize-win32',
+                  'msvc_helper-win32',
+                  'msvc_helper_main-win32']:
+@@ -556,7 +558,9 @@ if platform.is_windows():
+         objs += cxx('minidump-win32', variables=cxxvariables)
+     objs += cc('getopt')
+ else:
+-    objs += cxx('subprocess-posix')
++    for name in ['subprocess-posix',
++                 'tokenpool-gnu-make-posix']:
++        objs += cxx(name)
+ if platform.is_aix():
+     objs += cc('getopt')
+ if platform.is_msvc():
+@@ -639,6 +643,7 @@ if gtest_src_dir:
+         'string_piece_util_test',
+         'subprocess_test',
+         'test',
++        'tokenpool_test',
+         'util_test',
+     ]
+     if platform.is_windows():
+--- a/src/build.cc
++++ b/src/build.cc
+@@ -39,6 +39,7 @@
+ #include "state.h"
+ #include "status.h"
+ #include "subprocess.h"
++#include "tokenpool.h"
+ #include "util.h"
+ 
+ using namespace std;
+@@ -50,24 +51,29 @@ struct DryRunCommandRunner : public Comm
+   virtual ~DryRunCommandRunner() {}
+ 
+   // Overridden from CommandRunner:
+-  virtual size_t CanRunMore() const;
++  virtual size_t CanRunMore();
++  virtual bool AcquireToken();
+   virtual bool StartCommand(Edge* edge);
+-  virtual bool WaitForCommand(Result* result);
++  virtual bool WaitForCommand(Result* result, bool more_ready);
+ 
+  private:
+   queue<Edge*> finished_;
+ };
+ 
+-size_t DryRunCommandRunner::CanRunMore() const {
++size_t DryRunCommandRunner::CanRunMore() {
+   return SIZE_MAX;
+ }
+ 
++bool DryRunCommandRunner::AcquireToken() {
++  return true;
++}
++
+ bool DryRunCommandRunner::StartCommand(Edge* edge) {
+   finished_.push(edge);
+   return true;
+ }
+ 
+-bool DryRunCommandRunner::WaitForCommand(Result* result) {
++bool DryRunCommandRunner::WaitForCommand(Result* result, bool more_ready) {
+    if (finished_.empty())
+      return false;
+ 
+@@ -160,7 +166,7 @@ void Plan::EdgeWanted(const Edge* edge)
+ }
+ 
+ Edge* Plan::FindWork() {
+-  if (ready_.empty())
++  if (!more_ready())
+     return NULL;
+ 
+   Edge* work = ready_.top();
+@@ -595,19 +601,39 @@ void Plan::Dump() const {
+ }
+ 
+ struct RealCommandRunner : public CommandRunner {
+-  explicit RealCommandRunner(const BuildConfig& config) : config_(config) {}
+-  virtual ~RealCommandRunner() {}
+-  virtual size_t CanRunMore() const;
++  explicit RealCommandRunner(const BuildConfig& config);
++  virtual ~RealCommandRunner();
++  virtual size_t CanRunMore();
++  virtual bool AcquireToken();
+   virtual bool StartCommand(Edge* edge);
+-  virtual bool WaitForCommand(Result* result);
++  virtual bool WaitForCommand(Result* result, bool more_ready);
+   virtual vector<Edge*> GetActiveEdges();
+   virtual void Abort();
+ 
+   const BuildConfig& config_;
++  // copy of config_.max_load_average; can be modified by TokenPool setup
++  double max_load_average_;
+   SubprocessSet subprocs_;
++  TokenPool* tokens_;
+   map<const Subprocess*, Edge*> subproc_to_edge_;
+ };
+ 
++RealCommandRunner::RealCommandRunner(const BuildConfig& config) : config_(config) {
++  max_load_average_ = config.max_load_average;
++  if ((tokens_ = TokenPool::Get()) != NULL) {
++    if (!tokens_->Setup(config_.parallelism_from_cmdline,
++                        config_.verbosity == BuildConfig::VERBOSE,
++                        max_load_average_)) {
++      delete tokens_;
++      tokens_ = NULL;
++    }
++  }
++}
++
++RealCommandRunner::~RealCommandRunner() {
++  delete tokens_;
++}
++
+ vector<Edge*> RealCommandRunner::GetActiveEdges() {
+   vector<Edge*> edges;
+   for (map<const Subprocess*, Edge*>::iterator e = subproc_to_edge_.begin();
+@@ -618,9 +644,11 @@ vector<Edge*> RealCommandRunner::GetActi
+ 
+ void RealCommandRunner::Abort() {
+   subprocs_.Clear();
++  if (tokens_)
++    tokens_->Clear();
+ }
+ 
+-size_t RealCommandRunner::CanRunMore() const {
++size_t RealCommandRunner::CanRunMore() {
+   size_t subproc_number =
+       subprocs_.running_.size() + subprocs_.finished_.size();
+ 
+@@ -635,6 +663,13 @@ size_t RealCommandRunner::CanRunMore() c
+   if (capacity < 0)
+     capacity = 0;
+ 
++  if (tokens_) {
++    if (AcquireToken())
++      return SIZE_MAX;
++    else
++      capacity = 0;
++  }
++
+   if (capacity == 0 && subprocs_.running_.empty())
+     // Ensure that we make progress.
+     capacity = 1;
+@@ -642,24 +677,42 @@ size_t RealCommandRunner::CanRunMore() c
+   return capacity;
+ }
+ 
++bool RealCommandRunner::AcquireToken() {
++  return (!tokens_ || tokens_->Acquire());
++}
++
+ bool RealCommandRunner::StartCommand(Edge* edge) {
+   string command = edge->EvaluateCommand();
+   Subprocess* subproc = subprocs_.Add(command, edge->use_console());
+   if (!subproc)
+     return false;
++  if (tokens_)
++    tokens_->Reserve();
+   subproc_to_edge_.insert(make_pair(subproc, edge));
+ 
+   return true;
+ }
+ 
+-bool RealCommandRunner::WaitForCommand(Result* result) {
++bool RealCommandRunner::WaitForCommand(Result* result, bool more_ready) {
+   Subprocess* subproc;
+-  while ((subproc = subprocs_.NextFinished()) == NULL) {
+-    bool interrupted = subprocs_.DoWork();
++  subprocs_.ResetTokenAvailable();
++  while (((subproc = subprocs_.NextFinished()) == NULL) &&
++         !subprocs_.IsTokenAvailable()) {
++    bool interrupted = subprocs_.DoWork(more_ready ? tokens_ : NULL);
+     if (interrupted)
+       return false;
+   }
+ 
++  // token became available
++  if (subproc == NULL) {
++    result->status = ExitTokenAvailable;
++    return true;
++  }
++
++  // command completed
++  if (tokens_)
++    tokens_->Release();
++
+   result->status = subproc->Finish();
+   result->output = subproc->GetOutput();
+ 
+@@ -790,7 +843,8 @@ bool Builder::Build(string* err) {
+   // Second, we attempt to wait for / reap the next finished command.
+   while (plan_.more_to_do()) {
+     // See if we can start any more commands.
+-    if (failures_allowed) {
++    bool can_run_more = failures_allowed && plan_.more_ready();
++    if (can_run_more) {
+       size_t capacity = command_runner_->CanRunMore();
+       while (capacity > 0) {
+         Edge* edge = plan_.FindWork();
+@@ -833,7 +887,7 @@ bool Builder::Build(string* err) {
+     // See if we can reap any finished commands.
+     if (pending_commands) {
+       CommandRunner::Result result;
+-      if (!command_runner_->WaitForCommand(&result) ||
++      if (!command_runner_->WaitForCommand(&result, can_run_more) ||
+           result.status == ExitInterrupted) {
+         Cleanup();
+         status_->BuildFinished();
+@@ -841,6 +895,10 @@ bool Builder::Build(string* err) {
+         return false;
+       }
+ 
++      // We might be able to start another command; start the main loop over.
++      if (result.status == ExitTokenAvailable)
++        continue;
++
+       --pending_commands;
+       if (!FinishCommand(&result, err)) {
+         Cleanup();
+--- a/src/build.h
++++ b/src/build.h
+@@ -51,6 +51,9 @@ struct Plan {
+   /// Returns true if there's more work to be done.
+   bool more_to_do() const { return wanted_edges_ > 0 && command_edges_ > 0; }
+ 
++  /// Returns true if there's more edges ready to start
++  bool more_ready() const { return !ready_.empty(); }
++
+   /// Dumps the current state of the plan.
+   void Dump() const;
+ 
+@@ -145,7 +148,8 @@ private:
+ /// RealCommandRunner is an implementation that actually runs commands.
+ struct CommandRunner {
+   virtual ~CommandRunner() {}
+-  virtual size_t CanRunMore() const = 0;
++  virtual size_t CanRunMore() = 0;
++  virtual bool AcquireToken() = 0;
+   virtual bool StartCommand(Edge* edge) = 0;
+ 
+   /// The result of waiting for a command.
+@@ -157,7 +161,9 @@ struct CommandRunner {
+     bool success() const { return status == ExitSuccess; }
+   };
+   /// Wait for a command to complete, or return false if interrupted.
+-  virtual bool WaitForCommand(Result* result) = 0;
++  /// If more_ready is true then the optional TokenPool is monitored too
++  /// and we return when a token becomes available.
++  virtual bool WaitForCommand(Result* result, bool more_ready) = 0;
+ 
+   virtual std::vector<Edge*> GetActiveEdges() { return std::vector<Edge*>(); }
+   virtual void Abort() {}
+@@ -165,7 +171,8 @@ struct CommandRunner {
+ 
+ /// Options (e.g. verbosity, parallelism) passed to a build.
+ struct BuildConfig {
+-  BuildConfig() : verbosity(NORMAL), dry_run(false), parallelism(1),
++  BuildConfig() : verbosity(NORMAL), dry_run(false),
++                  parallelism(1), parallelism_from_cmdline(false),
+                   failures_allowed(1), max_load_average(-0.0f) {}
+ 
+   enum Verbosity {
+@@ -177,6 +184,7 @@ struct BuildConfig {
+   Verbosity verbosity;
+   bool dry_run;
+   int parallelism;
++  bool parallelism_from_cmdline;
+   int failures_allowed;
+   /// The maximum load average we must not exceed. A negative value
+   /// means that we do not have any limit.
+--- /dev/null
++++ b/src/tokenpool-gnu-make.cc
+@@ -0,0 +1,108 @@
++// Copyright 2016-2018 Google Inc. All Rights Reserved.
++//
++// Licensed under the Apache License, Version 2.0 (the "License");
++// you may not use this file except in compliance with the License.
++// You may obtain a copy of the License at
++//
++//     http://www.apache.org/licenses/LICENSE-2.0
++//
++// Unless required by applicable law or agreed to in writing, software
++// distributed under the License is distributed on an "AS IS" BASIS,
++// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
++// See the License for the specific language governing permissions and
++// limitations under the License.
++
++#include "tokenpool-gnu-make.h"
++
++#include <stdlib.h>
++#include <stdio.h>
++#include <string.h>
++
++#include "line_printer.h"
++
++// TokenPool implementation for GNU make jobserver - common bits
++// every instance owns an implicit token -> available_ == 1
++GNUmakeTokenPool::GNUmakeTokenPool() : available_(1), used_(0) {
++}
++
++GNUmakeTokenPool::~GNUmakeTokenPool() {
++}
++
++bool GNUmakeTokenPool::Setup(bool ignore,
++                             bool verbose,
++                             double& max_load_average) {
++  const char* value = GetEnv("MAKEFLAGS");
++  if (!value)
++    return false;
++
++  // GNU make <= 4.1
++  const char* jobserver = strstr(value, "--jobserver-fds=");
++  if (!jobserver)
++    // GNU make => 4.2
++    jobserver = strstr(value, "--jobserver-auth=");
++  if (jobserver) {
++    LinePrinter printer;
++
++    if (ignore) {
++      printer.PrintOnNewLine("ninja: warning: -jN forced on command line; ignoring GNU make jobserver.\n");
++    } else {
++      if (ParseAuth(jobserver)) {
++        const char* l_arg = strstr(value, " -l");
++        int load_limit = -1;
++
++        if (verbose) {
++          printer.PrintOnNewLine("ninja: using GNU make jobserver.\n");
++        }
++
++        // translate GNU make -lN to ninja -lN
++        if (l_arg &&
++            (sscanf(l_arg + 3, "%d ", &load_limit) == 1) &&
++            (load_limit > 0)) {
++          max_load_average = load_limit;
++        }
++
++        return true;
++      }
++    }
++  }
++
++  return false;
++}
++
++bool GNUmakeTokenPool::Acquire() {
++  if (available_ > 0)
++    return true;
++
++  if (AcquireToken()) {
++    // token acquired
++    available_++;
++    return true;
++  }
++
++  // no token available
++  return false;
++}
++
++void GNUmakeTokenPool::Reserve() {
++  available_--;
++  used_++;
++}
++
++void GNUmakeTokenPool::Return() {
++  if (ReturnToken())
++    available_--;
++}
++
++void GNUmakeTokenPool::Release() {
++  available_++;
++  used_--;
++  if (available_ > 1)
++    Return();
++}
++
++void GNUmakeTokenPool::Clear() {
++  while (used_ > 0)
++    Release();
++  while (available_ > 1)
++    Return();
++}
+--- /dev/null
++++ b/src/tokenpool.h
+@@ -0,0 +1,42 @@
++// Copyright 2016-2018 Google Inc. All Rights Reserved.
++//
++// Licensed under the Apache License, Version 2.0 (the "License");
++// you may not use this file except in compliance with the License.
++// You may obtain a copy of the License at
++//
++//     http://www.apache.org/licenses/LICENSE-2.0
++//
++// Unless required by applicable law or agreed to in writing, software
++// distributed under the License is distributed on an "AS IS" BASIS,
++// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
++// See the License for the specific language governing permissions and
++// limitations under the License.
++
++#ifdef _WIN32
++#include <windows.h>
++#endif
++
++// interface to token pool
++struct TokenPool {
++  virtual ~TokenPool() {}
++
++  virtual bool Acquire() = 0;
++  virtual void Reserve() = 0;
++  virtual void Release() = 0;
++  virtual void Clear() = 0;
++
++  // returns false if token pool setup failed
++  virtual bool Setup(bool ignore, bool verbose, double& max_load_average) = 0;
++
++#ifdef _WIN32
++  virtual void WaitForTokenAvailability(HANDLE ioport) = 0;
++  // returns true if a token has become available
++  // key is result from GetQueuedCompletionStatus()
++  virtual bool TokenIsAvailable(ULONG_PTR key) = 0;
++#else
++  virtual int GetMonitorFd() = 0;
++#endif
++
++  // returns NULL if token pool is not available
++  static TokenPool* Get();
++};
+--- a/src/build_test.cc
++++ b/src/build_test.cc
+@@ -15,6 +15,7 @@
+ #include "build.h"
+ 
+ #include <assert.h>
++#include <stdarg.h>
+ #include <climits>
+ #include <stdint.h>
+ 
+@@ -521,9 +522,10 @@ struct FakeCommandRunner : public Comman
+       max_active_edges_(1), fs_(fs) {}
+ 
+   // CommandRunner impl
+-  virtual size_t CanRunMore() const;
++  virtual size_t CanRunMore();
++  virtual bool AcquireToken();
+   virtual bool StartCommand(Edge* edge);
+-  virtual bool WaitForCommand(Result* result);
++  virtual bool WaitForCommand(Result* result, bool more_ready);
+   virtual vector<Edge*> GetActiveEdges();
+   virtual void Abort();
+ 
+@@ -622,13 +624,17 @@ void BuildTest::RebuildTarget(const stri
+   builder.command_runner_.release();
+ }
+ 
+-size_t FakeCommandRunner::CanRunMore() const {
++size_t FakeCommandRunner::CanRunMore() {
+   if (active_edges_.size() < max_active_edges_)
+     return SIZE_MAX;
+ 
+   return 0;
+ }
+ 
++bool FakeCommandRunner::AcquireToken() {
++  return true;
++}
++
+ bool FakeCommandRunner::StartCommand(Edge* edge) {
+   assert(active_edges_.size() < max_active_edges_);
+   assert(find(active_edges_.begin(), active_edges_.end(), edge)
+@@ -720,7 +726,7 @@ bool FakeCommandRunner::StartCommand(Edg
+   return true;
+ }
+ 
+-bool FakeCommandRunner::WaitForCommand(Result* result) {
++bool FakeCommandRunner::WaitForCommand(Result* result, bool more_ready) {
+   if (active_edges_.empty())
+     return false;
+ 
+@@ -4380,3 +4386,355 @@ TEST_F(BuildTest, ValidationWithCircular
+   EXPECT_FALSE(builder_.AddTarget("out", &err));
+   EXPECT_EQ("dependency cycle: validate -> validate_in -> validate", err);
+ }
++
++/// The token tests are concerned with the main loop functionality when
++// the CommandRunner has an active TokenPool. It is therefore intentional
++// that the plan doesn't complete and that builder_.Build() returns false!
++
++/// Fake implementation of CommandRunner that simulates a TokenPool
++struct FakeTokenCommandRunner : public CommandRunner {
++  explicit FakeTokenCommandRunner() {}
++
++  // CommandRunner impl
++  virtual bool CanRunMore();
++  virtual bool AcquireToken();
++  virtual bool StartCommand(Edge* edge);
++  virtual bool WaitForCommand(Result* result, bool more_ready);
++  virtual vector<Edge*> GetActiveEdges();
++  virtual void Abort();
++
++  vector<string> commands_ran_;
++  vector<Edge *> edges_;
++
++  vector<bool> acquire_token_;
++  vector<bool> can_run_more_;
++  vector<bool> wait_for_command_;
++};
++
++bool FakeTokenCommandRunner::CanRunMore() {
++  if (can_run_more_.size() == 0) {
++    EXPECT_FALSE("unexpected call to CommandRunner::CanRunMore()");
++    return false;
++  }
++
++  bool result = can_run_more_[0];
++
++  can_run_more_.erase(
++    can_run_more_.begin()
++  );
++
++  return result;
++}
++
++bool FakeTokenCommandRunner::AcquireToken() {
++  if (acquire_token_.size() == 0) {
++    EXPECT_FALSE("unexpected call to CommandRunner::AcquireToken()");
++    return false;
++  }
++
++  bool result = acquire_token_[0];
++  acquire_token_.erase(acquire_token_.begin());
++  return result;
++}
++
++bool FakeTokenCommandRunner::StartCommand(Edge* edge) {
++  commands_ran_.push_back(edge->EvaluateCommand());
++  edges_.push_back(edge);
++  return true;
++}
++
++bool FakeTokenCommandRunner::WaitForCommand(Result* result, bool more_ready) {
++  if (wait_for_command_.size() == 0) {
++    EXPECT_FALSE("unexpected call to CommandRunner::WaitForCommand()");
++    return false;
++  }
++
++  bool expected = wait_for_command_[0];
++  if (expected != more_ready) {
++    EXPECT_EQ(expected, more_ready);
++    return false;
++  }
++  wait_for_command_.erase(wait_for_command_.begin());
++
++  if (edges_.size() == 0)
++    return false;
++
++  Edge* edge = edges_[0];
++  result->edge = edge;
++
++  if (more_ready &&
++      (edge->rule().name() == "token-available")) {
++    result->status = ExitTokenAvailable;
++  } else {
++    edges_.erase(edges_.begin());
++    result->status = ExitSuccess;
++  }
++
++  return true;
++}
++
++vector<Edge*> FakeTokenCommandRunner::GetActiveEdges() {
++  return edges_;
++}
++
++void FakeTokenCommandRunner::Abort() {
++  edges_.clear();
++}
++
++struct BuildTokenTest : public BuildTest {
++  virtual void SetUp();
++  virtual void TearDown();
++
++  FakeTokenCommandRunner token_command_runner_;
++
++  void ExpectAcquireToken(int count, ...);
++  void ExpectCanRunMore(int count, ...);
++  void ExpectWaitForCommand(int count, ...);
++
++private:
++  void EnqueueBooleans(vector<bool>& booleans, int count, va_list ap);
++};
++
++void BuildTokenTest::SetUp() {
++  BuildTest::SetUp();
++
++  // replace FakeCommandRunner with FakeTokenCommandRunner
++  builder_.command_runner_.release();
++  builder_.command_runner_.reset(&token_command_runner_);
++}
++void BuildTokenTest::TearDown() {
++  EXPECT_EQ(0u, token_command_runner_.acquire_token_.size());
++  EXPECT_EQ(0u, token_command_runner_.can_run_more_.size());
++  EXPECT_EQ(0u, token_command_runner_.wait_for_command_.size());
++
++  BuildTest::TearDown();
++}
++
++void BuildTokenTest::ExpectAcquireToken(int count, ...) {
++  va_list ap;
++  va_start(ap, count);
++  EnqueueBooleans(token_command_runner_.acquire_token_, count, ap);
++  va_end(ap);
++}
++
++void BuildTokenTest::ExpectCanRunMore(int count, ...) {
++  va_list ap;
++  va_start(ap, count);
++  EnqueueBooleans(token_command_runner_.can_run_more_, count, ap);
++  va_end(ap);
++}
++
++void BuildTokenTest::ExpectWaitForCommand(int count, ...) {
++  va_list ap;
++  va_start(ap, count);
++  EnqueueBooleans(token_command_runner_.wait_for_command_, count, ap);
++  va_end(ap);
++}
++
++void BuildTokenTest::EnqueueBooleans(vector<bool>& booleans, int count, va_list ap) {
++  while (count--) {
++    int value = va_arg(ap, int);
++    booleans.push_back(!!value); // force bool
++  }
++}
++
++TEST_F(BuildTokenTest, DoNotAquireToken) {
++  // plan should execute one command
++  string err;
++  EXPECT_TRUE(builder_.AddTarget("cat1", &err));
++  ASSERT_EQ("", err);
++
++  // pretend we can't run anything
++  ExpectCanRunMore(1, false);
++
++  EXPECT_FALSE(builder_.Build(&err));
++  EXPECT_EQ("stuck [this is a bug]", err);
++
++  EXPECT_EQ(0u, token_command_runner_.commands_ran_.size());
++}
++
++TEST_F(BuildTokenTest, DoNotStartWithoutToken) {
++  // plan should execute one command
++  string err;
++  EXPECT_TRUE(builder_.AddTarget("cat1", &err));
++  ASSERT_EQ("", err);
++
++  // we could run a command but do not have a token for it
++  ExpectCanRunMore(1,   true);
++  ExpectAcquireToken(1, false);
++
++  EXPECT_FALSE(builder_.Build(&err));
++  EXPECT_EQ("stuck [this is a bug]", err);
++
++  EXPECT_EQ(0u, token_command_runner_.commands_ran_.size());
++}
++
++TEST_F(BuildTokenTest, CompleteOneStep) {
++  // plan should execute one command
++  string err;
++  EXPECT_TRUE(builder_.AddTarget("cat1", &err));
++  ASSERT_EQ("", err);
++
++  // allow running of one command
++  ExpectCanRunMore(1,   true);
++  ExpectAcquireToken(1, true);
++  // block and wait for command to finalize
++  ExpectWaitForCommand(1, false);
++
++  EXPECT_TRUE(builder_.Build(&err));
++  EXPECT_EQ("", err);
++
++  EXPECT_EQ(1u, token_command_runner_.commands_ran_.size());
++  EXPECT_TRUE(token_command_runner_.commands_ran_[0] == "cat in1 > cat1");
++}
++
++TEST_F(BuildTokenTest, AcquireOneToken) {
++  // plan should execute more than one command
++  string err;
++  EXPECT_TRUE(builder_.AddTarget("cat12", &err));
++  ASSERT_EQ("", err);
++
++  // allow running of one command
++  ExpectCanRunMore(3,     true, false, false);
++  ExpectAcquireToken(1,   true);
++  // block and wait for command to finalize
++  ExpectWaitForCommand(1, false);
++
++  EXPECT_FALSE(builder_.Build(&err));
++  EXPECT_EQ("stuck [this is a bug]", err);
++
++  EXPECT_EQ(1u, token_command_runner_.commands_ran_.size());
++  // any of the two dependencies could have been executed
++  EXPECT_TRUE(token_command_runner_.commands_ran_[0] == "cat in1 > cat1" ||
++              token_command_runner_.commands_ran_[0] == "cat in1 in2 > cat2");
++}
++
++TEST_F(BuildTokenTest, WantTwoTokens) {
++  // plan should execute more than one command
++  string err;
++  EXPECT_TRUE(builder_.AddTarget("cat12", &err));
++  ASSERT_EQ("", err);
++
++  // allow running of one command
++  ExpectCanRunMore(3,     true, true, false);
++  ExpectAcquireToken(2,   true, false);
++  // wait for command to finalize or token to become available
++  ExpectWaitForCommand(1, true);
++
++  EXPECT_FALSE(builder_.Build(&err));
++  EXPECT_EQ("stuck [this is a bug]", err);
++
++  EXPECT_EQ(1u, token_command_runner_.commands_ran_.size());
++  // any of the two dependencies could have been executed
++  EXPECT_TRUE(token_command_runner_.commands_ran_[0] == "cat in1 > cat1" ||
++              token_command_runner_.commands_ran_[0] == "cat in1 in2 > cat2");
++}
++
++TEST_F(BuildTokenTest, CompleteTwoSteps) {
++  ASSERT_NO_FATAL_FAILURE(AssertParse(&state_,
++"build out1: cat in1\n"
++"build out2: cat out1\n"));
++
++  // plan should execute more than one command
++  string err;
++  EXPECT_TRUE(builder_.AddTarget("out2", &err));
++  ASSERT_EQ("", err);
++
++  // allow running of two commands
++  ExpectCanRunMore(2,     true, true);
++  ExpectAcquireToken(2,   true, true);
++  // wait for commands to finalize
++  ExpectWaitForCommand(2, false, false);
++
++  EXPECT_TRUE(builder_.Build(&err));
++  EXPECT_EQ("", err);
++
++  EXPECT_EQ(2u, token_command_runner_.commands_ran_.size());
++  EXPECT_TRUE(token_command_runner_.commands_ran_[0] == "cat in1 > out1");
++  EXPECT_TRUE(token_command_runner_.commands_ran_[1] == "cat out1 > out2");
++}
++
++TEST_F(BuildTokenTest, TwoCommandsInParallel) {
++  ASSERT_NO_FATAL_FAILURE(AssertParse(&state_,
++"rule token-available\n"
++"  command = cat $in > $out\n"
++"build out1: token-available in1\n"
++"build out2: token-available in2\n"
++"build out12: cat out1 out2\n"));
++
++  // plan should execute more than one command
++  string err;
++  EXPECT_TRUE(builder_.AddTarget("out12", &err));
++  ASSERT_EQ("", err);
++
++  // 1st command: token available -> allow running
++  // 2nd command: no token available but becomes available later
++  ExpectCanRunMore(4,     true, true,  true,  false);
++  ExpectAcquireToken(3,   true, false, true);
++  // 1st call waits for command to finalize or token to become available
++  // 2nd call waits for command to finalize
++  // 3rd call waits for command to finalize
++  ExpectWaitForCommand(3, true, false, false);
++
++  EXPECT_FALSE(builder_.Build(&err));
++  EXPECT_EQ("stuck [this is a bug]", err);
++
++  EXPECT_EQ(2u, token_command_runner_.commands_ran_.size());
++  EXPECT_TRUE((token_command_runner_.commands_ran_[0] == "cat in1 > out1" &&
++               token_command_runner_.commands_ran_[1] == "cat in2 > out2") ||
++              (token_command_runner_.commands_ran_[0] == "cat in2 > out2" &&
++               token_command_runner_.commands_ran_[1] == "cat in1 > out1"));
++}
++
++TEST_F(BuildTokenTest, CompleteThreeStepsSerial) {
++  // plan should execute more than one command
++  string err;
++  EXPECT_TRUE(builder_.AddTarget("cat12", &err));
++  ASSERT_EQ("", err);
++
++  // allow running of all commands
++  ExpectCanRunMore(4,     true, true,  true,  true);
++  ExpectAcquireToken(4,   true, false, true,  true);
++  // wait for commands to finalize
++  ExpectWaitForCommand(3, true, false, false);
++
++  EXPECT_TRUE(builder_.Build(&err));
++  EXPECT_EQ("", err);
++
++  EXPECT_EQ(3u, token_command_runner_.commands_ran_.size());
++  EXPECT_TRUE((token_command_runner_.commands_ran_[0] == "cat in1 > cat1"     &&
++               token_command_runner_.commands_ran_[1] == "cat in1 in2 > cat2") ||
++              (token_command_runner_.commands_ran_[0] == "cat in1 in2 > cat2" &&
++               token_command_runner_.commands_ran_[1] == "cat in1 > cat1"    ));
++  EXPECT_TRUE(token_command_runner_.commands_ran_[2] == "cat cat1 cat2 > cat12");
++}
++
++TEST_F(BuildTokenTest, CompleteThreeStepsParallel) {
++  ASSERT_NO_FATAL_FAILURE(AssertParse(&state_,
++"rule token-available\n"
++"  command = cat $in > $out\n"
++"build out1: token-available in1\n"
++"build out2: token-available in2\n"
++"build out12: cat out1 out2\n"));
++
++  // plan should execute more than one command
++  string err;
++  EXPECT_TRUE(builder_.AddTarget("out12", &err));
++  ASSERT_EQ("", err);
++
++  // allow running of all commands
++  ExpectCanRunMore(4,     true, true,  true,  true);
++  ExpectAcquireToken(4,   true, false, true,  true);
++  // wait for commands to finalize
++  ExpectWaitForCommand(4, true, false, false, false);
++
++  EXPECT_TRUE(builder_.Build(&err));
++  EXPECT_EQ("", err);
++
++  EXPECT_EQ(3u, token_command_runner_.commands_ran_.size());
++  EXPECT_TRUE((token_command_runner_.commands_ran_[0] == "cat in1 > out1" &&
++               token_command_runner_.commands_ran_[1] == "cat in2 > out2") ||
++              (token_command_runner_.commands_ran_[0] == "cat in2 > out2" &&
++               token_command_runner_.commands_ran_[1] == "cat in1 > out1"));
++  EXPECT_TRUE(token_command_runner_.commands_ran_[2] == "cat out1 out2 > out12");
++}
+--- a/src/exit_status.h
++++ b/src/exit_status.h
+@@ -18,7 +18,8 @@
+ enum ExitStatus {
+   ExitSuccess,
+   ExitFailure,
+-  ExitInterrupted
++  ExitTokenAvailable,
++  ExitInterrupted,
+ };
+ 
+ #endif  // NINJA_EXIT_STATUS_H_
+--- a/src/subprocess-posix.cc
++++ b/src/subprocess-posix.cc
+@@ -13,6 +13,7 @@
+ // limitations under the License.
+ 
+ #include "subprocess.h"
++#include "tokenpool.h"
+ 
+ #include <sys/select.h>
+ #include <assert.h>
+@@ -249,7 +250,7 @@ Subprocess *SubprocessSet::Add(const str
+ }
+ 
+ #ifdef USE_PPOLL
+-bool SubprocessSet::DoWork() {
++bool SubprocessSet::DoWork(TokenPool* tokens) {
+   vector<pollfd> fds;
+   nfds_t nfds = 0;
+ 
+@@ -263,6 +264,12 @@ bool SubprocessSet::DoWork() {
+     ++nfds;
+   }
+ 
++  if (tokens) {
++    pollfd pfd = { tokens->GetMonitorFd(), POLLIN | POLLPRI, 0 };
++    fds.push_back(pfd);
++    ++nfds;
++  }
++
+   interrupted_ = 0;
+   int ret = ppoll(&fds.front(), nfds, NULL, &old_mask_);
+   if (ret == -1) {
+@@ -295,11 +302,20 @@ bool SubprocessSet::DoWork() {
+     ++i;
+   }
+ 
++  if (tokens) {
++    pollfd *pfd = &fds[nfds - 1];
++    if (pfd->fd >= 0) {
++      assert(pfd->fd == tokens->GetMonitorFd());
++      if (pfd->revents != 0)
++        token_available_ = true;
++    }
++  }
++
+   return IsInterrupted();
+ }
+ 
+ #else  // !defined(USE_PPOLL)
+-bool SubprocessSet::DoWork() {
++bool SubprocessSet::DoWork(TokenPool* tokens) {
+   fd_set set;
+   int nfds = 0;
+   FD_ZERO(&set);
+@@ -314,6 +330,13 @@ bool SubprocessSet::DoWork() {
+     }
+   }
+ 
++  if (tokens) {
++    int fd = tokens->GetMonitorFd();
++    FD_SET(fd, &set);
++    if (nfds < fd+1)
++      nfds = fd+1;
++  }
++
+   interrupted_ = 0;
+   int ret = pselect(nfds, &set, 0, 0, 0, &old_mask_);
+   if (ret == -1) {
+@@ -342,6 +365,12 @@ bool SubprocessSet::DoWork() {
+     ++i;
+   }
+ 
++  if (tokens) {
++    int fd = tokens->GetMonitorFd();
++    if ((fd >= 0) && FD_ISSET(fd, &set))
++    token_available_ = true;
++  }
++
+   return IsInterrupted();
+ }
+ #endif  // !defined(USE_PPOLL)
+--- a/src/subprocess-win32.cc
++++ b/src/subprocess-win32.cc
+@@ -13,6 +13,7 @@
+ // limitations under the License.
+ 
+ #include "subprocess.h"
++#include "tokenpool.h"
+ 
+ #include <assert.h>
+ #include <stdio.h>
+@@ -251,11 +252,14 @@ Subprocess *SubprocessSet::Add(const str
+   return subprocess;
+ }
+ 
+-bool SubprocessSet::DoWork() {
++bool SubprocessSet::DoWork(TokenPool* tokens) {
+   DWORD bytes_read;
+   Subprocess* subproc;
+   OVERLAPPED* overlapped;
+ 
++  if (tokens)
++    tokens->WaitForTokenAvailability(ioport_);
++
+   if (!GetQueuedCompletionStatus(ioport_, &bytes_read, (PULONG_PTR)&subproc,
+                                  &overlapped, INFINITE)) {
+     if (GetLastError() != ERROR_BROKEN_PIPE)
+@@ -266,6 +270,11 @@ bool SubprocessSet::DoWork() {
+                 // delivered by NotifyInterrupted above.
+     return true;
+ 
++  if (tokens && tokens->TokenIsAvailable((ULONG_PTR)subproc)) {
++    token_available_ = true;
++    return false;
++  }
++
+   subproc->OnPipeReady();
+ 
+   if (subproc->Done()) {
+--- a/src/subprocess.h
++++ b/src/subprocess.h
+@@ -76,6 +76,8 @@ struct Subprocess {
+   friend struct SubprocessSet;
+ };
+ 
++struct TokenPool;
++
+ /// SubprocessSet runs a ppoll/pselect() loop around a set of Subprocesses.
+ /// DoWork() waits for any state change in subprocesses; finished_
+ /// is a queue of subprocesses as they finish.
+@@ -84,13 +86,17 @@ struct SubprocessSet {
+   ~SubprocessSet();
+ 
+   Subprocess* Add(const std::string& command, bool use_console = false);
+-  bool DoWork();
++  bool DoWork(TokenPool* tokens);
+   Subprocess* NextFinished();
+   void Clear();
+ 
+   std::vector<Subprocess*> running_;
+   std::queue<Subprocess*> finished_;
+ 
++  bool token_available_;
++  bool IsTokenAvailable() { return token_available_; }
++  void ResetTokenAvailable() { token_available_ = false; }
++
+ #ifdef _WIN32
+   static BOOL WINAPI NotifyInterrupted(DWORD dwCtrlType);
+   static HANDLE ioport_;
+--- a/src/subprocess_test.cc
++++ b/src/subprocess_test.cc
+@@ -13,6 +13,7 @@
+ // limitations under the License.
+ 
+ #include "subprocess.h"
++#include "tokenpool.h"
+ 
+ #include "test.h"
+ 
+@@ -34,8 +35,30 @@ const char* kSimpleCommand = "cmd /c dir
+ const char* kSimpleCommand = "ls /";
+ #endif
+ 
++struct TestTokenPool : public TokenPool {
++  bool Acquire()     { return false; }
++  void Reserve()     {}
++  void Release()     {}
++  void Clear()       {}
++  bool Setup(bool ignore_unused, bool verbose, double& max_load_average) { return false; }
++
++#ifdef _WIN32
++  bool _token_available;
++  void WaitForTokenAvailability(HANDLE ioport) {
++    if (_token_available)
++      // unblock GetQueuedCompletionStatus()
++      PostQueuedCompletionStatus(ioport, 0, (ULONG_PTR) this, NULL);
++  }
++  bool TokenIsAvailable(ULONG_PTR key) { return key == (ULONG_PTR) this; }
++#else
++  int _fd;
++  int GetMonitorFd() { return _fd; }
++#endif
++};
++
+ struct SubprocessTest : public testing::Test {
+   SubprocessSet subprocs_;
++  TestTokenPool tokens_;
+ };
+ 
+ }  // anonymous namespace
+@@ -45,10 +68,12 @@ TEST_F(SubprocessTest, BadCommandStderr)
+   Subprocess* subproc = subprocs_.Add("cmd /c ninja_no_such_command");
+   ASSERT_NE((Subprocess *) 0, subproc);
+ 
++  subprocs_.ResetTokenAvailable();
+   while (!subproc->Done()) {
+     // Pretend we discovered that stderr was ready for writing.
+-    subprocs_.DoWork();
++    subprocs_.DoWork(NULL);
+   }
++  ASSERT_FALSE(subprocs_.IsTokenAvailable());
+ 
+   EXPECT_EQ(ExitFailure, subproc->Finish());
+   EXPECT_NE("", subproc->GetOutput());
+@@ -59,10 +84,12 @@ TEST_F(SubprocessTest, NoSuchCommand) {
+   Subprocess* subproc = subprocs_.Add("ninja_no_such_command");
+   ASSERT_NE((Subprocess *) 0, subproc);
+ 
++  subprocs_.ResetTokenAvailable();
+   while (!subproc->Done()) {
+     // Pretend we discovered that stderr was ready for writing.
+-    subprocs_.DoWork();
++    subprocs_.DoWork(NULL);
+   }
++  ASSERT_FALSE(subprocs_.IsTokenAvailable());
+ 
+   EXPECT_EQ(ExitFailure, subproc->Finish());
+   EXPECT_NE("", subproc->GetOutput());
+@@ -78,9 +105,11 @@ TEST_F(SubprocessTest, InterruptChild) {
+   Subprocess* subproc = subprocs_.Add("kill -INT $$");
+   ASSERT_NE((Subprocess *) 0, subproc);
+ 
++  subprocs_.ResetTokenAvailable();
+   while (!subproc->Done()) {
+-    subprocs_.DoWork();
++    subprocs_.DoWork(NULL);
+   }
++  ASSERT_FALSE(subprocs_.IsTokenAvailable());
+ 
+   EXPECT_EQ(ExitInterrupted, subproc->Finish());
+ }
+@@ -90,7 +119,7 @@ TEST_F(SubprocessTest, InterruptParent)
+   ASSERT_NE((Subprocess *) 0, subproc);
+ 
+   while (!subproc->Done()) {
+-    bool interrupted = subprocs_.DoWork();
++    bool interrupted = subprocs_.DoWork(NULL);
+     if (interrupted)
+       return;
+   }
+@@ -102,9 +131,11 @@ TEST_F(SubprocessTest, InterruptChildWit
+   Subprocess* subproc = subprocs_.Add("kill -TERM $$");
+   ASSERT_NE((Subprocess *) 0, subproc);
+ 
++  subprocs_.ResetTokenAvailable();
+   while (!subproc->Done()) {
+-    subprocs_.DoWork();
++    subprocs_.DoWork(NULL);
+   }
++  ASSERT_FALSE(subprocs_.IsTokenAvailable());
+ 
+   EXPECT_EQ(ExitInterrupted, subproc->Finish());
+ }
+@@ -114,7 +145,7 @@ TEST_F(SubprocessTest, InterruptParentWi
+   ASSERT_NE((Subprocess *) 0, subproc);
+ 
+   while (!subproc->Done()) {
+-    bool interrupted = subprocs_.DoWork();
++    bool interrupted = subprocs_.DoWork(NULL);
+     if (interrupted)
+       return;
+   }
+@@ -126,9 +157,11 @@ TEST_F(SubprocessTest, InterruptChildWit
+   Subprocess* subproc = subprocs_.Add("kill -HUP $$");
+   ASSERT_NE((Subprocess *) 0, subproc);
+ 
++  subprocs_.ResetTokenAvailable();
+   while (!subproc->Done()) {
+-    subprocs_.DoWork();
++    subprocs_.DoWork(NULL);
+   }
++  ASSERT_FALSE(subprocs_.IsTokenAvailable());
+ 
+   EXPECT_EQ(ExitInterrupted, subproc->Finish());
+ }
+@@ -138,7 +171,7 @@ TEST_F(SubprocessTest, InterruptParentWi
+   ASSERT_NE((Subprocess *) 0, subproc);
+ 
+   while (!subproc->Done()) {
+-    bool interrupted = subprocs_.DoWork();
++    bool interrupted = subprocs_.DoWork(NULL);
+     if (interrupted)
+       return;
+   }
+@@ -153,9 +186,11 @@ TEST_F(SubprocessTest, Console) {
+         subprocs_.Add("test -t 0 -a -t 1 -a -t 2", /*use_console=*/true);
+     ASSERT_NE((Subprocess*)0, subproc);
+ 
++    subprocs_.ResetTokenAvailable();
+     while (!subproc->Done()) {
+-      subprocs_.DoWork();
++      subprocs_.DoWork(NULL);
+     }
++    ASSERT_FALSE(subprocs_.IsTokenAvailable());
+ 
+     EXPECT_EQ(ExitSuccess, subproc->Finish());
+   }
+@@ -167,9 +202,11 @@ TEST_F(SubprocessTest, SetWithSingle) {
+   Subprocess* subproc = subprocs_.Add(kSimpleCommand);
+   ASSERT_NE((Subprocess *) 0, subproc);
+ 
++  subprocs_.ResetTokenAvailable();
+   while (!subproc->Done()) {
+-    subprocs_.DoWork();
++    subprocs_.DoWork(NULL);
+   }
++  ASSERT_FALSE(subprocs_.IsTokenAvailable());
+   ASSERT_EQ(ExitSuccess, subproc->Finish());
+   ASSERT_NE("", subproc->GetOutput());
+ 
+@@ -200,12 +237,13 @@ TEST_F(SubprocessTest, SetWithMulti) {
+     ASSERT_EQ("", processes[i]->GetOutput());
+   }
+ 
++  subprocs_.ResetTokenAvailable();
+   while (!processes[0]->Done() || !processes[1]->Done() ||
+          !processes[2]->Done()) {
+     ASSERT_GT(subprocs_.running_.size(), 0u);
+-    subprocs_.DoWork();
++    subprocs_.DoWork(NULL);
+   }
+-
++  ASSERT_FALSE(subprocs_.IsTokenAvailable());
+   ASSERT_EQ(0u, subprocs_.running_.size());
+   ASSERT_EQ(3u, subprocs_.finished_.size());
+ 
+@@ -237,8 +275,10 @@ TEST_F(SubprocessTest, SetWithLots) {
+     ASSERT_NE((Subprocess *) 0, subproc);
+     procs.push_back(subproc);
+   }
++  subprocs_.ResetTokenAvailable();
+   while (!subprocs_.running_.empty())
+-    subprocs_.DoWork();
++    subprocs_.DoWork(NULL);
++  ASSERT_FALSE(subprocs_.IsTokenAvailable());
+   for (size_t i = 0; i < procs.size(); ++i) {
+     ASSERT_EQ(ExitSuccess, procs[i]->Finish());
+     ASSERT_NE("", procs[i]->GetOutput());
+@@ -254,10 +294,91 @@ TEST_F(SubprocessTest, SetWithLots) {
+ // that stdin is closed.
+ TEST_F(SubprocessTest, ReadStdin) {
+   Subprocess* subproc = subprocs_.Add("cat -");
++  subprocs_.ResetTokenAvailable();
+   while (!subproc->Done()) {
+-    subprocs_.DoWork();
++    subprocs_.DoWork(NULL);
+   }
++  ASSERT_FALSE(subprocs_.IsTokenAvailable());
+   ASSERT_EQ(ExitSuccess, subproc->Finish());
+   ASSERT_EQ(1u, subprocs_.finished_.size());
+ }
+ #endif  // _WIN32
++
++TEST_F(SubprocessTest, TokenAvailable) {
++  Subprocess* subproc = subprocs_.Add(kSimpleCommand);
++  ASSERT_NE((Subprocess *) 0, subproc);
++
++  // simulate GNUmake jobserver pipe with 1 token
++#ifdef _WIN32
++  tokens_._token_available = true;
++#else
++  int fds[2];
++  ASSERT_EQ(0u, pipe(fds));
++  tokens_._fd = fds[0];
++  ASSERT_EQ(1u, write(fds[1], "T", 1));
++#endif
++
++  subprocs_.ResetTokenAvailable();
++  subprocs_.DoWork(&tokens_);
++#ifdef _WIN32
++  tokens_._token_available = false;
++  // we need to loop here as we have no control where the token
++  // I/O completion post ends up in the queue
++  while (!subproc->Done() && !subprocs_.IsTokenAvailable()) {
++    subprocs_.DoWork(&tokens_);
++  }
++#endif
++
++  EXPECT_TRUE(subprocs_.IsTokenAvailable());
++  EXPECT_EQ(0u, subprocs_.finished_.size());
++
++  // remove token to let DoWork() wait for command again
++#ifndef _WIN32
++  char token;
++  ASSERT_EQ(1u, read(fds[0], &token, 1));
++#endif
++
++  while (!subproc->Done()) {
++    subprocs_.DoWork(&tokens_);
++  }
++
++#ifndef _WIN32
++  close(fds[1]);
++  close(fds[0]);
++#endif
++
++  EXPECT_EQ(ExitSuccess, subproc->Finish());
++  EXPECT_NE("", subproc->GetOutput());
++
++  EXPECT_EQ(1u, subprocs_.finished_.size());
++}
++
++TEST_F(SubprocessTest, TokenNotAvailable) {
++  Subprocess* subproc = subprocs_.Add(kSimpleCommand);
++  ASSERT_NE((Subprocess *) 0, subproc);
++
++  // simulate GNUmake jobserver pipe with 0 tokens
++#ifdef _WIN32
++  tokens_._token_available = false;
++#else
++  int fds[2];
++  ASSERT_EQ(0u, pipe(fds));
++  tokens_._fd = fds[0];
++#endif
++
++  subprocs_.ResetTokenAvailable();
++  while (!subproc->Done()) {
++    subprocs_.DoWork(&tokens_);
++  }
++
++#ifndef _WIN32
++  close(fds[1]);
++  close(fds[0]);
++#endif
++
++  EXPECT_FALSE(subprocs_.IsTokenAvailable());
++  EXPECT_EQ(ExitSuccess, subproc->Finish());
++  EXPECT_NE("", subproc->GetOutput());
++
++  EXPECT_EQ(1u, subprocs_.finished_.size());
++}
+--- a/src/ninja.cc
++++ b/src/ninja.cc
+@@ -1466,6 +1466,7 @@ int ReadFlags(int* argc, char*** argv,
+         // We want to run N jobs in parallel. For N = 0, INT_MAX
+         // is close enough to infinite for most sane builds.
+         config->parallelism = value > 0 ? value : INT_MAX;
++        config->parallelism_from_cmdline = true;
+         deferGuessParallelism.needGuess = false;
+         break;
+       }
+--- /dev/null
++++ b/src/tokenpool_test.cc
+@@ -0,0 +1,279 @@
++// Copyright 2018 Google Inc. All Rights Reserved.
++//
++// Licensed under the Apache License, Version 2.0 (the "License");
++// you may not use this file except in compliance with the License.
++// You may obtain a copy of the License at
++//
++//     http://www.apache.org/licenses/LICENSE-2.0
++//
++// Unless required by applicable law or agreed to in writing, software
++// distributed under the License is distributed on an "AS IS" BASIS,
++// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
++// See the License for the specific language governing permissions and
++// limitations under the License.
++
++#include "tokenpool.h"
++
++#include "test.h"
++
++#ifdef _WIN32
++#include <windows.h>
++#else
++#include <unistd.h>
++#endif
++
++#include <stdio.h>
++#include <stdlib.h>
++
++#ifdef _WIN32
++// should contain all valid characters
++#define SEMAPHORE_NAME      "abcdefghijklmnopqrstwxyz01234567890_"
++#define AUTH_FORMAT(tmpl)   "foo " tmpl "=%s bar"
++#define ENVIRONMENT_CLEAR() SetEnvironmentVariable("MAKEFLAGS", NULL)
++#define ENVIRONMENT_INIT(v) SetEnvironmentVariable("MAKEFLAGS", v)
++#else
++#define AUTH_FORMAT(tmpl)   "foo " tmpl "=%d,%d bar"
++#define ENVIRONMENT_CLEAR() unsetenv("MAKEFLAGS")
++#define ENVIRONMENT_INIT(v) setenv("MAKEFLAGS", v, true)
++#endif
++
++namespace {
++
++const double kLoadAverageDefault = -1.23456789;
++
++struct TokenPoolTest : public testing::Test {
++  double load_avg_;
++  TokenPool* tokens_;
++  char buf_[1024];
++#ifdef _WIN32
++  const char* semaphore_name_;
++  HANDLE semaphore_;
++#else
++  int fds_[2];
++
++  char random() {
++    return int((rand() / double(RAND_MAX)) * 256);
++  }
++#endif
++
++  virtual void SetUp() {
++    load_avg_ = kLoadAverageDefault;
++    tokens_ = NULL;
++    ENVIRONMENT_CLEAR();
++#ifdef _WIN32
++    semaphore_name_ = SEMAPHORE_NAME;
++    if ((semaphore_ = CreateSemaphore(0, 0, 2, SEMAPHORE_NAME)) == NULL)
++#else
++    if (pipe(fds_) < 0)
++#endif
++      ASSERT_TRUE(false);
++  }
++
++  void CreatePool(const char* format, bool ignore_jobserver = false) {
++    if (format) {
++      sprintf(buf_, format,
++#ifdef _WIN32
++              semaphore_name_
++#else
++              fds_[0], fds_[1]
++#endif
++      );
++      ENVIRONMENT_INIT(buf_);
++    }
++    if ((tokens_ = TokenPool::Get()) != NULL) {
++      if (!tokens_->Setup(ignore_jobserver, false, load_avg_)) {
++        delete tokens_;
++        tokens_ = NULL;
++      }
++    }
++  }
++
++  void CreateDefaultPool() {
++    CreatePool(AUTH_FORMAT("--jobserver-auth"));
++  }
++
++  virtual void TearDown() {
++    if (tokens_)
++      delete tokens_;
++#ifdef _WIN32
++    CloseHandle(semaphore_);
++#else
++    close(fds_[0]);
++    close(fds_[1]);
++#endif
++    ENVIRONMENT_CLEAR();
++  }
++};
++
++} // anonymous namespace
++
++// verifies none implementation
++TEST_F(TokenPoolTest, NoTokenPool) {
++  CreatePool(NULL, false);
++
++  EXPECT_EQ(NULL, tokens_);
++  EXPECT_EQ(kLoadAverageDefault, load_avg_);
++}
++
++TEST_F(TokenPoolTest, SuccessfulOldSetup) {
++  // GNUmake <= 4.1
++  CreatePool(AUTH_FORMAT("--jobserver-fds"));
++
++  EXPECT_NE(NULL, tokens_);
++  EXPECT_EQ(kLoadAverageDefault, load_avg_);
++}
++
++TEST_F(TokenPoolTest, SuccessfulNewSetup) {
++  // GNUmake => 4.2
++  CreateDefaultPool();
++
++  EXPECT_NE(NULL, tokens_);
++  EXPECT_EQ(kLoadAverageDefault, load_avg_);
++}
++
++TEST_F(TokenPoolTest, IgnoreWithJN) {
++  CreatePool(AUTH_FORMAT("--jobserver-auth"), true);
++
++  EXPECT_EQ(NULL, tokens_);
++  EXPECT_EQ(kLoadAverageDefault, load_avg_);
++}
++
++TEST_F(TokenPoolTest, HonorLN) {
++  CreatePool(AUTH_FORMAT("-l9 --jobserver-auth"));
++
++  EXPECT_NE(NULL, tokens_);
++  EXPECT_EQ(9.0, load_avg_);
++}
++
++#ifdef _WIN32
++TEST_F(TokenPoolTest, SemaphoreNotFound) {
++  semaphore_name_ = SEMAPHORE_NAME "_foobar";
++  CreateDefaultPool();
++
++  EXPECT_EQ(NULL, tokens_);
++  EXPECT_EQ(kLoadAverageDefault, load_avg_);
++}
++
++TEST_F(TokenPoolTest, TokenIsAvailable) {
++  CreateDefaultPool();
++
++  ASSERT_NE(NULL, tokens_);
++  EXPECT_EQ(kLoadAverageDefault, load_avg_);
++
++  EXPECT_TRUE(tokens_->TokenIsAvailable((ULONG_PTR)tokens_));
++}
++#else
++TEST_F(TokenPoolTest, MonitorFD) {
++  CreateDefaultPool();
++
++  ASSERT_NE(NULL, tokens_);
++  EXPECT_EQ(kLoadAverageDefault, load_avg_);
++
++  EXPECT_EQ(fds_[0], tokens_->GetMonitorFd());
++}
++#endif
++
++TEST_F(TokenPoolTest, ImplicitToken) {
++  CreateDefaultPool();
++
++  ASSERT_NE(NULL, tokens_);
++  EXPECT_EQ(kLoadAverageDefault, load_avg_);
++
++  EXPECT_TRUE(tokens_->Acquire());
++  tokens_->Reserve();
++  EXPECT_FALSE(tokens_->Acquire());
++  tokens_->Release();
++  EXPECT_TRUE(tokens_->Acquire());
++}
++
++TEST_F(TokenPoolTest, TwoTokens) {
++  CreateDefaultPool();
++
++  ASSERT_NE(NULL, tokens_);
++  EXPECT_EQ(kLoadAverageDefault, load_avg_);
++
++  // implicit token
++  EXPECT_TRUE(tokens_->Acquire());
++  tokens_->Reserve();
++  EXPECT_FALSE(tokens_->Acquire());
++
++  // jobserver offers 2nd token
++#ifdef _WIN32
++  LONG previous;
++  ASSERT_TRUE(ReleaseSemaphore(semaphore_, 1, &previous));
++  ASSERT_EQ(0, previous);
++#else
++  char test_tokens[1] = { random() };
++  ASSERT_EQ(1u, write(fds_[1], test_tokens, sizeof(test_tokens)));
++#endif
++  EXPECT_TRUE(tokens_->Acquire());
++  tokens_->Reserve();
++  EXPECT_FALSE(tokens_->Acquire());
++
++  // release 2nd token
++  tokens_->Release();
++  EXPECT_TRUE(tokens_->Acquire());
++
++  // release implicit token - must return 2nd token back to jobserver
++  tokens_->Release();
++  EXPECT_TRUE(tokens_->Acquire());
++
++  // there must be one token available
++#ifdef _WIN32
++  EXPECT_EQ(WAIT_OBJECT_0, WaitForSingleObject(semaphore_, 0));
++  EXPECT_TRUE(ReleaseSemaphore(semaphore_, 1, &previous));
++  EXPECT_EQ(0, previous);
++#else
++  EXPECT_EQ(1u, read(fds_[0], buf_, sizeof(buf_)));
++  EXPECT_EQ(test_tokens[0], buf_[0]);
++#endif
++
++  // implicit token
++  EXPECT_TRUE(tokens_->Acquire());
++}
++
++TEST_F(TokenPoolTest, Clear) {
++  CreateDefaultPool();
++
++  ASSERT_NE(NULL, tokens_);
++  EXPECT_EQ(kLoadAverageDefault, load_avg_);
++
++  // implicit token
++  EXPECT_TRUE(tokens_->Acquire());
++  tokens_->Reserve();
++  EXPECT_FALSE(tokens_->Acquire());
++
++  // jobserver offers 2nd & 3rd token
++#ifdef _WIN32
++  LONG previous;
++  ASSERT_TRUE(ReleaseSemaphore(semaphore_, 2, &previous));
++  ASSERT_EQ(0, previous);
++#else
++  char test_tokens[2] = { random(), random() };
++  ASSERT_EQ(2u, write(fds_[1], test_tokens, sizeof(test_tokens)));
++#endif
++  EXPECT_TRUE(tokens_->Acquire());
++  tokens_->Reserve();
++  EXPECT_TRUE(tokens_->Acquire());
++  tokens_->Reserve();
++  EXPECT_FALSE(tokens_->Acquire());
++
++  tokens_->Clear();
++  EXPECT_TRUE(tokens_->Acquire());
++
++  // there must be two tokens available
++#ifdef _WIN32
++  EXPECT_EQ(WAIT_OBJECT_0, WaitForSingleObject(semaphore_, 0));
++  EXPECT_EQ(WAIT_OBJECT_0, WaitForSingleObject(semaphore_, 0));
++  EXPECT_TRUE(ReleaseSemaphore(semaphore_, 2, &previous));
++  EXPECT_EQ(0, previous);
++#else
++  EXPECT_EQ(2u, read(fds_[0], buf_, sizeof(buf_)));
++  // tokens are pushed onto a stack, hence returned in reverse order
++  EXPECT_EQ(test_tokens[0], buf_[1]);
++  EXPECT_EQ(test_tokens[1], buf_[0]);
++#endif
++
++  // implicit token
++  EXPECT_TRUE(tokens_->Acquire());
++}
+--- /dev/null
++++ b/src/tokenpool-gnu-make-posix.cc
+@@ -0,0 +1,214 @@
++// Copyright 2016-2018 Google Inc. All Rights Reserved.
++//
++// Licensed under the Apache License, Version 2.0 (the "License");
++// you may not use this file except in compliance with the License.
++// You may obtain a copy of the License at
++//
++//     http://www.apache.org/licenses/LICENSE-2.0
++//
++// Unless required by applicable law or agreed to in writing, software
++// distributed under the License is distributed on an "AS IS" BASIS,
++// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
++// See the License for the specific language governing permissions and
++// limitations under the License.
++
++#include "tokenpool-gnu-make.h"
++
++#include <errno.h>
++#include <fcntl.h>
++#include <poll.h>
++#include <unistd.h>
++#include <signal.h>
++#include <sys/time.h>
++#include <stdio.h>
++#include <string.h>
++#include <stdlib.h>
++#include <stack>
++
++// TokenPool implementation for GNU make jobserver - POSIX implementation
++// (http://make.mad-scientist.net/papers/jobserver-implementation/)
++struct GNUmakeTokenPoolPosix : public GNUmakeTokenPool {
++  GNUmakeTokenPoolPosix();
++  virtual ~GNUmakeTokenPoolPosix();
++
++  virtual int GetMonitorFd();
++
++  virtual const char* GetEnv(const char* name) { return getenv(name); };
++  virtual bool ParseAuth(const char* jobserver);
++  virtual bool AcquireToken();
++  virtual bool ReturnToken();
++
++ private:
++  int rfd_;
++  int wfd_;
++
++  struct sigaction old_act_;
++  bool restore_;
++
++  // See https://www.gnu.org/software/make/manual/html_node/POSIX-Jobserver.html
++  //
++  //   It’s important that when you release the job slot, you write back
++  //   the same character you read. Don’t assume that all tokens are the
++  //   same character different characters may have different meanings to
++  //   GNU make. The order is not important, since make has no idea in
++  //   what order jobs will complete anyway.
++  //
++  std::stack<char> tokens_;
++
++  static int dup_rfd_;
++  static void CloseDupRfd(int signum);
++
++  bool CheckFd(int fd);
++  bool SetAlarmHandler();
++};
++
++GNUmakeTokenPoolPosix::GNUmakeTokenPoolPosix() : rfd_(-1), wfd_(-1), restore_(false) {
++}
++
++GNUmakeTokenPoolPosix::~GNUmakeTokenPoolPosix() {
++  Clear();
++  if (restore_)
++    sigaction(SIGALRM, &old_act_, NULL);
++}
++
++bool GNUmakeTokenPoolPosix::CheckFd(int fd) {
++  if (fd < 0)
++    return false;
++  int ret = fcntl(fd, F_GETFD);
++  return ret >= 0;
++}
++
++int GNUmakeTokenPoolPosix::dup_rfd_ = -1;
++
++void GNUmakeTokenPoolPosix::CloseDupRfd(int signum) {
++  close(dup_rfd_);
++  dup_rfd_ = -1;
++}
++
++bool GNUmakeTokenPoolPosix::SetAlarmHandler() {
++  struct sigaction act;
++  memset(&act, 0, sizeof(act));
++  act.sa_handler = CloseDupRfd;
++  if (sigaction(SIGALRM, &act, &old_act_) < 0) {
++    perror("sigaction:");
++    return false;
++  }
++  restore_ = true;
++  return true;
++}
++
++bool GNUmakeTokenPoolPosix::ParseAuth(const char* jobserver) {
++  int rfd = -1;
++  int wfd = -1;
++  if ((sscanf(jobserver, "%*[^=]=%d,%d", &rfd, &wfd) == 2) &&
++      CheckFd(rfd) &&
++      CheckFd(wfd) &&
++      SetAlarmHandler()) {
++    rfd_ = rfd;
++    wfd_ = wfd;
++    return true;
++  }
++
++  return false;
++}
++
++bool GNUmakeTokenPoolPosix::AcquireToken() {
++  // Please read
++  //
++  //   http://make.mad-scientist.net/papers/jobserver-implementation/
++  //
++  // for the reasoning behind the following code.
++  //
++  // Try to read one character from the pipe. Returns true on success.
++  //
++  // First check if read() would succeed without blocking.
++#ifdef USE_PPOLL
++  pollfd pollfds[] = {{rfd_, POLLIN, 0}};
++  int ret = poll(pollfds, 1, 0);
++#else
++  fd_set set;
++  struct timeval timeout = { 0, 0 };
++  FD_ZERO(&set);
++  FD_SET(rfd_, &set);
++  int ret = select(rfd_ + 1, &set, NULL, NULL, &timeout);
++#endif
++  if (ret > 0) {
++    // Handle potential race condition:
++    //  - the above check succeeded, i.e. read() should not block
++    //  - the character disappears before we call read()
++    //
++    // Create a duplicate of rfd_. The duplicate file descriptor dup_rfd_
++    // can safely be closed by signal handlers without affecting rfd_.
++    dup_rfd_ = dup(rfd_);
++
++    if (dup_rfd_ != -1) {
++      struct sigaction act, old_act;
++      int ret = 0;
++      char buf;
++
++      // Temporarily replace SIGCHLD handler with our own
++      memset(&act, 0, sizeof(act));
++      act.sa_handler = CloseDupRfd;
++      if (sigaction(SIGCHLD, &act, &old_act) == 0) {
++        struct itimerval timeout;
++
++        // install a 100ms timeout that generates SIGALARM on expiration
++        memset(&timeout, 0, sizeof(timeout));
++        timeout.it_value.tv_usec = 100 * 1000; // [ms] -> [usec]
++        if (setitimer(ITIMER_REAL, &timeout, NULL) == 0) {
++          // Now try to read() from dup_rfd_. Return values from read():
++          //
++          // 1. token read                               ->  1
++          // 2. pipe closed                              ->  0
++          // 3. alarm expires                            -> -1 (EINTR)
++          // 4. child exits                              -> -1 (EINTR)
++          // 5. alarm expired before entering read()     -> -1 (EBADF)
++          // 6. child exited before entering read()      -> -1 (EBADF)
++          // 7. child exited before handler is installed -> go to 1 - 3
++          ret = read(dup_rfd_, &buf, 1);
++
++          // disarm timer
++          memset(&timeout, 0, sizeof(timeout));
++          setitimer(ITIMER_REAL, &timeout, NULL);
++        }
++
++        sigaction(SIGCHLD, &old_act, NULL);
++      }
++
++      CloseDupRfd(0);
++
++      // Case 1 from above list
++      if (ret > 0) {
++        tokens_.push(buf);
++        return true;
++      }
++    }
++  }
++
++  // read() would block, i.e. no token available,
++  // cases 2-6 from above list or
++  // select() / poll() / dup() / sigaction() / setitimer() failed
++  return false;
++}
++
++bool GNUmakeTokenPoolPosix::ReturnToken() {
++  const char buf = tokens_.top();
++  while (1) {
++    int ret = write(wfd_, &buf, 1);
++    if (ret > 0) {
++      tokens_.pop();
++      return true;
++    }
++    if ((ret != -1) || (errno != EINTR))
++      return false;
++    // write got interrupted - retry
++  }
++}
++
++int GNUmakeTokenPoolPosix::GetMonitorFd() {
++  return rfd_;
++}
++
++TokenPool* TokenPool::Get() {
++  return new GNUmakeTokenPoolPosix;
++}
+--- /dev/null
++++ b/src/tokenpool-gnu-make-win32.cc
+@@ -0,0 +1,239 @@
++// Copyright 2018 Google Inc. All Rights Reserved.
++//
++// Licensed under the Apache License, Version 2.0 (the "License");
++// you may not use this file except in compliance with the License.
++// You may obtain a copy of the License at
++//
++//     http://www.apache.org/licenses/LICENSE-2.0
++//
++// Unless required by applicable law or agreed to in writing, software
++// distributed under the License is distributed on an "AS IS" BASIS,
++// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
++// See the License for the specific language governing permissions and
++// limitations under the License.
++
++#include "tokenpool-gnu-make.h"
++
++// Always include this first.
++// Otherwise the other system headers don't work correctly under Win32
++#include <windows.h>
++
++#include <ctype.h>
++#include <stdlib.h>
++#include <string.h>
++
++#include "util.h"
++
++// TokenPool implementation for GNU make jobserver - Win32 implementation
++// (https://www.gnu.org/software/make/manual/html_node/Windows-Jobserver.html)
++struct GNUmakeTokenPoolWin32 : public GNUmakeTokenPool {
++  GNUmakeTokenPoolWin32();
++  virtual ~GNUmakeTokenPoolWin32();
++
++  virtual void WaitForTokenAvailability(HANDLE ioport);
++  virtual bool TokenIsAvailable(ULONG_PTR key);
++
++  virtual const char* GetEnv(const char* name);
++  virtual bool ParseAuth(const char* jobserver);
++  virtual bool AcquireToken();
++  virtual bool ReturnToken();
++
++ private:
++  // Semaphore for GNU make jobserver protocol
++  HANDLE semaphore_jobserver_;
++  // Semaphore Child -> Parent
++  // - child releases it before entering wait on jobserver semaphore
++  // - parent blocks on it to know when child enters wait
++  HANDLE semaphore_enter_wait_;
++  // Semaphore Parent -> Child
++  // - parent releases it to allow child to restart loop
++  // - child blocks on it to know when to restart loop
++  HANDLE semaphore_restart_;
++  // set to false if child should exit loop and terminate thread
++  bool running_;
++  // child thread
++  HANDLE child_;
++  // I/O completion port from SubprocessSet
++  HANDLE ioport_;
++
++
++  DWORD SemaphoreThread();
++  void ReleaseSemaphore(HANDLE semaphore);
++  void WaitForObject(HANDLE object);
++  static DWORD WINAPI SemaphoreThreadWrapper(LPVOID param);
++  static void NoopAPCFunc(ULONG_PTR param);
++};
++
++GNUmakeTokenPoolWin32::GNUmakeTokenPoolWin32() : semaphore_jobserver_(NULL),
++                                                 semaphore_enter_wait_(NULL),
++                                                 semaphore_restart_(NULL),
++                                                 running_(false),
++                                                 child_(NULL),
++                                                 ioport_(NULL) {
++}
++
++GNUmakeTokenPoolWin32::~GNUmakeTokenPoolWin32() {
++  Clear();
++  CloseHandle(semaphore_jobserver_);
++  semaphore_jobserver_ = NULL;
++
++  if (child_) {
++    // tell child thread to exit
++    running_ = false;
++    ReleaseSemaphore(semaphore_restart_);
++
++    // wait for child thread to exit
++    WaitForObject(child_);
++    CloseHandle(child_);
++    child_ = NULL;
++  }
++
++  if (semaphore_restart_) {
++    CloseHandle(semaphore_restart_);
++    semaphore_restart_ = NULL;
++  }
++
++  if (semaphore_enter_wait_) {
++    CloseHandle(semaphore_enter_wait_);
++    semaphore_enter_wait_ = NULL;
++  }
++}
++
++const char* GNUmakeTokenPoolWin32::GetEnv(const char* name) {
++  // getenv() does not work correctly together with tokenpool_tests.cc
++  static char buffer[MAX_PATH + 1];
++  if (GetEnvironmentVariable(name, buffer, sizeof(buffer)) == 0)
++    return NULL;
++  return buffer;
++}
++
++bool GNUmakeTokenPoolWin32::ParseAuth(const char* jobserver) {
++  // match "--jobserver-auth=gmake_semaphore_<INTEGER>..."
++  const char* start = strchr(jobserver, '=');
++  if (start) {
++    const char* end = start;
++    unsigned int len;
++    char c, *auth;
++
++    while ((c = *++end) != '\0')
++      if (!(isalnum(c) || (c == '_')))
++        break;
++    len = end - start; // includes string terminator in count
++
++    if ((len > 1) && ((auth = (char*)malloc(len)) != NULL)) {
++      strncpy(auth, start + 1, len - 1);
++      auth[len - 1] = '\0';
++
++      if ((semaphore_jobserver_ =
++           OpenSemaphore(SEMAPHORE_ALL_ACCESS, /* Semaphore access setting */
++                         FALSE,                /* Child processes DON'T inherit */
++                         auth                  /* Semaphore name */
++                        )) != NULL) {
++        free(auth);
++        return true;
++      }
++
++      free(auth);
++    }
++  }
++
++  return false;
++}
++
++bool GNUmakeTokenPoolWin32::AcquireToken() {
++  return WaitForSingleObject(semaphore_jobserver_, 0) == WAIT_OBJECT_0;
++}
++
++bool GNUmakeTokenPoolWin32::ReturnToken() {
++  ReleaseSemaphore(semaphore_jobserver_);
++  return true;
++}
++
++DWORD GNUmakeTokenPoolWin32::SemaphoreThread() {
++  while (running_) {
++    // indicate to parent that we are entering wait
++    ReleaseSemaphore(semaphore_enter_wait_);
++
++    // alertable wait forever on token semaphore
++    if (WaitForSingleObjectEx(semaphore_jobserver_, INFINITE, TRUE) == WAIT_OBJECT_0) {
++      // release token again for AcquireToken()
++      ReleaseSemaphore(semaphore_jobserver_);
++
++      // indicate to parent on ioport that a token might be available
++      if (!PostQueuedCompletionStatus(ioport_, 0, (ULONG_PTR) this, NULL))
++        Win32Fatal("PostQueuedCompletionStatus");
++    }
++
++    // wait for parent to allow loop restart
++    WaitForObject(semaphore_restart_);
++    // semaphore is now in nonsignaled state again for next run...
++  }
++
++  return 0;
++}
++
++DWORD WINAPI GNUmakeTokenPoolWin32::SemaphoreThreadWrapper(LPVOID param) {
++  GNUmakeTokenPoolWin32* This = (GNUmakeTokenPoolWin32*) param;
++  return This->SemaphoreThread();
++}
++
++void GNUmakeTokenPoolWin32::NoopAPCFunc(ULONG_PTR param) {
++}
++
++void GNUmakeTokenPoolWin32::WaitForTokenAvailability(HANDLE ioport) {
++  if (child_ == NULL) {
++    // first invocation
++    //
++    // subprocess-win32.cc uses I/O completion port (IOCP) which can't be
++    // used as a waitable object. Therefore we can't use WaitMultipleObjects()
++    // to wait on the IOCP and the token semaphore at the same time. Create
++    // a child thread that waits on the semaphore and posts an I/O completion
++    ioport_ = ioport;
++
++    // create both semaphores in nonsignaled state
++    if ((semaphore_enter_wait_ = CreateSemaphore(NULL, 0, 1, NULL))
++        == NULL)
++      Win32Fatal("CreateSemaphore/enter_wait");
++    if ((semaphore_restart_ = CreateSemaphore(NULL, 0, 1, NULL))
++        == NULL)
++      Win32Fatal("CreateSemaphore/restart");
++
++    // start child thread
++    running_ = true;
++    if ((child_ = CreateThread(NULL, 0, &SemaphoreThreadWrapper, this, 0, NULL))
++        == NULL)
++      Win32Fatal("CreateThread");
++
++  } else {
++    // all further invocations - allow child thread to loop
++    ReleaseSemaphore(semaphore_restart_);
++  }
++
++  // wait for child thread to enter wait
++  WaitForObject(semaphore_enter_wait_);
++  // semaphore is now in nonsignaled state again for next run...
++
++  // now SubprocessSet::DoWork() can enter GetQueuedCompletionStatus()...
++}
++
++bool GNUmakeTokenPoolWin32::TokenIsAvailable(ULONG_PTR key) {
++  // alert child thread to break wait on token semaphore
++  QueueUserAPC((PAPCFUNC)&NoopAPCFunc, child_, (ULONG_PTR)NULL);
++
++  // return true when GetQueuedCompletionStatus() returned our key
++  return key == (ULONG_PTR) this;
++}
++
++void GNUmakeTokenPoolWin32::ReleaseSemaphore(HANDLE semaphore) {
++  if (!::ReleaseSemaphore(semaphore, 1, NULL))
++    Win32Fatal("ReleaseSemaphore");
++}
++
++void GNUmakeTokenPoolWin32::WaitForObject(HANDLE object) {
++  if (WaitForSingleObject(object, INFINITE) != WAIT_OBJECT_0)
++    Win32Fatal("WaitForSingleObject");
++}
++
++TokenPool* TokenPool::Get() {
++  return new GNUmakeTokenPoolWin32;
++}
+--- /dev/null
++++ b/src/tokenpool-gnu-make.h
+@@ -0,0 +1,40 @@
++// Copyright 2016-2018 Google Inc. All Rights Reserved.
++//
++// Licensed under the Apache License, Version 2.0 (the "License");
++// you may not use this file except in compliance with the License.
++// You may obtain a copy of the License at
++//
++//     http://www.apache.org/licenses/LICENSE-2.0
++//
++// Unless required by applicable law or agreed to in writing, software
++// distributed under the License is distributed on an "AS IS" BASIS,
++// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
++// See the License for the specific language governing permissions and
++// limitations under the License.
++
++#include "tokenpool.h"
++
++// interface to GNU make token pool
++struct GNUmakeTokenPool : public TokenPool {
++  GNUmakeTokenPool();
++  ~GNUmakeTokenPool();
++
++  // token pool implementation
++  virtual bool Acquire();
++  virtual void Reserve();
++  virtual void Release();
++  virtual void Clear();
++  virtual bool Setup(bool ignore, bool verbose, double& max_load_average);
++
++  // platform specific implementation
++  virtual const char* GetEnv(const char* name) = 0;
++  virtual bool ParseAuth(const char* jobserver) = 0;
++  virtual bool AcquireToken() = 0;
++  virtual bool ReturnToken() = 0;
++
++ private:
++  int available_;
++  int used_;
++
++  void Return();
++};
+--- a/CMakeLists.txt
++++ b/CMakeLists.txt
+@@ -142,6 +142,7 @@ add_library(libninja OBJECT
+ 	src/state.cc
+ 	src/status.cc
+ 	src/string_piece_util.cc
++	src/tokenpool-gnu-make.cc
+ 	src/util.cc
+ 	src/version.cc
+ )
+@@ -153,13 +154,17 @@ if(WIN32)
+ 		src/msvc_helper_main-win32.cc
+ 		src/getopt.c
+ 		src/minidump-win32.cc
++		src/tokenpool-gnu-make-win32.cc
+ 	)
+ 	# Build getopt.c, which can be compiled as either C or C++, as C++
+ 	# so that build environments which lack a C compiler, but have a C++
+ 	# compiler may build ninja.
+ 	set_source_files_properties(src/getopt.c PROPERTIES LANGUAGE CXX)
+ else()
+-	target_sources(libninja PRIVATE src/subprocess-posix.cc)
++	target_sources(libninja PRIVATE
++		src/subprocess-posix.cc
++		src/tokenpool-gnu-make-posix.cc
++	)
+ 	if(CMAKE_SYSTEM_NAME STREQUAL "OS400" OR CMAKE_SYSTEM_NAME STREQUAL "AIX")
+ 		target_sources(libninja PRIVATE src/getopt.c)
+ 		# Build getopt.c, which can be compiled as either C or C++, as C++
+@@ -286,6 +291,7 @@ if(BUILD_TESTING)
+     src/string_piece_util_test.cc
+     src/subprocess_test.cc
+     src/test.cc
++    src/tokenpool_test.cc
+     src/util_test.cc
+   )
+   if(WIN32)