diff --git a/Help/manual/cmake-variables.7.rst b/Help/manual/cmake-variables.7.rst
index 181fbbcd1..ec741ae12 100644
--- a/Help/manual/cmake-variables.7.rst
+++ b/Help/manual/cmake-variables.7.rst
@@ -281,6 +281,7 @@ Variables that Control the Build
    /variable/CMAKE_MAP_IMPORTED_CONFIG_CONFIG
    /variable/CMAKE_MODULE_LINKER_FLAGS_CONFIG
    /variable/CMAKE_MODULE_LINKER_FLAGS
+   /variable/CMAKE_NINJA_OUTPUT_PATH_PREFIX
    /variable/CMAKE_NO_BUILTIN_CHRPATH
    /variable/CMAKE_NO_SYSTEM_FROM_IMPORTED
    /variable/CMAKE_OSX_ARCHITECTURES
diff --git a/Help/release/dev/ninja-output-path-prefix.rst b/Help/release/dev/ninja-output-path-prefix.rst
new file mode 100644
index 000000000..47a96603a
--- /dev/null
+++ b/Help/release/dev/ninja-output-path-prefix.rst
@@ -0,0 +1,6 @@
+ninja-output-path-prefix
+------------------------
+
+* The :generator:`Ninja` generator learned to read a new
+  :variable:`CMAKE_NINJA_OUTPUT_PATH_PREFIX` variable to configure
+  the generated ``build.ninja`` file for use as a ``subninja``.
diff --git a/Help/variable/CMAKE_NINJA_OUTPUT_PATH_PREFIX.rst b/Help/variable/CMAKE_NINJA_OUTPUT_PATH_PREFIX.rst
new file mode 100644
index 000000000..64091aaaf
--- /dev/null
+++ b/Help/variable/CMAKE_NINJA_OUTPUT_PATH_PREFIX.rst
@@ -0,0 +1,27 @@
+CMAKE_NINJA_OUTPUT_PATH_PREFIX
+------------------------------
+
+Set output files path prefix for the :generator:`Ninja` generator.
+
+Every output files listed in the generated ``build.ninja`` will be
+prefixed by the contents of this variable (a trailing slash is
+appended if missing).  This is useful when the generated ninja file is
+meant to be embedded as a ``subninja`` file into a *super* ninja
+project.  For example, a ninja build file generated with a command
+like::
+
+  cd top-build-dir/sub &&
+  cmake -G Ninja -DCMAKE_NINJA_OUTPUT_PATH_PREFIX=sub/ path/to/source
+
+can be embedded in ``top-build-dir/build.ninja`` with a directive like
+this::
+
+  subninja sub/build.ninja
+
+The ``auto-regeneration`` rule in ``top-build-dir/build.ninja`` must have an
+order-only dependency on ``sub/build.ninja``.
+
+.. note::
+  When ``CMAKE_NINJA_OUTPUT_PATH_PREFIX`` is set, the project generated
+  by CMake cannot be used as a standalone project.  No default targets
+  are specified.
diff --git a/Source/cmAlgorithms.h b/Source/cmAlgorithms.h
index 76acaca8f..ee803c8e8 100644
--- a/Source/cmAlgorithms.h
+++ b/Source/cmAlgorithms.h
@@ -379,4 +379,19 @@ std::reverse_iterator<Iter> cmMakeReverseIterator(Iter it)
   return std::reverse_iterator<Iter>(it);
 }
 
+inline bool cmHasSuffix(const std::string& str, const std::string& suffix)
+{
+  if (str.size() < suffix.size()) {
+    return false;
+  }
+  return str.compare(str.size() - suffix.size(), suffix.size(), suffix) == 0;
+}
+
+inline void cmStripSuffixIfExists(std::string& str, const std::string& suffix)
+{
+  if (cmHasSuffix(str, suffix)) {
+    str.resize(str.size() - suffix.size());
+  }
+}
+
 #endif
diff --git a/Source/cmGlobalNinjaGenerator.cxx b/Source/cmGlobalNinjaGenerator.cxx
index 012ef9010..d65b463de 100644
--- a/Source/cmGlobalNinjaGenerator.cxx
+++ b/Source/cmGlobalNinjaGenerator.cxx
@@ -488,6 +488,10 @@ void cmGlobalNinjaGenerator::Generate()
   this->OpenBuildFileStream();
   this->OpenRulesFileStream();
 
+  this->InitOutputPathPrefix();
+  this->TargetAll = this->NinjaOutputPath("all");
+  this->CMakeCacheFile = this->NinjaOutputPath("CMakeCache.txt");
+
   this->PolicyCMP0058 =
     this->LocalGenerators[0]->GetMakefile()->GetPolicyStatus(
       cmPolicies::CMP0058);
@@ -714,11 +718,29 @@ void cmGlobalNinjaGenerator::CloseRulesFileStream()
   }
 }
 
+static void EnsureTrailingSlash(std::string& path)
+{
+  if (path.empty()) {
+    return;
+  }
+  std::string::value_type last = path[path.size() - 1];
+#ifdef _WIN32
+  if (last != '\\') {
+    path += '\\';
+  }
+#else
+  if (last != '/') {
+    path += '/';
+  }
+#endif
+}
+
 std::string cmGlobalNinjaGenerator::ConvertToNinjaPath(const std::string& path)
 {
   cmLocalNinjaGenerator* ng =
     static_cast<cmLocalNinjaGenerator*>(this->LocalGenerators[0]);
   std::string convPath = ng->Convert(path, cmOutputConverter::HOME_OUTPUT);
+  convPath = this->NinjaOutputPath(convPath);
 #ifdef _WIN32
   cmSystemTools::ReplaceString(convPath, "/", "\\");
 #endif
@@ -731,6 +753,7 @@ std::string cmGlobalNinjaGenerator::ConvertToNinjaFolderRule(
   cmLocalNinjaGenerator* ng =
     static_cast<cmLocalNinjaGenerator*>(this->LocalGenerators[0]);
   std::string convPath = ng->Convert(path + "/all", cmOutputConverter::HOME);
+  convPath = this->NinjaOutputPath(convPath);
 #ifdef _WIN32
   cmSystemTools::ReplaceString(convPath, "/", "\\");
 #endif
@@ -836,22 +859,17 @@ void cmGlobalNinjaGenerator::AppendTargetOutputs(
     }
     case cmState::OBJECT_LIBRARY:
     case cmState::UTILITY: {
-      std::string path = this->ConvertToNinjaPath(
-        target->GetLocalGenerator()->GetCurrentBinaryDirectory());
-      if (path.empty() || path == ".")
-        outputs.push_back(target->GetName());
-      else {
-        path += "/";
-        path += target->GetName();
-        outputs.push_back(path);
-      }
+      std::string path =
+        target->GetLocalGenerator()->GetCurrentBinaryDirectory() +
+        std::string("/") + target->GetName();
+      outputs.push_back(this->ConvertToNinjaPath(path));
       break;
     }
 
     case cmState::GLOBAL_TARGET:
       // Always use the target in HOME instead of an unused duplicate in a
       // subdirectory.
-      outputs.push_back(target->GetName());
+      outputs.push_back(this->NinjaOutputPath(target->GetName()));
       break;
 
     default:
@@ -885,6 +903,7 @@ void cmGlobalNinjaGenerator::AppendTargetDepends(
 void cmGlobalNinjaGenerator::AddTargetAlias(const std::string& alias,
                                             cmGeneratorTarget* target)
 {
+  std::string buildAlias = this->NinjaOutputPath(alias);
   cmNinjaDeps outputs;
   this->AppendTargetOutputs(target, outputs);
   // Mark the target's outputs as ambiguous to ensure that no other target uses
@@ -895,7 +914,7 @@ void cmGlobalNinjaGenerator::AddTargetAlias(const std::string& alias,
   // Insert the alias into the map.  If the alias was already present in the
   // map and referred to another target, mark it as ambiguous.
   std::pair<TargetAliasMap::iterator, bool> newAlias =
-    TargetAliases.insert(std::make_pair(alias, target));
+    TargetAliases.insert(std::make_pair(buildAlias, target));
   if (newAlias.second && newAlias.first->second != target)
     newAlias.first->second = 0;
 }
@@ -1043,7 +1062,7 @@ void cmGlobalNinjaGenerator::WriteUnknownExplicitDependencies(std::ostream& os)
       }
     }
   }
-  knownDependencies.insert("CMakeCache.txt");
+  knownDependencies.insert(this->CMakeCacheFile);
 
   for (TargetAliasMap::const_iterator i = this->TargetAliases.begin();
        i != this->TargetAliases.end(); ++i) {
@@ -1064,7 +1083,7 @@ void cmGlobalNinjaGenerator::WriteUnknownExplicitDependencies(std::ostream& os)
   // should all match now.
 
   std::vector<std::string> unknownExplicitDepends;
-  this->CombinedCustomCommandExplicitDependencies.erase("all");
+  this->CombinedCustomCommandExplicitDependencies.erase(this->TargetAll);
 
   std::set_difference(this->CombinedCustomCommandExplicitDependencies.begin(),
                       this->CombinedCustomCommandExplicitDependencies.end(),
@@ -1130,13 +1149,15 @@ void cmGlobalNinjaGenerator::WriteBuiltinTargets(std::ostream& os)
 void cmGlobalNinjaGenerator::WriteTargetAll(std::ostream& os)
 {
   cmNinjaDeps outputs;
-  outputs.push_back("all");
+  outputs.push_back(this->TargetAll);
 
   this->WritePhonyBuild(os, "The main all target.", outputs,
                         this->AllDependencies);
 
-  cmGlobalNinjaGenerator::WriteDefault(os, outputs,
-                                       "Make the all target the default.");
+  if (!this->HasOutputPathPrefix()) {
+    cmGlobalNinjaGenerator::WriteDefault(os, outputs,
+                                         "Make the all target the default.");
+  }
 }
 
 void cmGlobalNinjaGenerator::WriteTargetRebuildManifest(std::ostream& os)
@@ -1171,7 +1192,7 @@ void cmGlobalNinjaGenerator::WriteTargetRebuildManifest(std::ostream& os)
       implicitDeps.push_back(this->ConvertToNinjaPath(*fi));
     }
   }
-  implicitDeps.push_back("CMakeCache.txt");
+  implicitDeps.push_back(this->CMakeCacheFile);
 
   std::sort(implicitDeps.begin(), implicitDeps.end());
   implicitDeps.erase(std::unique(implicitDeps.begin(), implicitDeps.end()),
@@ -1184,9 +1205,10 @@ void cmGlobalNinjaGenerator::WriteTargetRebuildManifest(std::ostream& os)
     variables["pool"] = "console";
   }
 
+  std::string const ninjaBuildFile = this->NinjaOutputPath(NINJA_BUILD_FILE);
   this->WriteBuild(os, "Re-run CMake if any of its inputs changed.",
                    "RERUN_CMAKE",
-                   /*outputs=*/cmNinjaDeps(1, NINJA_BUILD_FILE),
+                   /*outputs=*/cmNinjaDeps(1, ninjaBuildFile),
                    /*explicitDeps=*/cmNinjaDeps(), implicitDeps,
                    /*orderOnlyDeps=*/cmNinjaDeps(), variables);
 
@@ -1223,7 +1245,7 @@ void cmGlobalNinjaGenerator::WriteTargetClean(std::ostream& os)
             /*restat=*/"",
             /*generator=*/false);
   WriteBuild(os, "Clean all the built files.", "CLEAN",
-             /*outputs=*/cmNinjaDeps(1, "clean"),
+             /*outputs=*/cmNinjaDeps(1, this->NinjaOutputPath("clean")),
              /*explicitDeps=*/cmNinjaDeps(),
              /*implicitDeps=*/cmNinjaDeps(),
              /*orderOnlyDeps=*/cmNinjaDeps(),
@@ -1242,9 +1264,35 @@ void cmGlobalNinjaGenerator::WriteTargetHelp(std::ostream& os)
             /*restat=*/"",
             /*generator=*/false);
   WriteBuild(os, "Print all primary targets available.", "HELP",
-             /*outputs=*/cmNinjaDeps(1, "help"),
+             /*outputs=*/cmNinjaDeps(1, this->NinjaOutputPath("help")),
              /*explicitDeps=*/cmNinjaDeps(),
              /*implicitDeps=*/cmNinjaDeps(),
              /*orderOnlyDeps=*/cmNinjaDeps(),
              /*variables=*/cmNinjaVars());
 }
+
+void cmGlobalNinjaGenerator::InitOutputPathPrefix()
+{
+  this->OutputPathPrefix =
+    this->LocalGenerators[0]->GetMakefile()->GetSafeDefinition(
+      "CMAKE_NINJA_OUTPUT_PATH_PREFIX");
+  EnsureTrailingSlash(this->OutputPathPrefix);
+}
+
+std::string cmGlobalNinjaGenerator::NinjaOutputPath(std::string const& path)
+{
+  if (!this->HasOutputPathPrefix() || cmSystemTools::FileIsFullPath(path)) {
+    return path;
+  }
+  return this->OutputPathPrefix + path;
+}
+
+void cmGlobalNinjaGenerator::StripNinjaOutputPathPrefixAsSuffix(
+  std::string& path)
+{
+  if (path.empty()) {
+    return;
+  }
+  EnsureTrailingSlash(path);
+  cmStripSuffixIfExists(path, this->OutputPathPrefix);
+}
diff --git a/Source/cmGlobalNinjaGenerator.h b/Source/cmGlobalNinjaGenerator.h
index 881104fa9..6d9bfe835 100644
--- a/Source/cmGlobalNinjaGenerator.h
+++ b/Source/cmGlobalNinjaGenerator.h
@@ -314,6 +314,10 @@ public:
   static std::string RequiredNinjaVersionForConsolePool() { return "1.5"; }
   bool SupportsConsolePool() const;
 
+  std::string NinjaOutputPath(std::string const& path);
+  bool HasOutputPathPrefix() const { return !this->OutputPathPrefix.empty(); }
+  void StripNinjaOutputPathPrefixAsSuffix(std::string& path);
+
 protected:
   virtual void Generate();
 
@@ -397,6 +401,13 @@ private:
 
   std::string NinjaCommand;
   std::string NinjaVersion;
+
+private:
+  void InitOutputPathPrefix();
+
+  std::string OutputPathPrefix;
+  std::string TargetAll;
+  std::string CMakeCacheFile;
 };
 
 #endif // ! cmGlobalNinjaGenerator_h
diff --git a/Source/cmLocalNinjaGenerator.cxx b/Source/cmLocalNinjaGenerator.cxx
index 671d8a089..c7e1a90f8 100644
--- a/Source/cmLocalNinjaGenerator.cxx
+++ b/Source/cmLocalNinjaGenerator.cxx
@@ -123,7 +123,8 @@ cmGlobalNinjaGenerator* cmLocalNinjaGenerator::GetGlobalNinjaGenerator()
 std::string cmLocalNinjaGenerator::ConvertToLinkReference(
   std::string const& lib, OutputFormat format)
 {
-  return this->Convert(lib, HOME_OUTPUT, format);
+  std::string path = this->GetGlobalNinjaGenerator()->ConvertToNinjaPath(lib);
+  return this->ConvertToOutputFormat(path, format);
 }
 
 std::string cmLocalNinjaGenerator::ConvertToIncludeReference(
@@ -224,8 +225,13 @@ void cmLocalNinjaGenerator::WriteNinjaFilesInclusion(std::ostream& os)
   cmGlobalNinjaGenerator::WriteDivider(os);
   os << "# Include auxiliary files.\n"
      << "\n";
-  cmGlobalNinjaGenerator::WriteInclude(
-    os, cmGlobalNinjaGenerator::NINJA_RULES_FILE, "Include rules file.");
+  cmGlobalNinjaGenerator* ng = this->GetGlobalNinjaGenerator();
+  std::string const ninjaRulesFile =
+    ng->NinjaOutputPath(cmGlobalNinjaGenerator::NINJA_RULES_FILE);
+  std::string const rulesFilePath =
+    ng->EncodeIdent(ng->EncodePath(ninjaRulesFile), os);
+  cmGlobalNinjaGenerator::WriteInclude(os, rulesFilePath,
+                                       "Include rules file.");
   os << "\n";
 }
 
diff --git a/Source/cmNinjaNormalTargetGenerator.cxx b/Source/cmNinjaNormalTargetGenerator.cxx
index 831d44b9b..8d7a89272 100644
--- a/Source/cmNinjaNormalTargetGenerator.cxx
+++ b/Source/cmNinjaNormalTargetGenerator.cxx
@@ -652,7 +652,8 @@ void cmNinjaNormalTargetGenerator::WriteLinkStatement()
         cmNinjaDeps(1, targetOutputReal), emptyDeps, emptyDeps, symlinkVars);
     } else {
       cmNinjaDeps symlinks;
-      const std::string soName = this->GetTargetFilePath(this->TargetNameSO);
+      std::string const soName =
+        this->ConvertToNinjaPath(this->GetTargetFilePath(this->TargetNameSO));
       // If one link has to be created.
       if (targetOutputReal == soName || targetOutput == soName) {
         symlinkVars["SONAME"] = soName;
diff --git a/Source/cmNinjaTargetGenerator.cxx b/Source/cmNinjaTargetGenerator.cxx
index c214c8a4a..4d58242a5 100644
--- a/Source/cmNinjaTargetGenerator.cxx
+++ b/Source/cmNinjaTargetGenerator.cxx
@@ -521,8 +521,10 @@ void cmNinjaTargetGenerator::WriteObjectBuildStatement(
   std::string const language = source->GetLanguage();
   std::string const sourceFileName =
     language == "RC" ? source->GetFullPath() : this->GetSourceFilePath(source);
-  std::string const objectDir = this->GeneratorTarget->GetSupportDirectory();
-  std::string const objectFileName = this->GetObjectFilePath(source);
+  std::string const objectDir =
+    this->ConvertToNinjaPath(this->GeneratorTarget->GetSupportDirectory());
+  std::string const objectFileName =
+    this->ConvertToNinjaPath(this->GetObjectFilePath(source));
   std::string const objectFileDir =
     cmSystemTools::GetFilenamePath(objectFileName);
 
@@ -582,9 +584,9 @@ void cmNinjaTargetGenerator::WriteObjectBuildStatement(
   EnsureParentDirectoryExists(objectFileName);
 
   vars["OBJECT_DIR"] = this->GetLocalGenerator()->ConvertToOutputFormat(
-    ConvertToNinjaPath(objectDir), cmLocalGenerator::SHELL);
+    objectDir, cmLocalGenerator::SHELL);
   vars["OBJECT_FILE_DIR"] = this->GetLocalGenerator()->ConvertToOutputFormat(
-    ConvertToNinjaPath(objectFileDir), cmLocalGenerator::SHELL);
+    objectFileDir, cmLocalGenerator::SHELL);
 
   this->addPoolNinjaVariable("JOB_POOL_COMPILE", this->GetGeneratorTarget(),
                              vars);
@@ -667,10 +669,12 @@ void cmNinjaTargetGenerator::EnsureDirectoryExists(
   if (cmSystemTools::FileIsFullPath(path.c_str())) {
     cmSystemTools::MakeDirectory(path.c_str());
   } else {
-    const std::string fullPath = std::string(this->GetGlobalGenerator()
-                                               ->GetCMakeInstance()
-                                               ->GetHomeOutputDirectory()) +
-      "/" + path;
+    cmGlobalNinjaGenerator* gg = this->GetGlobalGenerator();
+    std::string fullPath =
+      std::string(gg->GetCMakeInstance()->GetHomeOutputDirectory());
+    // Also ensures their is a trailing slash.
+    gg->StripNinjaOutputPathPrefixAsSuffix(fullPath);
+    fullPath += path;
     cmSystemTools::MakeDirectory(fullPath.c_str());
   }
 }
diff --git a/Source/cmNinjaUtilityTargetGenerator.cxx b/Source/cmNinjaUtilityTargetGenerator.cxx
index b0b11476e..d07341c80 100644
--- a/Source/cmNinjaUtilityTargetGenerator.cxx
+++ b/Source/cmNinjaUtilityTargetGenerator.cxx
@@ -33,6 +33,8 @@ void cmNinjaUtilityTargetGenerator::Generate()
 {
   std::string utilCommandName = cmake::GetCMakeFilesDirectoryPostSlash();
   utilCommandName += this->GetTargetName() + ".util";
+  utilCommandName =
+    this->GetGlobalGenerator()->NinjaOutputPath(utilCommandName);
 
   std::vector<std::string> commands;
   cmNinjaDeps deps, outputs, util_outputs(1, utilCommandName);
diff --git a/Tests/RunCMake/Ninja/CheckNoPrefixSubDir.cmake b/Tests/RunCMake/Ninja/CheckNoPrefixSubDir.cmake
new file mode 100644
index 000000000..b845f2f4a
--- /dev/null
+++ b/Tests/RunCMake/Ninja/CheckNoPrefixSubDir.cmake
@@ -0,0 +1,7 @@
+add_custom_target(check_no_prefix_sub_dir ALL
+  COMMAND "${CMAKE_COMMAND}"
+          "-DNINJA_OUTPUT_PATH_PREFIX=${CMAKE_NINJA_OUTPUT_PATH_PREFIX}"
+          "-DCUR_BIN_DIR=${CMAKE_CURRENT_BINARY_DIR}"
+          -P "${CMAKE_CURRENT_SOURCE_DIR}/CheckNoPrefixSubDirScript.cmake"
+  VERBATIM
+  )
diff --git a/Tests/RunCMake/Ninja/CheckNoPrefixSubDirScript.cmake b/Tests/RunCMake/Ninja/CheckNoPrefixSubDirScript.cmake
new file mode 100644
index 000000000..5a03fcb7e
--- /dev/null
+++ b/Tests/RunCMake/Ninja/CheckNoPrefixSubDirScript.cmake
@@ -0,0 +1,8 @@
+# Check that the prefix sub-directory is not repeated.
+
+if(EXISTS "${CUR_BIN_DIR}/${NINJA_OUTPUT_PATH_PREFIX}")
+  message(FATAL_ERROR
+    "no sub directory named after the CMAKE_NINJA_OUTPUT_PATH_PREFIX "
+    "should be in the binary directory."
+    )
+endif()
diff --git a/Tests/RunCMake/Ninja/CheckOutput.cmake b/Tests/RunCMake/Ninja/CheckOutput.cmake
new file mode 100644
index 000000000..ddb35a75e
--- /dev/null
+++ b/Tests/RunCMake/Ninja/CheckOutput.cmake
@@ -0,0 +1,23 @@
+# Add rules to check the generated executable works.
+
+set(hello_output "${CMAKE_CURRENT_BINARY_DIR}/hello.output")
+add_custom_command(
+  OUTPUT "${hello_output}"
+  COMMAND "$<TARGET_FILE:hello>" > "${hello_output}"
+  DEPENDS hello
+  VERBATIM
+  )
+
+if(NOT DEFINED HELLO_OUTPUT_STRING)
+  set(HELLO_OUTPUT_STRING "Hello world!\n")
+endif()
+
+set(hello_output_ref "${CMAKE_CURRENT_BINARY_DIR}/hello.output.ref")
+file(WRITE "${hello_output_ref}" "${HELLO_OUTPUT_STRING}")
+
+add_custom_target(check_output ALL
+  COMMAND "${CMAKE_COMMAND}" -E compare_files
+          "${hello_output}" "${hello_output_ref}"
+  DEPENDS "${hello_output}" "${hello_output_ref}"
+  VERBATIM
+  )
diff --git a/Tests/RunCMake/Ninja/CustomCommandWorkingDirectory.cmake b/Tests/RunCMake/Ninja/CustomCommandWorkingDirectory.cmake
new file mode 100644
index 000000000..8e01c8c65
--- /dev/null
+++ b/Tests/RunCMake/Ninja/CustomCommandWorkingDirectory.cmake
@@ -0,0 +1,13 @@
+cmake_minimum_required(VERSION 3.5)
+project(hello NONE)
+
+add_custom_command(
+  OUTPUT hello.copy.c
+  COMMAND "${CMAKE_COMMAND}" -E copy
+          "${CMAKE_CURRENT_SOURCE_DIR}/hello.c"
+          hello.copy.c
+  WORKING_DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}"
+  )
+add_custom_target(copy ALL DEPENDS "${CMAKE_CURRENT_BINARY_DIR}/hello.copy.c")
+
+include(CheckNoPrefixSubDir.cmake)
diff --git a/Tests/RunCMake/Ninja/Executable.cmake b/Tests/RunCMake/Ninja/Executable.cmake
new file mode 100644
index 000000000..4e17d6889
--- /dev/null
+++ b/Tests/RunCMake/Ninja/Executable.cmake
@@ -0,0 +1,5 @@
+cmake_minimum_required(VERSION 3.5)
+project(hello C)
+add_executable(hello hello.c)
+include(CheckOutput.cmake)
+include(CheckNoPrefixSubDir.cmake)
diff --git a/Tests/RunCMake/Ninja/RunCMakeTest.cmake b/Tests/RunCMake/Ninja/RunCMakeTest.cmake
index 4e068882d..c73f852ae 100644
--- a/Tests/RunCMake/Ninja/RunCMakeTest.cmake
+++ b/Tests/RunCMake/Ninja/RunCMakeTest.cmake
@@ -1,5 +1,20 @@
 include(RunCMake)
 
+# Detect ninja version so we know what tests can be supported.
+execute_process(
+  COMMAND "${RunCMake_MAKE_PROGRAM}" --version
+  OUTPUT_VARIABLE ninja_out
+  ERROR_VARIABLE ninja_out
+  RESULT_VARIABLE ninja_res
+  OUTPUT_STRIP_TRAILING_WHITESPACE
+  )
+if(ninja_res EQUAL 0 AND "x${ninja_out}" MATCHES "^x[0-9]+\\.[0-9]+")
+  set(ninja_version "${ninja_out}")
+  message(STATUS "ninja version: ${ninja_version}")
+else()
+  message(FATAL_ERROR "'ninja --version' reported:\n${ninja_out}")
+endif()
+
 function(run_CMP0058 case)
   # Use a single build tree for a few tests without cleaning.
   set(RunCMake_TEST_BINARY_DIR ${RunCMake_BINARY_DIR}/CMP0058-${case}-build)
@@ -32,3 +47,153 @@ function(run_SubDir)
   run_cmake_command(SubDir-build ${CMAKE_COMMAND} --build . --target ${SubDir_all})
 endfunction()
 run_SubDir()
+
+function(run_ninja dir)
+  execute_process(
+    COMMAND "${RunCMake_MAKE_PROGRAM}"
+    WORKING_DIRECTORY "${dir}"
+    OUTPUT_VARIABLE ninja_stdout
+    ERROR_VARIABLE ninja_stderr
+    RESULT_VARIABLE ninja_result
+    )
+  if(NOT ninja_result EQUAL 0)
+    message(STATUS "
+============ beginning of ninja's stdout ============
+${ninja_stdout}
+=============== end of ninja's stdout ===============
+")
+    message(STATUS "
+============ beginning of ninja's stderr ============
+${ninja_stderr}
+=============== end of ninja's stderr ===============
+")
+    message(FATAL_ERROR
+      "top ninja build failed exited with status ${ninja_result}")
+  endif()
+endfunction(run_ninja)
+
+function(sleep delay)
+  execute_process(
+    COMMAND ${CMAKE_COMMAND} -E sleep ${delay}
+    RESULT_VARIABLE result
+    )
+  if(NOT result EQUAL 0)
+    message(FATAL_ERROR "failed to sleep for ${delay} second.")
+  endif()
+endfunction(sleep)
+
+function(touch path)
+  execute_process(
+    COMMAND ${CMAKE_COMMAND} -E touch ${path}
+    RESULT_VARIABLE result
+    )
+  if(NOT result EQUAL 0)
+    message(FATAL_ERROR "failed to touch main ${path} file.")
+  endif()
+endfunction(touch)
+
+macro(ninja_escape_path path out)
+  string(REPLACE "\$ " "\$\$" "${out}" "${path}")
+  string(REPLACE " " "\$ " "${out}" "${${out}}")
+  string(REPLACE ":" "\$:" "${out}" "${${out}}")
+endmacro(ninja_escape_path)
+
+macro(shell_escape string out)
+  string(REPLACE "\"" "\\\"" "${out}" "${string}")
+endmacro(shell_escape)
+
+function(run_sub_cmake test ninja_output_path_prefix)
+  set(top_build_dir "${RunCMake_BINARY_DIR}/${test}-build/")
+  file(REMOVE_RECURSE "${top_build_dir}")
+  file(MAKE_DIRECTORY "${top_build_dir}")
+
+  ninja_escape_path("${ninja_output_path_prefix}"
+    escaped_ninja_output_path_prefix)
+
+  # Generate top build ninja file.
+  set(top_build_ninja "${top_build_dir}/build.ninja")
+  shell_escape("${top_build_ninja}" escaped_top_build_ninja)
+  set(build_ninja_dep "${top_build_dir}/build_ninja_dep")
+  ninja_escape_path("${build_ninja_dep}" escaped_build_ninja_dep)
+  shell_escape("${CMAKE_COMMAND}" escaped_CMAKE_COMMAND)
+  file(WRITE "${build_ninja_dep}" "fake dependency of top build.ninja file\n")
+  if(WIN32)
+    set(cmd_prefix "cmd.exe /C \"")
+    set(cmd_suffix "\"")
+  else()
+    set(cmd_prefix "")
+    set(cmd_suffix "")
+  endif()
+  file(WRITE "${top_build_ninja}" "\
+subninja ${escaped_ninja_output_path_prefix}/build.ninja
+default ${escaped_ninja_output_path_prefix}/all
+
+# Sleep for 1 second before to regenerate to make sure the timestamp of
+# the top build.ninja will be strictly greater than the timestamp of the
+# sub/build.ninja file. We assume the system as 1 sec timestamp resolution.
+rule RERUN
+  command = ${cmd_prefix}\"${escaped_CMAKE_COMMAND}\" -E sleep 1 && \"${escaped_CMAKE_COMMAND}\" -E touch \"${escaped_top_build_ninja}\"${cmd_suffix}
+  description = Testing regeneration
+  generator = 1
+
+build build.ninja: RERUN ${escaped_build_ninja_dep} || ${escaped_ninja_output_path_prefix}/build.ninja
+  pool = console
+")
+
+  # Run sub cmake project.
+  set(RunCMake_TEST_OPTIONS "-DCMAKE_NINJA_OUTPUT_PATH_PREFIX=${ninja_output_path_prefix}")
+  set(RunCMake_TEST_BINARY_DIR "${top_build_dir}/${ninja_output_path_prefix}")
+  run_cmake(${test})
+
+  # Check there is no 'default' statement in Ninja file generated by CMake.
+  set(sub_build_ninja "${RunCMake_TEST_BINARY_DIR}/build.ninja")
+  file(READ "${sub_build_ninja}" sub_build_ninja_file)
+  if(sub_build_ninja_file MATCHES "\ndefault [^\n][^\n]*all\n")
+    message(FATAL_ERROR
+      "unexpected 'default' statement found in '${sub_build_ninja}'")
+  endif()
+
+  # Run ninja from the top build directory.
+  run_ninja("${top_build_dir}")
+
+  # Test regeneration rules run in order.
+  set(main_cmakelists "${RunCMake_SOURCE_DIR}/CMakeLists.txt")
+  sleep(1) # Assume the system as 1 sec timestamp resolution.
+  touch("${main_cmakelists}")
+  touch("${build_ninja_dep}")
+  run_ninja("${top_build_dir}")
+  file(TIMESTAMP "${main_cmakelists}" mtime_main_cmakelists UTC)
+  file(TIMESTAMP "${sub_build_ninja}" mtime_sub_build_ninja UTC)
+  file(TIMESTAMP "${top_build_ninja}" mtime_top_build_ninja UTC)
+
+  # Check sub build.ninja is regenerated.
+  if(mtime_main_cmakelists STRGREATER mtime_sub_build_ninja)
+    message(FATAL_ERROR
+      "sub build.ninja not regenerated:
+  CMakeLists.txt  = ${mtime_main_cmakelists}
+  sub/build.ninja = ${mtime_sub_build_ninja}")
+  endif()
+
+  # Check top build.ninja is regenerated after sub build.ninja.
+  if(NOT mtime_top_build_ninja STRGREATER mtime_sub_build_ninja)
+    message(FATAL_ERROR
+      "top build.ninja not regenerated strictly after sub build.ninja:
+  sub/build.ninja = ${mtime_sub_build_ninja}
+  build.ninja     = ${mtime_top_build_ninja}")
+  endif()
+
+endfunction(run_sub_cmake)
+
+if("${ninja_version}" VERSION_LESS 1.6)
+  message(WARNING "Ninja is too old; skipping rest of test.")
+  return()
+endif()
+
+foreach(ninja_output_path_prefix "sub space" "sub")
+  run_sub_cmake(Executable "${ninja_output_path_prefix}")
+  run_sub_cmake(StaticLib  "${ninja_output_path_prefix}")
+  run_sub_cmake(SharedLib "${ninja_output_path_prefix}")
+  run_sub_cmake(TwoLibs "${ninja_output_path_prefix}")
+  run_sub_cmake(SubDirPrefix "${ninja_output_path_prefix}")
+  run_sub_cmake(CustomCommandWorkingDirectory "${ninja_output_path_prefix}")
+endforeach(ninja_output_path_prefix)
diff --git a/Tests/RunCMake/Ninja/SharedLib.cmake b/Tests/RunCMake/Ninja/SharedLib.cmake
new file mode 100644
index 000000000..1a78390e3
--- /dev/null
+++ b/Tests/RunCMake/Ninja/SharedLib.cmake
@@ -0,0 +1,8 @@
+cmake_minimum_required(VERSION 3.5)
+project(hello C)
+add_library(greeting SHARED greeting.c)
+include_directories(${CMAKE_CURRENT_SOURCE_DIR})
+add_executable(hello hello_with_greeting.c)
+target_link_libraries(hello greeting)
+include(CheckOutput.cmake)
+include(CheckNoPrefixSubDir.cmake)
diff --git a/Tests/RunCMake/Ninja/StaticLib.cmake b/Tests/RunCMake/Ninja/StaticLib.cmake
new file mode 100644
index 000000000..0f815ae5e
--- /dev/null
+++ b/Tests/RunCMake/Ninja/StaticLib.cmake
@@ -0,0 +1,9 @@
+cmake_minimum_required(VERSION 3.5)
+project(hello C)
+add_definitions(-DGREETING_STATIC)
+add_library(greeting STATIC greeting.c)
+include_directories(${CMAKE_CURRENT_SOURCE_DIR})
+add_executable(hello hello_with_greeting.c)
+target_link_libraries(hello greeting)
+include(CheckOutput.cmake)
+include(CheckNoPrefixSubDir.cmake)
diff --git a/Tests/RunCMake/Ninja/SubDirPrefix.cmake b/Tests/RunCMake/Ninja/SubDirPrefix.cmake
new file mode 100644
index 000000000..30ad1e607
--- /dev/null
+++ b/Tests/RunCMake/Ninja/SubDirPrefix.cmake
@@ -0,0 +1,8 @@
+cmake_minimum_required(VERSION 3.5)
+project(hello C)
+set(CMAKE_RUNTIME_OUTPUT_DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}/bin")
+add_subdirectory(SubDirPrefix)
+include_directories(${CMAKE_CURRENT_SOURCE_DIR})
+add_executable(hello hello_sub_greeting.c)
+target_link_libraries(hello greeting)
+include(CheckOutput.cmake)
diff --git a/Tests/RunCMake/Ninja/SubDirPrefix/CMakeLists.txt b/Tests/RunCMake/Ninja/SubDirPrefix/CMakeLists.txt
new file mode 100644
index 000000000..575597d48
--- /dev/null
+++ b/Tests/RunCMake/Ninja/SubDirPrefix/CMakeLists.txt
@@ -0,0 +1,2 @@
+add_library(greeting SHARED greeting.c)
+include_directories(${CMAKE_CURRENT_SOURCE_DIR})
diff --git a/Tests/RunCMake/Ninja/SubDirPrefix/greeting.c b/Tests/RunCMake/Ninja/SubDirPrefix/greeting.c
new file mode 100644
index 000000000..ba3e55beb
--- /dev/null
+++ b/Tests/RunCMake/Ninja/SubDirPrefix/greeting.c
@@ -0,0 +1,9 @@
+#include <stdio.h>
+
+#if defined(_WIN32) && !defined(GREETING_STATIC)
+__declspec(dllexport)
+#endif
+  void greeting(void)
+{
+  printf("Hello world!\n");
+}
diff --git a/Tests/RunCMake/Ninja/SubDirPrefix/greeting.h b/Tests/RunCMake/Ninja/SubDirPrefix/greeting.h
new file mode 100644
index 000000000..ee4053ef7
--- /dev/null
+++ b/Tests/RunCMake/Ninja/SubDirPrefix/greeting.h
@@ -0,0 +1,4 @@
+#if defined(_WIN32) && !defined(GREETING_STATIC)
+__declspec(dllimport)
+#endif
+  void greeting(void);
diff --git a/Tests/RunCMake/Ninja/TwoLibs.cmake b/Tests/RunCMake/Ninja/TwoLibs.cmake
new file mode 100644
index 000000000..666452f34
--- /dev/null
+++ b/Tests/RunCMake/Ninja/TwoLibs.cmake
@@ -0,0 +1,17 @@
+cmake_minimum_required(VERSION 3.5)
+project(hello C)
+
+set(CMAKE_RUNTIME_OUTPUT_DIRECTORY "${CMAKE_BINARY_DIR}/bin")
+set(CMAKE_ARCHIVE_OUTPUT_DIRECTORY "${CMAKE_BINARY_DIR}/lib-static")
+set(CMAKE_LIBRARY_OUTPUT_DIRECTORY "${CMAKE_BINARY_DIR}/lib")
+
+add_library(greeting SHARED greeting.c)
+add_library(greeting2 STATIC greeting2.c)
+include_directories(${CMAKE_CURRENT_SOURCE_DIR})
+add_executable(hello hello_with_two_greetings.c)
+target_link_libraries(hello greeting greeting2)
+
+set(HELLO_OUTPUT_STRING "Hello world!\nHello world 2!\n")
+include(CheckOutput.cmake)
+
+include(CheckNoPrefixSubDir.cmake)
diff --git a/Tests/RunCMake/Ninja/greeting.c b/Tests/RunCMake/Ninja/greeting.c
new file mode 100644
index 000000000..ba3e55beb
--- /dev/null
+++ b/Tests/RunCMake/Ninja/greeting.c
@@ -0,0 +1,9 @@
+#include <stdio.h>
+
+#if defined(_WIN32) && !defined(GREETING_STATIC)
+__declspec(dllexport)
+#endif
+  void greeting(void)
+{
+  printf("Hello world!\n");
+}
diff --git a/Tests/RunCMake/Ninja/greeting.h b/Tests/RunCMake/Ninja/greeting.h
new file mode 100644
index 000000000..ee4053ef7
--- /dev/null
+++ b/Tests/RunCMake/Ninja/greeting.h
@@ -0,0 +1,4 @@
+#if defined(_WIN32) && !defined(GREETING_STATIC)
+__declspec(dllimport)
+#endif
+  void greeting(void);
diff --git a/Tests/RunCMake/Ninja/greeting2.c b/Tests/RunCMake/Ninja/greeting2.c
new file mode 100644
index 000000000..c6ed87daa
--- /dev/null
+++ b/Tests/RunCMake/Ninja/greeting2.c
@@ -0,0 +1,6 @@
+#include <stdio.h>
+
+void greeting2(void)
+{
+  printf("Hello world 2!\n");
+}
diff --git a/Tests/RunCMake/Ninja/greeting2.h b/Tests/RunCMake/Ninja/greeting2.h
new file mode 100644
index 000000000..c4d8f9b29
--- /dev/null
+++ b/Tests/RunCMake/Ninja/greeting2.h
@@ -0,0 +1 @@
+void greeting2(void);
diff --git a/Tests/RunCMake/Ninja/hello.c b/Tests/RunCMake/Ninja/hello.c
new file mode 100644
index 000000000..aac8b4e0f
--- /dev/null
+++ b/Tests/RunCMake/Ninja/hello.c
@@ -0,0 +1,7 @@
+#include <stdio.h>
+
+int main(void)
+{
+  printf("Hello world!\n");
+  return 0;
+}
diff --git a/Tests/RunCMake/Ninja/hello_sub_greeting.c b/Tests/RunCMake/Ninja/hello_sub_greeting.c
new file mode 100644
index 000000000..fc4bd60f1
--- /dev/null
+++ b/Tests/RunCMake/Ninja/hello_sub_greeting.c
@@ -0,0 +1,7 @@
+#include <SubDirPrefix/greeting.h>
+
+int main(void)
+{
+  greeting();
+  return 0;
+}
diff --git a/Tests/RunCMake/Ninja/hello_with_greeting.c b/Tests/RunCMake/Ninja/hello_with_greeting.c
new file mode 100644
index 000000000..dbf90e314
--- /dev/null
+++ b/Tests/RunCMake/Ninja/hello_with_greeting.c
@@ -0,0 +1,7 @@
+#include <greeting.h>
+
+int main(void)
+{
+  greeting();
+  return 0;
+}
diff --git a/Tests/RunCMake/Ninja/hello_with_two_greetings.c b/Tests/RunCMake/Ninja/hello_with_two_greetings.c
new file mode 100644
index 000000000..cbbdaadc0
--- /dev/null
+++ b/Tests/RunCMake/Ninja/hello_with_two_greetings.c
@@ -0,0 +1,9 @@
+#include <greeting.h>
+#include <greeting2.h>
+
+int main(void)
+{
+  greeting();
+  greeting2();
+  return 0;
+}