cmake: Allow arbitrary args passed to CMake script

Help/manual/cmake.1.rst

@@ -481,13 +481,17 @@ Run a Script
 
 .. code-block:: shell
 
-  cmake [{-D <var>=<value>}...] -P <cmake-script-file>
+  cmake [{-D <var>=<value>}...] -P <cmake-script-file> [-- <unparsed-options>...]
 
 Process the given cmake file as a script written in the CMake
 language.  No configure or generate step is performed and the cache
 is not modified.  If variables are defined using ``-D``, this must be
 done before the ``-P`` argument.
 
+Any options after ``--`` are not parsed by CMake, but they are still included
+in the set of :variable:`CMAKE_ARGV<n> <CMAKE_ARGV0>` variables passed to the
+script (including the ``--`` itself).
+
 
 Run a Command-Line Tool
 =======================

Source/cmake.cxx

@@ -289,7 +289,8 @@ void cmake::CleanupCommandsAndMacros()
 // Parse the args
 bool cmake::SetCacheArgs(const std::vector<std::string>& args)
 {
-  bool findPackageMode = false;
+  auto findPackageMode = false;
+  auto seenScriptOption = false;
   for (unsigned int i = 1; i < args.size(); ++i) {
     std::string const& arg = args[i];
     if (cmHasLiteralPrefix(arg, "-D")) {
@@ -444,6 +445,11 @@ bool cmake::SetCacheArgs(const std::vector<std::string>& args)
       this->SetHomeOutputDirectory(
         cmSystemTools::GetCurrentWorkingDirectory());
       this->ReadListFile(args, path);
+      seenScriptOption = true;
+    } else if (arg == "--" && seenScriptOption) {
+      // Stop processing CMake args and avoid possible errors
+      // when arbitrary args are given to CMake script.
+      break;
     } else if (cmHasLiteralPrefix(arg, "--find-package")) {
       findPackageMode = true;
     }

Tests/RunCMake/CommandLine/P_arbitrary_args.cmake

@@ -0,0 +1,3 @@
+if(NOT ("${CMAKE_ARGV3}" STREQUAL "--" AND "${CMAKE_ARGV4}" STREQUAL "-DFOO"))
+    message(FATAL_ERROR "`-DFOO` shouldn't trigger an error after `--`")
+endif()

Tests/RunCMake/CommandLine/RunCMakeTest.cmake

@@ -46,6 +46,7 @@ run_cmake_command(G_no-arg ${CMAKE_COMMAND} -B DummyBuildDir -G)
 run_cmake_command(G_bad-arg ${CMAKE_COMMAND} -B DummyBuildDir -G NoSuchGenerator)
 run_cmake_command(P_no-arg ${CMAKE_COMMAND} -P)
 run_cmake_command(P_no-file ${CMAKE_COMMAND} -P nosuchscriptfile.cmake)
+run_cmake_command(P_arbitrary_args ${CMAKE_COMMAND} -P "${RunCMake_SOURCE_DIR}/P_arbitrary_args.cmake" -- -DFOO)
 
 run_cmake_command(build-no-dir
   ${CMAKE_COMMAND} --build)