Tests: Optionally configure tests exclusively, with an external CMake

Add an undocumented CMake_TEST_EXTERNAL_CMAKE option to name an external
CMake 'bin' directory.  Skip all main CMake binary builds and instead
configure the Tests directory to run using the external CMake provided.
This will provide a means to exercise the CMake test suite generating
for target platforms and compilers with which the CMake source does not
build.  That will allow us to raise the level of C++ features required
of a compiler to build our source while retaining tests for generating
projects with older compiler tools.

CMakeLists.txt

@@ -21,7 +21,9 @@ if(CMAKE_BOOTSTRAP)
   unset(CMAKE_BOOTSTRAP CACHE)
 endif()
 
+if(NOT CMake_TEST_EXTERNAL_CMAKE)
   set(CMake_BIN_DIR ${CMake_BINARY_DIR}/bin)
+endif()
 
 if("${CMake_SOURCE_DIR}" STREQUAL "${CMAKE_SOURCE_DIR}")
   # Disallow architecture-specific try_run.  It may not run on the host.
@@ -102,10 +104,12 @@ endmacro()
 
 
 
+if(NOT CMake_TEST_EXTERNAL_CMAKE)
   set(CMAKE_BUILD_ON_VISUAL_STUDIO 0)
   if(WIN32 AND NOT UNIX AND NOT BORLAND AND NOT MINGW )
     set(CMAKE_BUILD_ON_VISUAL_STUDIO 1)
   endif()
+endif()
 
 
 #-----------------------------------------------------------------------
@@ -126,10 +130,20 @@ macro(CMAKE_SETUP_TESTING)
     # the ctest from this cmake is used for testing
     # and not the ctest from the cmake building and testing
     # cmake.
+    if(CMake_TEST_EXTERNAL_CMAKE)
+      set(CMAKE_CTEST_COMMAND "${CMake_TEST_EXTERNAL_CMAKE}/ctest")
+      set(CMAKE_CMAKE_COMMAND "${CMake_TEST_EXTERNAL_CMAKE}/cmake")
+      set(CMAKE_CPACK_COMMAND "${CMake_TEST_EXTERNAL_CMAKE}/cpack")
+      foreach(exe cmake ctest cpack)
+        add_executable(${exe} IMPORTED)
+        set_property(TARGET ${exe} PROPERTY IMPORTED_LOCATION ${CMake_TEST_EXTERNAL_CMAKE}/${exe})
+      endforeach()
+    else()
       set(CMAKE_CTEST_COMMAND "${CMake_BIN_DIR}/ctest")
       set(CMAKE_CMAKE_COMMAND "${CMake_BIN_DIR}/cmake")
       set(CMAKE_CPACK_COMMAND "${CMake_BIN_DIR}/cpack")
     endif()
+  endif()
 
   # configure some files for testing
   configure_file("${CMAKE_CURRENT_SOURCE_DIR}/Templates/CTestScript.cmake.in"
@@ -362,6 +376,7 @@ macro (CMAKE_BUILD_UTILITIES)
 endmacro ()
 
 #-----------------------------------------------------------------------
+if(NOT CMake_TEST_EXTERNAL_CMAKE)
   if(CMAKE_CXX_PLATFORM_ID MATCHES "OpenBSD")
     execute_process(COMMAND ${CMAKE_CXX_COMPILER}
       ${CMAKE_CXX_COMPILER_ARG1} -dumpversion
@@ -376,6 +391,7 @@ if(CMAKE_CXX_PLATFORM_ID MATCHES "OpenBSD")
         "${CMAKE_CXX_COMPILER} version is: ${_GXX_VERSION}")
     endif()
   endif()
+endif()
 
 #-----------------------------------------------------------------------
 # The main section of the CMakeLists file
@@ -392,6 +408,7 @@ include (${CMAKE_ROOT}/Modules/Dart.cmake)
 set_directory_properties(PROPERTIES
   TEST_INCLUDE_FILE "${CMake_BINARY_DIR}/Tests/EnforceConfig.cmake")
 
+if(NOT CMake_TEST_EXTERNAL_CMAKE)
   # where to write the resulting executables and libraries
   set(BUILD_SHARED_LIBS OFF)
   set(EXECUTABLE_OUTPUT_PATH "" CACHE INTERNAL "No configurable exe dir.")
@@ -416,6 +433,7 @@ include(CompileFlags.cmake)
   include(CheckSymbolExists)
   CHECK_SYMBOL_EXISTS(unsetenv "stdlib.h" HAVE_UNSETENV)
   CHECK_SYMBOL_EXISTS(environ "stdlib.h" HAVE_ENVIRON_NOT_REQUIRE_PROTOTYPE)
+endif()
 
 # CMAKE_TESTS_CDASH_SERVER: CDash server used by CMake/Tests.
 #
@@ -434,6 +452,7 @@ if("x${CMAKE_TESTS_CDASH_SERVER}" STREQUAL "x")
   set(CMAKE_TESTS_CDASH_SERVER "http://www.cdash.org/CDash")
 endif()
 
+if(NOT CMake_TEST_EXTERNAL_CMAKE)
   # build the utilities (a macro defined in this file)
   CMAKE_BUILD_UTILITIES()
 
@@ -498,6 +517,8 @@ add_custom_target(uninstall
 
   include (CMakeCPack.cmake)
 
+endif()
+
 # setup some Testing support (a macro defined in this file)
 CMAKE_SETUP_TESTING()
 configure_file(
@@ -505,6 +526,7 @@ configure_file(
   "${CMAKE_CURRENT_BINARY_DIR}/DartLocal.conf"
   COPYONLY)
 
+if(NOT CMake_TEST_EXTERNAL_CMAKE)
   if(NOT CMake_VERSION_IS_RELEASE)
     if("${CMAKE_C_COMPILER_ID}" STREQUAL "GNU" AND
         NOT "${CMAKE_C_COMPILER_VERSION}" VERSION_LESS 4.2)
@@ -532,8 +554,11 @@ endif()
   # build the remaining subdirectories
   add_subdirectory(Source)
   add_subdirectory(Utilities)
+endif()
+
 add_subdirectory(Tests)
 
+if(NOT CMake_TEST_EXTERNAL_CMAKE)
   if(BUILD_TESTING)
     CMAKE_SET_TARGET_FOLDER(CMakeLibTests "Tests")
   endif()
@@ -541,11 +566,13 @@ CMAKE_SET_TARGET_FOLDER(cmw9xcom "Utilities/Win9xCompat")
   if(TARGET documentation)
     CMAKE_SET_TARGET_FOLDER(documentation "Documentation")
   endif()
+endif()
 
 # add a test
 add_test(SystemInformationNew "${CMAKE_CMAKE_COMMAND}"
   --system-information  -G "${CMAKE_GENERATOR}" )
 
+if(NOT CMake_TEST_EXTERNAL_CMAKE)
   # Install license file as it requires.
   install(FILES Copyright.txt DESTINATION ${CMAKE_DOC_DIR})
 
@@ -564,3 +591,4 @@ install(
 
   # Install auxiliary files integrating with other tools.
   add_subdirectory(Auxiliary)
+endif()

Tests/CMakeLists.txt

@@ -57,9 +57,11 @@ if(BUILD_TESTING)
     set(CMake_TEST_EXPLICIT_MAKE_PROGRAM "${CMAKE_MAKE_PROGRAM}")
   endif()
 
+  if(NOT CMake_TEST_EXTERNAL_CMAKE)
     if("${CMAKE_GENERATOR}" MATCHES "Unix Makefiles" OR ("${CMAKE_GENERATOR}" MATCHES Ninja AND NOT WIN32))
       set(TEST_CompileCommandOutput 1)
     endif()
+  endif()
 
   set(MAKE_IS_GNU )
   if(CMAKE_MAKE_PROGRAM MATCHES make)
@@ -95,13 +97,17 @@ if(BUILD_TESTING)
     list(APPEND build_options -DCMAKE_MAKE_PROGRAM:FILEPATH=${CMake_TEST_EXPLICIT_MAKE_PROGRAM})
   endif()
 
+  if(NOT CMake_TEST_EXTERNAL_CMAKE)
     add_subdirectory(CMakeLib)
+  endif()
   add_subdirectory(CMakeOnly)
   add_subdirectory(RunCMake)
 
   add_subdirectory(FindPackageModeMakefileTest)
 
+  if(NOT CMake_TEST_EXTERNAL_CMAKE)
     add_subdirectory(CTestTestMemcheck)
+  endif()
 
   # Collect a list of all test build directories.
   set(TEST_BUILD_DIRS)
@@ -248,7 +254,9 @@ if(BUILD_TESTING)
   ADD_TEST_MACRO(SetLang SetLang)
   ADD_TEST_MACRO(EmptyProperty EmptyProperty)
   ADD_TEST_MACRO(ExternalOBJ ExternalOBJ)
+  if(NOT CMake_TEST_EXTERNAL_CMAKE)
     ADD_TEST_MACRO(LoadCommand LoadedCommand)
+  endif()
   ADD_TEST_MACRO(LinkDirectory bin/LinkDirectory)
   ADD_TEST_MACRO(LinkLanguage LinkLanguage)
   ADD_TEST_MACRO(LinkLine LinkLine)
@@ -1018,6 +1026,7 @@ ${CMake_BINARY_DIR}/bin/cmake -DVERSION=master -P ${CMake_SOURCE_DIR}/Utilities/
       "${CMake_BINARY_DIR}/Tests/CMakeTestMultipleConfigures")
   endif()
 
+  if(NOT CMake_TEST_EXTERNAL_CMAKE)
     add_test(LoadedCommandOneConfig  ${CMAKE_CTEST_COMMAND}
       --build-and-test
       "${CMake_SOURCE_DIR}/Tests/LoadCommandOneConfig"
@@ -1028,6 +1037,7 @@ ${CMake_BINARY_DIR}/bin/cmake -DVERSION=master -P ${CMake_SOURCE_DIR}/Utilities/
       --test-command  LoadedCommand
       )
     list(APPEND TEST_BUILD_DIRS "${CMake_BINARY_DIR}/Tests/LoadCommandOneConfig")
+  endif()
 
   add_test(complex  ${CMAKE_CTEST_COMMAND}
     --build-and-test
@@ -2771,5 +2781,7 @@ ${CMake_BINARY_DIR}/bin/cmake -DVERSION=master -P ${CMake_SOURCE_DIR}/Utilities/
       WORKING_DIRECTORY ${CMake_BINARY_DIR}/Utilities/KWStyle)
   endif()
 
+  if(NOT CMake_TEST_EXTERNAL_CMAKE)
     add_subdirectory(CMakeTests)
   endif()
+endif()