Languages: Add support for Objective-C++

Add entries in Modules and Modules/Platform to support
Objective-C++ compiler determination and identification.
Add Modules to check Objective-C++ compiler flags, source
compilations, program checks, etc...

Use OBJCXX as the designator of the language, eg:

project(foo OBJCXX)

Add various tests for Objective-C++ language features.  Add
tests to preserve C++ handling of .M and .mm files when
Objective-C++ is not a configured language.

Co-authored-by: Cristian Adam <cristian.adam@gmail.com>

1 files changed, 93 insertions, 0 deletions

diff --git a/Modules/CMakeTestOBJCXXCompiler.cmake b/Modules/CMakeTestOBJCXXCompiler.cmake
new file mode 100644
index 0000000..bcce2f1
--- /dev/null
+++ b/Modules/CMakeTestOBJCXXCompiler.cmake
@@ -0,0 +1,93 @@
+# Distributed under the OSI-approved BSD 3-Clause License.  See accompanying
+# file Copyright.txt or https://cmake.org/licensing for details.
+
+
+if(CMAKE_OBJCXX_COMPILER_FORCED)
+  # The compiler configuration was forced by the user.
+  # Assume the user has configured all compiler information.
+  set(CMAKE_OBJCXX_COMPILER_WORKS TRUE)
+  return()
+endif()
+
+include(CMakeTestCompilerCommon)
+
+# work around enforced code signing and / or missing exectuable target type
+set(__CMAKE_SAVED_TRY_COMPILE_TARGET_TYPE ${CMAKE_TRY_COMPILE_TARGET_TYPE})
+if(_CMAKE_FEATURE_DETECTION_TARGET_TYPE)
+  set(CMAKE_TRY_COMPILE_TARGET_TYPE ${_CMAKE_FEATURE_DETECTION_TARGET_TYPE})
+endif()
+
+# Remove any cached result from an older CMake version.
+# We now store this in CMakeOBJCXXCompiler.cmake.
+unset(CMAKE_OBJCXX_COMPILER_WORKS CACHE)
+
+# This file is used by EnableLanguage in cmGlobalGenerator to
+# determine that the selected Objective-C++ compiler can actually compile
+# and link the most basic of programs.   If not, a fatal error
+# is set and cmake stops processing commands and will not generate
+# any makefiles or projects.
+if(NOT CMAKE_OBJCXX_COMPILER_WORKS)
+  PrintTestCompilerStatus("OBJCXX" "")
+  __TestCompiler_setTryCompileTargetType()
+  file(WRITE ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeTmp/testOBJCXXCompiler.mm
+    "#ifndef __cplusplus\n"
+    "# error \"The CMAKE_OBJCXX_COMPILER is set to a C compiler\"\n"
+    "#endif\n"
+    "#ifndef __OBJC__\n"
+    "# error \"The CMAKE_OBJCXX_COMPILER is not an Objective-C++ compiler\"\n"
+    "#endif\n"
+    "int main(){return 0;}\n")
+  try_compile(CMAKE_OBJCXX_COMPILER_WORKS ${CMAKE_BINARY_DIR}
+    ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeTmp/testOBJCXXCompiler.mm
+    OUTPUT_VARIABLE __CMAKE_OBJCXX_COMPILER_OUTPUT)
+  # Move result from cache to normal variable.
+  set(CMAKE_OBJCXX_COMPILER_WORKS ${CMAKE_OBJCXX_COMPILER_WORKS})
+  unset(CMAKE_OBJCXX_COMPILER_WORKS CACHE)
+  set(OBJCXX_TEST_WAS_RUN 1)
+  __TestCompiler_restoreTryCompileTargetType()
+endif()
+
+if(NOT CMAKE_OBJCXX_COMPILER_WORKS)
+  PrintTestCompilerStatus("OBJCXX" " -- broken")
+  file(APPEND ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeError.log
+    "Determining if the Objective-C++ compiler works failed with "
+    "the following output:\n${__CMAKE_OBJCXX_COMPILER_OUTPUT}\n\n")
+  string(REPLACE "\n" "\n  " _output "${__CMAKE_OBJCXX_COMPILER_OUTPUT}")
+  message(FATAL_ERROR "The Objective-C++ compiler\n  \"${CMAKE_OBJCXX_COMPILER}\"\n"
+    "is not able to compile a simple test program.\nIt fails "
+    "with the following output:\n  ${_output}\n\n"
+    "CMake will not be able to correctly generate this project.")
+else()
+  if(OBJCXX_TEST_WAS_RUN)
+    PrintTestCompilerStatus("OBJCXX" " -- works")
+    file(APPEND ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeOutput.log
+      "Determining if the Objective-C++ compiler works passed with "
+      "the following output:\n${__CMAKE_OBJCXX_COMPILER_OUTPUT}\n\n")
+  endif()
+
+  # Try to identify the ABI and configure it into CMakeOBJCXXCompiler.cmake
+  include(${CMAKE_ROOT}/Modules/CMakeDetermineCompilerABI.cmake)
+  CMAKE_DETERMINE_COMPILER_ABI(OBJCXX ${CMAKE_ROOT}/Modules/CMakeOBJCXXCompilerABI.mm)
+  # Try to identify the compiler features
+  include(${CMAKE_ROOT}/Modules/CMakeDetermineCompileFeatures.cmake)
+  CMAKE_DETERMINE_COMPILE_FEATURES(OBJCXX)
+
+  # Re-configure to save learned information.
+  configure_file(
+    ${CMAKE_ROOT}/Modules/CMakeOBJCXXCompiler.cmake.in
+    ${CMAKE_PLATFORM_INFO_DIR}/CMakeOBJCXXCompiler.cmake
+    @ONLY
+    )
+  include(${CMAKE_PLATFORM_INFO_DIR}/CMakeOBJCXXCompiler.cmake)
+
+  if(CMAKE_OBJCXX_SIZEOF_DATA_PTR)
+    foreach(f ${CMAKE_OBJCXX_ABI_FILES})
+      include(${f})
+    endforeach()
+    unset(CMAKE_OBJCXX_ABI_FILES)
+  endif()
+endif()
+
+set(CMAKE_TRY_COMPILE_TARGET_TYPE ${__CMAKE_SAVED_TRY_COMPILE_TARGET_TYPE})
+unset(__CMAKE_SAVED_TRY_COMPILE_TARGET_TYPE)
+unset(__CMAKE_OBJCXX_COMPILER_OUTPUT)