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 OBJC as the designator of the language, eg:

project(foo OBJC)

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

Co-Authored-By: Cristian Adam <cristian.adam@gmail.com>

1 files changed, 188 insertions, 0 deletions

diff --git a/Modules/CMakeOBJCInformation.cmake b/Modules/CMakeOBJCInformation.cmake
new file mode 100644
index 0000000..2baad4a
--- /dev/null
+++ b/Modules/CMakeOBJCInformation.cmake
@@ -0,0 +1,188 @@
+# Distributed under the OSI-approved BSD 3-Clause License.  See accompanying
+# file Copyright.txt or https://cmake.org/licensing for details.
+
+
+# This file sets the basic flags for the Objective-C language in CMake.
+# It also loads the available platform file for the system-compiler
+# if it exists.
+# It also loads a system - compiler - processor (or target hardware)
+# specific file, which is mainly useful for crosscompiling and embedded systems.
+
+include(CMakeLanguageInformation)
+
+# some compilers use different extensions (e.g. sdcc uses .rel)
+# so set the extension here first so it can be overridden by the compiler specific file
+set(CMAKE_OBJC_OUTPUT_EXTENSION .o)
+
+if(NOT CMAKE_INCLUDE_FLAG_OBJC)
+  set(CMAKE_INCLUDE_FLAG_OBJC ${CMAKE_INCLUDE_FLAG_C})
+endif()
+
+set(_INCLUDED_FILE 0)
+
+# Load compiler-specific information.
+if(CMAKE_OBJC_COMPILER_ID)
+  include(Compiler/${CMAKE_OBJC_COMPILER_ID}-OBJC OPTIONAL)
+endif()
+
+set(CMAKE_BASE_NAME)
+get_filename_component(CMAKE_BASE_NAME "${CMAKE_OBJC_COMPILER}" NAME_WE)
+if(CMAKE_COMPILER_IS_GNUOBJC)
+  set(CMAKE_BASE_NAME gcc)
+endif()
+
+
+# load a hardware specific file, mostly useful for embedded compilers
+if(CMAKE_SYSTEM_PROCESSOR)
+  if(CMAKE_OBJC_COMPILER_ID)
+    include(Platform/${CMAKE_EFFECTIVE_SYSTEM_NAME}-${CMAKE_OBJC_COMPILER_ID}-OBJC-${CMAKE_SYSTEM_PROCESSOR} OPTIONAL RESULT_VARIABLE _INCLUDED_FILE)
+  endif()
+  if (NOT _INCLUDED_FILE)
+    include(Platform/${CMAKE_EFFECTIVE_SYSTEM_NAME}-${CMAKE_BASE_NAME}-${CMAKE_SYSTEM_PROCESSOR} OPTIONAL)
+  endif ()
+endif()
+
+
+# load the system- and compiler specific files
+if(CMAKE_OBJC_COMPILER_ID)
+  include(Platform/${CMAKE_EFFECTIVE_SYSTEM_NAME}-${CMAKE_OBJC_COMPILER_ID}-OBJC
+    OPTIONAL RESULT_VARIABLE _INCLUDED_FILE)
+endif()
+if (NOT _INCLUDED_FILE)
+  include(Platform/${CMAKE_EFFECTIVE_SYSTEM_NAME}-${CMAKE_BASE_NAME}
+    OPTIONAL RESULT_VARIABLE _INCLUDED_FILE)
+endif ()
+
+# load any compiler-wrapper specific information
+if (CMAKE_OBJC_COMPILER_WRAPPER)
+  __cmake_include_compiler_wrapper(OBJC)
+endif ()
+
+# We specify the compiler information in the system file for some
+# platforms, but this language may not have been enabled when the file
+# was first included.  Include it again to get the language info.
+# Remove this when all compiler info is removed from system files.
+if (NOT _INCLUDED_FILE)
+  include(Platform/${CMAKE_SYSTEM_NAME} OPTIONAL)
+endif ()
+
+if(CMAKE_OBJC_SIZEOF_DATA_PTR)
+  foreach(f ${CMAKE_OBJC_ABI_FILES})
+    include(${f})
+  endforeach()
+  unset(CMAKE_OBJC_ABI_FILES)
+endif()
+
+# This should be included before the _INIT variables are
+# used to initialize the cache.  Since the rule variables
+# have if blocks on them, users can still define them here.
+# But, it should still be after the platform file so changes can
+# be made to those values.
+
+if(CMAKE_USER_MAKE_RULES_OVERRIDE)
+  # Save the full path of the file so try_compile can use it.
+  include(${CMAKE_USER_MAKE_RULES_OVERRIDE} RESULT_VARIABLE _override)
+  set(CMAKE_USER_MAKE_RULES_OVERRIDE "${_override}")
+endif()
+
+if(CMAKE_USER_MAKE_RULES_OVERRIDE_OBJC)
+  # Save the full path of the file so try_compile can use it.
+  include(${CMAKE_USER_MAKE_RULES_OVERRIDE_OBJC} RESULT_VARIABLE _override)
+  set(CMAKE_USER_MAKE_RULES_OVERRIDE_OBJC "${_override}")
+endif()
+
+
+# for most systems a module is the same as a shared library
+# so unless the variable CMAKE_MODULE_EXISTS is set just
+# copy the values from the LIBRARY variables
+if(NOT CMAKE_MODULE_EXISTS)
+  set(CMAKE_SHARED_MODULE_OBJC_FLAGS ${CMAKE_SHARED_LIBRARY_OBJC_FLAGS})
+  set(CMAKE_SHARED_MODULE_CREATE_OBJC_FLAGS ${CMAKE_SHARED_LIBRARY_CREATE_OBJC_FLAGS})
+endif()
+
+set(CMAKE_OBJC_FLAGS_INIT "$ENV{OBJCFLAGS} ${CMAKE_OBJC_FLAGS_INIT}")
+
+cmake_initialize_per_config_variable(CMAKE_OBJC_FLAGS "Flags used by the Objective-C compiler")
+
+if(CMAKE_OBJC_STANDARD_LIBRARIES_INIT)
+  set(CMAKE_OBJC_STANDARD_LIBRARIES "${CMAKE_OBJC_STANDARD_LIBRARIES_INIT}"
+    CACHE STRING "Libraries linked by default with all Objective-C applications.")
+  mark_as_advanced(CMAKE_OBJC_STANDARD_LIBRARIES)
+endif()
+
+include(CMakeCommonLanguageInclude)
+
+# now define the following rule variables
+
+# CMAKE_OBJC_CREATE_SHARED_LIBRARY
+# CMAKE_OBJC_CREATE_SHARED_MODULE
+# CMAKE_OBJC_COMPILE_OBJECT
+# CMAKE_OBJC_LINK_EXECUTABLE
+
+# variables supplied by the generator at use time
+# <TARGET>
+# <TARGET_BASE> the target without the suffix
+# <OBJECTS>
+# <OBJECT>
+# <LINK_LIBRARIES>
+# <FLAGS>
+# <LINK_FLAGS>
+
+# Objective-C compiler information
+# <CMAKE_OBJC_COMPILER>
+# <CMAKE_SHARED_LIBRARY_CREATE_OBJC_FLAGS>
+# <CMAKE_SHARED_MODULE_CREATE_OBJC_FLAGS>
+# <CMAKE_OBJC_LINK_FLAGS>
+
+# Static library tools
+# <CMAKE_AR>
+# <CMAKE_RANLIB>
+
+
+# create an Objective-C shared library
+if(NOT CMAKE_OBJC_CREATE_SHARED_LIBRARY)
+  set(CMAKE_OBJC_CREATE_SHARED_LIBRARY
+      "<CMAKE_OBJC_COMPILER> <CMAKE_SHARED_LIBRARY_OBJC_FLAGS> <LANGUAGE_COMPILE_FLAGS> <LINK_FLAGS> <CMAKE_SHARED_LIBRARY_CREATE_OBJC_FLAGS> <SONAME_FLAG><TARGET_SONAME> -o <TARGET> <OBJECTS> <LINK_LIBRARIES>")
+endif()
+
+# create an Objective-C shared module just copy the shared library rule
+if(NOT CMAKE_OBJC_CREATE_SHARED_MODULE)
+  set(CMAKE_OBJC_CREATE_SHARED_MODULE ${CMAKE_OBJC_CREATE_SHARED_LIBRARY})
+endif()
+
+# Create an static archive incrementally for large object file counts.
+# If CMAKE_OBJC_CREATE_STATIC_LIBRARY is set it will override these.
+if(NOT DEFINED CMAKE_OBJC_ARCHIVE_CREATE)
+  set(CMAKE_OBJC_ARCHIVE_CREATE "<CMAKE_AR> qc <TARGET> <LINK_FLAGS> <OBJECTS>")
+endif()
+if(NOT DEFINED CMAKE_OBJC_ARCHIVE_APPEND)
+  set(CMAKE_OBJC_ARCHIVE_APPEND "<CMAKE_AR> q  <TARGET> <LINK_FLAGS> <OBJECTS>")
+endif()
+if(NOT DEFINED CMAKE_OBJC_ARCHIVE_FINISH)
+  set(CMAKE_OBJC_ARCHIVE_FINISH "<CMAKE_RANLIB> <TARGET>")
+endif()
+
+# compile an Objective-C file into an object file
+if(NOT CMAKE_OBJC_COMPILE_OBJECT)
+  set(CMAKE_OBJC_COMPILE_OBJECT
+    "<CMAKE_OBJC_COMPILER> <DEFINES> <INCLUDES> <FLAGS> -o <OBJECT>   -c <SOURCE>")
+endif()
+
+if(NOT CMAKE_OBJC_LINK_EXECUTABLE)
+  set(CMAKE_OBJC_LINK_EXECUTABLE
+    "<CMAKE_OBJC_COMPILER> <FLAGS> <CMAKE_OBJC_LINK_FLAGS> <LINK_FLAGS> <OBJECTS>  -o <TARGET> <LINK_LIBRARIES>")
+endif()
+
+if(NOT CMAKE_EXECUTABLE_RUNTIME_OBJC_FLAG)
+  set(CMAKE_EXECUTABLE_RUNTIME_OBJC_FLAG ${CMAKE_SHARED_LIBRARY_RUNTIME_OBJC_FLAG})
+endif()
+
+if(NOT CMAKE_EXECUTABLE_RUNTIME_OBJC_FLAG_SEP)
+  set(CMAKE_EXECUTABLE_RUNTIME_OBJC_FLAG_SEP ${CMAKE_SHARED_LIBRARY_RUNTIME_OBJC_FLAG_SEP})
+endif()
+
+if(NOT CMAKE_EXECUTABLE_RPATH_LINK_OBJC_FLAG)
+  set(CMAKE_EXECUTABLE_RPATH_LINK_OBJC_FLAG ${CMAKE_SHARED_LIBRARY_RPATH_LINK_OBJC_FLAG})
+endif()
+
+set(CMAKE_OBJC_INFORMATION_LOADED 1)