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, 20 insertions, 0 deletions

diff --git a/Modules/CMakeOBJCXXCompilerABI.mm b/Modules/CMakeOBJCXXCompilerABI.mm
new file mode 100644
index 0000000..288a58c
--- /dev/null
+++ b/Modules/CMakeOBJCXXCompilerABI.mm
@@ -0,0 +1,20 @@
+#ifndef __cplusplus
+# error "A C compiler has been selected for Objective-C++."
+#endif
+
+/*--------------------------------------------------------------------------*/
+
+#include "CMakeCompilerABI.h"
+
+/*--------------------------------------------------------------------------*/
+
+int main(int argc, char *argv[])
+{
+  int require = 0;
+  require += info_sizeof_dptr[argc];
+#if defined(ABI_ID)
+  require += info_abi[argc];
+#endif
+  (void)argv;
+  return require;
+}