Recently, I have one problem. The clang can translate Objective-C to c++ use -rewrite-objc. So I think, the first step. clang compile Objective-C to C++. And then compile only can use c++ compiler. Is it do like this? clang first translate Objective-C to C++ with runTime, and then compile to the machine code?
-rewrite-objc exists to translate ObjC to C++ so it can be compiled in the Visual Studio. It is still Objective-C semantics and you still need the objective-c runtime. It is not magically converting Objective-C to the C++ OO architecture.
This is much more like when Objective-C was implemented as a pre-compiler extension.
It all relies on the fact that Objective-C classes are just C structures with fancy behavior and objective-c method calls all can be translated to calls to objc_msgSend().
来源：https://stackoverflow.com/questions/44561285/rewrite-objc-and-objective-c-in-clang