UB throws a huge wrench into all of this. The behavior of a C++ program is defined by a combination of the code, the compiler, the compiler flags, and the targe

UB throws a huge wrench into all of this. The behavior of a C++ program is defined by a combination of the code, the compiler, the compiler flags, and the target archecture. You can't write a source to source translator that preserves the semantics of a program with UB without that extra information about how it was compiled. It's a very hairy problem.