That's why you'd need to have a common formally defined semantics underneath, that all syntaxes will be forced to comply with. Solves the halting problem (unless somebody invents a truly weird syntax with meta-meta-templates and context-dependent grammar or whatever - like the "look, I can use C++ templates to implement a compile time Lisp interpreter" horror"), but, yeah, inventing a practical way to enforce that formally defined semantics is a hard problem in itself, and waaaay above may level of compsi knowledge :)