The sad part is, in the general case it's impossible for the parser (or any other process overviewing it) to decide if it's actually caught in an infinite loop or not, that's why they call it undecidability.
(The hard limit is how C++ gets parsed, I think. Since parsing C++ is also undecidable thanks to weird interactions with template metaprogramming.)
https://github.com/knome/metabrainfuck/blob/master/bf.cpp
Does attempting to autocomplete such a template cause issues for IDEs? I used emacs when writing it, so I've never tested such a thing.
For C++ even precise syntax colouring would be undecidable---and just hard to get the logic right. There are two ways out: (1) implement an approximation and the occasional impression, (2) ask the compiler for help. I think the llvm project helps with the latter.
(What does emacs have to do with things? Or do you mean you are using emacs without any special support for C++? With the right modes you can turn your emacs (or vim etc) into basically a fully fledged IDE.)