"In my experience a modern C program executes faster than a modern C++ program, due to the extra scaffolding of the latter."
Your experience is lying to you. If you write the same program in C and C++ and compile it with GCC you will get the same object code because they use the same code generator and optimizer. Even exceptions these days are compiled so that exception handling generates code only on the throw path, and of course you can compile C++ without exceptions at all. The "extra scaffolding" you speak of does not exist, unless you ask for it and that is entirely up to you.