How to see the added code in C++ by the compiler?
E.g., we know that when an object of some class goes out of scope, the destructor for that object is called, but how do you see the specific code that does the destructor call? Is that code still written in C++?
There's not necessarily any "code" that gets added. C++ is pretty clear on when such things happen, and for the compiler, making a new object clearly means calling its constructor -- no additional "code" anywhere.
You're right, however, things like calls to the constructor or destructor must end up somewhere in the assembly -- but there's absolutely no guarantee that having a look at the assembly reveals much more than what you'd have known without. C++ compilers are pretty mature in these aspects, and inline a lot of things in cases where that makes sense, making the same code look different in different places.
The closest thing you'll get is adding debug symbols to your build and using a debugger to get a call graph -- that will make sure that you notice when what you see as code gets called.