Pointer aliasing- in C++0x

Question

I'm thinking about (just as an idea) disjointed pointer aliasing in C++0x. I was thinking about seeing if it could be implemented similarly to const correctness- that is, enforced by the compiler. What would be the requirements for such a thing? As this is more of a thought experiment, I'm perfectly happy to look at solutions that destroy legacy code or redefine half the language and that kind of thing.

What I'd really rather not do is have, say, restrict from C99 where the programmer just promises it. It should be enforced.

I was thinking about having unique_ptr be not part of the library, but part of the language. That way, the compiler can perform special optimizations on it and write their own unique pointer classes if they need to.

Answer 1

The Standard C++ Library (including std::unique_ptr) is a part of the language.

Also, conforming programs are not allowed to add declarations and definitions to the namespace std.

Upon seeing an instantiation of std::unique_ptr<T>, the compiler knows everything about the behavior of this instantiation - it's exactly that behavior which was implemented as a part of the language implementation the compiler itself is a part of and the compiler is free to perform "special optimizations" coming from the guarantees of the C++ standard.

As an example for something coming from the same line of thinking, GCC already does this with a number of standard C99 functions in hosted mode - it may replace standard function calls with inline insn sequence or with calls to other functions - precisely because GCC knows the exact semantics by just knowing the name of the function.