A few questions about declaration semantics

Question

Which of these are more correct and more widely used? The actualy question is the last one, I think the behavior changes.

int *test; //for this, it is probably both?
int* test;


int& test;
int &test;

Actual question:

const int test;
int const test;


const int* test;
int* const test; //<-- I guess this also have a different meaning if I consider the last one?


const int& test;
int const& test; //also, considering last one, any difference?


const int*& test;
int* const& test; //<-- this is the correct one for stating "I won't modify the passed object, but I may modify the one pointed"? I have had problems with the other one sometimes, does the other one has some other meaning?
const int* const& test; //<-- another meaning?

Also I would be glad if you could point out if you know any visual "ambiguations" in this subject.

Answer 1

Where you place the space around & or * (or indeed if you have one or more spaces one or both sides) makes absolutely no difference. The placement of const does make a difference;

const int *test;

means that what test points to isn't being changed. So:

int b = 42;
*test = 42;
test = &b;

The *test = 42; would be illegal, but assigning test to a new address is valid.

int * const test;

means that test doesn't can't change it's value, but what it points to can:

int b = 42;
*test = 42;
test = &b;

now test = &b; is invalid.

const int& test;
int const& test; //also, considering last one, any difference?

Both the same. The const and int are the same side of &.

This one:

const int*& test;

means we have a reference to a int * where the value can't be changed. Perfectly valid, we can use the following:

test = &b;

these two:

int* const& test
const int* const& test;

is a reference to an int * and const int * respectively, and we can't change the pointer itself - so no point in passing it by reference.