Top-level const doesn't influence a function signature

Question

From the C++ Primer 5th Edition, it says:

int f(int){ /* can write to parameter */}
int f(const int){ /* cannot write to parameter */}

The

Answer 1

In "The C++ Programming Language", fourth edition, Bjarne Stroustrup writes (§12.1.3):

Unfortunately, to preserve C compatibility, a const is ignored at the highest level of an argument type. For example, this is two declarations of the same function:

void f(int);
void f(const int);

So, it seems that, contrarily to some of the other answers, this rule of C++ was not chosen because of the indistinguishability of the two functions, or other similar rationales, but instead as a less-than-optimal solution, for the sake of compatibility.

Indeed, in the D programming language, it is possible to have those two overloads. Yet, contrarily to what other answers to this question might suggest, the non-const overload is preferred if the function is called with a literal:

void f(int);
void f(const int);

f(42); // calls void f(int);

Of course, you should provide equivalent semantics for your overloads, but that is not specific to this overloading scenario, with nearly indistinguishable overloading functions.