Why is const-correctness specific to C++?

Question

Disclaimer: I am aware that there are two questions about the usefulness of const-correctness, however, none discussed how const-correctness is necessary in C++ as oppos

Answer 1

In C, Java and C# you can tell by looking at the call site if a passed object can be modified by a function:

• in Java you know it definitely can be.
• in C you know it only can be if there is a '&', or equivalent.
• in c# you need to say 'ref' at the call site too.

In C++ in general you can't tell this, as a non-const reference call looks identical to pass-by-value. Having const references allows you to set up and enforce the C convention.

This can make a fairly major difference in readability of any code that calls functions. Which is probably enough to justify a language feature.