I’ve read many times that making value parameters in a function const is a bad thing to do because it’s unnecessary. However, I find it occasionally helpful to me as a check that my implementation doesn’t do something I don’t intend (as in the example at the end of your question). So, while it may … Read more
As I said in my comment, once you modified the const value you are in undefined behaviour land, so it doesn’t make much sense to talk about what is happening. But what the hell.. cout << *w << endl; // (3) outputs 5 cout << e << endl; // (4) outputs 2 At a guess, … Read more
[Edit: OK so this question is more subtle than I thought at first.] Declaring a pointer-to-const or reference-of-const never helps any compiler to optimize anything. (Although see the Update at the bottom of this answer.) The const declaration only indicates how an identifier will be used within the scope of its declaration; it does not … Read more
I had this same problem a few years ago and it irked me to no end. The rules in C are more simply stated (i.e. they don’t list exceptions like converting char** to const char*const*). Consequenlty, it’s just not allowed. With the C++ standard, they included more rules to allow cases like this. In the … Read more
This is the definitive article on “const correctness”: https://isocpp.org/wiki/faq/const-correctness. In a nutshell, using const is good practice because… It protects you from accidentally changing variables that aren’t intended be changed, It protects you from making accidental variable assignments, and The compiler can optimize it. For instance, you are protected from if( x = y ) … Read more
From the standard: const char c=”c”; char* pc; const char** pcc = &pc; // not allowed *pcc = &c; *pc=”C”; // would allow to modify a const object