char pointers, char arrays, and strings in the context of a function call

Question

What is the difference between the line that does not compile and the line that does compile? The line that does not compile gives this warning: deprecated conversion from string constant to 'char*'

Also, I'm aware casting (char *) on the string being passed in to the function would solve the problem, but I would like to understand why that's even necessary when the 2nd line compiles just fine.

class Student {

  public:

    Student( char name[] ) {

    }

}

int main() {

  Student stud( "Kacy" ); //does not compile
  char name[20] = "Kacy";   //compiles just fine

}

Answer 1

The char[] signature in the parameter is exactly the same as char*. In C++, it is illegal to convert a string constant char const* (the string "Kacy") to a char* because strings are immutable.

Your second example compiles because the name is an actual array. There is no change to char*.

As a solution, change your parameter to take a const string array:

Student(char const name[]);

which again is the same as

String(char const *name);

though you're better off using std::string:

#include <string>

class String
{
    public:
        String(std::string name);
};