Functions returning pointers

Question

C++ noob here. I have a very basic question about a construct I found in the C++ book I am reading.

// class declaration
class CStr {
  char sData[256];
 public:
  char* get(void);
};

// implementation of the function
char* CStr::get(void) {
  return sData;
}

So the Cstr::get function is obviously meant to return a character pointer, but the function is passing what looks like the value (return sData). Does C++ know to return the address of the returned object? My guess would have been that the function definition would be return &sData.

Answer 1

For C and C++, array's degrade to pointers. An array cannot be returned as the value of a function, only a pointer can be returned. Returning the array is equivalent to returning the address of the first element of the array:

return &sData[0];

Answer 2

Does C++ know to return the address of the returned object?

In this case, yes. An array's name is a constant pointer to the first element in the array. So, when

char* CStr::get(void) {
    return sData;
}

is executed, pointer to the first element of the array is returned. So, the caller can reference the array and do a traversal. Run the following code. You'll see the output "hello, world".

#include <iostream>
#include <string>

class CStr {
    char sData[256];
public:
    CStr(std::string str);
    char* get(void);
};

CStr::CStr(std::string str) {
    if (str.length() >= 256) {
        sData[0] = '\n';
        return;
    }

    str.append("\n");
    str.copy(sData, str.length());
}

char* CStr::get(void) {
    return sData;
}

int main() {
    CStr msg("hello, world");
    char* str = msg.get();

    while (*str != '\n')
        std::cout << *str++;

    return 0;
}

Answer 3

In C and C++ returning the name of an array is same as returning the Address of the first element in an array hence you can return the same address in three different ways :

1. return sData;
2. return &sData;
3. return &sData[0];

all the three statements return the same address.