Passing address of a char* C++

Question

void Display(char* word)
{
  static char* pointerToWord = word;
  cout << pointerToWord;
}
void initialise(char* word)
{
  Display(word);
}
void main()
{
  char* word[3];
  char* currentWord;

  word[0] = "Hello";
  word[1] = "World";
  word[2] = "hahahaha";

  currentWord = word[0];
  initialise(currentWord);
  
  currentWord = word[1];
  //Displays word[0]
  Display(0);
  currentWord = word[2];
  //Still Displays word[0]
  Display(0);
}

Char* were always a bit of a pain in the neck. Can you help me get syntax right?

All I want is

initialise() Display()'s pointer to a current word
use Display() to display wherever the pointer is pointing to

In reality I've got a few classes involved, but this example pretty much illustrates the problem. Also I have no intention of modifying the string, so the strings are constant.

I'm not sure what you're asking for. Are you wanting to call `Display()` to output the currently-pointed-at-word? — GreatAndPowerfulOz, Oct 27 '15 at 17:05
I just want to pass the address of currentWord pointer to static char* pointerToWord at Display() — P.C. Blazkowicz, Oct 27 '15 at 17:08
Assigning a static value from a function argument always reassigns the value. It's distinct from static initialization. — Jason, Oct 27 '15 at 17:16
Possible duplicate of [Why is address of char data not displayed?](http://stackoverflow.com/questions/4860788/why-is-address-of-char-data-not-displayed) — Julian, Oct 27 '15 at 17:25

score 1 · Answer 1 · answered Oct 27 '15 at 17:11

1

Change the code as follows: first put pointerToWord at global scope:

static char* pointerToWord = "";

overload Display function:

void Display()
{
    cout << pointerToWord;
}

void Display(char* word)
{
    pointerToWord = word;
    Display();
}

answered Oct 27 '15 at 17:11

GreatAndPowerfulOz

1,767
13
19

Global scope wont work. Thats why I added passOnce() because the pointer to a currentWord is passed by few functions. – P.C. Blazkowicz Oct 27 '15 at 17:21
@MilesOrton you'll need to adapt the answer to your 'greater context' since I don't know your actual code. – GreatAndPowerfulOz Oct 27 '15 at 17:24

Vlad from Moscow · Answer 2 · 2015-10-27T17:36:00.997

I think you mean something like the following

void Display( const char* word = nullptr )
{
  static const char* pointerToWord;

  if ( word != nullptr )  pointerToWord = word;

  if ( pointerToWord != nullptr ) std::cout << pointerToWord;
}

Take into account that the function behaviour will be undefined if the object pointed to by pointerToWord is not alive.

Otherwise you should store a copy of the object in the function.

For example

#include <iostream>
#include <memory>
#include <cstring>

void Display( const char *word = nullptr )
{
    static std::unique_ptr<char[]> pointerToWord;


    if ( word != nullptr )
    {        
        pointerToWord.reset( std::strcpy( new char[std::strlen( word ) + 1], word ) );
    }        

    if ( pointerToWord != nullptr ) std::cout << pointerToWord.get() << std::endl;
}

int main()
{
    const char *word[2] = { "Hello", "World" };

    Display( word[0] );
    Display();

    Display( word[1] );
    Display();

    return 0;
}

The program output is

Hello
Hello
World
World

Take into account that function main in C++ shall have return type int and string literals have types of constant character arrays.

Passing address of a char* C++

2 Answers2