simple strcpy from string to string crashes entire programme

Question

sorry if this is a commonly asked question but I'm not sure as to why this code will not output anything:

#include <stdio.h>
#include <string.h>

int main()
{
char source[] = "hello world!";

char **destination;

strcpy(destination[0], source);

puts(destination[0]);
puts("string copied!");

return 0;
}

it looks like it is crashing at strcpy() as "string copied!" does not appear in the terminal either

Answer 1

Your problem is that char **destination is an empty pointer to a pointer. destination[0] points to absolutely nothing.

Here is how you would actually do it:

#include <stdio.h>
#include <string.h>

int main()
{
  char source[] = "hello world!";

  char destination[100];

  strcpy(destination, source);

  puts(destination);
  puts("string copied!");

  return 0;
}

Or if you want to determine the size of destination dynamically:

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

int main()
{
  char source[] = "hello world!";

  char *destination = malloc(strlen(source) * sizeof(char)+1); // +1 because of null character

  strcpy(destination, source);

  puts(destination);
  puts("string copied!");


  free(destination); // IMPORTANT!!!!
  return 0;
}

Make sure you free(destination) because it is allocated on the heap and thus must be freed manually.