C Programming - Return Pointer to Freed

Question

I have a function, foo(), that allocates memory and returns it. Is it standard practice for me to free it at the end of my main function?

char* foo(){
 char * p;

 p = malloc(sizeof(char) * 4); /* edit - thanks to msg board */
 p[0] = 'a';
 p[1] = 'b';
 p[2] = 'c';
 p[3] = '/0'; /* edit: thanks to the msg board. */

 return p;
}

int main(int argc, char *argv[])
{
 char * p2;

 p2 = foo();

 printf("%s", p2);    

 free(p2);

 return 0;
}

Answer 1

Freeing at the end of main() would be the correct thing to do, yes. You might think about null terminating that string, though. A more idiomatic design is do to all the memory management "at the same level", so to speak. Something like:

void foo(char *p)
{
  p[0] = 'a';
  p[1] = 'b';
  p[2] = 'c';
  p[3] = '\0';
}

int main(int argc, char **argv)
{
  char *p2 = malloc(4);
  foo(p2);
  printf("%s", p2);
  free(p2);
  return 0;
}