Review the example stringcopy.c, excerpted below; it is buggy and triggers a segmentation fault!

  • Copy the stringcopy.c program into your own directory, and compile it: 
    cp /thayerfs/courses/22fall/cosc050/workspace/activities/day9/stringcopy.c .
mygcc -o stringcopy stringcopy.c
  • Explain the pointer notation used in the parameters.
  • Explain the pointer notation used in the conditional.
  • Explain what happens inside the loop.
  • Why is there an assignment after the loop?
  • Where is the bug in main()?
  • What might go wrong inside stringcopy?
#include <stdio.h>
#include <stdlib.h>

void stringcopy(char *sp, char *dp);

int main()
{
  char *src = "CS 50";
  char *dest = ""; 

  // copy src to dest and print them out
  stringcopy(src, dest);
  printf("src  = '%s'\n", src);
  printf("dest = '%s'\n", dest);
  return 0;
}

/* stringcopy - copy string from source sp to destination dp */
void stringcopy(char *sp, char *dp)
{
  while (*sp != '\0') {
    *dp++ = *sp++;
  }
  *dp = '\0';
}

This code causes a segfault when run. Explain why.

Solution

stringcopy-fixed.c