Question

I was trying to write out some of the implementations of the string functions available in C. My code is:

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

char *mystrcpy(char *s1, char *s2)
{
    while(*s1++ = *s2++);
    return s1;
}

int mystrlen(char *s)
{
    int len = 0;
    while(*s != '\0')
    {
        len++;
    }
    return len;
}

int main(void)
{
    char arr = "Hi";
    char arr1[10];
    char arr2[] = "Hello";
    int length;

    mystrcpy(arr1, arr2);
    printf("%s", arr1);

    length = mystrlen(arr);
    printf("%d", length);

    return 0;
}

mystrcpy works fine, but the other method mystrlen does no execute. What could be the error? The following is the program termination note:

Process terminated with status -1073741510 (0 minutes, 4 seconds)

Also, there are few warnings related to casts. Is there any place in the code where I should be using any cast?

Answer 1

First, your mystrlen has an infinite loop.

Fixed code:

int mystrlen(const char *s)
{
    int len = 0;
    while (*s++ /* increment to next character every loop */ != '\0')
    {
        len++;
    }
    return len;
}

Also added const since you never change the data referred to by *s

Second, the assignment: char arr="Hi"; is not valid.

You are attempting to assign a char[] array to a char variable. The correct form would be one of the following:

char arr[]="Hi"; // array syntax
char *arr="Hi";  // pointer syntax

Given your invalid arr assignment, your runtime error is most likely caused by mystrlen attempting to incorrectly deference arr.

What compiler are you using? Most conforming compilers should have caught the second issue. If using GCC, add the -Wall flag to your makefile.