strcpy from scratch

my_strcpy.c

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

char *my_strcpy(char *strDest, const char *strSrc)
{
    if (strSrc == NULL || strDest == NULL)
        return NULL;

    char *dest = strDest;

    while ((*strDest++ = *strSrc++) != '\0');

    return dest;
}

int main()
{
    char *src = "Hello world";
    char *dest = (char *)malloc(strlen(src)+1);

    my_strcpy(dest, src);
    printf("%s\n", dest);

    free(dest);
    return 0;
}