How to use malloc in this situation?

Question

I'm a bit of a newbie at C, so please bear with me...

I have a function to count char in a string called char strLength, but I have to create a function that uses this function to count the number of characters in a passed string, mallocates a new string with space for a NULL terminator, copies the string and then returns the copy.

Here's what I have:

character counter

int strLength(char* toCount)
{
    int count = 0;

    while(*toCount != '\0')
    {
        count++;
        toCount++;
    }

    return count;
}

and here's the beginning of the sought-after function

char* strCopy(char *s)
{
    int length = strLength(s);

}

Answer 1

1. You can use strdup() clib call.

2. You can write something like:

char* strCopy(char *s) {
  int length = strLength(s);
  char *rc = (char *)malloc(length + 1);
  return rc? strcpy(rc, s) : NULL;
}

Answer 2

You want strdup. However, since I suspect this is a learning exercise:

char *strCopy(const char *src)
{
    size_t l = strlen(src) + 1;
    char *r = malloc(l);
    if (r)
       memcpy(r, src, l);
    return r;
}

If you are curious how to copy strings yourself, you could replace the memcpy with something like:

char *dst = r;
while (*src)
   *dst++ = *src++;
*dst = 0;

However I would suggest using library functions: if not strdup, then malloc + memcpy.

Answer 3

Since you are struggling with malloc, here is how the next line should look:

char* strCopy(char *s)
{
    int length = strLength(s);
    char *res = malloc(length+1);
    // Copy s into res; stop when you reach '\0'
    ...
    return res;
}