内存分配和内存泄漏：C

Question

I'm fairly new with C. I have a function called kstrfrom that needs to create and return a new kstring object that contains a copy of the contents of a null-terminated C string, including the null terminator.

The .length member of the returned kstring should be the length of cstr, plus one for the null terminator. The .data member should be a pointer to newly-allocated memory, into which you have copied the contents of cstr, including the null byte at the end.

If there is an error allocating memory, this function should call abort() or throw an uncaught exception.

    kstring kstrfrom(const char *cstr)
    {
        int length=1;    
        while(*cstr!='\0')
        {
            cstr+=1;
            length+=1;
        }
        int i = 0;
        kstring cdest={NULL,0};
        cdest.data = malloc(length+1);
        if(cdest.data == '\0')
        {
            abort();
        }
        else{
            while(cstr[i] != '\0')
            {
                cdest.data[i] = cstr[i];
                i++;
            }
       }
       cdest.data[i] = '\0';
       cdest.data[++i] = '\0';

       return cdest;
  }

I've ran a few test cases:

  Test   9/ 26: kstrfrom gives correct length                      skipped (0)
  Test  10/ 26: kstrfrom contains null byte                        succeeded (1)
  Test  11/ 26: kstrfrom contains correct data                     skipped (0)
  Test  12/ 26: kstrfrom copies, not shares, data                  skipped (0)

As you can see I need help with giving correct link, containing correct data and copying data.

Answer 1

At the end of

    while(*cstr!='\0')
    {
        cstr+=1;
        length+=1;
    }

You have lost the initial value of cstr

try

    int length=1;    
    char * tmp = cstr;
    while(*tmp!='\0')
    {
        tmp+=1;
        length+=1;
    }

You are not setting the length member...

cdest.length = length + 1;

Returning the kstring is problematic.

kstring res;
res = kstrfrom( "My String" ); /* works */
kstrfrom( "Another string" );  /* leaks memory */

Other comments are describing how you are ignoring language features. Your code can be achieved more easily with...

kstring kstrfrom(const char *cstr)
{
    kstring cdest={NULL,0};
    cdest.data = strdup( cstr );
    if( cdest.data == NULL ){
         abort();
    }
    cdest.length = strlen( cstr ) + 1;  /* not done in original example */
    return cdest;
}