[splint-discuss] incomplete deallocation

[Brian Quinlan]

On Fri, 2008-11-07 at 20:28 -0600, Greg White wrote:
> Hi again,
> 
> I do the following in my code:
> 
>   n = malloc(sizeof(nk_hdr));
>   if (n == NULL) {
>     (void)snprintf(error, 50, "can't allocate memory for n\n");
>     return -1;
>   }
>   memset(n, 0, sizeof(n));
> 
> nkhdr looks like:
> typedef struct _nk_hdr {
>   short int    name_len;
>   short int    classname_len;
>   unsigned char    *key_name; 
> } nk_hdr;
> 
> when I do a free(n); 
> splint says:
> Only storage n->key_name (type unsigned char *) derived from
>                     released storage is not released (memory leak): n
>   A storage leak due to incomplete deallocation of a structure or deep pointer
>   is suspected. Unshared storage that is reachable from a reference that is
>   being deallocated has not yet been deallocated. Splint assumes when an object
>   is passed as an out only void pointer that the outer object will be
>   deallocated, but the inner objects will not. (Use -compdestroy to inhibit
>   warning)
> 
> What did I do wrong?
> 
Hi Greg,
The problem is that the key_name pointer is not annotated, so it
defaults to "only" storage, i.e., splint assumes that key_name has the
only reference to the memory. For splint this means that when n is
freed, the program loses the only reference to the memory pointed to by
key_name, i.e., a memory leak. See the Memory Management section of
Appendix C of the manual for a list of relevant annotations.

Bye,
Brian