Re: So You Think You Can Const?

On 1/8/2025 8:24 AM, Julio Di Egidio wrote:

On 08/01/2025 17:05, Julio Di Egidio wrote:

On 08/01/2025 16:16, Ben Bacarisse wrote:

<snip>

More relevant to a discussion of const is to ask what you plan to do
with pT since you can't (without a cast) assign any useful value to the
allocated object.

>
Say my program unit implements AVL trees, with (conceptually speaking) constructors/destructors, navigation and retrieval, and of course manipulation (inserting, deleting, etc.).
>
My idea (but I would think this is pretty "canonical" and, if it isn't, I am missing the mark) is: my public functions take/give "sealed" instances (with const members to const data), as the user is not supposed to directly manipulate/edit the data, OTOH of course my implementation is all about in-place editing...

 P.S.  To be clear, as I am still being a bit quick: I do not also mean "public destructors" should take a const pointer in input, i.e. apply as appropriate...
 And here is what my construction/destruction code is looking like at the moment, which should also make clear what I meant by "a private method implementing a public interface" and why:

Sometimes I think the following can be kind of useful:
struct foo
{
    [...]
};
void foo_bar(struct foo const* const self, [...])
{
     // self cannot change without a warning
     // self is const pointer to a const struct foo
     self = NULL; // zap!
}
;^)

 ```c
static AvlTree_t const *AvlTree_node(
     void const *pk, AvlTree_t const *pL, AvlTree_t const *pR
) {
     AvlTree_t *pT;
      pT = malloc(sizeof(AvlTree_t));
      if (!pT) {
         return NULL;
     }
      pT->pk = pk;
     pT->pL = pL;
     pT->pR = pR;
      return pT;
}
 static int AvlTree_free_(AvlTree_t const *pT) {
     assert(pT);
      free((AvlTree_t *)pT);
      return 0;
}
 AvlTree_t const *AvlTree_create(void const *pk) {
     return AvlTree_node(pk, NULL, NULL);
}
 void AvlTree_destroy(AvlTree_t *pT) {
     AvlTree_visitPost(AvlTree_free_, pT);
}
```
 -Julio