[libcxx-commits] [PATCH] D152327: [libc++] Fix an exception safety issue in `forward_list` and add tests.

[Louis Dionne via Phabricator via libcxx-commits]

ldionne added inline comments.


================
Comment at: libcxx/include/forward_list:1254-1256
         unique_ptr<__node, _Dp> __h(__node_traits::allocate(__a, 1), _Dp(__a, 1));
+        __h->__next_ = nullptr;
         __node_traits::construct(__a, _VSTD::addressof(__h->__value_), __v);
----------------
ldionne wrote:
> This makes me wonder whether we should instead be constructing this with e.g. `make_unique`. Why don't we have a proper constructor for `__node` and call that instead, it would make sure that we never forget to initialize some of its members. Do you have thoughts about this?
This is what I had in mind:

```
unique_ptr<__node, _Dp> __h = std::make_unique<__node>(__node(__v, __next=nullptr) _Dp(__a, 1));
```

Now we need to allocate using the right allocator, so we might need to use something like `__allocation_guard` instead:

```
__allocation_guard<__node_allocator> __h(__a, 1);
std::construct_at(__h.__get(), __v, /*next*/nullptr); // this is nicer here cause we call the node's constructor for real
__node_pointer __first = __h.__release();
```


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D152327/new/

https://reviews.llvm.org/D152327