[libcxx-commits] [libcxx] [lldb] [libcxx] adds size-based `__split_buffer` representation to unstable ABI (PR #139632)

[Christopher Di Bella via libcxx-commits]

================
@@ -253,30 +436,35 @@ _LIBCPP_CONSTEXPR_SINCE_CXX20 void __split_buffer<_Tp, _Allocator>::__construct_
 template <class _Tp, class _Allocator>
 _LIBCPP_CONSTEXPR_SINCE_CXX20 void
 __split_buffer<_Tp, _Allocator>::__construct_at_end(size_type __n, const_reference __x) {
-  _ConstructTransaction __tx(std::addressof(this->__end_), __n);
+  _ConstructTransaction __tx(this, __data_.end(), __n);
   for (; __tx.__pos_ != __tx.__end_; ++__tx.__pos_) {
-    __alloc_traits::construct(__alloc_, std::__to_address(__tx.__pos_), __x);
+    __alloc_traits::construct(__data_.__alloc_, std::__to_address(__tx.__pos_), __x);
   }
 }
 
-template <class _Tp, class _Allocator>
-template <class _Iterator, class _Sentinel>
+template<class _Tp, class _Allocator>
+template<class _Iterator, class _Sentinel>
 _LIBCPP_CONSTEXPR_SINCE_CXX20 void
 __split_buffer<_Tp, _Allocator>::__construct_at_end_with_sentinel(_Iterator __first, _Sentinel __last) {
-  __alloc_rr& __a = __alloc_;
+  __alloc_rr& __a = __data_.__alloc_;
   for (; __first != __last; ++__first) {
-    if (__end_ == __cap_) {
-      size_type __old_cap = __cap_ - __first_;
+    if (__data_.__back_spare() == 0) {
+      size_type __old_cap = __data_.capacity();
       size_type __new_cap = std::max<size_type>(2 * __old_cap, 8);
       __split_buffer __buf(__new_cap, 0, __a);
-      for (pointer __p = __begin_; __p != __end_; ++__p, (void)++__buf.__end_)
-        __alloc_traits::construct(__buf.__alloc_, std::__to_address(__buf.__end_), std::move(*__p));
+      pointer __buf_end = __buf.__data_.end();
+      pointer __end = __data_.end();
+      for (pointer __p = __data_.__begin_; __p != __end; ++__p, (void)++__buf_end)
+        __alloc_traits::construct(__buf.__data_.__alloc_, std::__to_address(__buf_end), std::move(*__p));
+      __buf.__data_.__update_sentinel(__buf_end);
       swap(__buf);
     }
-    __alloc_traits::construct(__a, std::__to_address(this->__end_), *__first);
-    ++this->__end_;
+
+    __alloc_traits::construct(__a, std::__to_address(__data_.end()), *__first);
+    __data_.__update_sentinel(size() + 1);
----------------
cjdb wrote:

We can't do that here because `__buf_end` depends on `__buf`, which really shouldn't be moved out of its current scope.

https://github.com/llvm/llvm-project/pull/139632