[libcxx-commits] [libcxx] [libcxx] adds a size-based representation for `vector`'s unstable ABI (PR #155330)

[Christopher Di Bella via libcxx-commits]

================
@@ -577,25 +609,127 @@ class vector {
 
   _LIBCPP_CONSTEXPR_SINCE_CXX20 _LIBCPP_HIDE_FROM_ABI bool __invariants() const;
 
+#ifdef _LIBCPP_ABI_SIZE_BASED_VECTOR
+
 private:
+  using __sentinel_type _LIBCPP_NODEBUG = size_type;
+
+  [[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX20 _LIBCPP_HIDE_FROM_ABI size_type __raw_sentinel() const _NOEXCEPT {
+    return __size_;
+  }
+
+  [[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX20 _LIBCPP_HIDE_FROM_ABI pointer __end_pointer() const _NOEXCEPT {
+    return __begin_ + __size_;
+  }
+
+  [[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX20 _LIBCPP_HIDE_FROM_ABI size_type
+  __remaining_capacity() const _NOEXCEPT {
+    return __cap_ - __size_;
+  }
+
+  [[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX20 _LIBCPP_HIDE_FROM_ABI bool __is_full() const _NOEXCEPT {
+    return __size_ == __cap_;
+  }
+
+  _LIBCPP_CONSTEXPR_SINCE_CXX20 _LIBCPP_HIDE_FROM_ABI void __set_valid_range(pointer __begin, pointer __end) _NOEXCEPT {
+    __begin_ = __begin;
+    __size_  = __end - __begin_;
+  }
+
+  _LIBCPP_CONSTEXPR_SINCE_CXX20 _LIBCPP_HIDE_FROM_ABI void
+  __set_valid_range(pointer __begin, size_type __size) _NOEXCEPT {
+    __begin_ = __begin;
+    __size_  = __size;
+  }
+
+  _LIBCPP_CONSTEXPR_SINCE_CXX20 _LIBCPP_HIDE_FROM_ABI void __set_sentinel(size_type __size) _NOEXCEPT {
+    __size_ = __size;
+  }
+
+  _LIBCPP_CONSTEXPR_SINCE_CXX20 _LIBCPP_HIDE_FROM_ABI void __set_sentinel(pointer __pos) _NOEXCEPT {
+    __size_ = static_cast<size_type>(__pos - __begin_);
+  }
+
+  _LIBCPP_CONSTEXPR_SINCE_CXX20 _LIBCPP_HIDE_FROM_ABI void __set_capacity(size_type __cap) _NOEXCEPT { __cap_ = __cap; }
+
+  _LIBCPP_CONSTEXPR_SINCE_CXX20 _LIBCPP_HIDE_FROM_ABI void __set_capacity(pointer __pos) _NOEXCEPT {
+    __cap_ = static_cast<size_type>(__pos - __begin_);
+  }
+
+  pointer __begin_  = nullptr;
----------------
cjdb wrote:

I've just pushed a new layout type. What do you think about this particular design?

https://github.com/llvm/llvm-project/pull/155330