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

[Christopher Di Bella via libcxx-commits]

================
@@ -409,50 +424,50 @@ class vector {
   //
   [[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX20 _LIBCPP_HIDE_FROM_ABI reference operator[](size_type __n) _NOEXCEPT {
     _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__n < size(), "vector[] index out of bounds");
-    return this->__begin_[__n];
+    return this->__begin_ptr()[__n];
   }
   [[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX20 _LIBCPP_HIDE_FROM_ABI const_reference
   operator[](size_type __n) const _NOEXCEPT {
     _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__n < size(), "vector[] index out of bounds");
-    return this->__begin_[__n];
+    return this->__begin_ptr()[__n];
   }
   [[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX20 _LIBCPP_HIDE_FROM_ABI reference at(size_type __n) {
     if (__n >= size())
       this->__throw_out_of_range();
-    return this->__begin_[__n];
+    return this->__begin_ptr()[__n];
   }
   [[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX20 _LIBCPP_HIDE_FROM_ABI const_reference at(size_type __n) const {
     if (__n >= size())
       this->__throw_out_of_range();
-    return this->__begin_[__n];
+    return this->__begin_ptr()[__n];
   }
 
   [[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX20 _LIBCPP_HIDE_FROM_ABI reference front() _NOEXCEPT {
     _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(!empty(), "front() called on an empty vector");
-    return *this->__begin_;
+    return *this->__begin_ptr();
   }
   [[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX20 _LIBCPP_HIDE_FROM_ABI const_reference front() const _NOEXCEPT {
     _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(!empty(), "front() called on an empty vector");
-    return *this->__begin_;
+    return *this->__begin_ptr();
   }
   [[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX20 _LIBCPP_HIDE_FROM_ABI reference back() _NOEXCEPT {
     _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(!empty(), "back() called on an empty vector");
-    return *(this->__end_ - 1);
+    return __base_type::back();
----------------
cjdb wrote:

I've done this for everything except for `swap`. Should we apply this to customisation points too?

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