[libcxx-commits] [libcxx] [libc++] Refactor memory allocation in basic_string (PR #128423)

[Louis Dionne via libcxx-commits]

================
@@ -3481,31 +3435,29 @@ inline _LIBCPP_CONSTEXPR_SINCE_CXX20 void basic_string<_CharT, _Traits, _Allocat
 
   if (__fits_in_sso(__target_capacity)) {
     __annotation_guard __g(*this);
+    auto __allocation = __get_internal_long_buffer();
     __set_short_size(__size);
-    traits_type::copy(std::__to_address(__get_short_pointer()), std::__to_address(__ptr), __size + 1);
-    __alloc_traits::deallocate(__alloc_, __ptr, __cap);
+    traits_type::copy(std::__to_address(__get_short_pointer()), std::__to_address(__allocation.ptr), __size + 1);
+    __deallocate_long_buffer(__alloc_, __allocation);
     return;
   }
 
 #  if _LIBCPP_HAS_EXCEPTIONS
   try {
 #  endif // _LIBCPP_HAS_EXCEPTIONS
     __annotation_guard __g(*this);
-    auto __allocation = std::__allocate_at_least(__alloc_, __target_capacity + 1);
+    auto __allocation = __allocate_long_buffer(__alloc_, size());
 
     // The Standard mandates shrink_to_fit() does not increase the capacity.
     // With equal capacity keep the existing buffer. This avoids extra work
     // due to swapping the elements.
-    if (__allocation.count - 1 >= capacity()) {
-      __alloc_traits::deallocate(__alloc_, __allocation.ptr, __allocation.count);
+    if (__allocation.count - 1 > capacity()) {
+      __deallocate_long_buffer(__alloc_, __allocation);
       return;
     }
 
-    __begin_lifetime(__allocation.ptr, __allocation.count);
-    traits_type::copy(std::__to_address(__allocation.ptr), std::__to_address(__ptr), __size + 1);
-    __alloc_traits::deallocate(__alloc_, __ptr, __cap);
-    __set_long_cap(__allocation.count);
-    __set_long_pointer(__allocation.ptr);
+    traits_type::copy(std::__to_address(__allocation.ptr), std::__to_address(__get_long_pointer()), __size + 1);
+    __replace_internal_buffer(__allocation, size());
----------------
ldionne wrote:

```suggestion
    __replace_internal_buffer(__allocation, __size);
```

https://github.com/llvm/llvm-project/pull/128423