[libcxx-commits] [libcxx] [libc++] Ensure that `std::expected` has no tail padding (PR #69673)

[Louis Dionne via libcxx-commits]

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@@ -955,8 +956,17 @@ class expected {
     _LIBCPP_NO_UNIQUE_ADDRESS _ErrorType __unex_;
   };
 
+  _LIBCPP_HIDE_FROM_ABI static constexpr auto __calculate_padding() {
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ldionne wrote:

This won't work if there is no tail padding, since we'll end up creating a `char __padding_[0];` below. This is the case for e.g. `std::expected<char, char>`. Needs tests.

https://github.com/llvm/llvm-project/pull/69673