<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/141103>141103</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            std::construct_at() seems to bypass [[clang::require_explicit_initialization]]
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            clang
      </td>
    </tr>

    <tr>
      <th>Assignees</th>
      <td>
      </td>
    </tr>

    <tr>
      <th>Reporter</th>
      <td>
          higher-performance
      </td>
    </tr>
</table>

<pre>
    ```
#include <memory>
#include <utility>

struct S {
    unsigned char v [[clang::require_explicit_initialization]];
};

template <class T, class... U>
constexpr T* my_construct_at(T* ptr, U&&... args) {
  return ::new (static_cast<void*>(ptr)) T(std::forward<U>(args)...);
}

int main() {
    unsigned char buf[sizeof(S)];
 std::construct_at(reinterpret_cast<S*>(buf));
    // my_construct_at(reinterpret_cast<S*>(buf));
}
```
This code produces:
```
<source>:10:42: error: field in 'S' requires explicit initialization but is not explicitly initialized [-Werror,-Wuninitialized-explicit-init]
   10 |   return ::new (static_cast<void*>(ptr)) T(std::forward<U>(args)...);
      | ^
<source>:16:5: note: in instantiation of function template specialization 'my_construct_at<S>' requested here
   16 | my_construct_at(reinterpret_cast<S*>(buf));
      | ^
<source>:5:19: note: 'v' declared here
    5 |     unsigned char v [[clang::require_explicit_initialization]];
      | ^
```
However, it runs fine if `my_construct_at(...)` is commented out.

It appears the compiler is treating `std::construct_at` specially somehow -- either disabling warnings on it, or rewriting it internally in some way. This should not be possible. It breaks the initialization guarantee of `[[clang::require_explicit_initialization]]`.
</pre>
<img width="1" height="1" alt="" src="http://email.email.llvm.org/o/eJy8VVuP2zYT_TX0y8CCRNmS_aAHrZPFl-fNIo8LShpZ85UiVXJkx_n1BelLvJeiaFrUMCCCHJ45c-ZC5T3tDWIl1g9i_WmhZh6sqwbaD-iWE7reulGZFheN7U6VKNLLP62FzMm0eu4QRL4bcbTuJPLP705mJk18PUprz25uGZ5AlA8irQEAZhNZdNAOysEBIpmHViuzF3kt8trh7zM5fMHvk6aW-IUMMSlNPxSTNWL9KfzzgCfK6yKtGcdJK440Wq28h69C7iAukySB5zOp1hrP-H1y4biG8fQSdwLNF8VCbuL2xC5cfhayELII15XbeyG3t0Ac8uwMnCkbPIKQG8-KqX1plWeR7w6WOiHr4FZuIuA2AHyNht35Ym_dUblO5Lvns93FTZIkwfwWZIyQDMOoyAi5uWfyVtJm7sX6wdMPtL2Qm6cAdBUMbp7fRO2QDKObHPKV_9ONfECM5C8gACDko5CPH8j3d4Aukd3V2deBPLS2Q5ic7eYWfWD72kbkO29n12LAzOssFXm9kiKvAZ2zLix6Qt0BGRCyfBKyhEtNebgWFbwuKmhmBvJgLN9M9OmnEXahTpffzh7kbvltNneHy-udZdgMakeVshREuYP_slgg_oJXsf78gViFyOt1kMhYxvAlA2Q8K8N0VsL20M-mjetbT_kJ2zu1hCzfZj6kOZA6a42esYMBHV6UKCKnf1YufxFbCCvb3scmZHkIjDpstXKvCMH6kpp_dyC9o3hXt_-zRzxgnCvE4GbjoSeDQD2IIn0vzSWtRQqxJ8YRTRDVzpyc58EXBjVNqJwHHjCYTKTRBXN2qJjMPiB_3PJFek2qPoG3Iw72CMslIPGADjryqtEB4aicIbP3YA0QB_bWgcOjo-ggthKjMxGITMSCozolEJvZD3bWXWysBmGy3lOjMYEvDI1D9duZ-5tu3M_KKcOIoRqDer-WkiJNFl2Vd9t8qxZYZeWq3OZ5sckXQ5WtZbbJN6oom67byn6VKblJi6xsy23fZOWCKpnKdbqWMivTTZolW0xXHa6xVVJhIRuxSnFUpBOtD2Ni3X5B3s9YZassS_OFVg1qH99aKc_UpQzPrqvChWUz771YpZo8-58QTKyx-rMpHUaCRxw9sIXmNIVX7te0WcxOVwPzFAdsHOZ74mFuktaOQj4GQpfPcnL2_9iykI8xQC_k4yXGQyX_CAAA___gtZgK">