<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/113503>113503</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            -Waddress-of-packed-member misses some formations of const&s
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            new issue
      </td>
    </tr>

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

    <tr>
      <th>Reporter</th>
      <td>
          gburgessiv
      </td>
    </tr>
</table>

<pre>
    The following code sample produces no `-Waddress-of-packed-member` diagnostics on Clang 19:

```
struct Packed {
    int foo;
} __attribute__((packed));

const Packed *get_packed_struct();
void use_const_int_ref(const int &);

void foo() {
    use_const_int_ref(get_packed_struct()->foo);
    const Packed *p = get_packed_struct();
 use_const_int_ref(p->foo);
}
```

Clang warns about this for pointers: https://godbolt.org/z/nMdEGcc4s which have the same alignment requirements as references.

A reduced version of the 'real-world' code motivating this bug looked something like:

```
struct Packed {
 int foo;
} __attribute__((packed));

const Packed *get_packed_struct();
std::optional<int> foo() {
  const Packed *p = get_packed_struct();
  // std::optional's ctor takes this as a `const int&`, which requires alignof(int).
  // If this function didn't have an implicit conversion to optional, this would work
  // fine, since Clang emits IR assuming 1-byte alignment for this load.
  return p->foo; 
}
```
</pre>
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