<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/143065>143065</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            ubsan has stopped identifying a mismatch between static and dynamic type of an argument to typeid()
        </td>
    </tr>

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

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

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

<pre>
    A post on C++'s std-proposals said some clearly UB code did not trigger a sanitizer failure, which was somewhat confusion, but after investigating it's a regression since clang 20.

```cpp
#include <typeinfo>
struct Foo {
   virtual ~Foo(){}
};
struct Bar {
   virtual ~Bar(){}
};

int main(int arc, char**) {
   Foo f;
   Bar *b = reinterpret_cast<Bar*>(&f);
   (void)typeid(*b);
   return 0;
}
```

Compiling with `-fsanitize=undefined` and running reports an error in 20, but passes in trunk
</pre>
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