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      <base href="https://bugs.llvm.org/">
    </head>
    <body><table border="1" cellspacing="0" cellpadding="8">
        <tr>
          <th>Bug ID</th>
          <td><a class="bz_bug_link 
          bz_status_NEW "
   title="NEW - UBSan: No warning for constructing global reference to misaligned data"
   href="https://bugs.llvm.org/show_bug.cgi?id=32364">32364</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>UBSan: No warning for constructing global reference to misaligned data
          </td>
        </tr>

        <tr>
          <th>Product</th>
          <td>clang
          </td>
        </tr>

        <tr>
          <th>Version</th>
          <td>trunk
          </td>
        </tr>

        <tr>
          <th>Hardware</th>
          <td>PC
          </td>
        </tr>

        <tr>
          <th>OS</th>
          <td>All
          </td>
        </tr>

        <tr>
          <th>Status</th>
          <td>NEW
          </td>
        </tr>

        <tr>
          <th>Severity</th>
          <td>normal
          </td>
        </tr>

        <tr>
          <th>Priority</th>
          <td>P
          </td>
        </tr>

        <tr>
          <th>Component</th>
          <td>LLVM Codegen
          </td>
        </tr>

        <tr>
          <th>Assignee</th>
          <td>unassignedclangbugs@nondot.org
          </td>
        </tr>

        <tr>
          <th>Reporter</th>
          <td>vsk@apple.com
          </td>
        </tr>

        <tr>
          <th>CC</th>
          <td>llvm-bugs@lists.llvm.org
          </td>
        </tr></table>
      <p>
        <div>
        <pre>Currently, there is no compile-time diagnostic, and no run-time UBSan
diagnostic, for constructing a global reference to misaligned data. Test case:

```
// RUN: %clangxx -fsanitize=alignment %s -o %t -w
// RUN: %run %t 2>&1 | FileCheck %s

char padding[8] __attribute__((aligned(8)));

int &global = *(int *)&padding[1];

int main() {
  // >>> BUG <<<: No diagnostic for store into misaligned data.
  global = 42;

  // CHECK: [[@LINE+1]]:16: runtime error: reference binding to misaligned
address
  int &local = *(int *)&padding[1];

  return 0;
}
```

In the IR, we get:

@padding = global [8 x i8] zeroinitializer, align 8
@global = constant i32* bitcast (i8* getelementptr inbounds ([8 x i8], [8 x
i8]* @padding, i32 0, i64 1) to i32*), align 8

We could fix this by emitting the normal reference binding check in a static
initializer function.</pre>
        </div>
      </p>


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