<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/54895>54895</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            Improvement: diagnose undefined behavior: missing terminating " character
        </td>
    </tr>

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

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

    <tr>
      <th>Reporter</th>
      <td>
          pmor13
      </td>
    </tr>
</table>

<pre>
    ```
#if 0
"
#endif
```
Expected:
```
warning: missing terminating " character
```

C11:
> The categories of preprocessing tokens are: header names,
identifiers, preprocessing numbers, character constants, string literals, punctuators, and
single non-white-space characters that do not lexically match the other preprocessing
token categories.69) If a ' or a " character matches the last category, the **behavior is
undefined**.
</pre>
<img width="1px" height="1px" alt="" src="http://email.email.llvm.org/o/eJyNUsuOozAQ_Bq4WEFgHhkOHLLzkOa-P9CxG_CssZFtksnfbxvymFnNYSVk3F3uqnK3j1ZeuqTJr1_-kuSHhJeqZ_eA37NopOqv0feS188ZRUCZlIcf8TM4o8xAMJuU97RlAd2kDIS4JxEmRnBAHO5Hgm19LoqHQvnKfo_IBAQcrFPome3Z7HB2VuBVw_5B4xk4jMojgkTHDEzoE_680SiJJqheoYu5f-rNMh2vwN0eE9b4ACasaR9cPKgVIaA3isWIsECwWyEYuSlFRo3MWLM7j3R-52cQ-CD2LIwQmLR0JDCNn0qA1hc2QRAjYcgsLe67xY16veeXTmRNm_CWvfcMqLd7Zt26-dLkjRX9yqvBh1v1JXqOyYTTyA9HHOGkqF75TWoxEntlaNQrnqWyK2VbtpAGFTR27xOZO-FEXY09lwoGYz2yex27Uf7XY0gXp7sxhNnHwfM3-gYVxuWYCTtRoPXp9tuR8Ae9QgqJdYkzfqurp7ZOx66sRdMiFw22suyh5k95ta-KvagQnopapBqOqH2X1L9I3uCZrRTx8dcvqep4znleFWXRlC2vsrbJW1HyvIEGi7oWSZXjBEpn0Udm3ZC6brV0XAZPoFY--AcIdOnBIK5yxA9LGK3r5sm6okxX5W51_hdRcSe7">