<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/142614>142614</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [Clang] Different `-Wunused-value` output in preprocessed source code
        </td>
    </tr>

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

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

    <tr>
      <th>Reporter</th>
      <td>
          iii-i
      </td>
    </tr>
</table>

<pre>
    Clang reports `-Wunused-value` for the following code:

```
int f(void);
void g(void) { (long)f(); }
```

but not the following:

```
int f(void);
#define MACRO() (long)f()
void g(void) { MACRO(); }
```

This is because `DiagnoseUnused()` calls `S.SourceMgr.isMacroBodyExpansion()`.
This is problematic when one tries to work with preprocessed source code, for example, using `icecc` to build it on a remote machine.
Is there a way to preserve macro expansion information, in order to make `isMacroBodyExpansion()` return identical values for both preprocessed and non-preprocessed source code?
</pre>
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