<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/126398>126398</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [Modules] `-Wembedded-directive` warning missing for pp-module in macro arguments
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            clang:frontend,
            clang:modules
      </td>
    </tr>

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

    <tr>
      <th>Reporter</th>
      <td>
          hubert-reinterpretcast
      </td>
    </tr>
</table>

<pre>
    The `-Wembedded-directive` warning is intended to identify the undefined behaviour specified in https://wg21.link/cpp.replace.general; however, it does not trigger for _pp-module_ (and likely other module-related forms of preprocessing directives).

A proposal (P2843) to require a diagnostic for such cases is before WG 21: https://github.com/cplusplus/papers/issues/1548

https://godbolt.org/z/seTaYE6nj

### Source (`<stdin>`)
```cpp
export module A;
#define A(X) # X

export char x[] = A(
module : private;
#if 0
#endif
);
```

### Compiler invocation
```
clang++ -fsyntax-only -std=c++20 -Wall -Wextra -pedantic -xc++ -
```

### Actual compiler output
```
<stdin>:6:2: warning: embedding a directive within macro arguments has undefined behavior [-Wembedded-directive]
    6 | #if 0
      |  ^
1 warning generated.
```

### Expected compiler output
(warning also for line 5)

### Compiler version info (`clang++ -v`)
```
clang version 21.0.0git (https://github.com/llvm/llvm-project.git e6e8ac59ba45e03da92aebec1f4561c1fa970df1)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /opt/wandbox/clang-head/bin
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/13
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/14
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/14
Candidate multilib: .;@m64
Selected multilib: .;@m64
```
</pre>
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