<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/153638>153638</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            Override file of '-foverride-record-layout' is not read when C++ Modules are enabled
        </td>
    </tr>

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

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

    <tr>
      <th>Reporter</th>
      <td>
          sks75220
      </td>
    </tr>
</table>

<pre>
    The lit test "clang/test/CodeGenCXX/override-layout-nameless-struct-union.cpp" fails when C++ Modules are enabled.  We encountered this internally because we have set the default dialect to C++20 for PlayStation, exposing this problem.

The test case includes the following code:
```
// RUN: %clang_cc1 -w -fdump-record-layouts-simple -foverride-record-layout=%S/Inputs/override-layout-nameless-struct-union.layout %s | FileCheck %s
// CHECK: Type: struct S
// CHECK:   Size:64
// CHECK: Alignment:32
// CHECK:   FieldOffsets: [0, 32, 32]
struct S {
  short _s;
//union {
    int _su0;
    char _su1;
//};
};
```
It is an attempt to compile this struct with a non-standard layout specified in the input file.

However, if modules are enabled (either explicitly via -fmodules or implicitly via -std=c++20, or that being the default of the compiler) that layout file is never read, leading to the test failure. 

It appears to be a bug in the order of operations in clang/lib/Frontend/FrontEndAction.cpp in presence of modules.

This isn't urgent for us, because we are working around it by suppressing C++ Modules via adding the switch -fno-cxx-modules in the test's RUN line.  But regardless, I thought I should report it
</pre>
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