<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/83270>83270</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [Flang] Preprocessing lower case .f## file should report on preprocessor directives unless -cpp is given (gfortran compability)
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            flang:frontend,
            flang,
            flang:semantics
      </td>
    </tr>

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

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

<pre>
    flang-new silently skips -DMACRO flag if it preprocesses lower case *.f## file unless -cpp flag is given. Proof:
Source file:
``` 
#ifdef TEST
#define A 1
#else
#define A 0
#endif

program main
  print *, A
end program
``` 
compilation command:
` flang-new -DTEST file.f90`
Output:
``` 
> ./a.out
0 //Expected output 1, because of -DTEST
``` 
gfrotran reports that preprocessor macros are not handled:
``` 
gfortran -DTEST file.f90

    1 | #ifdef TEST
 |  1
Warning: Illegal preprocessor directive
``` 
</pre>
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