<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/82261>82261</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            Mach-O check for improperly nested .cfi_* regions doesn't take .alt_entry into account
        </td>
    </tr>

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

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

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

<pre>
    This issue was hit in https://github.com/Amanieu/corosensei/issues/23 where we have code that looks like this:
```asm
.globl _stack_init_trampoline
.private_extern _stack_init_trampoline
_stack_init_trampoline:
.cfi_startproc
[...]
.alt_entry _stack_init_trampoline_return
.globl _stack_init_trampoline_return
.private_extern _stack_init_trampoline_return
_stack_init_trampoline_return:
[...]
.cfi_endproc
```

This currently produces the following error due to https://reviews.llvm.org/D155245:

```
error: non-private labels cannot appear between .cfi_startproc / .cfi_endproc pairs
```

However I think (I am not an expert in Mach-O) that this should be valid since the inner label is properly marked with `.alt_entry`.

cc @jroelofs
</pre>
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