<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/140953>140953</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [LLVM] LTO usage errors incorrectly reported to the user as crashes/bugs
        </td>
    </tr>

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

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

    <tr>
      <th>Reporter</th>
      <td>
          bd1976bris
      </td>
    </tr>
</table>

<pre>
    Usage errors in `LTOBackend.cpp` are incorrectly reported to users as crashes/bugs.

For example, see the COFF LLD test [`lto-cache-errors.ll`](https://github.com/llvm/llvm-project/blob/e165bea1d4ec2de96ee0548cece79d71a75ce8f8/lld/test/COFF/lto-cache-errors.ll) and note the use of `not --crash` in this test.

This issue is more problematic on Windows than on Linux. On Windows, fatal errors typically produce additional output, including a stack trace and a message urging users to report a bug. For example, using the official LLVM 19 toolchain binaries, specifying an overly long cache directory results in the following output on my Windows 11 machine:

```
"lld-link.exe" msvc.bc /lldltocache:<too long dir name> /entry:main /out:a.out
LLVM ERROR: can't create cache directory <too long dir name>: invalid argument

PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace.
Exception Code: 0xC000001D
 #0 0x00007ff6b392cf36 xmlLinkGetData (c:\x\clang+llvm-19.1.0-x86_64-pc-windows-msvc\bin\lld-link.exe+0x180cf36)
 #1 0x00007ff6b38622d2 xmlLinkGetData (c:\x\clang+llvm-19.1.0-x86_64-pc-windows-msvc\bin\lld-link.exe+0x17422d2)
<...>
```

This kind of reporting is not appropriate for usage errors and recently confused one of Sony’s customers, who submitted a bug report (as instructed by the toolchain) after specifying an invalid LTO cache directory.

**Internal tracker:** TOOLCHAIN-17744
</pre>
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