<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/81209>81209</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            llvm-cxxfilt help text/documentation conflates "gnu" (legacy) format with Itanium
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            tools:llvm-cxxfilt
      </td>
    </tr>

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

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

<pre>
    The documentation claims:

> `llvm-cxxfilt` is a symbol demangler that can be used as a replacement for the GNU `c++filt` tool.

`llvm-cxxfilt` claims to support `gnu` "GNU/Itanium" style mangling; however, `gnu` is not Itanium-style mangling for GNU `c++filt` (`gnu-v3` is).

For example:
```
$ c++filt --format=gnu foo__Fv _Z3foov
foo(void)
_Z3foov
$ c++filt --format=gnu-v3 foo__Fv _Z3foov
foo__Fv
foo()
```

>From the output of `llvm-cxxfilt --help`:
```
  --format=<value>      Specify mangling format. Currently ignored because only 'gnu' is supported
```

and in the documentation (https://llvm.org/docs/CommandGuide/llvm-cxxfilt.html):

> `--format=`<value>, `-s`
> Mangling scheme to assume. Valid values are auto (default, auto-detect the style) and gnu (assume GNU/Itanium style).

It seems an update from `gnu` to `gnu-v3` is in order. The option does not appear to check what is passed to it, so it is probably just an update to the text.

</pre>
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