false positive - cpp/unused-static-function

**Description of the false positive**

Every instance of this on the OpenZFS codebase that I have checked appears to be a false positive.

For example, it reports `rrw_enter_read_impl()` is unused, when it is used in `rrw_enter_read()`, which is the next function definition:

https://github.com/ryao/zfs/security/code-scanning/184

The same happens with `abd_fletcher_4_impl()`:

https://github.com/ryao/zfs/security/code-scanning/203

And again with `zfs_rangelock_enter_writer()`, which is used in `zfs_rangelock_enter_impl()`:

https://github.com/ryao/zfs/security/code-scanning/202

Then there is `zfs_rangelock_enter_impl()`, which is used in `zfs_rangelock_enter()`:

https://github.com/ryao/zfs/security/code-scanning/200

zfs_ace_byteswap(), used in `zfs_acl_byteswap()`:

https://github.com/ryao/zfs/security/code-scanning/199

`chksum_run()`, used in `chksum_benchit()`:

https://github.com/ryao/zfs/security/code-scanning/198

`zap_cursor_init_impl()`, used in `zap_cursor_init_serialized()`, `zap_cursor_init()` and `zap_cursor_init_noprefetch()`:

https://github.com/ryao/zfs/security/code-scanning/197

`vdev_indirect_mapping_entry_for_offset_impl()`, used in multiple functions:

https://github.com/ryao/zfs/security/code-scanning/196

`vdev_open_children_impl()`, used in `vdev_open_children()`:

https://github.com/ryao/zfs/security/code-scanning/195

`space_reftree_add_node()`, used in `space_reftree_add_seg()`:

https://github.com/ryao/zfs/security/code-scanning/194

I suspect that all 43 reports are false positives, although so far, I have only explicitly checked about half of them. I have glanced at the ones that I did not explicitly check and I would be very surprised if any of those functions are unused since they are almost entirely important functions in the codebase.

Unused static functions tend to be pruned from the codebase fairly quickly, so I suspect that every report against the OpenZFS codebase is a false positive.

This is probably a duplicate of #10442. However, I figured I would file an issue anyway since the OpenZFS codebase should serve as a decent corpus on which to develop a revised query.