Re: [PATCH v2 1/2][next] UAPI: ethtool: Use __struct_group() in struct ethtool_link_settings
From: Jakub Kicinski
Date: Sat Nov 09 2024 - 13:02:24 EST
On Tue, 29 Oct 2024 15:55:35 -0600 Gustavo A. R. Silva wrote:
> Use the `__struct_group()` helper to create a new tagged
> `struct ethtool_link_settings_hdr`. This structure groups together
> all the members of the flexible `struct ethtool_link_settings`
> except the flexible array. As a result, the array is effectively
> separated from the rest of the members without modifying the memory
> layout of the flexible structure.
>
> This new tagged struct will be used to fix problematic declarations
> of middle-flex-arrays in composite structs[1].
Possibly a very noob question, but I'm updating a C++ library with
new headers and I think this makes it no longer compile.
$ cat > /tmp/t.cpp<<EOF
extern "C" {
#include "include/uapi/linux/ethtool.h"
}
int func() { return 0; }
EOF
$ g++ /tmp/t.cpp -I../linux -o /dev/null -c -W -Wall -O2
In file included from /usr/include/linux/posix_types.h:5,
from /usr/include/linux/types.h:9,
from ../linux/include/uapi/linux/ethtool.h:18,
from /tmp/t.cpp:2:
../linux/include/uapi/linux/ethtool.h:2515:24: error: ‘struct ethtool_link_settings::<unnamed union>::ethtool_link_settings_hdr’ invalid; an anonymous union may only have public non-static data members [-fpermissive]
2515 | __struct_group(ethtool_link_settings_hdr, hdr, /* no attrs */,
| ^~~~~~~~~~~~~~~~~~~~~~~~~
I don't know much about C++, tho, so quite possibly missing something
obvious.