Re: enabling -Werror=assign-enum for kernel

On 8/26/26 12:23, Gleb Smirnoff wrote:
>    John,
> 
> On Wed, Aug 26, 2026 at 01:15:27PM -0400, John Baldwin wrote:
> J> > J> Note that C++ doesn't allow this at the language level.  When I converted ctld to
> J> > J> C++ I had to adjust some enums to be simple #define's instead in the ctl headers.
> J> >
> J> > Noted.  I can't make a judgement if it is a smart restriction by C++ or not.
> J> > In our case using enums as flags is common and handy and Werror=assign-enum in
> J> > combination with __attribute__((flag_enum)) will make this use fortified
> J> > against mistakes.
> J>
> J> Mostly my point is that over time we may be forced to convert away from enums to
> J> plain constants if more of the base system starts using C++ anyway.  At least for
> J> enums exposed to userspace.
> 
> But if C++ doesn't allow flag enums in principle, then they just can't go into
> userspace headers, no matter how we compile the kernel.  Basically we already
> are there, and enabling Werror=assign-enum for kernel won't change anything,
> will it?
> 
I don't really have comments on the rest of this, but at least one of our downstreams does
use C++ in the kernel and it'd be nice if we didn't have anything too critical require too
heavy of patching to work in that environment.

Thanks,

Kyle Evans