Re: [PATCH v1 2/2] io_uring: uapi: Don't use a zero-size array

[Ammar Faizi <ammarfaizi2@gnuweeb.org>]

On 11/16/22 5:14 PM, Pavel Begunkov wrote:
> On 11/15/22 21:29, Ammar Faizi wrote:
>> From: Ammar Faizi <ammarfaizi2@gnuweeb.org>
>>
>> Don't use a zero-size array because it doesn't allow the user to
>> compile an app that uses liburing with the `-pedantic-errors` flag:
> 
> Ammar, I'd strongly encourage you to at least compile your
> patches or even better actually test them. There is an explicit
> BUILD_BUG_ON() violated by this change.

Oh yeah, I didn't realize that. This patch breaks this assertion:

   BUILD_BUG_ON failed: sizeof_field(struct io_uring_sqe, cmd) != 0

This assertion wants the size of cmd[] to be zero. Which is obviously
violated in this patch.

I only tested a liburing app that uses this header and validated
that the struct size is the same, but not its field. That's my
mistake.

I'm *not* going to send a v2 per Jens' comment.

-- 
Ammar Faizi