Re: [PATCH 2/3] uapi: get rid of STATX_ALL

From: Florian Weimer
Date: Thu Oct 18 2018 - 12:11:33 EST

* Amir Goldstein:

> On Thu, Oct 18, 2018 at 4:11 PM Miklos Szeredi <mszeredi@xxxxxxxxxx> wrote:
>> Constants of the *_ALL type can be actively harmful due to the fact that
>> developers will usually fail to consider the possible effects of future
>> changes to the definition.
>> Remove STATX_ALL from the uapi, while no damage has been done yet.
> Look. When Linus says "let's see if somebody notices" and referring to ABI
> it means sooner or later someone will upgrade to newer kernel and complain
> if something breaks.
> But what does it mean with UAPI change? How often do people
> re-build existing programs? I, for one, build master for my
> testing, but never install uapi headers from master. I just can't
> wrap my head around the backward compatibiltiy nightmare a change
> like this could create.

So it appears that people use #ifdef STATX_ALL to check for struct
statx availability. So the backwards compatibility impact is that you
silently lose features in a consistent manner, which is very hard to
spot. 8-(

Probably not a good idea, then.