Re: [PATCH] err_ptr.h: introduce ERR_PTR_SAFE()

[David Laight]

On Fri, 15 May 2026 21:26:04 +0200
Amir Goldstein <amir73il@xxxxxxxxx> wrote:

> On Fri, May 15, 2026 at 8:30 PM David Laight
> <david.laight.linux@xxxxxxxxx> wrote:
> >
> > On Thu, 14 May 2026 22:01:29 +0200
> > Amir Goldstein <amir73il@xxxxxxxxx> wrote:
> >  
...
> >
> > The object code bloat would be noticeable if this were used everywhere.
> > But you could make it a bit simpler:
> >         if (__builtin_constant_p(__e))
> >                 BUILD_BUG_ON(__e && !IS_ERR_VALUE(__e));
> >         else if WARN_ON(__e && !IS_ERR_VALUE(__e))
> >                 __e = -MAX_ERRNO; // Or maybe -EINVAL to stop and other boundary errors
> >         (void *)__e;  
> 
> Yeh that's nicer thanks.

Actually this might be better still (or just more succinct):
	void *__e = (void *)error;
	BUILD_BUG_ON(!statically_true(IS_ERR_OR_NULL(__e));
	if (WARN_ON(!IS_ERR_OR_NULL(__e))
		__e = (void *)-EINVAL;
	__e;

The WARN_ON() will be optimised away (valid) constants.

> > The check for constants may be fairly pointless.
> > One of the static checkers may already detect the obvious fubar ERR_PTR(EINVAL).  
> 
> True, but I figured it didn't add much overhead if we are placing
> the runtime assertions anyway?

The 'size' check in READ_ONCE() measurably slows down the kernel compilation.
But there are a lot of those.
I think I know the main reason - the extern for the 'error message function'.

-- David

> 
> Thanks,
> Amir.