linux-kernel - Re: Clarifying confusion of our variable placement rules caused by cleanup.h

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Message-ID: <20251118173412.1a43125a@gandalf.local.home>
Date: Tue, 18 Nov 2025 17:34:12 -0500
From: Steven Rostedt <rostedt@...dmis.org>
To: James Bottomley <James.Bottomley@...senPartnership.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>, Bart Van Assche
 <bvanassche@....org>, ksummit@...ts.linux.dev, Dan Williams
 <dan.j.williams@...el.com>, linux-kernel <linux-kernel@...r.kernel.org>,
 Dan Carpenter <dan.carpenter@...aro.org>
Subject: Re: Clarifying confusion of our variable placement rules caused by
 cleanup.h

On Tue, 18 Nov 2025 16:10:00 -0500
James Bottomley <James.Bottomley@...senPartnership.com> wrote:

> > 
> > 	{
> > 		struct foo *var __free(kfree) = kmalloc(...)
> > 
> > 		[...]
> > 
> > 		return func(..., var);
> > 	}
> > 
> > It seems a bit strange to have the final return of a function from
> > within an explicit scope block.  
> 
> Well, you did that ... the return could equally well have been outside
> the block.  However, I do think additional scoped blocks for variables
> looks most readable when the scope of the variable is less than the
> code on both sides.  If the variable doesn't go out of scope until the
> final return, I can see an argument for just doing an interior
> declaration.

I guess you mean by adding a ret value?

	{
		struct foo *var __free(kfree) = kmalloc(...)

		[...]

		ret = func(..., var);
	}

	return ret;

As the var that is passed to the function that this function is retuning
(tail call) is only scoped inside the brackets. But anyway, I don't plan on
changing the code in question here.

I do quite often use the scoped_guard() as that does document exactly what
the guard is protecting.

-- Steve