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

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Message-ID: <20251125073224.30e24755@phoenix.local>
Date: Tue, 25 Nov 2025 07:32:24 -0800
From: Stephen Hemminger <stephen@...workplumber.org>
To: Alexey Dobriyan <adobriyan@...il.com>
Cc: James Bottomley <James.Bottomley@...senPartnership.com>,
 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, 25 Nov 2025 17:25:19 +0300
Alexey Dobriyan <adobriyan@...il.com> wrote:

> On Tue, Nov 18, 2025 at 11:39:26AM -0500, James Bottomley wrote:
> 
> > So which should we do?  
> 
> The best way to understand that C89 style of declaring in the beginning
> of the function is pointless rule is to write some code in a language
> which doesn't enforce it. You should see that nothing bad happens.
> 
> It increases bug rate due to increased variable scope allowing typos.
> 
> It bloats LOC -- in many cases declaration and initializer can fit
> into a single line.
> 
> It prevents adding "const" qualifier if necessary.
> 
> Pressing PageUp and PageDown when adding new variable is pointless
> busywork and distracts, breaks the tempo(flow?) so to speak.
> 
> C89 style provokes substyles(!) which makes adding new variables even
> more obnoxious: some subsystems have(had?) a rule saying that declarations
> (with initializers) must be sorted by length, so not only programmer has
> to PageUp to the beginning of the block, but then aim carefully and
> insert new declaration.
> 
> None of this is necessary (or possible) if the rule says "declare as low
> as possible".
> 
> There was variation of this type of nonsense with headers (not only it has
> to be sorted alphabetically but by length too!)
> 
> There is no practical difference between code and declarations:
> declarations can have initializers which can be arbitrary complex,
> just like "real" code. So the only difference is superficial.
> 
> 
> C89 declaration style is pointless and dumb, no wonder other programming
> languages dumped it (or never had), it should be simply discarded.
> 
> It will also make Linux slightly less white crow to newcomers
> (C++ doesn't have this rule after all).
> 

Agree with everything you said.
But I don't want to see patches that are just to rearrange existing
code to move declarations around. So yes, but no more churn please.