linux-kernel - Re: [PATCH v2 1/8] minmax: Put all the clamp() definitions together

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Message-ID: <CAHk-=whwrXgtOrr6AKQTSYSG5V820cSsMcUjRhapnoqCh+Ciog@mail.gmail.com>
Date: Wed, 31 Jul 2024 08:38:20 -0700
From: Linus Torvalds <torvalds@...uxfoundation.org>
To: David Laight <David.Laight@...lab.com>
Cc: Arnd Bergmann <arnd@...nel.org>, 
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, Jens Axboe <axboe@...nel.dk>, 
	Matthew Wilcox <willy@...radead.org>, Christoph Hellwig <hch@...radead.org>, 
	Andrew Morton <akpm@...ux-foundation.org>, 
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>, 
	Dan Carpenter <dan.carpenter@...aro.org>, "Jason A . Donenfeld" <Jason@...c4.com>, 
	"pedro.falcato@...il.com" <pedro.falcato@...il.com>, Mateusz Guzik <mjguzik@...il.com>, 
	"linux-mm@...ck.org" <linux-mm@...ck.org>, Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Subject: Re: [PATCH v2 1/8] minmax: Put all the clamp() definitions together

On Wed, 31 Jul 2024 at 01:10, David Laight <David.Laight@...lab.com> wrote:
>
> The __UNIQUE_ID_() define just seemed excessive - especially
> since all compiler versions support __COUNTER__.

Yes, we could probably just simplify it.

The thing is, "all compiler versions support __COUNTER__" wasn't
historically true.

We used to have this:

  /* Not-quite-unique ID. */
  #ifndef __UNIQUE_ID
  # define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __LINE__)
  #endif

because __COUNTER__ is such a new-fangled thing and only got
introduced in gcc-4 or something like that.

So that "prefix" literally exists because it literally wasn't unique
enough without it.

And the "__UNIQUE_ID_" thing is probably because that way it was
clearer what was going on when something went wrong.

But together they really end up being a somewhat unreadable mess.

That said, I did end up liking the "prefix" part when looking at
expansions, because it helps show "which" expansion it is (ie "x_123"
and "y_124" were clearer than just some pure counter value that
doesn't have any relationship to the origin at all in the name).

But I did change it to "x_" from "__x", because that way it was
minimal, yet clearly separate from the counter number (ie "x_123" was
better than "__x123").

It was the repeated useless "__UNIQUE_ID_" part of the expansion that
ended up annoying. Not quite annoying enough to change it to just
"___" or something, but I was close.

           Linus