linux-kernel - Re: [PATCH v2] <sys/param.h>: Add nitems() and snitems() macros

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Message-ID: <a7f33e89-4815-2210-7627-14757198a666@gmail.com>
Date:   Fri, 25 Sep 2020 19:46:04 +0200
From:   Alejandro Colomar <colomar.6.4.3@...il.com>
To:     Jonathan Wakely <jwakely@...hat.com>
Cc:     fweimer@...hat.com, linux-man@...r.kernel.org,
        libc-alpha@...rceware.org, gcc@....gnu.org, rusty@...tcorp.com.au,
        linux-kernel@...r.kernel.org, libstdc++@....gnu.org,
        libc-coord@...ts.openwall.com, enh@...gle.com
Subject: Re: [PATCH v2] <sys/param.h>: Add nitems() and snitems() macros



On 2020-09-25 19:39, Jonathan Wakely wrote:
 > Yes, I'm aware of all the rationale. I already said that it makes
 > sense in C++ where you have generic code. I am not convinced that it's
 > necessary to add to <sys/param.h> when all it does is a cast from
 > size_t to ptrdiff_t.
 >

While I would prefer a signed version, I could live with only 
'nitems()'.  Having all the __must_be_array thing is the most important 
part.

On 2020-09-25 19:42, Jonathan Wakely wrote:
> On 25/09/20 18:30 +0200, Alejandro Colomar via Libstdc++ wrote:
>> I have a similar number of ARRAY_SIZE() and ARRAY_SSIZE().
>> I could have '#define snitems(arr) ((ptrdiff_t)nitems(arr))' in my 
>> projects,
>> but is it really necessary?
> 
> The barrier for adding something to glibc headers should be a LOT
> higher than "I could [do it in my own code], but is it really
> necessary?"
> 
>> Did I convince you? :-)
> 
> No.
> 
> 

Well, you convinced me :)

I'll rewrite the patch, and the problem about <stddef.h> will vanish.

Cheers,

Alex