From: Rafael Aquini <aquini@redhat.com>
To: Rasmus Villemoes <rasmus.villemoes@prevas.dk>
Cc: Audra Mitchell <audra@redhat.com>,
linux-kernel@vger.kernel.org, tj@kernel.org,
jiangshanlai@gmail.com, hirokazu.yamauchi.hk@hitachi.com,
ddouwsma@redhat.com, loberman@redhat.com, raquini@redhat.com
Subject: Re: [PATCH v2] workqueue.c: Increase workqueue name length
Date: Wed, 10 Jan 2024 18:08:23 -0500 [thread overview]
Message-ID: <ZZ8jZ3J63jf4Ap3y@optiplex-fbsd> (raw)
In-Reply-To: <ace8c8db-ff33-465f-9415-dfcb1c522f4f@prevas.dk>
On Wed, Jan 10, 2024 at 11:52:38PM +0100, Rasmus Villemoes wrote:
> On 10/01/2024 23.31, Rafael Aquini wrote:
> > On Wed, Jan 10, 2024 at 11:06:22PM +0100, Rasmus Villemoes wrote:
> >> On 10/01/2024 22.52, Rafael Aquini wrote:
>
> >>> The extra vsnprintf call is required because the return of the existing
> >>> vsnprintf() is going to be already capped by sizeof(wq->name).
> >>
> >> No, it is not. vsnprintf() returns the length of the would-be-created
> >> string if the buffer was big enough. That is independent of whether one
> >> does a dummy NULL,0 call or just calls it with a real, but possibly too
> >> small, buffer.
> >>
> >> This is true for userspace (as required by posix) as well as the kernel
> >> implementation of vsnprintf(). What makes you think otherwise?
> >>
> >
> > this snippet from PRINTF(3) man page
> >
> > RETURN VALUE
> > Upon successful return, these functions return the number of characters
> > printed (excluding the null byte used to end output to strings).
> >
>
> Assuming we have the same man pages installed, try reading the very next
> paragraph:
>
> The functions snprintf() and vsnprintf() do not write more than size
> bytes (including the terminating null byte ('\0')). If the output was
> truncated due to this limit, then the return value is the number of
> characters (excluding the terminating null byte) which would have been
> written to the final string if enough space had been available. Thus,
> a return value of size or more means that the output was truncated.
>
> How else would you even expect the vsnprintf(NULL, 0, ...) thing to work?
>
OK, that's my bad! Sorry for the noise.
-- Rafael
next prev parent reply other threads:[~2024-01-10 23:08 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-12-15 19:39 [PATCH] workqueue.c: Change workqueue to accept variable length name Audra Mitchell
2023-12-21 21:39 ` Tejun Heo
[not found] ` <CA+bDH-v6T5vvyOwsphseHwgihdGQta7TZ9tOtt-Fnij92kvU6A@mail.gmail.com>
2023-12-22 17:53 ` Tejun Heo
2024-01-09 13:29 ` Audra Mitchell
2024-01-10 20:29 ` [PATCH v2] workqueue.c: Increase workqueue name length Audra Mitchell
2024-01-10 20:47 ` Rasmus Villemoes
2024-01-10 21:52 ` Rafael Aquini
2024-01-10 22:06 ` Rasmus Villemoes
2024-01-10 22:31 ` Rafael Aquini
2024-01-10 22:45 ` Rafael Aquini
2024-01-10 22:58 ` Rasmus Villemoes
2024-01-10 22:52 ` Rasmus Villemoes
2024-01-10 23:08 ` Rafael Aquini [this message]
2024-01-15 17:08 ` [PATCH v3] " Audra Mitchell
2024-01-16 18:31 ` Tejun Heo
2024-01-17 14:40 ` Audra Mitchell
2024-01-17 17:09 ` Tejun Heo
2024-01-19 20:30 ` Audra Mitchell
2024-01-19 23:44 ` Tejun Heo
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