Re: [PATCH] strbuf_write: omit system call when length is zero

From: Stefan Beller <sbeller@google.com>
Date: Feb 26, 2016, 17:09 UTC
Message-ID: <CAGZ79kZYqf3K5mR0_1eeQHO-n675BRfEQvC_-YCb+gOPTJ5xXA@mail.gmail.com>
In-Reply-To: <xmqqy4a8l04f.fsf@gitster.mtv.corp.google.com>

On Thu, Feb 25, 2016 at 5:40 PM, Junio C Hamano <gitster@pobox.com> wrote:

Show 15 quoted lines

> Duy Nguyen <pclouds@gmail.com> writes:
>
>> On Fri, Feb 26, 2016 at 5:34 AM, Stefan Beller <sbeller@google.com> wrote:
>>> In case the length of the buffer is zero, we do not need to call the
>>> fwrite system call as a performance improvement.
>>
>> fwrite is a libc call, not system call. Are you sure it always calls
>> write() (assuming buffering is off)?
>
> I do not think so, but I suspect that the patch misstates its
> rationale (I said I get uncomfortable every time I see a function
> that takes size and nelem separately used by a caller that can
> potentially pass nleme=0, when I wondered it it is OK that no caller
> of this funtion checks its return value).
>

This is exactly what happened. I assumed fwrite would be a system call eventually.