Re: [PATCH 3/3] introduce "format" date-mode

From: Eric Sunshine <sunshine@sunshineco.com>
Date: Jun 30, 2015, 18:13 UTC
Message-ID: <CAPig+cSJXZjrZ=OcV+C6bkCEHQFrw35-cjQ3At_Qo5KrpYxaQA@mail.gmail.com>
In-Reply-To: <20150630175852.GB5349@peff.net>

On Tue, Jun 30, 2015 at 1:58 PM, Jeff King <peff@peff.net> wrote:

Show 7 quoted lines

> On Tue, Jun 30, 2015 at 12:58:33PM -0400, Eric Sunshine wrote:
>> Beyond the extra allocation, I was also concerned about the
>> sledgehammer approach of "%s " to append a single character when there
>> are much less expensive ways to do so.
>
> I don't think there's any other way. We have to feed a contiguous buffer
> to strftime, and we don't own the buffer, so we have to make a new copy.

Sorry, I meant that the interpolation expense of "%s ". A cheaper (but more verbose) alternative might be:

    size_t n = strlen(fmt);
    const char *f = xmalloc(n + 2);
    strcpy(f, fmt);
    f[n] = ' ';
    f[n + 1] = '\0';
    ...
    free(f);

or something similar.