From: Jeff King <peff@peff.net>
To: "erik elfström" <erik.elfstrom@gmail.com>
Cc: Jonathan Nieder <jrnieder@gmail.com>,
Git List <git@vger.kernel.org>,
Junio C Hamano <gitster@pobox.com>
Subject: Re: [PATCH v5 1/5] setup: add gentle version of read_gitfile
Date: Tue, 28 Apr 2015 16:19:19 -0400 [thread overview]
Message-ID: <20150428201918.GA10902@peff.net> (raw)
In-Reply-To: <CAMpP7Nb3aiMoTjtPJNJPv38G54ZawS8B+NDX0x2iNe6FA-L+Lw@mail.gmail.com>
On Tue, Apr 28, 2015 at 10:07:43PM +0200, erik elfström wrote:
> On Tue, Apr 28, 2015 at 8:17 AM, Jeff King <peff@peff.net> wrote:
> >
> > There was a discussion not too long ago on strategies for returning
> > errors, and one of the suggestions was to return an "error strbuf"
> > rather than a code[1]. That's less flexible, as the caller can't react
> > differently based on the type of error. But for cases like this, where
> > the only fate for the code is to get converted back into a message,
> > it can reduce the boilerplate.
> >
> > What you have here is OK to me, and I don't want to hold up your patch
> > series in a flamewar about error-reporting techniques. But I think it's
> > an interesting case study.
> >
> > -Peff
>
> Thanks. I haven't had time to look through that thread yet, I'll try
> to get to that later.
>
> My initial reaction is a bit skeptical though. For this case we
> currently don't want any error reporting, the NULL return is
> sufficient and even allocating and sending in the int* is pure noise.
> Allocating and releasing a strbuf seems like a lot more overhead for
> this type of caller? The one other potential candidate caller for
> read_gitfile_gently that I have seen (clone.c:get_repo_path) don't
> want any error code or message either as far as i can tell.
I had envisioned that the strbuf would be optional. I.e., you would
have:
/* like error(), but dump the message in a strbuf instead of stderr */
int error_buf(struct strbuf *buf, const char *fmt, ...)
{
if (buf) {
va_list ap;
va_start(ap, fmt);
strbuf_vaddf(buf, fmt, ap);
va_end(ap);
}
return -1;
}
and then in the error-reporting function:
const char *read_gitfile_gently(const char *path, struct strbuf *err)
{
...
fd = open(path, O_RDONLY);
if (fd < 0) {
error_buf(err, "unable to open %s: %s", path, strerror(errno));
return NULL; /* or goto cleanup if necessary */
}
}
and then one caller can do:
if (!read_gitfile_gently(path, NULL)) {
/* we know there was an error, but we did not ask for details */
...
}
and the non-gentle read_gitfile() becomes:
const char *read_gitfile(const char *path)
{
struct strbuf err = STRBUF_INIT;
const char *ret = read_gitfile_gently(path, &err);
if (!ret)
die("%s", err.buf);
/* no need to free err; if there was no error, nothing was written */
return path;
}
Note that the "return -1" from error_buf() is not useful here, but it
might be used as a shortcut in other situations (e.g., the same places
we call "return error()" now).
> Also if it turns out that we actually need to treat the "file too
> large" error differently in clean (as discussed in thread on the file
> size check) then we can no longer communicate that back using the
> strbuf interface.
Yeah, agreed. This system breaks down as soon as you need to
programatically know which error happened.
-Peff
next prev parent reply other threads:[~2015-04-28 20:19 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-04-25 9:06 [PATCH v4 0/5] Improving performance of git clean Erik Elfström
2015-04-25 9:06 ` [PATCH v4 1/5] setup: add gentle version of read_gitfile Erik Elfström
2015-04-25 16:51 ` Junio C Hamano
2015-04-25 16:54 ` Junio C Hamano
2015-04-25 9:06 ` [PATCH v4 2/5] setup: sanity check file size in read_gitfile_gently Erik Elfström
2015-04-25 16:47 ` Junio C Hamano
2015-04-25 17:59 ` Erik Elfström
2015-04-26 4:29 ` Junio C Hamano
2015-04-26 6:49 ` [PATCH v5 0/5] Improving performance of git clean Erik Elfström
2015-04-26 6:49 ` [PATCH v5 1/5] setup: add gentle version of read_gitfile Erik Elfström
2015-04-28 6:17 ` Jeff King
2015-04-28 20:07 ` erik elfström
2015-04-28 20:19 ` Jeff King [this message]
2015-04-28 20:34 ` Jonathan Nieder
2015-04-28 20:36 ` Jeff King
2015-04-28 20:42 ` Jonathan Nieder
2015-04-28 20:48 ` Jeff King
2015-04-28 21:06 ` Jonathan Nieder
2015-04-28 23:34 ` Junio C Hamano
2015-04-29 23:47 ` Stefan Beller
2015-04-30 1:35 ` Junio C Hamano
2015-04-26 6:49 ` [PATCH v5 2/5] setup: sanity check file size in read_gitfile_gently Erik Elfström
2015-04-28 6:02 ` Jeff King
2015-04-28 7:21 ` Windows path limites, was " Johannes Schindelin
2015-04-28 15:33 ` Doug Kelly
2015-04-28 16:20 ` Windows path limits, " Johannes Schindelin
2015-04-28 19:28 ` erik elfström
2015-04-29 15:42 ` Junio C Hamano
2015-04-26 6:49 ` [PATCH v5 3/5] t7300: add tests to document behavior of clean and nested git Erik Elfström
2015-04-26 6:49 ` [PATCH v5 4/5] p7300: add performance tests for clean Erik Elfström
2015-04-28 6:33 ` Jeff King
2015-04-28 19:36 ` erik elfström
2015-04-26 6:49 ` [PATCH v5 5/5] clean: improve performance when removing lots of directories Erik Elfström
2015-04-28 6:24 ` Jeff King
2015-04-28 20:31 ` erik elfström
2015-04-25 9:06 ` [PATCH v4 3/5] t7300: add tests to document behavior of clean and nested git Erik Elfström
2015-04-25 9:06 ` [PATCH v4 4/5] p7300: add performance tests for clean Erik Elfström
2015-04-25 9:06 ` [PATCH v4 5/5] clean: improve performance when removing lots of directories Erik Elfström
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