git.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Jeff King <peff@peff.net>
To: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Cc: Alexandr Miloslavskiy <alexandr.miloslavskiy@syntevo.com>,
	Alexandr Miloslavskiy via GitGitGadget  <gitgitgadget@gmail.com>,
	git@vger.kernel.org, Junio C Hamano <gitster@pobox.com>
Subject: Re: [PATCH v2 1/1] vreportf: Fix interleaving issues, remove 4096 limitation
Date: Fri, 25 Oct 2019 18:11:19 -0400	[thread overview]
Message-ID: <20191025221118.GA29213@sigill.intra.peff.net> (raw)
In-Reply-To: <nycvar.QRO.7.76.6.1910251548560.46@tvgsbejvaqbjf.bet>

On Fri, Oct 25, 2019 at 04:02:36PM +0200, Johannes Schindelin wrote:

> ... and indeed, I verified that this patch fixes the problem:
> 
> -- snip --
> diff --git a/usage.c b/usage.c
> index 2fdb20086bd..7f5bdfb0f40 100644
> --- a/usage.c
> +++ b/usage.c
> @@ -10,13 +10,16 @@ void vreportf(const char *prefix, const char *err, va_list params)
>  {
>  	char msg[4096];
>  	char *p;
> -
> -	vsnprintf(msg, sizeof(msg), err, params);
> +	size_t off = strlcpy(msg, prefix, sizeof(msg));
> +	int ret = vsnprintf(msg + off, sizeof(msg) - off, err, params);
>  	for (p = msg; *p; p++) {
>  		if (iscntrl(*p) && *p != '\t' && *p != '\n')
>  			*p = '?';
>  	}
> -	fprintf(stderr, "%s%s\n", prefix, msg);
> +	if (ret > 0) {
> +		msg[off + ret] = '\n'; /* we no longer need a NUL */
> +		write_in_full(2, msg, off + ret + 1);
> +	}
>  }

Heh. This is quite similar to what I posted in:

  https://public-inbox.org/git/20190828145412.GB14432@sigill.intra.peff.net/

though I missed the cleverness with "we no longer need a NUL" to get an
extra byte. ;)

> > except truncation to 4096. Then I would expect a patch to increase
> > buffer size to 8192 in the next couple years. And if you also try to
> > solve truncation, it will get you very close to my code.
> 
> My point is: I don't want to "fix" truncation. I actually think of it as
> a feature. An error message that is longer than the average news article
> I read is too long, period.

Yeah. As the person responsible for many of the "avoid truncation" works
referenced in the original patch, I have come to the conclusion that it
is not worth the complexity. Even when we do manage to produce a
gigantic error message correctly, it's generally not very readable.

That's basically what I came here to say, and I was pleased to find that
you had already argued for it quite well. So I'll just add my support
for the direction you've taken the conversation.

I _do_ wish we could do the truncation more intelligently. I'd much
rather see:

  error: unable to open 'absurdly-long-file-name...': permission denied

than:

  error: unable to open 'absurdly-long-file-name-that-goes-on-forever-and-ev

But I don't think it's possible without reimplementing snprintf
ourselves.

-Peff

  parent reply	other threads:[~2019-10-25 22:11 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-22 14:39 [PATCH 0/1] " Alexandr Miloslavskiy via GitGitGadget
2019-10-22 14:39 ` [PATCH 1/1] " Alexandr Miloslavskiy via GitGitGadget
2019-10-22 14:45 ` [PATCH v2 0/1] " Alexandr Miloslavskiy via GitGitGadget
2019-10-22 14:45   ` [PATCH v2 1/1] " Alexandr Miloslavskiy via GitGitGadget
2019-10-25 11:37     ` Johannes Schindelin
2019-10-25 12:38       ` Alexandr Miloslavskiy
2019-10-25 14:02         ` Johannes Schindelin
2019-10-25 14:15           ` Alexandr Miloslavskiy
2019-10-25 21:28             ` Johannes Schindelin
2019-10-25 22:11           ` Jeff King [this message]
2019-10-26  8:02             ` Alexandr Miloslavskiy
2019-10-26 20:56             ` Johannes Schindelin
2019-10-26 21:36               ` Jeff King
2019-10-28 16:05                 ` Johannes Schindelin
2019-10-26 21:56               ` Johannes Schindelin
2019-10-26 22:05                 ` Johannes Schindelin

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20191025221118.GA29213@sigill.intra.peff.net \
    --to=peff@peff.net \
    --cc=Johannes.Schindelin@gmx.de \
    --cc=alexandr.miloslavskiy@syntevo.com \
    --cc=git@vger.kernel.org \
    --cc=gitgitgadget@gmail.com \
    --cc=gitster@pobox.com \
    --subject='Re: [PATCH v2 1/1] vreportf: Fix interleaving issues, remove 4096 limitation' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).