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From: Jeff King <peff@peff.net>
To: Doan Tran Cong Danh <congdanhqx@gmail.com>
Cc: git@vger.kernel.org
Subject: Re: [PATCH 1/3] t0028: eliminate non-standard usage of printf
Date: Thu, 31 Oct 2019 13:41:18 -0400	[thread overview]
Message-ID: <20191031174118.GA2133@sigill.intra.peff.net> (raw)
In-Reply-To: <20191031092618.29073-2-congdanhqx@gmail.com>

On Thu, Oct 31, 2019 at 04:26:16PM +0700, Doan Tran Cong Danh wrote:

> man 1p printf:
>    In addition to the escape sequences shown in the Base Definitions
>    volume of POSIX.1‐2008, Chapter 5, File Format Notation ('\\',
>    '\a', '\b', '\f', '\n', '\r', '\t', '\v'), "\ddd", where ddd is a
>    one, two, or three-digit octal number, shall be written as a byte
>    with the numeric value specified by the octal number.
> 
> printf '\xfe\xff' in an extension of some libc.

I don't think it's libc here at all, but rather the shell.

And as you note, dash does not handle this:

> With dash:
> $ printf '\xfe\xff' | xxd
> 00000000: 5c78 6665 5c78 6666                      \xfe\xff

Which makes me wonder how these tests worked at all for people on say,
Debian systems.

I think the answer is that they don't trigger this prereq:

>  write_utf16 () {
>  	if test_have_prereq NO_UTF16_BOM
>  	then
> -		printf '\xfe\xff'
> +		printf '\376\377'
>  	fi &&
>  	iconv -f UTF-8 -t UTF-16
>  }

which comes from:

  test_lazy_prereq NO_UTF16_BOM '
          test $(printf abc | iconv -f UTF-8 -t UTF-16 | wc -c) = 6
  '

Presumably on your system iconv is using musl's internal iconv, which
behaves differently than the glibc one.

So I think your patch is the right thing to do (hex escapes in shell
printf are definitely not portable), but we might want to note something
like:

  This wasn't caught by most people running the tests, even though
  common shells like dash don't handle hex escapes, because their
  systems don't trigger the NO_UTF16_BOM prereq. But systems with musl
  libc do; when combined with dash, the test fails.

-Peff

  reply	other threads:[~2019-10-31 17:41 UTC|newest]

Thread overview: 89+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-31  9:26 [PATCH 0/3] Linux with musl libc improvement Doan Tran Cong Danh
2019-10-31  9:26 ` [PATCH 1/3] t0028: eliminate non-standard usage of printf Doan Tran Cong Danh
2019-10-31 17:41   ` Jeff King [this message]
2019-11-01  1:33     ` Danh Doan
2019-10-31 19:50   ` brian m. carlson
2019-10-31  9:26 ` [PATCH 2/3] configure.ac: define ICONV_OMITS_BOM if necessary Doan Tran Cong Danh
2019-10-31 18:11   ` Jeff King
2019-10-31 20:02     ` brian m. carlson
2019-11-01  1:40     ` Danh Doan
2019-10-31  9:26 ` [PATCH 3/3] sequencer: reencode to utf-8 before arrange rebase's todo list Doan Tran Cong Danh
2019-10-31 10:38   ` Johannes Schindelin
2019-10-31 19:26     ` Jeff King
2019-11-01  4:49       ` Danh Doan
2019-11-01  8:25 ` [PATCH v2 0/3] Linux with musl libc improvement Doan Tran Cong Danh
2019-11-01  8:25   ` [PATCH v2 1/3] t0028: eliminate non-standard usage of printf Doan Tran Cong Danh
2019-11-01 16:54     ` Jeff King
2019-11-01  8:25   ` [PATCH v2 2/3] configure.ac: define ICONV_OMITS_BOM if necessary Doan Tran Cong Danh
2019-11-01 16:56     ` Jeff King
2019-11-02  0:43       ` Danh Doan
2019-11-01  8:25   ` [PATCH v2 3/3] sequencer: reencode to utf-8 before arrange rebase's todo list Doan Tran Cong Danh
2019-11-01 16:59     ` Jeff King
2019-11-02  1:02       ` Danh Doan
2019-11-02 12:20         ` Danh Doan
2019-11-05  8:00         ` Jeff King
2019-11-06  1:30           ` Junio C Hamano
2019-11-06  4:03             ` Jeff King
2019-11-06 10:03               ` Danh Doan
2019-11-07  5:56                 ` Jeff King
2019-11-06  9:19 ` [PATCH v3 0/8] Correct internal working and output encoding Doan Tran Cong Danh
2019-11-06  9:19   ` [PATCH v3 1/8] t0028: eliminate non-standard usage of printf Doan Tran Cong Danh
2019-11-06  9:20   ` [PATCH v3 2/8] configure.ac: define ICONV_OMITS_BOM if necessary Doan Tran Cong Danh
2019-11-06  9:20   ` [PATCH v3 3/8] t3900: demonstrate git-rebase problem with multi encoding Doan Tran Cong Danh
2019-11-06  9:20   ` [PATCH v3 4/8] sequencer: reencode to utf-8 before arrange rebase's todo list Doan Tran Cong Danh
2019-11-06  9:20   ` [PATCH v3 5/8] sequencer: reencode revert/cherry-pick's " Doan Tran Cong Danh
2019-11-06  9:20   ` [PATCH v3 6/8] sequencer: reencode squashing commit's message Doan Tran Cong Danh
2019-11-06  9:20   ` [PATCH v3 7/8] sequencer: reencode old merge-commit message Doan Tran Cong Danh
2019-11-06 15:39     ` Eric Sunshine
2019-11-06  9:20   ` [PATCH v3 8/8] sequencer: reencode commit message for am/rebase --show-current-patch Doan Tran Cong Danh
2019-11-07  2:56 ` [PATCH v4 0/8] Correct internal working and output encoding Doan Tran Cong Danh
2019-11-07  2:56   ` [PATCH v4 1/8] t0028: eliminate non-standard usage of printf Doan Tran Cong Danh
2019-11-07  2:56   ` [PATCH v4 2/8] configure.ac: define ICONV_OMITS_BOM if necessary Doan Tran Cong Danh
2019-11-07  6:18     ` Junio C Hamano
2019-11-07  2:56   ` [PATCH v4 3/8] t3900: demonstrate git-rebase problem with multi encoding Doan Tran Cong Danh
2019-11-07  6:02     ` Jeff King
2019-11-07  6:48       ` Danh Doan
2019-11-07  8:02         ` Jeff King
2019-11-07 10:51           ` Danh Doan
2019-11-11  8:22             ` Jeff King
2019-11-07  2:56   ` [PATCH v4 4/8] sequencer: reencode to utf-8 before arrange rebase's todo list Doan Tran Cong Danh
2019-11-07  6:04     ` Jeff King
2019-11-07  2:56   ` [PATCH v4 5/8] sequencer: reencode revert/cherry-pick's " Doan Tran Cong Danh
2019-11-07  6:06     ` Jeff King
2019-11-07  2:56   ` [PATCH v4 6/8] sequencer: reencode squashing commit's message Doan Tran Cong Danh
2019-11-07  6:15     ` Jeff King
2019-11-07  2:56   ` [PATCH v4 7/8] sequencer: reencode old merge-commit message Doan Tran Cong Danh
2019-11-07  2:56   ` [PATCH v4 8/8] sequencer: reencode commit message for am/rebase --show-current-patch Doan Tran Cong Danh
2019-11-07  6:32     ` Jeff King
2019-11-07  7:48       ` Danh Doan
2019-11-07  8:03         ` Jeff King
2019-11-07 16:32           ` Danh Doan
2019-11-08  9:43 ` [PATCH v5 0/9] Improve odd encoding integration Doan Tran Cong Danh
2019-11-08  9:43   ` [PATCH v5 1/9] t0028: eliminate non-standard usage of printf Doan Tran Cong Danh
2019-11-08  9:43   ` [PATCH v5 2/9] configure.ac: define ICONV_OMITS_BOM if necessary Doan Tran Cong Danh
2019-11-08  9:43   ` [PATCH v5 3/9] t3900: demonstrate git-rebase problem with multi encoding Doan Tran Cong Danh
2019-11-08  9:43   ` [PATCH v5 4/9] sequencer: reencode to utf-8 before arrange rebase's todo list Doan Tran Cong Danh
2019-11-08  9:43   ` [PATCH v5 5/9] sequencer: reencode revert/cherry-pick's " Doan Tran Cong Danh
2019-11-08  9:43   ` [PATCH v5 6/9] sequencer: reencode squashing commit's message Doan Tran Cong Danh
2019-11-08  9:43   ` [PATCH v5 7/9] sequencer: reencode old merge-commit message Doan Tran Cong Danh
2019-11-08  9:43   ` [PATCH v5 8/9] sequencer: reencode commit message for am/rebase --show-current-patch Doan Tran Cong Danh
2019-11-08  9:43   ` [PATCH v5 9/9] sequencer: fallback to sane label in making rebase todo list Doan Tran Cong Danh
2019-11-11  1:22   ` [PATCH v5 0/9] Improve odd encoding integration Junio C Hamano
2019-11-11  4:02   ` Junio C Hamano
2019-11-11  4:43     ` Danh Doan
2019-11-11  6:14     ` Junio C Hamano
2019-11-11  6:03 ` [PATCH v6 0/9] sequencer: handle other encoding better Doan Tran Cong Danh
2019-11-11  6:03   ` [PATCH v6 1/9] t0028: eliminate non-standard usage of printf Doan Tran Cong Danh
2019-11-11  6:03   ` [PATCH v6 2/9] configure.ac: define ICONV_OMITS_BOM if necessary Doan Tran Cong Danh
2019-11-11  6:03   ` [PATCH v6 3/9] t3900: demonstrate git-rebase problem with multi encoding Doan Tran Cong Danh
2019-11-11  6:03   ` [PATCH v6 4/9] sequencer: reencode to utf-8 before arrange rebase's todo list Doan Tran Cong Danh
2019-11-11  6:03   ` [PATCH v6 5/9] sequencer: reencode revert/cherry-pick's " Doan Tran Cong Danh
2019-11-11  6:03   ` [PATCH v6 6/9] sequencer: reencode squashing commit's message Doan Tran Cong Danh
2019-11-11  6:03   ` [PATCH v6 7/9] sequencer: reencode old merge-commit message Doan Tran Cong Danh
2019-11-11  6:03   ` [PATCH v6 8/9] sequencer: reencode commit message for am/rebase --show-current-patch Doan Tran Cong Danh
2019-11-11  6:03   ` [PATCH v6 9/9] sequencer: fallback to sane label in making rebase todo list Doan Tran Cong Danh
2019-11-11  8:39     ` Jeff King
2019-11-11 16:22       ` Phillip Wood
2019-11-11 18:26     ` Johannes Schindelin
2019-11-12  4:17       ` Junio C Hamano
2019-11-11  8:40   ` [PATCH v6 0/9] sequencer: handle other encoding better Jeff King

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