From: ZheNing Hu <adlternative@gmail.com>
To: Junio C Hamano <gitster@pobox.com>
Cc: ZheNing Hu via GitGitGadget <gitgitgadget@gmail.com>,
Git List <git@vger.kernel.org>,
Christian Couder <christian.couder@gmail.com>,
Hariom Verma <hariom18599@gmail.com>,
Karthik Nayak <karthik.188@gmail.com>
Subject: Re: [PATCH 0/3] [GSOC][RFC] ref-filter: add contents:raw atom
Date: Wed, 26 May 2021 14:45:58 +0800 [thread overview]
Message-ID: <CAOLTT8ReZffY5gznSDD=Fgbt7YTtA5aJWX+f8Q8npcj0OwcuFQ@mail.gmail.com> (raw)
In-Reply-To: <xmqq8s42cnyb.fsf@gitster.g>
>
> Another thing to keep in mind is that not all host languages may be
> capable of expressing a string with NUL in it. Most notably, shell.
> The --shell quoting rule used by for-each-ref would produce an
> equivalent of the "script" produced like this:
>
> $ tr Q '\000' >script <<\EOF
> #!/bin/sh
> varname='varQname'
> echo "$varname"
> EOF
>
> but I do not think it would say 'var' followed by a NUL followed by
> 'name'. The NUL is likely lost when assigned to the variable.
>
Yes, in the following example you mentioned earlier, I have also
noticed the loss of '\0'.
> > git for-each-ref --format='
> > name=%(refname)
> > var=%(placeholder)
> > mkdir -p "$(dirname "$name")"
> > printf "%%s" "$var" >"$name"
> > ' --shell | /bin/sh
> >
> So for some host languages, binaries may be useless with or without
> quoting. But for ones that can use strings to hold arbitrary byte
> sequence, it should be OK to let for-each-ref to quote the byte
> sequence as a string literal for the language (so that the exact
> byte sequence will end up being in the variable after assignment).
>
I agree, and maybe some'\0' can be escaped appropriately to let host
languages recognize it....
> That reminds me of another thing. The --python thing was written
> back when Python3 was still a distant dream and strings were the
> appropriate type for a random sequence of bytes (as opposed to
> unicode, which cannot have a random sequence of bytes). Somebody
> needs to check if it needs any update to work with Python3.
$ printf '%b' "name='a\\\0b\\\0c'\nprint(name)" | python2.7 | od -c
0000000 a \0 b \0 c \n
0000006
$ printf '%b' "name='a\\\0b\\\0c'\necho -e \"\$name\"" | sh | od -c
0000000 a \0 b \0 c \n
0000006
In shell or python2/3, we can replace'\0' with "\\0".
In Tcl and perl, they are ok with '\0'.
$ printf '%b' "set name \"a\0b\0c\"\nputs \$name" | tclsh | od -c
0000000 ' a \0 b \0 c ' \n
0000010
$ printf '%b' "\$name = 'a\0b\0c';\n print \"\$name\"" | perl | od -c
0000000 a \0 b \0 c
0000005
So I currently think that a possible strategy is to modify
`python_quote_buf_with_size()` and `sq_quote_buf_with_size()` from
'\0' to "\\0".
Thanks!
--
ZheNing Hu
next prev parent reply other threads:[~2021-05-26 6:46 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-23 9:53 [PATCH 0/3] [GSOC][RFC] ref-filter: add contents:raw atom ZheNing Hu via GitGitGadget
2021-05-23 9:53 ` [PATCH 1/3] [GSOC] quote: add *.quote_buf_with_size functions ZheNing Hu via GitGitGadget
2021-05-23 9:53 ` [PATCH 2/3] [GSOC] ref-filter: support %(contents) for blob, tree ZheNing Hu via GitGitGadget
2021-05-25 5:03 ` Junio C Hamano
2021-05-25 5:47 ` Junio C Hamano
2021-05-25 9:28 ` ZheNing Hu
2021-05-25 17:11 ` Junio C Hamano
2021-05-26 7:48 ` ZheNing Hu
2021-05-23 9:53 ` [PATCH 3/3] [GSOC] ref-filter: add contents:raw atom ZheNing Hu via GitGitGadget
2021-05-24 1:09 ` [PATCH 0/3] [GSOC][RFC] " Junio C Hamano
2021-05-24 2:41 ` Felipe Contreras
2021-05-24 5:22 ` Bagas Sanjaya
2021-05-24 15:21 ` Junio C Hamano
2021-05-24 13:09 ` ZheNing Hu
2021-05-26 0:56 ` Junio C Hamano
2021-05-26 6:45 ` ZheNing Hu [this message]
2021-05-26 7:06 ` Junio C Hamano
2021-05-26 9:17 ` ZheNing Hu
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