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From: Stephane Chazelas <stephane@chazelas.org>
To: Bart Schaefer <schaefer@brasslantern.com>
Cc: Zsh hackers list <zsh-workers@zsh.org>
Subject: Re: [PATCH] (?) typeset array[position=index]=value
Date: Wed, 2 Jun 2021 10:11:45 +0100	[thread overview]
Message-ID: <20210602091145.xvyymjxdors6kqya@chazelas.org> (raw)
In-Reply-To: <CAH+w=7a+M7nTTqzmve+SZHwtEeRPTicQB5ZRy2XO6er4UhMb1w@mail.gmail.com>

2021-06-01 09:05:13 -0700, Bart Schaefer:
[...]
> > [...] unless we're happy to break backward
> > compatibility and make unset "assoc[$key]" work whatever the
> > value of $key (unset 'assoc[f\]oo]]' for unset the element of
> > key 'f\]oo]' for instance)
> 
> Hm, I'm not sure what backward-compatibility would be broken?  Do you
> mean that scripts that already have work-arounds for the current issue
> might stop working?

Yes, like that guy's unset_keys at
https://unix.stackexchange.com/questions/626393/in-zsh-how-do-i-unset-an-arbitrary-associative-array-element/626529#626529
mentioned earlier.

ATM, you need to do:

unset 'hash[\]]'

To unset the element of key "]" for instance.

Having said that, in practice, it's rare for values to be passed
literally. What you generally want to do is:

unset "hash[$key]"

With $key being any arbitrary string. And that's where the
problem is.

Maybe the best approach would be to make unset a dual
keyword/builtin like typeset/export... so one can do:

unset hash[$key]

And that hash[$key] being interpreted the same as when you do:

hash[$key]=value

Being able to do:

unset hash[(R)pattern]
unset hash[(I)pattern]

would also be useful. We don't want however subscript flags to
be interpreted in:

unset "hash[$key]"

as that would introduce command injection vulnerabilities, like
is already the case in things like:

$ key='(n:evil:)' evil='psvar[$(uname>&2)1]' zsh -c 'typeset -A a; (( a[$key]++ ))'
Linux
Linux

(though in that case, that's not limited to subscript flags,
key='x]+psvar[$(uname>&2)1' works as well, see
https://unix.stackexchange.com/questions/627474/how-to-use-associative-arrays-safely-inside-arithmetic-expressions/627475#627475
)


That's also why I was suggesting allowing:

hash[$key]=()

to unset an element, where you don't have the ambiguity of
whether the contents of $key is going to be interpreted
specially.

-- 
Stephane


  parent reply	other threads:[~2021-06-02  9:12 UTC|newest]

Thread overview: 58+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-16 21:10 regexp-replace and ^, word boundary or look-behind operators Stephane Chazelas
2019-12-16 21:27 ` Stephane Chazelas
2019-12-17  7:38   ` Stephane Chazelas
2019-12-17 11:11     ` [PATCH] " Stephane Chazelas
2019-12-18  0:22       ` Daniel Shahaf
2019-12-18  8:31         ` Stephane Chazelas
2020-01-01 14:03         ` [PATCH v2] " Stephane Chazelas
2021-04-30  6:11           ` Stephane Chazelas
2021-04-30 23:13             ` Bart Schaefer
2021-05-05 11:45               ` [PATCH v3] regexp-replace and ^, word boundary or look-behind operators (and more) Stephane Chazelas
2021-05-31  0:58                 ` Lawrence Velázquez
2021-05-31 18:18                 ` Bart Schaefer
2021-05-31 21:37                   ` [PATCH] (?) typeset array[position=index]=value Bart Schaefer
2021-06-01  5:32                     ` Stephane Chazelas
2021-06-01 16:05                       ` Bart Schaefer
2021-06-02  2:51                         ` [PATCH] (take two?) typeset array[position=index]=value / unset hash[$stuff] Bart Schaefer
2021-06-02 10:06                           ` Stephane Chazelas
2021-06-02 14:52                             ` Bart Schaefer
2021-06-02 16:02                               ` Stephane Chazelas
2021-06-02  9:11                         ` Stephane Chazelas [this message]
2021-06-02 13:34                           ` [PATCH] (?) typeset array[position=index]=value Daniel Shahaf
2021-06-02 14:20                             ` Stephane Chazelas
2021-06-02 15:59                               ` Bart Schaefer
2021-06-03  2:04                                 ` [PATCH (not final)] (take three?) unset "array[$anything]" Bart Schaefer
2021-06-03  2:42                                   ` Bart Schaefer
2021-06-03  6:12                                     ` Bart Schaefer
2021-06-03  8:54                                       ` Peter Stephenson
2021-06-03 13:13                                         ` Stephane Chazelas
2021-06-03 14:41                                           ` Peter Stephenson
2021-06-04 19:25                                             ` Bart Schaefer
2021-06-05 18:18                                               ` Peter Stephenson
2021-06-09 23:31                                                 ` Bart Schaefer
2021-06-13 16:51                                                   ` Peter Stephenson
2021-06-13 18:04                                                     ` Bart Schaefer
2021-06-13 19:48                                                       ` Peter Stephenson
2021-06-13 21:44                                                         ` Bart Schaefer
2021-06-14  7:19                                                           ` Stephane Chazelas
2021-06-03 18:12                                           ` Bart Schaefer
2021-06-04  8:02                                             ` Stephane Chazelas
2021-06-04 18:36                                               ` Bart Schaefer
2021-06-04 20:21                                                 ` Stephane Chazelas
2021-06-05  0:20                                                   ` Bart Schaefer
2021-06-05 17:05                                                     ` Stephane Chazelas
2021-06-10  0:14                                                       ` Square brackets in command position Bart Schaefer
2021-06-03  6:05                                   ` [PATCH (not final)] (take three?) unset "array[$anything]" Stephane Chazelas
2021-06-03  6:43                                     ` Bart Schaefer
2021-06-03  7:31                                       ` Stephane Chazelas
2021-06-10  0:21                         ` [PATCH] (?) typeset array[position=index]=value Bart Schaefer
2021-06-05  4:29                     ` Mikael Magnusson
2021-06-05  5:49                       ` Bart Schaefer
2021-06-05 11:06                         ` Mikael Magnusson
2021-06-05 16:22                           ` Bart Schaefer
2021-06-18 10:53                         ` Mikael Magnusson
2024-03-08 15:30                 ` [PATCH v3] regexp-replace and ^, word boundary or look-behind operators (and more) Stephane Chazelas
2024-03-09  8:41                   ` [PATCH v5] " Stephane Chazelas
2024-03-09  9:21                     ` MBEGIN when =~ finds bytes inside characters (Was: [PATCH v5] regexp-replace and ^, word boundary or look-behind operators (and more).) Stephane Chazelas
2024-03-09 13:03                   ` [PATCH v3] regexp-replace and ^, word boundary or look-behind operators (and more) Stephane Chazelas
2024-03-10 19:52                     ` [PATCH v6] " Stephane Chazelas

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