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Re: V+=1 doesn't work if V is a reference to an integer array element

From: Chet Ramey
Subject: Re: V+=1 doesn't work if V is a reference to an integer array element
Date: Thu, 14 Jan 2021 15:10:37 -0500
User-agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.6.0

On 1/14/21 10:31 AM, Léa Gris wrote:
Le 14/01/2021 à 16:15, Chet Ramey écrivait :
On 1/13/21 4:40 PM, Léa Gris wrote:
Le 13/01/2021 à 22:13, Chet Ramey écrivait :
The `-i' forces arithmetic evaluation, which makes this expand to the equivalent of `declare -n b=1'. That's an invalid name for a nameref,
which you'd see if you used `declare -n b=1' instead. The assignment
error causes `declare' to return an non-zero status, but the error
message checks the original value, not the result of arithmetic
evaluation, and the `a[0]' is valid.

I guess I never thought people would try to use integer variables as
namerefs, since nameref values can't be digits.

Sorry Chet, this does not make sense to me. There is no error message.

OK, let's be clear that this sequence of commands from your message is what
we're talking about:

unset a b
declare -ai a=(1)
declare -in b="a[0]"
declare -p a b

I get this result:

declare -ai a=([0]="1")
x4: line 4: declare: b: not found

and I explained why there is no variable `b'.

Not the same issue and not exactly same sequence of commands:

OK, so this is a new question.

unset a; unset -n b
declare -ai a=(1)
declare -n b="a[0]" # No i flag at that point for b
typeset -ni b # Now b also has a int flag alongside the nameref

Yeah, that probably shouldn't be allowed, but it currently is.

b+=2 # This is only allowed if b has the int flag


As Oğuz wrote:
Seems to be another bug. `bind_variable_internal' calls both
`assign_array_element' and `make_variable_value' with ASS_APPEND in flags (
https://git.savannah.gnu.org/cgit/bash.git/tree/variables.c#n3140 ), the
latter returns 6 (4 + 2), the former adds it to a[0]'s value.

It's all the same problem. That code has been in bash since 2012.

``The lyf so short, the craft so long to lerne.'' - Chaucer
                 ``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, UTech, CWRU    chet@case.edu    http://tiswww.cwru.edu/~chet/

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