Re: [Assignements to variables with integer attribute are expanded recursively]

[Andreas Kähäri]

Je Wed, Jan 08, 2025 at 08:01:23PM +0100, joergboe--- via Bug reports for the 
GNU Bourne Again SHell skribis:
> Configuration Information [Automatically generated, do not change]:
> Machine: x86_64
> OS: linux-gnu
> Compiler: gcc
> Compilation CFLAGS: -O2 -Wall -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=3 
> -fstack-protector-strong -funwind-tables -fasynchronous-unwind-tables 
> -fstack-clash-protection -Werror=return-type -flto=auto -g  -D_GNU_SOURCE 
> -DRECYCLES_PIDS -Wall -g -Wuninitialized -Wextra -Wno-switch-enum 
> -Wno-unused-variable -Wno-unused-parameter -Wno-parentheses 
> -ftree-loop-linear -pipe -DBNC382214=0 -DIMPORT_FUNCTIONS_DEF=0 
> -DDEFAULT_LOADABLE_BUILTINS_PATH='/usr/lib64/bash'
> uname output: Linux pluto 6.12.8-1-default #1 SMP PREEMPT_DYNAMIC Thu Jan  2 
> 12:47:33 UTC 2025 (ab2dfe6) x86_64 x86_64 x86_64 GNU/Linux
> Machine Type: x86_64-suse-linux-gnu
> 
> Bash Version: 5.2
> Patch Level: 37
> Release Status: release
> 
> Description:
>       [Assignments to variables with attribute 'integer' behave unexpectedly 
> if the right side has not an integer value.
>       It seems that the value is interpreted as a variable name and expansion 
> is done recursively.
>       This is not what I would expect.]
> 
> Repeat-By:
>       [
>       > aa=123456
>       > x=aa
>       > declare -i i=x
>       > echo $i
>       123456
>       ]
> 
> 

>From the manual:

        Shell variables are allowed as operands; parameter expansion
        is performed before the expression is evaluated.  Within an
        expression, shell variables may also be referenced by name
        without using the parameter expansion syntax. [...] The value of
        a variable is evaluated as an arithmetic expression when it is
        referenced, or when a variable which has been given the integer
        attribute using declare -i is assigned a value.

The "The value of a variable is evaluated as an arithmetic expression"
effectively allows for recursive arithmetic expansion of the right-hand
side of an assignment to a variable with the integer attribute.
Recursive, that is, until the right-hand side is no longer a variable's
name, at which point the expansion stops and the value is assigned (or
an error is generated if the value is not a valid integer).




-- 
Andreas (Kusalananda) Kähäri
Uppsala, Sweden

.