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Re: Variable references (declare -n, "nameref") are limited to a depth o

From: Andrej Podzimek
Subject: Re: Variable references (declare -n, "nameref") are limited to a depth of 8.
Date: Sun, 26 Apr 2020 05:46:15 +0200 (GMT+02:00)

>> Description:
>>   While looking for a way to share a "cache" array with a recursive function
>>   call stack (using local -n (nameref)), I hit a well-known problem with
>>   "circular name reference" (which has been around for a long time). 
> Yes, that's how it does loop detection.

There are, however, no loops involved in my $a … $k example; it is merely a 
chain of declare -n references starting from a regular variable $a. The chain 
breaks unexpectedly and silently after 8 links ($j and $k appear to be empty).

Better options, IMHO, would include:

(a) An unlimited number of declare -n resolution steps (as long as there are no 
cycles, i.e., no variable name(*) is encountered twice). This may have 
performance consequences when abused, but it would be better than unexpected 
empty values after >8 steps.

(b) An error message when trying to dereference $j or $k (links No. 9 and 10 in 
the chain example), saying e.g. “maximum nameref depth (8) exceeded”. This 
would at least make the problem obvious and easy to debug.

(*) More precisely, this would be [function context, variable name] pairs in 
case of local variables referenced by declare -n.


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