Configuration Information [Automatically generated, do not change]:
Machine: x86_64
OS: linux-gnu
Compiler: gcc
Compilation CFLAGS: -march=x86-64 -mtune=generic -O2 -pipe -fno-plt
-DDEFAULT_PATH_VALUE='/usr/local/sbin:/usr/local/bin:/usr/bin'
-DSTANDARD_UTILS_PATH='/usr/bin' -DSYS_BASHRC='/etc/bash.bashrc'
-DSYS_BASH_LOGOUT='/etc/bash.bash_logout' -DNON_INTERACTIVE_LOGIN_SHELLS
-Wno-parentheses -Wno-format-security
uname output: Linux charon 5.6.4-arch1-1-user-regd #1 SMP PREEMPT Fri, 17 Apr
2020 12:06:27 +0000 x86_64 GNU/Linux
Machine Type: x86_64-pc-linux-gnu
Bash Version: 5.0
Patch Level: 16
Release Status: release
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). The problem
can be circumvented by renaming the variable twice per recursion level:
recursive_function() {
...
local -r cache_name="cache_${#FUNCNAME[@]}"
local -n "$cache_name"="$1"
local -n cache="$cache_name"
...
recursive_function "$cache_name" 'other' 'arguments' ...
...
}
Now "${cache[@]}" references the shared variable under a consistent name,
regardless call stack depth, and without the "circular name reference" issue.
Sadly, this stops working at a certain (very small) call stack depth. There is
no warning or error message; the ${cache[@]} just becomes empty unexpectedly.
Importantly, this is also reproducible with a plain string variable and
without any functions or (recursive) calls involved:
Repeat-By:
previous=a
declare ${previous}='This is set!'
for var in {b..k}; do
declare -n ${var}=${previous}
previous="${var}"
done
for var in {a..k}; do
echo "${var}: '${!var}'"
done
Actual output:
a: 'This is set!'
b: 'This is set!'
c: 'This is set!'
d: 'This is set!'
e: 'This is set!'
f: 'This is set!'
g: 'This is set!'
h: 'This is set!'
i: 'This is set!'
j: ''
k: ''
Expected output:
a: 'This is set!'
b: 'This is set!'
c: 'This is set!'
d: 'This is set!'
e: 'This is set!'
f: 'This is set!'
g: 'This is set!'
h: 'This is set!'
i: 'This is set!'
j: 'This is set!'
k: 'This is set!'
