Incorrect LINENO with exported nested functions with loops

[Tom Coleman]

Configuration Information [Automatically generated, do not change]:
Machine: x86_64
OS: linux-gnu
Compiler: gcc
Compilation CFLAGS:  -DPROGRAM='bash' -DCONF_HOSTTYPE='x86_64'
-DCONF_OSTYPE='linux-gnu' -DCONF_MACHTYPE='x86_64-redhat-linux-gnu'
-DCONF_VENDOR='redhat' -DLOCALEDIR='/usr/share/locale' -DPACKAGE='bash'
-DSHELL -DHAVE_CONFIG_H   -I.  -I. -I./include -I./lib  -D_GNU_SOURCE
-DRECYCLES_PIDS -DDEFAULT_PATH_VALUE='/usr/local/bin:/usr/bin'
 -DSYSLOG_HISTORY -O2 -g -pipe -Wall -Werror=format-security
-Wp,-D_FORTIFY_SOURCE=2 -Wp,-D_GLIBCXX_ASSERTIONS -fexceptions
-fstack-protector-strong -grecord-gcc-switches
-specs=/usr/lib/rpm/redhat/redhat-hardened-cc1
-specs=/usr/lib/rpm/redhat/redhat-annobin-cc1 -m64 -mtune=generic
-fasynchronous-unwind-tables -fstack-clash-protection -fcf-protection
-Wno-parentheses -Wno-format-security
uname output: Linux gadi-login-06.gadi.nci.org.au
4.18.0-305.19.1.el8.nci.x86_64 #1 SMP Mon Sep 27 03:06:23 UTC 2021 x86_64
x86_64 x86_64 GNU/Linux
Machine Type: x86_64-redhat-linux-gnu

Bash Version: 4.4
Patch Level: 20
Release Status: release

Description:
        If you have a function, which exports another function, and that
exported function contains a generic for loop, the LINENO variable is
incorrect for loops in future functions which contain another loop which
uses ((..)) notation.

        Whilst the above system information says bash 4.4.20 20, I have
seen it in 3.2.51 and 4.2.46 too.

Repeat-By:
        Below is a sample script to replicate the bug in LINENO.

        The LINENO variable for the 'i' loop which is printed out by the
PS4 is incorrect when that DO_BACKUP function is exported, and the second
'j' loop is uncommented. If you instead uncomment the first 'j' loop, the
LINENO variables are correct. If DO_BACKUP does not have a loop inside it,
the LINENO variables are all correct.

#!/bin/bash
export PS4='+L$LINENO + '
setup() {
DO_BACKUP() {
  for d in 1 2 3; do
    break
  done
}
export -f DO_BACKUP
}
run() {
    for i in 1; do
        #for j in 1; do  # Uncomment this 'j' loop instead of the next and
LINENO is correct
        #for ((j=1; j<=2; j++)); do  # Uncomment this 'j' loop and LINENO
is incorrect
            true
        done
    done
}
set -x
setup
run

########

Example output with first 'j' loop uncommented:

$ bash run.sh
+L20 + setup
+L9 + export -f DO_BACKUP
+L21 + run
+L12 + for i in 1
+L13 + for j in 1
+L15 + true

Example output with the second 'j' loop uncommented:

$ bash run.sh
+L20 + setup
+L9 + export -f DO_BACKUP
+L21 + run
+L5 + for i in 1
+L14 + (( j=1 ))
+L14 + (( j<=1 ))
+L15 + true
+L14 + (( j++ ))
+L14 + (( j<=1 ))


Regards,
Tom Coleman