Bash unbound variable array (script: s3-bash)

Question

I am working with: s3-bash, when I run it in my local environment (OS X 10.10.1) I don't have any problems, when I try to run it on a ubuntu server 14.04.1 I get the following error:

./s3-common-functions: line 66: temporaryFiles: unbound variable
./s3-common-functions: line 85: temporaryFiles: unbound variable

I've looked at the s3-common-functions script and the variable looks to be initialized properly (as an array):

# Globals
declare -a temporaryFiles

But there is a note in the comment, and I'm sure if it's related:

# Do not use this from directly. Due to a bug in bash, array assignments do not work when the function is used with command substitution
function createTemporaryFile
{
    local temporaryFile="$(mktemp "$temporaryDirectory/$$.$1.XXXXXXXX")" || printErrorHelpAndExit "Environment Error: Could not create a temporary file. Please check you /tmp folder permissions allow files and folders to be created and disc space." $invalidEnvironmentExitCode
    local length="${#temporaryFiles[@]}"
    temporaryFiles[$length]="$temporaryFile"
}

Answer 1

There appears to be a bash behaviour change at play here.

Found by kojiro: CHANGES

hhhh. Fixed a bug that caused `declare' and `test' to find variables that had been given attributes but not assigned values. Such variables are not set.

$ bash --version
GNU bash, version 3.2.25(1)-release (x86_64-redhat-linux-gnu)
Copyright (C) 2005 Free Software Foundation, Inc.
$ set -u
$ declare -a tF
$ echo "${#tF[@]}"
0

vs.

$ bash --version
GNU bash, version 4.1.2(1)-release (x86_64-redhat-linux-gnu)
Copyright (C) 2009 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>

This is free software; you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
$ set -u
$ declare -a tF
$ echo "${#tF[@]}"
0

vs.

$ bash --version
GNU bash, version 4.3.30(1)-release (x86_64-pc-linux-gnu)
Copyright (C) 2013 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>

This is free software; you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
$ set -u
$ declare -a tF
$ echo "${#tF[@]}"
-bash: tF: unbound variable

You can use declare -a tF=() on the newer bash versions to work around this.

$ declare -a tF=()
$ echo "${#tF[@]}"
0