diff --git a/completions/tar b/completions/tar
index 26df2efcbd4..e4423b154bb 100644
--- a/completions/tar
+++ b/completions/tar
@@ -59,7 +59,7 @@
 _comp_deprecate_var 2.12 \
     COMP_TAR_INTERNAL_PATHS BASH_COMPLETION_CMD_TAR_INTERNAL_PATHS
 
-_comp_cmd_gtar__parse_help_opt()
+_comp_cmd_gtar__init_parse_help_opt()
 {
     local opttype arg opt separator optvar
     opttype=long
@@ -98,7 +98,7 @@ _comp_cmd_gtar__parse_help_opt()
     eval "$optvar=\"\$$optvar$separator\"\"$opt\""
 }
 
-_comp_cmd_gtar__parse_help_line()
+_comp_cmd_gtar__init_parse_help_line()
 {
     local i
     local -a tmp
@@ -107,7 +107,7 @@ _comp_cmd_gtar__parse_help_line()
             case "$i" in
                 # regular options
                 --* | -*)
-                    _comp_cmd_gtar__parse_help_opt "$i" "$2"
+                    _comp_cmd_gtar__init_parse_help_opt "$i" "$2"
                     ;;
 
                 # end once there is single non-option word
@@ -119,8 +119,21 @@ _comp_cmd_gtar__parse_help_line()
     done <<<"$1"
 }
 
-_comp_cmd_gtar__parse_help()
+# Parse the output of "tar --help" with GNU tar and store the parse results
+# in a global variable.
+#
+# @var[out] _comp_cmd_gtar__saved_opts
+#     The parse results are stored in this global variable in a form that can
+#     be evaluated by the builtin "eval".
+_comp_cmd_gtar__init_parse_help()
 {
+    local long_arg_none=""
+    local long_arg_opt=""
+    local long_arg_req=""
+    local short_arg_none=""
+    local short_arg_opt=""
+    local short_arg_req=""
+
     local str line arg
     while IFS= read -r line; do
         # Ok, this requires some comment probably.  The GNU help output prints
@@ -141,14 +154,49 @@ _comp_cmd_gtar__parse_help()
                 [[ ${BASH_REMATCH[1]} ]] && arg=opt || arg=req
             fi
 
-            _comp_cmd_gtar__parse_help_line "$str" "$arg"
+            _comp_cmd_gtar__init_parse_help_line "$str" "$arg"
         fi
     done <<<"$(tar --help)"
 
-    long_opts="\
-        $long_arg_none        $long_arg_opt        $long_arg_req"
+    local long_opts="$long_arg_none $long_arg_opt $long_arg_req"
+
+    local short_opts="$short_arg_none$short_arg_opt$short_arg_req"
+
+    printf -v _comp_cmd_gtar__saved_opts '%s=%q ' \
+        long_opts "$long_opts" \
+        short_opts "$short_opts" \
+        long_arg_none "$long_arg_none" \
+        long_arg_opt "$long_arg_opt" \
+        long_arg_req "$long_arg_req" \
+        short_arg_none "$short_arg_none" \
+        short_arg_opt "$short_arg_opt" \
+        short_arg_req "$short_arg_req"
 
-    short_opts="$short_arg_none$short_arg_opt$short_arg_req"
+    # Clean up functions only used in initialization
+    unset -f _comp_cmd_gtar__init_parse_help
+    unset -f _comp_cmd_gtar__init_parse_help_line
+    unset -f _comp_cmd_gtar__init_parse_help_opt
+}
+_comp_cmd_gtar__init_parse_help
+
+# Load the parse results of "tar --help" for GNU tar into variables.
+#
+# @var[out] long_opts
+# @var[out] short_opts
+# @var[out] long_arg_none
+# @var[out] long_arg_opt
+# @var[out] long_arg_req
+# @var[out] short_arg_none
+# @var[out] short_arg_opt
+# @var[out] short_arg_req
+#     The parse results are returned in these variables.
+#
+# @var[in] _comp_cmd_gtar__saved_opts
+#     The parse results are obtained by evaluating this variable with the
+#     "eval" builtin.
+_comp_cmd_gtar__load_opts()
+{
+    eval -- "$_comp_cmd_gtar__saved_opts"
 }
 
 # Hack: parse --warning keywords from tar's error output
@@ -165,8 +213,15 @@ _comp_cmd_gtar__parse_warnings()
     _comp_compgen -- -W '"${warnings[@]}"'
 }
 
+# @var[out] old_opt_progress
+# @var[out] old_opt_used
+# @var[out,array] old_opt_parsed
 _comp_cmd_tar__parse_old_opt()
 {
+    old_opt_progress=""
+    old_opt_used=""
+    old_opt_parsed=()
+
     local first_word char
 
     # current word is the first word
@@ -193,6 +248,10 @@ _comp_cmd_tar__parse_old_opt()
 }
 
 # Make the analysis of whole command line.
+#
+# @var[out] old_opt_progress
+# @var[out] old_opt_used
+# @var[out,array] old_opt_parsed
 _comp_cmd_tar__preparse_cmdline()
 {
     local first_arg=set i modes="ctxurdA"
@@ -507,11 +566,7 @@ _comp_cmd_tar__detect_ext()
 
 _comp_cmd_tar__gnu()
 {
-    local long_opts short_opts basic_tar="" \
-        long_arg_none="" long_arg_opt="" long_arg_req="" \
-        short_arg_none="" short_arg_opt="" short_arg_req="" \
-        tar_mode tar_mode_arg old_opt_progress="" \
-        old_opt_used="" old_opt_parsed=()
+    local basic_tar=""
 
     # Main mode, e.g. "x" or "c" or the long forms "extract" or "create"
     local tar_mode=none
@@ -528,12 +583,15 @@ _comp_cmd_tar__gnu()
     fi
 
     local cur prev words cword was_split comp_args
-
     _comp_initialize -s -- "$@" || return
 
     # Fill the {long,short}_{opts,arg*}
-    _comp_cmd_gtar__parse_help
+    local long_opts short_opts \
+        long_arg_none long_arg_opt long_arg_req \
+        short_arg_none short_arg_opt short_arg_req
+    _comp_cmd_gtar__load_opts
 
+    local old_opt_progress old_opt_used old_opt_parsed
     _comp_cmd_tar__preparse_cmdline "${words[@]}"
 
     local ext
@@ -694,11 +752,7 @@ _comp_cmd_tar__posix_prev_handle()
 
 _comp_cmd_tar__posix()
 {
-    local long_opts short_opts basic_tar=set \
-        long_arg_none="" long_arg_opt long_arg_req="" \
-        short_arg_none short_arg_opt short_arg_req \
-        tar_mode tar_mode_arg old_opt_progress="" \
-        old_opt_used=set old_opt_parsed=()
+    local basic_tar=set
 
     # Main mode, e.g. -x or -c (extract/creation)
     local tar_mode=none
@@ -710,15 +764,25 @@ _comp_cmd_tar__posix()
     local tar_compression_mode=none
 
     local cur prev words cword was_split comp_args
-
     _comp_initialize -s -- "$@" || return
 
+    # Initialize option variables:
     # relatively compatible modes are {c,t,x}
     # relatively compatible options {b,f,m,v,w}
+    # Note: long_{opts,arg_{none,opt}} and short_arg_opt are currently unused
+    local long_opts short_opts \
+        long_arg_none long_arg_opt long_arg_req \
+        short_arg_none short_arg_opt short_arg_req
+    long_arg_none=""
+    long_arg_opt=""
+    long_arg_req=""
+    long_opts=""
     short_arg_req="fb"
+    short_arg_opt=""
     short_arg_none="wmv"
     short_opts="$short_arg_req$short_arg_none"
 
+    local old_opt_progress old_opt_used old_opt_parsed
     _comp_cmd_tar__preparse_cmdline "${words[@]}"
 
     local ext