hush: fix segfault in ${?:N:M}

function                                             old     new   delta
expand_vars_to_list                                 2374    2409     +35
builtin_umask                                        132     133      +1
builtin_exit                                          47      48      +1
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 3/0 up/down: 37/0)               Total: 37 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 15 insertions, 0 deletions

diff --git a/shell/hush_test/hush-vars/param_expand_bash_substring.tests b/shell/hush_test/hush-vars/param_expand_bash_substring.tests
index a80523add..5c9552dba 100755
--- a/shell/hush_test/hush-vars/param_expand_bash_substring.tests
+++ b/shell/hush_test/hush-vars/param_expand_bash_substring.tests
@@ -55,6 +55,21 @@ f=0123456789; echo "f::2 =|${f::2}|"
 f=0123456789; echo "f:1: =|${f:1:}|"
 f=0123456789; echo "f::  =|${f::}|"
 
+echo "Substrings from special vars"
+echo '?    '"=|$?|"
+echo '?:1  '"=|${?:1}|"
+echo '?:1:2'"=|${?:1:2}|"
+echo '?::2 '"=|${?::2}|"
+echo '?:1: '"=|${?:1:}|"
+echo '?::  '"=|${?::}|"
+set -- 1 2 3 4 5 6 7 8 9 10 11
+echo '#    '"=|$#|"
+echo '#:1  '"=|${#:1}|"
+echo '#:1:2'"=|${#:1:2}|"
+echo '#::2 '"=|${#::2}|"
+echo '#:1: '"=|${#:1:}|"
+echo '#::  '"=|${#::}|"
+
 echo "Substrings with expressions"
 f=01234567; echo 'f            '"=|$f|"
 f=01234567; echo 'f:1+1:2+2    '"=|${f:1+1:2+2}|"