hush: fix handling of empty arguments

function                                             old     new   delta
builtin_exec                                          25      83     +58
parse_stream                                        2242    2261     +19
run_pipe                                            1782    1787      +5
static.pseudo_null_str                                 -       3      +3
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 3/0 up/down: 85/0)               Total: 85 bytes

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

2 files changed, 15 insertions, 0 deletions

diff --git a/shell/hush_test/hush-misc/empty_args.right b/shell/hush_test/hush-misc/empty_args.right
new file mode 100644
index 000000000..38ed8b8be
--- /dev/null
+++ b/shell/hush_test/hush-misc/empty_args.right
@@ -0,0 +1,6 @@
+Null 0th arg:
+hush: can't execute '': No such file or directory
+127
+Null 1st arg:
+0
+Null arg in exec:
diff --git a/shell/hush_test/hush-misc/empty_args.tests b/shell/hush_test/hush-misc/empty_args.tests
new file mode 100755
index 000000000..efce5494a
--- /dev/null
+++ b/shell/hush_test/hush-misc/empty_args.tests
@@ -0,0 +1,9 @@
+echo Null 0th arg:
+""
+echo $?
+echo Null 1st arg:
+# printf without args would print usage info
+printf ""
+echo $?
+echo Null arg in exec:
+exec printf ""