small change to brace expansion to inhibit some error messages; changes to printf builtin for precision and field widths

tests/printf6.sub

@@ -1,3 +1,24 @@
+#   This program is free software: you can redistribute it and/or modify
+#   it under the terms of the GNU General Public License as published by
+#   the Free Software Foundation, either version 3 of the License, or
+#   (at your option) any later version.
+#
+#   This program is distributed in the hope that it will be useful,
+#   but WITHOUT ANY WARRANTY; without even the implied warranty of
+#   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#   GNU General Public License for more details.
+#
+#   You should have received a copy of the GNU General Public License
+#   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+# this should echo nothing
+printf '%ls'
+# this should echo a null byte
+printf '%lc' | hexdump -b
+
+# this should echo a null byte per posix interp 1647
+printf '%lc' '' | hexdump -b
+
 # test %ls and %lc with multibyte characters
 
 V=ಇಳಿಕೆಗಳು
@@ -19,3 +40,6 @@ printf "%C\n" "$V3" | hexdump -b
 
 printf "%4.2lc\n" "$V3" | hexdump -b
 printf "%-4.2lc---\n" "$V3" | hexdump -b
+
+# make sure %ls handles 0 precision the same as %s
+printf '[%.0s][%.0ls]\n' X X