xargs: fix handling of quoted arguments, closes 11441

As reported in bug 11441 when presented with a large number of quoted
arguments xargs can return 'argument line too long':

   seq 10000 29999 | sed -e 's/^/"/' -e 's/$/"/' | busybox xargs echo

This happens because the variant of process_stdin() which handles quoted
arguments doesn't preserve state between calls.  If the allowed number
of characters is exceeded part way through a quoted argument the next
call to process_stdin() incorrectly treats the terminating quote as a
starting quote, thus quoting all of the argument separators.

function                                             old     new   delta
process_stdin                                        274     303     +29
xargs_main                                           731     745     +14
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 2/0 up/down: 43/0)               Total: 43 bytes

Signed-off-by: Ron Yorston <rmy@pobox.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 9 insertions, 0 deletions

diff --git a/testsuite/xargs.tests b/testsuite/xargs.tests
index 2d0a201b7..855b33bc2 100755
--- a/testsuite/xargs.tests
+++ b/testsuite/xargs.tests
@@ -41,4 +41,13 @@ testing "xargs -sNUM test 2" \
 	"echo 1 2 3 4 5 6 7 8 9 0\n""echo 1 2 3 4 5 6 7 8 9\n""echo 1 00\n" \
 	"" "2 3 4 5 6 7 8 9 0 2 3 4 5 6 7 8 9 00\n"
 
+# see that we don't get "argument line too long",
+# but do see the last word, 99999, instead
+optional FEATURE_XARGS_SUPPORT_QUOTES
+testing "xargs argument line too long" \
+	"seq 10000 99999 | sed -e 's/^/\"/' -e 's/$/\"/' | xargs echo | grep -o 99999; echo \$?" \
+	"99999\n0\n" \
+	"" ""
+SKIP=
+
 exit $FAILCOUNT