factor: avoid interspersed lines for parallel runs

* src/factor.c (n_out): A new global variable to track
how much data has been written to stdout.
(print_factors_single): Use n_out to determine whether
to flush the current (and previous) lines.
* tests/misc/factor-parallel.sh: Add a new test.
* tests/local.mk: Reference the new test.
* NEWS: Mention the bug fix.

2 files changed, 35 insertions, 0 deletions

diff --git a/tests/local.mk b/tests/local.mk
index d60f6cfec..3cd8f92c6 100644
--- a/tests/local.mk
+++ b/tests/local.mk
@@ -282,6 +282,7 @@ all_tests =					\
   tests/misc/expand.pl				\
   tests/misc/expr.pl				\
   tests/misc/factor.pl				\
+  tests/misc/factor-parallel.sh			\
   tests/misc/false-status.sh			\
   tests/misc/fold.pl				\
   tests/misc/groups-dash.sh			\
diff --git a/tests/misc/factor-parallel.sh b/tests/misc/factor-parallel.sh
new file mode 100755
index 000000000..8cec630ea
--- /dev/null
+++ b/tests/misc/factor-parallel.sh
@@ -0,0 +1,34 @@
+#!/bin/sh
+# Test for complete lines on output
+
+# Copyright (C) 2015 Free Software Foundation, Inc.
+
+# 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/>.
+
+. "${srcdir=.}/tests/init.sh"; path_prepend_ ./src
+print_ver_ factor
+
+
+odd() { LC_ALL=C sed '/[24680]$/d'; }
+primes() { LC_ALL=C sed 's/.*: //; / /d'; }
+
+# Before v8.24 the number reported here would vary
+# Note -u not supplied to split, increased batching of quickly processed items.
+# As processing cost increases it becomes advantageous to use -u to keep
+# the factor processes supplied with data.
+nprimes=$(seq 1e6 | odd | split -nr/4 --filter='factor' | primes | wc -l)
+
+test "$nprimes" = '78498' || fail=1
+
+Exit $fail