grep -F -x -o PAT would print an extra newline for each match

* src/kwsearch.c (Fexecute): Correctly compute the length of a match
by subtracting 2 (not 1) when match_lines is set.  With -x, we augment
the "line" by both prepending and appending an EOLBYTE to the search
pattern.  Here, we must correct for that.  However, to compensate,
when we are using -x (--line-regexp) and start_ptr is NULL, we have
to add 1 to the length so that we still print the trailing EOLBYTE.
Introduced by commit v2.18-85-g2c94326.
* tests/match-lines: Add a new test.
* tests/Makefile.am (TESTS): Add it.
* NEWS (Bug fixes): Mention it.

4 files changed, 45 insertions, 2 deletions

diff --git a/NEWS b/NEWS
index c4651627..15975288 100644
--- a/NEWS
+++ b/NEWS
@@ -41,6 +41,9 @@ GNU grep NEWS                                    -*- outline -*-
   implying that the match, "10" was on line 1.
   [bug introduced in grep-2.19]
 
+  grep -F -x -o no longer prints an extra newline for each match.
+  [bug introduced in grep-2.19]
+
   grep in a non-UTF8 multibyte locale could mistakenly match in the middle
   of a multibyte character when using a '^'-anchored alternate in a pattern,
   leading it to print non-matching lines.  [bug present since "the beginning"]
diff --git a/src/kwsearch.c b/src/kwsearch.c
index 6bd516a9..aa965f62 100644
--- a/src/kwsearch.c
+++ b/src/kwsearch.c
@@ -129,7 +129,7 @@ Fexecute (char const *buf, size_t size, size_t *match_size,
                                buf + size - beg + match_lines, &kwsmatch);
       if (offset == (size_t) -1)
         goto failure;
-      len = kwsmatch.size[0] - match_lines;
+      len = kwsmatch.size[0] - 2 * match_lines;
       if (!match_lines && MB_CUR_MAX > 1 && !using_utf8 ()
           && mb_goback (&mb_start, beg + offset, buf + size) != 0)
         {
@@ -142,7 +142,10 @@ Fexecute (char const *buf, size_t size, size_t *match_size,
       if (start_ptr && !match_words)
         goto success_in_beg_and_len;
       if (match_lines)
-        goto success_in_beg_and_len;
+        {
+          len += start_ptr == NULL;
+          goto success_in_beg_and_len;
+        }
       if (match_words)
         for (try = beg; ; )
           {
diff --git a/tests/Makefile.am b/tests/Makefile.am
index c006e582..217a731f 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -73,6 +73,7 @@ TESTS =						\
   invalid-multibyte-infloop			\
   khadafy					\
   long-line-vs-2GiB-read			\
+  match-lines					\
   max-count-overread				\
   max-count-vs-context				\
   mb-dot-newline				\
diff --git a/tests/match-lines b/tests/match-lines
new file mode 100755
index 00000000..51c039e9
--- /dev/null
+++ b/tests/match-lines
@@ -0,0 +1,36 @@
+#!/bin/sh
+# Trigger a bug in the DFA matcher that would make
+# grep -F -x -o PAT print an extra newline for each match.
+# This would fail for grep-2.19 and grep-2.20.
+
+# Copyright 2014 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/>.
+
+. "${srcdir=.}/init.sh"; path_prepend_ ../src
+
+printf 'a\n' > in || framework_failure_
+
+fail=0
+
+for locale in C en_US.UTF-8; do
+  for options in -x '-E -x' '-F -x'; do
+    for o in '' -o; do
+      LC_ALL=$locale grep $o $options a in > out || fail=1
+      compare out in || fail=1
+    done
+  done
+done
+
+Exit $fail