From 2e75efbf90869abfeafc0ab9fcd4fa4b453c0b2a Mon Sep 17 00:00:00 2001
From: Norihiro Tanaka <address@hidden>
Date: Sat, 21 Jan 2017 18:01:53 +0900
Subject: [PATCH] grep: fix matching not longest pattern with grep -Fo

* src/kwset.c (acexec): Fix it.
* tests/fgrep-longest: New test.
* tests/Makefile.am: Add the test.
* NEWS: Mention it.
---
 NEWS                |    3 +++
 src/kwset.c         |   17 ++++++++++++++---
 tests/fgrep-longest |   22 ++++++++++++++++++++++
 3 files changed, 39 insertions(+), 3 deletions(-)
 create mode 100755 tests/fgrep-longest

diff --git a/NEWS b/NEWS
index 3529f4e..7fcc0b1 100644
--- a/NEWS
+++ b/NEWS
@@ -4,6 +4,9 @@ GNU grep NEWS                                    -*- outline -*-
 
 ** Bug fixes
 
+  grep -Fo no longer matches not longest pattern.
+  [bug introduced in grep-2.26]
+
   When standard output is /dev/null, grep no longer fails when
   standard input is a file in the Linux /proc file system, or when
   standard input is a pipe and standard output is in append mode.
diff --git a/src/kwset.c b/src/kwset.c
index 39a1e15..258cff5 100644
--- a/src/kwset.c
+++ b/src/kwset.c
@@ -848,9 +848,20 @@ acexec_trans (kwset_t kwset, char const *text, ptrdiff_t len,
           struct trie const *accept1;
           char const *left1;
           unsigned char c = tr (trans, *tp++);
-          tree = trie->links;
-          while (tree && c != tree->label)
-            tree = c < tree->label ? tree->llink : tree->rlink;
+          while (true)
+            {
+              tree = trie->links;
+              while (tree && c != tree->label)
+                tree = c < tree->label ? tree->llink : tree->rlink;
+              if (tree)
+                break;
+              trie = trie->fail;
+              if (!trie)
+                break;
+              left1 = tp - trie->depth;
+              if (left1 > left)
+                break;
+            }
           if (!tree)
             break;
           trie = tree->trie;
diff --git a/tests/fgrep-longest b/tests/fgrep-longest
new file mode 100755
index 0000000..c8595a1
--- /dev/null
+++ b/tests/fgrep-longest
@@ -0,0 +1,22 @@
+#! /bin/sh
+# grep -F matches not longest pattern.
+# This bug affected grep versions 2.26 through 2.27.
+#
+# Copyright (C) 2017 Free Software Foundation, Inc.
+#
+# Copying and distribution of this file, with or without modification,
+# are permitted in any medium without royalty provided the copyright
+# notice and this notice are preserved.
+
+. "${srcdir=.}/init.sh"; path_prepend_ ../src
+
+fail=0
+
+printf 'abce\n' > in || framework_failure_
+printf 'abcd\nc\nbce\n' > pat || framework_failure_
+printf 'bce\n' > exp || framework_failure_
+
+LC_ALL=C grep -Fof pat in > out || fail=1
+compare exp out || fail=1
+
+Exit $fail
-- 
1.7.1