[PATCH] Fix grep -Fw '' against empty string

[Paolo Bonzini]

I found this bug while working on the hang.  I thought it could be
fixed only by almost-rewriting Fexecute, but this doesn't seem true.

Additional pairs of eyes are very welcome.

Paolo Bonzini (2):
  grep: fix matching the empty string with grep -Fw
  test: cover just-fixed bug

 NEWS           |    3 +++
 src/kwsearch.c |    4 +++-
 tests/empty    |    4 +---
 3 files changed, 7 insertions(+), 4 deletions(-)

>From c922b8607950b538e205700fd850c81feb31c683 Mon Sep 17 00:00:00 2001
From: Paolo Bonzini <address@hidden>
Date: Wed, 31 Mar 2010 10:22:46 +0200
Subject: [PATCH 1/2] grep: fix matching the empty string with grep -Fw

* NEWS: Document fix.
* src/kwsearch.c (Fexecute): The empty string is a valid match if it is
a whole word.
---
 NEWS           |    3 +++
 src/kwsearch.c |    4 +++-
 2 files changed, 6 insertions(+), 1 deletions(-)

diff --git a/NEWS b/NEWS
index eb94184..1c2f7f3 100644
--- a/NEWS
+++ b/NEWS
@@ -7,6 +7,9 @@ GNU grep NEWS                                    -*- outline -*-
   Searching with grep -F for an empty string in a multibyte locale
   would hang grep. [bug introduced in 2.6.2]
 
+  Searching with grep -Fw for an empty string would not match an
+  empty line. [bug present since "the beginning"]
+
   PCRE support is once again detected on systems with <pcre/pcre.h>
   [bug introduced in 2.6.2]
 
diff --git a/src/kwsearch.c b/src/kwsearch.c
index 973eb60..45d8dc1 100644
--- a/src/kwsearch.c
+++ b/src/kwsearch.c
@@ -133,12 +133,14 @@ Fexecute (char const *buf, size_t size, size_t 
*match_size,
          goto success;
        }
       else if (match_words)
-       for (try = beg; len; )
+       for (try = beg; ; )
          {
            if (try > buf && WCHAR((unsigned char) try[-1]))
              break;
            if (try + len < buf + size && WCHAR((unsigned char) try[len]))
              {
+               if (!len)
+                 break;
                offset = kwsexec (kwset, beg, --len, &kwsmatch);
                if (offset == (size_t) -1)
                  break;
-- 
1.6.6.1


>From 86cdd51eec00cf1ecc239531c51522b4dfacaf90 Mon Sep 17 00:00:00 2001
From: Paolo Bonzini <address@hidden>
Date: Wed, 31 Mar 2010 10:24:21 +0200
Subject: [PATCH 2/2] test: cover just-fixed bug

* tests/empty: Test -Fw too.
---
 tests/empty |    4 +---
 1 files changed, 1 insertions(+), 3 deletions(-)

diff --git a/tests/empty b/tests/empty
index 9e8f335..d3058f1 100755
--- a/tests/empty
+++ b/tests/empty
@@ -54,9 +54,7 @@ for locale in C en_US.UTF-8; do
        fi
     done
 
-    # -F -w omitted because it fails test #6, will be revisited after 2.6
-    # stabilizes.
-    for options in '-E -w' '-E -x' '-E -w -x' '-F -x' '-F -w -x'; do
+    for options in '-E -w' '-E -x' '-E -w -x' '-F -w' '-F -x' '-F -w -x'; do
 
        # should return 0 found a match
        echo "" | LC_ALL=$locale timeout 10s grep $options -e ''
-- 
1.6.6.1