From dae857d8d787c986761c37673b31a1aa0c7e74c2 Mon Sep 17 00:00:00 2001
From: Jim Meyering <address@hidden>
Date: Fri, 30 May 2014 09:19:33 -0700
Subject: [PATCH] grep: fix --max-count=N (-m N) to stop reading after Nth
 match

With --max-count=N (-m N), grep is supposed to stop reading input
after it has found the Nth match.  However, a recent context-
related change made it so grep would always read to end of file.
* src/grep.c (prtext): Don't let a negative "out_after" value
make "pending" line count negative.
* tests/max-count-overread: New test, for this.
* tests/Makefile.am (TESTS): Add it.
* NEWS (Bug fixes): Mention it.
This bug was introduced by commit v2.18-140-g6f07900.
Reported by Marc Aldorasi in http://bugs.gnu.org/17640.
---
 NEWS                     |  3 +++
 src/grep.c               |  2 +-
 tests/Makefile.am        |  1 +
 tests/max-count-overread | 12 ++++++++++++
 4 files changed, 17 insertions(+), 1 deletion(-)
 create mode 100755 tests/max-count-overread

diff --git a/NEWS b/NEWS
index 0caad22..0e9b2cb 100644
--- a/NEWS
+++ b/NEWS
@@ -4,6 +4,9 @@ GNU grep NEWS                                    -*- outline -*-

 ** Bug fixes

+  grep --max-count=N FILE would no longer stop reading after the Nth match.
+  [bug introduced in grep-2.19]
+
   A command like echo aa|grep -E 'a(b$|c$)' would mistakenly
   report the input as a matched line.
   [bug introduced in grep-2.19]
diff --git a/src/grep.c b/src/grep.c
index acc08c7..7c0f8a8 100644
--- a/src/grep.c
+++ b/src/grep.c
@@ -1043,7 +1043,7 @@ prtext (char const *beg, char const *lim)
     }

   after_last_match = bufoffset - (buflim - p);
-  pending = out_quiet ? 0 : out_after;
+  pending = out_quiet ? 0 : MAX (0, out_after);
   used = true;
   outleft -= n;
 }
diff --git a/tests/Makefile.am b/tests/Makefile.am
index a38f074..31e2a81 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -73,6 +73,7 @@ TESTS =						\
   invalid-multibyte-infloop			\
   khadafy					\
   long-line-vs-2GiB-read			\
+  max-count-overread				\
   max-count-vs-context				\
   mb-non-UTF8-performance			\
   multibyte-white-space				\
diff --git a/tests/max-count-overread b/tests/max-count-overread
new file mode 100755
index 0000000..56bc331
--- /dev/null
+++ b/tests/max-count-overread
@@ -0,0 +1,12 @@
+#!/bin/sh
+# Ensure that -m1 stops reading after the first match.
+# In grep-2.19, yes x|grep -m1 x would infloop.
+
+. "${srcdir=.}/init.sh"; path_prepend_ ../src
+require_timeout_
+
+fail=0
+
+yes x | timeout 3 grep -m1 x > out || fail=1
+
+Exit $fail
-- 
2.0.0.rc3