[PATCH] tail: fix an inconsequential bug spotted by coverity

[Jim Meyering]

FYI, as far as I can see this really is inconsequential.  I reviewed
the code and also ran strace before and after, exercising the affected
code.  There was no difference in syscalls, and there was no difference
in output when I used this as input to the tail'd fifo "f": (seq 10;
sleep 1; echo foo) > f

I tested both with and without ---disable-inotify.

>From e7b4bf4b57efb699c87f03c1173d812ea34cb618 Mon Sep 17 00:00:00 2001
From: Jim Meyering <address@hidden>
Date: Wed, 1 Jun 2011 13:48:12 +0200
Subject: [PATCH] tail: fix an inconsequential bug spotted by coverity

* src/tail.c (start_bytes): Increase *READ_POS (not READ_POS)
by the number of bytes read.  This is a real bug that happens
to have no consequence in practice.  First, this code is exercised
only when tailing-forever a non-regular file by bytes, and with a
start-relative offset, e.g., "mkfifo f; tail -f -c +3 f", but even
then, the invalid READ_POS value does not influence how tail works.
It is stored in the File_spec.size member, but that member is not
used at all in tail_forever_inotify, and in tail_forever, it is
used only when the File_spec refers to a regular file.
---
 src/tail.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/src/tail.c b/src/tail.c
index 714e278..f315776 100644
--- a/src/tail.c
+++ b/src/tail.c
@@ -818,7 +818,7 @@ start_bytes (const char *pretty_filename, int fd, uintmax_t 
n_bytes,
           error (0, errno, _("error reading %s"), quote (pretty_filename));
           return 1;
         }
-      read_pos += bytes_read;
+      *read_pos += bytes_read;
       if (bytes_read <= n_bytes)
         n_bytes -= bytes_read;
       else
--
1.7.5.3.716.g40fa6