Bug in varnishlog (-u and -o flags)

[Yvan Taviaud]

Hello,

I think I've found a bug after struggling for many hours with STDIN 
buffering. The fact is that I'm not a C developer, hence the time to 
understand the issue was in varnishlog took me hours :-)

So, I was trying to use it with the following command:

varnishlog -u -c -o TxStatus '^503$' > /tmp/varnish.test

(in order to match all 503 errors)

But this wasn't working good, as the output sent to the log file was 
buffered, even if the -u flag was used. I think the issue is here:
(bin/varnishlog.c, around line 388, release is 2.0.6)

        if (o_flag)
                do_order(vd, argc - optind, argv + optind);

       if (u_flag)
                setbuf(stdout, NULL);

So, as the do_order() is an infinite loop, the u_flag test is never 
seen. If I reverse both tests, everything seems to work as expected. Is 
there any issue inverting those tests?

Also I'd like to know if there's a reason to disable -w when -o is used? 
It can be really useful, for example in this case I'm trying to track 
503 errors, so logging to file with grouped requests would be great.

Best regards,
Yvan.