Re: pcap_compile() errors in libpcap beta and CVS

[Guy Harris <guy () alum mit edu>]

On Wed, Dec 17, 2003 at 09:00:39AM -0500, George Bakos wrote:
> It would appear that this is due to a change in optimize.c, as of the 1.73
> checkin. In opt_peep(b), using a continue statement, rather than a break,
> causes over-optimization in certain cases. It is possible, however I can't
> see when, that the following backout patch may lead to less optimization.
> Comments?

I've been looking at this - there is, I think, an optimizer bug
elsewhere, and his change might merely have exposed that bug.  I haven't
tracked it down yet, however.  (It's converting the "false" branch of
one jeq to go to the "ret #0" when it shouldn't be.  This might also be
the cause of a bug in the libpcap bug database on SourceForge.)

His changes fix some other problems:

        Date: Thu, 25 Apr 2002 07:20:47 +0900 (JST)                             
        To: patches () tcpdump org
        Subject: some fixes for complier and optimizer in libpcap
        From: YAMAMOTO Takashi <yamt () mwd biglobe ne jp>

        I made patches for libpcap.

        it includes:
        - make tcpdump "1 > 1" works correctly.
        - make things unsigned as in-kernel filter does.
        - fix a bug that prevents optimization. (and might cause bad codes)
          eg. "1 & len == 1"
        - fix wrong optimizations.
          eg. "0 >> len == 1", "0 - len == 1"
-
This is the TCPDUMP workers list. It is archived at
http://www.tcpdump.org/lists/workers/index.html
To unsubscribe use mailto:tcpdump-workers-request () tcpdump org?body=unsubscribe