From: Herbert Poetzl <herbert@13thfloor.at>
To: "Alexander E. Patrakov" <patrakov@ums.usu.ru>
Cc: qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] Overoptimization
Date: Fri, 28 May 2004 12:13:51 +0200 [thread overview]
Message-ID: <20040528101351.GA18592@MAIL.13thfloor.at> (raw)
In-Reply-To: <40B693A7.9050006@ums.usu.ru>
On Fri, May 28, 2004 at 07:19:35AM +0600, Alexander E. Patrakov wrote:
> The CFLAGS in Makefile.target are bad for gcc 3.3.2. This is not a my
> problem with my gcc, because it passes the "make check" testsuite except
> some known errors in libstdc++, which cannot affect qemu.
>
> The victim is the tcp_input function in slirp. When compiling with the
> decault CFLAGS, for some reason all packets are dropped as having a
> wrong TCP checksum. I tried debugging this by placing some debug printfs
> in tcp_input.c file, but the problem disappeared after I inserted them.
> I concluded that it is very strange and compiled this tcp_input.c file
> without my debug statements, but with -O1 instead of -O2. The problem
> went away.
gcc isn't supposed to change the semantics of
a program based on the optimization level.
nevertheless several cases are known where this
happened, and not seldom the bug was in gcc
testing the same opts with 3.3.3 or 3.4 will
show if gcc is to blame or not.
best,
Herbert
> Will this workaround (use of -O1 instead of -O2 for tcp_input.c) enter
> the qemu CVS?
>
> --
> Alexander E. Patrakov
>
>
> _______________________________________________
> Qemu-devel mailing list
> Qemu-devel@nongnu.org
> http://mail.nongnu.org/mailman/listinfo/qemu-devel
next prev parent reply other threads:[~2004-05-29 3:15 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-05-28 1:19 [Qemu-devel] Overoptimization Alexander E. Patrakov
2004-05-28 10:13 ` Herbert Poetzl [this message]
2004-05-28 10:58 ` Alexander E. Patrakov
2004-05-28 11:08 ` Herbert Poetzl
2004-05-28 13:50 ` [SOLVED] " Alexander E. Patrakov
2004-05-28 22:15 ` Lionel Ulmer
2004-05-29 18:18 ` [Qemu-devel] VNC patch, the 3rd version Johannes Schindelin
2004-05-31 2:00 ` Jim C. Brown
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