From: Andi Kleen <ak@suse.de>
To: "Dong Feng" <middle.fengdong@gmail.com>
Cc: "Paul Mackerras" <paulus@samba.org>,
"Christoph Lameter" <clameter@sgi.com>,
linux-kernel@vger.kernel.org
Subject: Re: Unnecessary Relocation Hiding?
Date: Fri, 25 Aug 2006 08:18:49 +0200 [thread overview]
Message-ID: <200608250818.49139.ak@suse.de> (raw)
In-Reply-To: <a2ebde260608241830p2d26b20bp6bfb9b1b5a267ec6@mail.gmail.com>
On Friday 25 August 2006 03:30, Dong Feng wrote:
> Sorry for perhaps extending the specific question to a more generic
> one. In which cases shall we, in current or future development,
> prevent gcc from knowing a pointer-addition in the way RELOC_HIDE? And
> in what cases shall we just write pure C point addition?
>
> After all, we are writing an OS in C not in pure assembly, so I am
> just trying to learn some generial rules to mimize the raw assembly in
> development.
In theory anything that is undefined in the C standard should be avoided
because gcc is free to make assumptions about it and generate unexpected
code.
In practice Linux does a lot of not-quite-legal-in-portable-C things
already, but tries to avoid areas that are known to have miscompiled in
the past.
Best is to avoid undefined behaviour in new code.
-Andi
next prev parent reply other threads:[~2006-08-25 6:22 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-08-23 12:00 Unnecessary Relocation Hiding? Dong Feng
2006-08-23 12:25 ` Dong Feng
2006-08-24 18:26 ` Christoph Lameter
2006-08-24 19:24 ` Andi Kleen
2006-08-24 23:31 ` Paul Mackerras
2006-08-25 1:30 ` Dong Feng
2006-08-25 3:49 ` Paul Mackerras
[not found] ` <a2ebde260608242329r12259e0k7e798ee1d8737d68@mail.gmail.com>
2006-08-25 6:39 ` Fwd: " Dong Feng
2006-08-25 6:18 ` Andi Kleen [this message]
2006-08-25 7:20 ` Paul Mackerras
2006-08-25 7:38 ` Andi Kleen
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