Date: Wed, 9 Nov 2005 15:40:02 -0800 (PST)
From: Vadim Lobanov <vlobanov@speakeasy.net>
To: Andreas Schwab <schwab@suse.de>
cc: "linux-os \\\\(Dick Johnson\\\\)" <linux-os@analogic.com>,
       linas <linas@austin.ibm.com>, "J.A. Magallon" <jamagallon@able.es>,
       Kyle Moffett <mrmacman_g4@mac.com>,
       Douglas McNaught <doug@mcnaught.org>,
       Steven Rostedt <rostedt@goodmis.org>, linux-kernel@vger.kernel.org
Subject: Re: typedefs and structs
In-Reply-To: <je3bm5qu2b.fsf@sykes.suse.de>
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On Thu, 10 Nov 2005, Andreas Schwab wrote:

> Vadim Lobanov <vlobanov@speakeasy.net> writes:
>
> > However, if the code is as follows:
> > 	void foo (void) {
> > 		int myvar = 0;
> > 		printf("%d\n", myvar);
> > 		bar(&myvar);
> > 		printf("%d\n", myvar);
> > 	}
> > If bar is declared in _another_ file as
> > 	void bar (const int * var);
> > then I think the compiler can validly cache the value of 'myvar' for the
> > second printf without re-reading it. Correct/incorrect?
>
> Incorrect. bar() may cast away const.  In C const does not mean readonly.

In that case, I stand corrected.

Is there any real reason to apply const to pointer targets, aside from
giving yourself a warning in the case you try to write the pointer
target directly? Seems to be a missed opportunity for optimizations
where the coder designates that it's okay to do so.

> Andreas.
>
> --
> Andreas Schwab, SuSE Labs, schwab@suse.de
> SuSE Linux Products GmbH, Maxfeldstra?e 5, 90409 N?rnberg, Germany
> PGP key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
> "And now for something completely different."
>

-Vadim Lobanov
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