From: Wayne Davison <wayned@users.sourceforge.net>
To: Peter Stephenson <pws@csr.com>
Cc: Zsh hackers list <zsh-workers@sunsite.dk>
Subject: Re: Strict-aliasing warnings
Date: Thu, 19 Feb 2004 02:50:13 -0800 [thread overview]
Message-ID: <20040219105013.GD26450@blorf.net> (raw)
In-Reply-To: <1728.1077186812@csr.com>
On Thu, Feb 19, 2004 at 10:33:32AM +0000, Peter Stephenson wrote:
> The warning is highly obscure but my guess is it's worried because it
> doesn't know that the type we're looking at really does look like a
> HashNode.
Kind of, but only in the context of modern aliasing restrictions. If
two aliases for a single memory location differ in type in a radical
enough manner, the compiler does not have to consider that the two
different references might affect one another. E.g. you could change a
variable from one pointer and not have that change get reflected in the
reading from another pointer (or the original variable) because the
compiler might have optimized away the memory-fetch. However, certain
casts force the compiler to be less aggressive in its optimizations
(such as (char *) and (void *)).
That is the intent of using the (void *) cast -- it _should_ let the
optimizer know that that variable needs to be refetched. However, I'm
not 100% sure that this is enough to make sure that the optimizations
are valid or if it's only enough to just silence the warnings.
..wayne..
next prev parent reply other threads:[~2004-02-19 10:50 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-02-19 10:20 Wayne Davison
2004-02-19 10:33 ` Peter Stephenson
2004-02-19 10:50 ` Wayne Davison [this message]
2004-02-19 11:04 ` Peter Stephenson
2004-02-26 3:18 ` Wayne Davison
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