From: Bernd Edlinger <bernd.edlinger@hotmail.de>
To: Joseph Myers <joseph@codesourcery.com>
Cc: "gcc-patches@gcc.gnu.org" <gcc-patches@gcc.gnu.org>,
Nathan Sidwell <nathan@acm.org>, Jason Merrill <jason@redhat.com>,
Marek Polacek <polacek@redhat.com>
Subject: Re: [PATCH] Add a -Wcast-align=strict warning
Date: Wed, 13 Sep 2017 19:52:00 -0000 [thread overview]
Message-ID: <AM5PR0701MB26579114FABD8F8F4D2CEB2CE46E0@AM5PR0701MB2657.eurprd07.prod.outlook.com> (raw)
In-Reply-To: <alpine.DEB.2.20.1709131701160.29579@digraph.polyomino.org.uk>
On 09/13/17 19:06, Joseph Myers wrote:
> What does this warning do in cases where a type has different alignments
> inside and outside structs? I'm thinking of something like
>
> struct s { long long x; } *p;
> /* ... */
> (long long *)p
>
> on 32-bit x86 - where long long's preferred alignment is 8 bytes, but in
> structures it's 4 bytes. (Likewise for double in place of long long.) I
> think a warning for a (long long *)p cast might be surprising in that
> case.
>
Well, yes this does get a warning. But doesn't that cast then violate
the underlying alignment requirement of long long* ?
Of course there is probably a reason why -Wcast-align is not enabled by
default, and likewise this warning emits a fair amount of false
positives, but nevertheless I think it is often worth looking at the
places where this warning flags a possible alignment issue.
However, neither -Wcast-align nor -Wcast-align=strict are enabled unless
explicitly requested.
Bernd.
next prev parent reply other threads:[~2017-09-13 19:52 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-04 8:07 Bernd Edlinger
2017-09-11 13:53 ` [PING] " Bernd Edlinger
2017-09-13 17:06 ` Joseph Myers
2017-09-13 19:52 ` Bernd Edlinger [this message]
2017-09-13 20:03 ` Joseph Myers
2017-09-13 20:55 ` Bernd Edlinger
2017-09-13 20:57 ` Joseph Myers
2017-09-14 16:33 ` [PATCHv2] " Bernd Edlinger
2017-09-15 15:51 ` Joseph Myers
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