From: Alexander Monakov <amonakov@ispras.ru>
To: "Markus Fröschle" <markus@mubf.de>
Cc: gcc@gcc.gnu.org
Subject: Re: Aw: Re: asking for __attribute__((aligned()) clarification
Date: Wed, 21 Aug 2019 14:29:00 -0000 [thread overview]
Message-ID: <alpine.LNX.2.20.13.1908211714420.32047@monopod.intra.ispras.ru> (raw)
In-Reply-To: <trinity-02ba671e-c260-4ad9-a277-b1169d3026c8-1566279973304@3c-app-1and1-bs05>
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On Tue, 20 Aug 2019, "Markus Fröschle" wrote:
> Thank you (and others) for your answers. Now I'm just as smart as before, however.
>
> Is it a supported, documented, 'long term' feature we can rely on or not?
>
> If yes, I would expect it to be properly documented. If not, never mind.
I think it's properly documented in gcc-9:
https://gcc.gnu.org/onlinedocs/gcc-9.2.0/gcc/Common-Type-Attributes.html
(the "old" behavior where the compiler would neither honor reduced alignment
nor issue a warning seems questionable, the new documentation promises a more
sensible approach)
In portable code one can also use memcpy to move unaligned data, the compiler
should translate it like an unaligned load/store when size is a suitable
constant:
int val;
memcpy(&val, ptr, sizeof val);
(or __builtin_memcpy when -ffreestanding is in effect)
Alexander
next prev parent reply other threads:[~2019-08-21 14:29 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-19 12:46 "Markus Fröschle"
2019-08-19 13:57 ` Paul Koning
2019-08-19 14:01 ` Richard Earnshaw (lists)
2019-08-19 14:08 ` Alexander Monakov
2019-08-19 14:12 ` Paul Koning
2019-08-20 5:46 ` Aw: " "Markus Fröschle"
2019-08-21 14:29 ` Alexander Monakov [this message]
2019-08-21 14:32 ` Paul Koning
2019-08-21 14:58 ` Alexander Monakov
2019-08-21 16:50 ` Paul Koning
2019-08-21 17:35 ` Jonathan Wakely
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