From: Jan-Benedict Glaw <jbglaw@lug-owl.de>
To: linux-c-programming <linux-c-programming@vger.kernel.org>
Subject: Re: memory_allocation
Date: Fri, 13 Aug 2004 15:01:53 +0200 [thread overview]
Message-ID: <20040813130153.GL16935@lug-owl.de> (raw)
In-Reply-To: <I2DXAF$7B97927BCA10A589B58FC0F34E16A58F@laposte.net>
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On Fri, 2004-08-13 14:27:51 +0200, simon.guinot <simon.guinot@laposte.net>
wrote in message <I2DXAF$7B97927BCA10A589B58FC0F34E16A58F@laposte.net>:
> hello,
>
> i have a problem with a structure memory allocation...
>
> struct dns_answer {
> unsigned short type;
> unsigned short class;
> unsigned int ttl;
> unsigned short rdlength;
> unsigned int addr_answer;
> } dns_answ;
>
> all this element are not adjacent in memory... i have two
> "free bytes" between rdlenght and addr_answer...
> since here, i have alway made my headers like this... and no
> problem...
You can add "__attribute__ ((packed))" to the declaration of that
struct to force GCC to pack it. However, keep in mind that the gap does
serve a purpose! Accessing those parts at unaligned offsets may cause
quite some speed penalty on some CPUs. However, if it's a binary
structure (as it looks like), that's okay. (NB: Is your coding
endianess-save in that case?)
MfG, JBG
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prev parent reply other threads:[~2004-08-13 13:01 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-08-13 12:27 memory_allocation simon.guinot
2004-08-13 12:34 ` memory_allocation Henry Margies
2004-08-13 13:01 ` Jan-Benedict Glaw [this message]
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