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Re: [Qemu-devel] [PATCH] fcntl64 fix

From: Paul Brook
Subject: Re: [Qemu-devel] [PATCH] fcntl64 fix
Date: Tue, 20 Mar 2007 23:43:35 +0000
User-agent: KMail/1.9.5

> Now that the dust has settled, I see where the change is probably a
> no-op anyway. A quick little test program indicates that on x86_64,
> l_start will have an offset of 8 wether the structure is packed or not,
> and wether the __pad member is present or not. The unsigned long long is
> always going to be aligned to a 8 byte boundary.

The __pad member is essential. Your logic is wrong is two ways:

a) The struct is packed. This overrides normal alignment and ensures the 
structure contains no padding.
b) long long has whatever alignment the host feels like giving it. There's no 
guarantee it's going to be 8 byte aligned. 


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