Date: Fri, 03 Apr 1998 18:02:34 -0800 From: Xiaomin Ye <xiaominy@tuns.ca> To: freebsd-questions@FreeBSD.ORG, ifair@newton.ccs.tuns.ca, Larry.Hughes@StMarys.ca Subject: bit and byte alignment on FreeBSD? Message-ID: <352594BA.2E58B3B8@tuns.ca>
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Dear Sir/Madam,
We encountered a strange problem while using FreeBSD.
The following structure can be compacted to be 8 bytes by means of cc
compiler on Open-VMS platform. But on FreeBSD, 12 bytes will be formed.
#pragma nomember_alignment
struct example_structure
{
unsigned type : 3;
unsigned c : 1;
signed mem1 : 12;
signed mem2 : 24;
signed mem2 : 24;
};
It seems that on FreeBSD the compiler can only provide one, two or
four bytes alignment,
"type" occupies 1 byte, "c" occupies 1, "mem1" 2 , "mem2" 4 bytes and
"mem3" 4 bytes, because is no bit alignment and 3-byte alignment.
However, on Open-VMS the compiler can provide the bit alignment,
"type", "c" and "mem1" take 2 byte space, and "mem2", "mem3" will occupy
3 bytes respectively. The total space will be only 8 bytes.
Is there any solution to this problem? Your kind will be very much
appreciated.
Regards,
Xiaomin
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