Question about "#pragma pack(n)"

[feng qiu]

In c-pragma.c file, #pragma pack(n) set the value of 
"maximum_field_alignment".
And in opts.c file,-fpack-struct set "flag_pack_struct = 1" .
But I don't known the relation between them. 

It seems that they relate to the four ariables¡ª¡ª
DECL_ALIGN,DECL_PACKED,TYPE_PACKED,and TYPE_ALIGN in stor-layout.c file,but 
what is the difference in them?Should I modify this file?

Thanks in advance,
Feng Qiu

>From: James E Wilson <wilson@specifixinc.com>
>To: feng qiu <fengqiu_tianjin@hotmail.com>
>CC: gcc@gcc.gnu.org
>Subject: Re: Question about "#pragma pack(n)"
>Date: Tue, 05 Apr 2005 18:37:53 -0700
>
>feng qiu wrote:
> > I want to modify the gcc source code,what should I do?
>
>Look at the c-pragma.c file, search for pack.  Also see -fpack-struct in
>common.opt and fpack_struct in opts.c.  Then expand your search from 
there.
>--
>Jim Wilson, GNU Tools Support, http://www.SpecifixInc.com

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