This case comes from kernel. It requires a strict alignment for the data.
In Adjust_Alignment, we trend to increase the alignment (for example, to 16
byte) for better performance. Usually, it is OK. But if the code specifies a
special alignment like this example, we need to follow it.
在 2011年8月25日 下午12:28，Mike Murphy <mmur...@nvidia.com>写道：
> The alignment is stored in the ty_idx (see TY_align), and then there are
> routines like Adjusted_Alignment in stblock that can modify it. I suspect
> the problem here is that the alignment is being put on the object rather
> than the type, and then is lost (but should still be possible, because the
> TY_align is like qualifiers that can vary from the base type). Does the
> alignment show up properly in the intermediate .B file?
>
> -----Original Message-----
> From: Sun Chan [mailto:sun.c...@gmail.com]
> Sent: Wednesday, August 24, 2011 7:51 PM
> To: 朱庆
> Cc: open64-devel@lists.sourceforge.net
> Subject: Re: [Open64-devel] Code Review request for bug832[wgen]
>
> The reason I asked for the file is that I think there has to be some
> alignment attribute somewhere. I am sure data alignment has been dealt
> with in the compiler. That it is due to user, or just language
> attribute might be irrelevant from compiler point of view.
>
> Mike or Murthy,
> Do you remember where alignment is handled? I only found Alignment
> field in BLK of the symtab_defs.h
>
> Sun
>
> 2011/8/25 朱庆 <zqing1...@gmail.com>:
> > Hi Sun,
> >
> > Attached symtab_defs.h.
> >
> > Thanks
> > zhuqing
> > 2011/8/24 Sun Chan <sun.c...@gmail.com>:
> >> can you send me the full symtab_defs.h?
> >> Sun
> >>
> >> On Wed, Aug 24, 2011 at 4:56 PM, 朱庆 <zqing1...@gmail.com> wrote:
> >>> Hi all,
> >>>
> >>> Can gatekeeper help review following fix for bug832?
> >>> https://bugs.open64.net/show_bug.cgi?id=832
> >>>
> >>> small case, a.c:
> >>> struct obs_kernel_param {
> >>> const char *str;
> >>> };
> >>>
> >>> const char str1[] = "acpi_parse_apic_instance=";
> >>> const char str2[] = "acpi_os_name";
> >>> struct obs_kernel_param var1
> >>> __attribute__ ((aligned ((sizeof (long))))) =
> >>> {str1};
> >>>
> >>> struct obs_kernel_param var2
> >>> __attribute__ ((aligned ((sizeof (long))))) =
> >>> {str2};
> >>>
> >>> when compile with opencc, nm a.o
> >>> 0000000000000000 D var1
> >>> 0000000000000010 D var2
> >>> compile with gcc, nm a.o
> >>> 0000000000000000 D var1
> >>> 0000000000000008 D var2
> >>> the offset of var1 and var2 are different, the problem with opencc is
> >>> :fixed align attribute does not work, this may cause some problems
> >>> when mix link two files with opencc and gcc.
> >>>
> >>> The fix is to add a new ST flag to record user_defined_align.
> >>>
> >>> Thanks
> >>> zhuqing
> >>>
> >>>
> ------------------------------------------------------------------------------
> >>> EMC VNX: the world's simplest storage, starting under $10K
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> >>> https://lists.sourceforge.net/lists/listinfo/open64-devel
> >>>
> >>>
> >>
> >
>
>
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--
Regards,
Lai Jian-Xin
------------------------------------------------------------------------------
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The only unified storage solution that offers unified management
Up to 160% more powerful than alternatives and 25% more efficient.
Guaranteed. http://p.sf.net/sfu/emc-vnx-dev2dev
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