Messages in this thread | | | Date | Mon, 03 Feb 2014 18:03:17 +0800 | From | Chen Gang <> | Subject | Re: [PATCH] drivers: staging: lustre: lustre: include: add "__attribute__((packed))" for the related union |
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On 02/03/2014 04:58 PM, Dan Carpenter wrote: > On Sat, Feb 01, 2014 at 09:57:39PM +0800, Chen Gang wrote: >> It seems, our kernel still stick to treate 'pack' region have effect >> with both 'align' and 'sizeof'. >> > > It's not about packed regions. It's about unions. It's saying the > sizeof() a union is a multiple of 4 unless it's packed. > > union foo { > short x; > short y; > }; > > The author intended the sizeof(union foo) to be 2 but on metag arch then > it is 4. >
Yeah, just like your original discussion. :-)
Hmm... can we say: "for metag compiler, in a pack region, it considers variables alignment, but does not consider about struct/union alignment (except append packed to each related struct/union)".
For compatible (consider about its ABI), it has to keep this features, but for kernel, it needs be changed.
So, I suggest to add one parameter to compiler to switch this feature, and append this parameter to KBUILD_CFLAGS in "arch/metag/Makefile" which can satisfy both ABI and kernel.
Thanks. -- Chen Gang
Open, share and attitude like air, water and life which God blessed
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