Re: [ECOS] structure alignment question

[Gary Thomas <gary at mlbassoc dot com>]

On Thu, 2004-02-05 at 22:45, mohanlal jangir wrote:
> I have some questions regarding structure alignment. If I declare a
> structure like
> 
> struct structure {
>   unsigned short  a;
>   unsigned char   b;
>   unsigned char pad[1];
> };
> 
> and then same structure like
> struct structure {
>   unsigned short  a;
>   unsigned short   b;
> };
> 
> Are both declaration free from alignment problem for any kind of access or
> it's only later one?
> 
> Another question is, if I have a structure like
> struct structure {
>     unsigned int a;
>     unsigned short b;
>     unsigned char c;
> };
> 
> struct structure temp;
> unsigned int *p = &(temp.a);
> unsigned short *q = &(temp.b);
> unsigned char *r = &(temp.c);
> 
> Do all pointers (p, q and r) need to be 4 byte boundary aligned or p at 4
> byte boundary, q at 2 byte boundary and r at 1 byte boundary will do?

The answers you seek are architecture (and even ABI) dependent.  You 
should ask on the GCC list to get authoratative answers.

-- 
Gary Thomas <gary@mlbassoc.com>
MLB Associates


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