Lpc2000

Hello,

Another solution I had last night which should fix the alignment-problem, because the union is
compiler will align this union to its biggest member:
===============================================================
union {
        char    u8[8];
        short   u16[4];
} buff = {1, 2, 3, 4, 5, 6, 7, 8};

int main(void) {
        short x[10], i;

        for (i = 0; i < 4; i++) {
                x[i] = buff.u16[i];
                printf(" %04x, ", x[i]);
        }

        return 0;
}
===============================================================

   Sten

brendanmurphy37 wrote:
> Dave,
> 
> Think about whet your saying here:
> 
> 
>>ip = (int *)&buf[5];
>>
>>should be treated by the compiler as:
>>
>>ip = (__packed int *)&buf[5];
>>
> 
> 
> "should" doesn't come into it! You have explicitley told the 
> compiler exectly how you want it treated (the "(int *)"). Now if you 
> had one of those magic "do what I mean, not what I say" compilers, 
> you'd be fine......
> 
> By the way, if you find that compiler, let me know!
> 
> Brendan
> 
> --- In lpc2000@yahoogroups.com, "dsidlauskas1" <dsidlauskas@...> 
> wrote:
> 
>>Jaya,
>>
>>I don't think I'm asking it to connect the two statements.
>>
>>What I'm expecting it to do is to recognize that buf is a byte 
> 
> packed
> 
>>object (the defalt for the compler)and when casting byte packed
>>objects the compiler should cast them to other byte packed objects.
>>
>>in otherwords;
>>
>>char buf[10];
>>int ip*;
>>
>>ip = (int *)&buf[5];
>>
>>should be treated by the compiler as:
>>
>>ip = (__packed int *)&buf[5];
>>
>>and this is because char buf[10] is a byte packed object for this
>>compiler.
>>
>>Dave
>>
>>
>>--- In lpc2000@yahoogroups.com, "jayasooriah" <jayasooriah@> wrote:
>>
>>>Dave,
>>>
>>>I think what you are asking of the compiler is to connect the two
>>>statements in the for() loop.  Compilers do not have this 
> 
> capability.
> 
>>> Even if it did, it would have to also consider the for() 
> 
> statement
> 
>>>too, as your code would be legitimate if the for() statement was:
>>>
>>>
>>>> for (i = 0; i < ...; i += 4)
>>>
>>>A purist would argue is that there is nothing wrong with the 
> 
> pointer
> 
>>>assignment given the explicit cast.  The error occurs only if 
> 
> (and
> 
>>>when) the pointer is dereferenced at runtime.
>>>
>>>Making it a packed array on these grounds may not be what the
>>>programmer intended.  Besides, packed array methods involve
>>>implementation issues.
>>>
>>>GCC was kind enough to allude you to the possibility of such an 
> 
> event
> 
>>>ocurring.  Note that it too did not make the relationship 
> 
> between the
> 
>>>two statements.  If it did, it would report an error, not a 
> 
> warning.
> 
>>>Jaya
>>>
>>>--- In lpc2000@yahoogroups.com, "dsidlauskas1" <dsidlauskas@> 
> 
> wrote:
> 
>>>>Jaya,
>>>>
>>>>Since the compiler knows that buf is a byte aligned object, 
> 
> woutldn't
> 
>>>>it be resonable for the compiler to treat
>>>>
>>>>(int *)&buf[i]
>>>>
>>>>as 
>>>>
>>>>(__packed int *)&buf[i]
>>>>
>>>>In general, if non-naturaly aligned objects are promoted by a 
> 
> cast,
> 
>>>>shouldn't, by default, the cast be of the proper non-aligned 
> 
> type?
> 
>>>>BTW. Really appreciate your discussion of interupts on your 
> 
> web site.
> 
>>>>Dave
>>>
> 
> 
> 
> 
> 
> 
>  
> Yahoo! Groups Links
> 
> 
> 
>  
> 
> 
> 


-- 
/************************************************
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