Interesting :
#include<iostream>
using namespace std;
int main()
{
struct p{
int i;
char j;
char k;
};
struct q{
char j;
int i;
char k;
};
printf("p=%u q=%u",sizeof(p),sizeof(q));
return 0;
}
o/p : p=8 q=12
On Sat, Aug 6, 2011 at 2:55 PM, Tushar Bindal <[email protected]> wrote:
> that means the order is immaterial.
> the sizeof the struct always remains same irrespective of the order and
> just depends on the type of variables???
> why char with double does not get size in multiples of 8??
>
>
> On Sat, Aug 6, 2011 at 12:54 PM, Puneet Gautam <[email protected]>wrote:
>
>> Sorry guys, int is 4 bytes on 64 bit and 2 bytes on 32 bit system..
>>
>> But padding rule remains same for both structures as mentioned above...
>>
>>
>>
>>
>> On 8/6/11, Puneet Gautam <[email protected]> wrote:
>> > There is no difference between the two...
>> >
>> > On 32 bit system, both structures need every address location where
>> > int and pointer are stored to be a multiple of 4(highest size is 4)..
>> >
>> > On 64 bit,
>> > even if pointer is 4bytes(say, in 64 bit system), and p1, p2 be
>> > structure variables, then p2 should start at address which is multiple
>> > of 8 as int data is 8bytes. So, if p1 starts at 0, it should end at 16
>> > not 12 so that p2 starts at 8's multiple.
>> >
>> > This is done by padding pointer by 4bytes in both I and II struct.
>> > declarations.
>> >
>> >
>> > Hope i made it clear...!
>> >
>> > Thanks.
>> >
>> >
>> >
>> >
>> > On 8/6/11, Tushar Bindal <[email protected]> wrote:
>> >>
>> http://www.serc.iisc.ernet.in/ComputingFacilities/systems/cluster/xlf/html/xlfug/ug35.htm
>> >> this says int is always 4 bytes and pointer is 8 bytes on 64 bit
>> >> compiler.
>> >>
>> >> so how does padding affect these structures because of the difference
>> in
>> >> size of int and pointer?
>> >>
>> >>
>> >> I tried this program
>> >> https://ideone.com/CRU6x#view_edit_box
>> >> char always gets 4 bytes whenever it has int or double in the same
>> struct
>> >> irrrespctive of the order of the declaration of variables.
>> >> I thought char should get size 8 when there is a double in the ame
>> struct
>> >> whereas it gets size 4 only.
>> >> what is the problem here?
>> >>
>> >> On Sat, Aug 6, 2011 at 4:40 AM, Shashank Jain <[email protected]>
>> >> wrote:
>> >>
>> >>> i dont understand the diff btw dem, could u plz elaborate?
>> >>>
>> >>> Shashank Jain
>> >>> IIIrd year
>> >>> Computer Engineering
>> >>> Delhi College of Engineering
>> >>>
>> >>>
>> >>>
>> >>> On Sat, Aug 6, 2011 at 12:32 AM, Kamakshii Aggarwal
>> >>> <[email protected]
>> >>> > wrote:
>> >>>
>> >>>> in case of 64 bit,
>> >>>> size of second structure will also be 16 not 8
>> >>>>
>> >>>>
>> >>>> On Fri, Aug 5, 2011 at 11:40 PM, UTKARSH SRIVASTAV <
>> >>>> [email protected]> wrote:
>> >>>>
>> >>>>> I think voth are just same..................
>> >>>>>
>> >>>>>
>> >>>>> On Fri, Aug 5, 2011 at 10:57 AM, priya v <[email protected]>
>> wrote:
>> >>>>>
>> >>>>>> in case of 64 bit machine y doesn't padding happen in the 2nd
>> >>>>>> structure?
>> >>>>>>
>> >>>>>>
>> >>>>>> On Fri, Aug 5, 2011 at 11:21 PM, hary rathor
>> >>>>>> <[email protected]>wrote:
>> >>>>>>
>> >>>>>>> no ,if u r using 32 bit machine . that will use 4 byte pointer
>> size
>> >>>>>>> ,
>> >>>>>>> but in 64 machine that enforce to be size of 8 . where padding
>> >>>>>>> will
>> >>>>>>> take int your given first structure
>> >>>>>>>
>> >>>>>>> so for 32 bit- size will 8 8 for both structure
>> >>>>>>> for 64 bit - size will 16 and 12 respectively cause of 4 bit
>> padding
>> >>>>>>> in
>> >>>>>>> one structure
>> >>>>>>>
>> >>>>>>> hence 2nd structure is good for use
>> >>>>>>>
>> >>>>>>> --
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>> >>>>>
>> >>>>> --
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>> >>>> Kamakshi
>> >>>> [email protected]
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>> >>
>> >>
>> >>
>> >> --
>> >> Tushar Bindal
>> >> Computer Engineering
>> >> Delhi College of Engineering
>> >> Mob: +919818442705
>> >> E-Mail : [email protected]
>> >> Website: www.jugadengg.com
>> >>
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>> >>
>> >>
>> >
>>
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>>
>
>
> --
> Tushar Bindal
> Computer Engineering
> Delhi College of Engineering
> Mob: +919818442705
> E-Mail : [email protected]
> Website: www.jugadengg.com
>
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>
--
Prashant Gupta
B.Tech Final Year
Computer Science and Engineering
NIT Trichy
Phone : +91 9894462744
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