Want to win a PS4? Go Premium and enter to win our High-Tech Treats giveaway. Enter to Win

x
?
Solved

Without using sizeof how do i calculte structure size

Posted on 2008-06-11
9
Medium Priority
?
628 Views
Last Modified: 2012-05-05
Hi,
I have one structure having two int and a char. how do i calculate size of the structure?
thanks,
santanu
0
Comment
Question by:arijit_rebaca
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 4
  • 2
  • 2
9 Comments
 
LVL 40

Expert Comment

by:evilrix
ID: 21758843
>> I have one structure having two int and a char.
The size of these is platform dependent (their size isn't defined in the standard)

>> how do i calculate size of the structure?
At best you can approximate it, by adding together the (assumed) size of the types it aggregates but structs can also contain padding and unless you also know how this has been implemented you'll not necessarily get the right result. In other words the sum of the parts might be less than the whole.
0
 
LVL 53

Expert Comment

by:Infinity08
ID: 21758851
sizeof is the easiest way :

        typedef struct Test {
            int i;
            char c;
        } Test;

        sizeof(Test);

Other methods will not be reliable due to padding that might be added to the struct.
0
 
LVL 53

Expert Comment

by:Infinity08
ID: 21758858
Any reason you don't want to use sizeof ?
0
Concerto's Cloud Advisory Services

Want to avoid the missteps to gaining all the benefits of the cloud? Learn more about the different assessment options from our Cloud Advisory team.

 
LVL 10

Accepted Solution

by:
peetm earned 500 total points
ID: 21759291
#include <stdio.h>

int main(void)
{
    struct thing
    {
        int     a;
        char    b;
        float   c;
    };
   
    struct thing t;

    struct thing * ptr = &t;

    printf("%u\n", (char *)(ptr + 1) - (char *)ptr);

    return 0;
}
0
 
LVL 53

Expert Comment

by:Infinity08
ID: 21759435
>> (char *)(ptr + 1)

Hehe ... that's cheating lol ... But true : sizeof is not used explicitly.
0
 
LVL 10

Expert Comment

by:peetm
ID: 21759455
>>Hehe ... that's cheating lol ... But true : sizeof is not used explicitly.

:-)

And, one would not of course want to have a struct larger than ptrdiff_t, and, I'm not so sure about using 'u' either - still I reckon it's the kind of thing that someone's got in mind here.
0
 
LVL 53

Expert Comment

by:Infinity08
ID: 21759491
>> still I reckon it's the kind of thing that someone's got in mind here.

There's a good chance of that :)
0

Featured Post

Concerto's Cloud Advisory Services

Want to avoid the missteps to gaining all the benefits of the cloud? Learn more about the different assessment options from our Cloud Advisory team.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Have you thought about creating an iPhone application (app), but didn't even know where to get started? Here's how: ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ Important pre-programming comments: I’ve never tri…
Examines three attack vectors, specifically, the different types of malware used in malicious attacks, web application attacks, and finally, network based attacks.  Concludes by examining the means of securing and protecting critical systems and inf…
The goal of this video is to provide viewers with basic examples to understand opening and writing to files in the C programming language.
The goal of this video is to provide viewers with basic examples to understand how to create, access, and change arrays in the C programming language.
Suggested Courses

650 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question