Solved

What 's different between two type aligns...

Posted on 2004-08-11
3
177 Views
Last Modified: 2010-04-15
Hi,Experts:
I use MSCV 6.0.
(1)
union Student{
   struct field
   {
      char sex;
      unsigned int age;
      double average;      
   };
   double align;
};
(2)
#pragma pack(push,8)      
struct Student
{
      char sex;
      unsigned int age;
      double average;      
};
#pragma pack(pop)      
(1) and (2) are  aligned on an 8-byte boundary.
Is there any different between them???
Thanks!
0
Comment
Question by:TKD
3 Comments
 
LVL 7

Accepted Solution

by:
aib_42 earned 20 total points
ID: 11788543
As it is, no.
However, the former may have a different alignment on a different platform/implementation.

Try adding a variable of type "__m128i" or "__m128d" or two into the struct. That should pull the alignment up to 16 bytes on a standard MSVC6 configuration.

Then compare the pragma'ed and the normal versions, you should see different alignments, as well as the fact that aligned SSE instructions would not work on the pragma'ed one.
0

Featured Post

Optimizing Cloud Backup for Low Bandwidth

With cloud storage prices going down a growing number of SMBs start to use it for backup storage. Unfortunately, business data volume rarely fits the average Internet speed. This article provides an overview of main Internet speed challenges and reveals backup best practices.

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…
Summary: This tutorial covers some basics of pointer, pointer arithmetic and function pointer. What is a pointer: A pointer is a variable which holds an address. This address might be address of another variable/address of devices/address of fu…
The goal of this video is to provide viewers with basic examples to understand how to use strings and some functions related to them in the C programming language.
The goal of this video is to provide viewers with basic examples to understand opening and reading files in the C programming language.

914 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

Need Help in Real-Time?

Connect with top rated Experts

13 Experts available now in Live!

Get 1:1 Help Now