Thread: please solve my #pragma pack problam

i getting the same solution for below program while changing the pack value in pragma

Code:

#include<stdio.h>
#pragma pack(2)
struct hai
{
char ch1;
char ch2;
char ch3;
char ch4;
char ch5;
}s;
int main()
{
printf("%d \n",sizeof(s));
return 0;
}

i getting output as :6 in both case of prgma pack vaues 2 and 4.

why i getting same values , please any body clear my confusion

What compiler are you using? What size are you expecting? 6 would indicate that it is aligning at 2 bytes (what you have up in your pragma). If you are using GCC, you'll need something like this:

Code:

#define PACK1 __attribute__((aligned (1),packed))

typedef struct something {
        int a, b;
        char c, d;
} PACK1 SOMETHING;

Now the sizeof (SOMETHING) would be 10.

hi canady,

i am using RHEL5 GCC 4.1.1 compiler. my mechine is x86 based pc. i think generally it will take 4 bytes everytime.

first time it will take four bytes .so
i expecting 8 in prgma pack 4


1.in case of #pragma pack 2

first 4 char variables will take 4 bytes.second char will take two bytes for pack 2.so totally 6 byes

2.in case of #pragma pack 4

first 4 char variables will take 4 bytes and next char will go to anoter pack ie second pak with 4 bytes. but character will take 1 bytes. but output caounts 6 bytes .

i expecting 8 bytes in pragma 4.

why it taking 2 bytes onlly in pragma 2 and prgma 4

i look for your further replys.