Thread: What would be the result...

Hi friends at present i am not having any compiler so please can any one conform the result of this program
what would be the size of this structure

Code:

struct str 
{ 
int data; 
struct str *pstr; 
char ch; 
int data1; 
};

what would be the size of this structure...

Assuming no padding, and chap = char

sizeof(int) + sizeof(struct str *) + sizeof(char) + sizeof(int)

And on most 32bit systems sizeof(int) = 4, and the size of a pointer is also 4. The standard also sets sizeof(char) must always equal _. Fill in the blanks, I aint doing your homework. It really depends on what this is compiled, the results will differ from 16bit, 32bit and 64bit compilers at least.

Or easier, sizeof(str)

Also consider that there are alignment issues with this struct, as the pointer pstr and integer data1 should be correctly aligned to the appropriate pointer and integer alignment respectively.
The alignment requirements varies depending on the architecture of the system as well as settings for the compiler [e.g. #pragma pack() and such like], so to fully answer the question you need to know:
1. The size of a int and pointer.
2. The alignments suitable for int and pointer.

--
Mats

On a 32-bit system, I would imagine it is. But why not try for yourself? sizeof(str).

Originally Posted by sreeramu

According to my calculation the size would be 16 bytes ....am i correct ..??

It is one possible result, yes. In a 64-bit system, the size would probably be 4 + (4) + 8 + 1 + (3) + 4 = 24 bytes instead. Numbers in parenthesis are the alignment additions. This is just ONE example of the possible answers - without knowing more of what the system configuration is , we can't really say.

--
Mats

Even without a compiler, testing the hypothesis that the size of the struct could be 16 with Comeau online

Code:

struct str 
{ 
int data; 
struct str *pstr; 
char ch; 
int data1; 
};

int main(void)
{
   int arr[10 / (sizeof(struct str) - 16)];
}

Which produces the following error message, confirming that (with these options) the size is indeed 16:

Code:

"ComeauTest.c", line 11: error: division by zero
     int arr[10 / (sizeof(struct str) - 16)];
                ^