Bug

[Mumit Khan]

Samy <hunter@gnet.com.eg> writes:
> Hi ,
>       I've gcc (egcs-2.91.66) running on Red Hat Linux 6.0 .
> and i've the following problem :
> 
> struct test {
>                      char i;          // one byte
>                       int b;           // 4 bytes       and total is 5
> bytes
>                    }test;
> int main (void)
> {
>   printf("%d",sizeof(test));
> 
> }
> 
> and the result is
> 8 .
> so can you explain it please
> Thanks

It's not a bug; the compiler follows alignment requirements when it lays 
out the struct members and you're seeing the effect of that. Here the
second member, an integer, is aligned to 4-byte boundary and you end up
with a total size of 8 bytes. 

If you really need "packed" layout, see GCC documentation for the packed 
attribute.  

If you declare struct test as following, you'll get 5 bytes:

  struct test {
    char i;          /* one byte */
    int b;           /* 4 bytes and total is 5 bytes */
  } __attribute__((packed)) test;

It's a bad in general to expect a certain layout of struct members.

Regards,
Mumit