On Thu, Nov 23, 2006 at 04:45:09PM +0100, Ren? Scharfe wrote:
> Andy Whitcroft schrieb:
> > You see packing attributes applied to similar things in the kernel.
> > Perhaps they are relevant here?
> > Is there not some kind of attribute thing we can apply to this structure
> > to prevent the padding? You see that in the kernel from time to time.
> >
> > struct foo {
> > } __attribute__((packed));
>
> Yes, that would be nice, but unfortunately __attribute__ is no standard
> C.
There is no standard C way to pack structures. Some compilers use
#pragma's, gcc uses __attribute__((packed)).
> Is there really a compiler that inserts padding between arrays of
> unsigned chars?
Yes, that compiler is called "gcc".
#include <stdio.h>
struct foo {
unsigned char a[3];
unsigned char b[3];
};
int main(void)
{
printf("%d\n", sizeof(struct foo));
return 0;
}
On i386 that prints 6, on ARM it prints 8.
Erik
--
+-- Erik Mouw -- www.harddisk-recovery.com -- +31 70 370 12 90 --
| Lab address: Delftechpark 26, 2628 XH, Delft, The Netherlands
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