Re: sizeof(struct ...)

From: René Scharfe <rene.scharfe@lsrfire.ath.cx>
Date: Nov 23, 2006, 16:14 UTC
Message-ID: <4565C8F4.6000606@lsrfire.ath.cx>
In-Reply-To: <20061123155431.GD6581@harddisk-recovery.com>

Erik Mouw schrieb:

Show 20 quoted lines

> On Thu, Nov 23, 2006 at 04:45:09PM +0100, René Scharfe wrote:
>>  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.

Does it add 1 byte after a and and 1 after b or two after b? I suspect it's the latter case -- otherwise Gerrit's patch, which started this thread, wouldn't help solve his problem. Or the pad sizing follows complicated rules that I do not understand at the moment.

Time to look for an ARM emulator, it seems.

Thanks,