Re: [Xen-devel] [xen-unstable test] 16231: regressions - FAIL

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Mon, 2013-02-25 at 09:19 +0000, Ian Campbell wrote:
> The problem is the use of '#pragma pack(4)' when building the foreign
> headers on x86_32.

IIRC this is to deal with the fact that on x86_32 8-byte types are
4-byte aligned when they are within a struct. This is not the case on
32-bit ARM. The following skanky test on armv7 returns:
        align of uint32_t 4
        align of uint64_t 8
        align of struct foo.t32 4
        align of struct foo.t64 8
Compared with x86_32:
        align of uint32_t 4
        align of uint64_t 8
        align of struct foo.t32 4
        align of struct foo.t64 4
        
Ian

#include <stdio.h>
#include <stdint.h>
#include <inttypes.h>

struct foo
{
        uint32_t t32;
        uint64_t t64;
};

int main (void)
{
        struct foo f;
        printf("align of uint32_t %d\n", __alignof__(uint32_t));
        printf("align of uint64_t %d\n", __alignof__(uint64_t));
        printf("align of struct foo.t32 %d\n", __alignof__(f.t32));
        printf("align of struct foo.t64 %d\n", __alignof__(f.t64));
        return 0;
}



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