Re: [PATCH v3] devres: Explicitly align datai[] to 64-bit

[Mark Rutland]

On Mon, Jul 09, 2018 at 05:45:21PM +0200, Peter Zijlstra wrote:
> On Mon, Jul 09, 2018 at 05:34:27PM +0200, Peter Zijlstra wrote:
> > On Mon, Jul 09, 2018 at 04:29:58PM +0100, Mark Rutland wrote:
> > > Shouldn't that be 8? AFAICT, __alignof__(unsigned long long) is 8 on
> > > x86_32:
> > 
> > Curious, I wonder why we put that align in atomic64_32 then.
> 
> Shiny, look at this: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=54188
> 

Ouch.

[mark@lakrids:~]% cat test.c
#include <stdio.h>

#define PRINT_TYPE_INFO(t) \
        printf("%10s %5d %5d\n", #t, sizeof(t), __alignof__(t))

struct ull {
        unsigned long long v;
};

int main(int argc, char *argv[])
{
        printf("%10s %5s %5s\n", "TYPE", "SIZE", "ALIGN");
        PRINT_TYPE_INFO(int);
        PRINT_TYPE_INFO(long);
        PRINT_TYPE_INFO(long long);
        PRINT_TYPE_INFO(struct ull);

        return 0;
}
[mark@lakrids:~]% gcc -m32 test.c -o test
[mark@lakrids:~]% ./test 
      TYPE  SIZE ALIGN
       int     4     4
      long     4     4
 long long     8     8
struct ull     8     4

Mark.