On Thu, Jul 4, 2019 at 12:18 AM Alistair Francis <[email protected]> wrote:
> On Wed, Jul 3, 2019 at 12:47 PM Arnd Bergmann <[email protected]> wrote:
> > On Wed, Jul 3, 2019 at 8:45 PM Alistair Francis <[email protected]>
> > wrote:
> > > What I don't understand though is how that impacted this struct, it
> > > doesn't use clock_t at all, everything in the struct is an int or
> > > void*.
> >
> > si_utime/si_stime in siginfo are clock_t.
>
> But they are further down the struct. I just assumed that GCC would
> align those as required, I guess it aligns the start of the struct to
> match some 64-bit members which seems strange.
These are the regular struct alignment rules. Essentially you would
get something like
struct s {
int a;
int b;
int c;
union {
int d;
long long e;
};
int f;
};
Since 'e' has 8 byte alignment, the same is true for the union,
and putting the union in a struct also requires the same alignment
for the struct itself, so now you get padding after 'c' and 'f'.
Arnd
