Re: [releng_6 tinderbox] failure on sparc64/sparc64

On 2006-02-13 00:34, Colin Percival <cperciva@xxxxxxxxxxx> wrote:
Giorgos Keramidas wrote:
On 2006-02-13 00:23, "M. Warner Losh" <imp@xxxxxxxxxx> wrote:
struct foo foo;
uint32_t value[sizeof(foo) / sizeof(uint32_t)];

memcpy(value, &foo);
// write out value one 32-bit word at a time

Is that right? Or at least 'proper' here means defined.

AFAIK, yes.

I agree that the behaviour of the above code is defined, but
I'd be much happier if value[] was defined to be an array of
length ((sizeof(foo) - 1) / sizeof(uint32_t) + 1), just in
case sizeof(foo) happens to not be a multiple of 4. :-)

Good thinking. It's probably a good idea to avoid copying random
garbage, and using something like:

struct foo foo;
uint32_t value[sizeof(uint32_t) * (sizeof(foo) / sizeof(uint32_t) + 1)];

and then copying only sizeof(foo) bytes. This is probably defined too
and won't allow overflowing of value[], but I don't really want to know
what it does on machines of varying endianess :-)

- Giorgos

_______________________________________________
freebsd-arch@xxxxxxxxxxx mailing list
http://lists.freebsd.org/mailman/listinfo/freebsd-arch
To unsubscribe, send any mail to "freebsd-arch-unsubscribe@xxxxxxxxxxx"