On 03/27/2014 02:03 AM, Wenchao Xia wrote: > This file holds some functions that do not need to be generated. > > Signed-off-by: Wenchao Xia <wenchaoq...@gmail.com> > --- > include/qapi/qmp-event.h | 27 +++++++++++++++++ > qapi/Makefile.objs | 1 + > qapi/qmp-event.c | 70 > ++++++++++++++++++++++++++++++++++++++++++++++ > 3 files changed, 98 insertions(+), 0 deletions(-) > create mode 100644 include/qapi/qmp-event.h > create mode 100644 qapi/qmp-event.c >
> + err = qemu_gettimeofday(&tv);
> + if (err < 0) {
> + /* Put -1 to indicate failure of getting host time */
> + tv.tv_sec = -1;
> + tv.tv_usec = -1;
You fixed the problem with C promotion here, but...
> + }
> +
> + obj = qobject_from_jsonf("{ 'seconds': %" PRId64 ", "
> + "'microseconds': %" PRId64 " }",
> + (int64_t) tv.tv_sec, (int64_t) tv.tv_usec);
...here, C promotion rules bite once again :( If tv_usec is uint32_t,
then it zero-extends rather than sign-extends into int64_t, and you may
end up with 0xffffffff instead of the intended -1. When doing
potentially widening casts, it is only safe if you know the signedness
of the pre-cast value; but with struct timeval, POSIX doesn't make that
easy.
Maybe it's easier to just rewrite things with known types:
int64_t sec;
int usec;
qemu_timval tv;
err = qemu_gettimeofday(&tv);
if (err < 0) {
sec = -1;
usec = -1;
} else {
sec = tv.tv_sec;
usec = tv.tv_usec;
}
qobject_from_jsonf("... %"PRId64 ", ...%d", sec, usec)
since 'int' is guaranteed to be large enough for all the usec values we
care about on all platforms we compile on (that is, we require 32-bit
int, even if C allows for a 16-bit int implementation).
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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