On Wed, Sep 21, 2016 at 10:00:23AM +0000, Felipe Franciosi wrote:
>
> > On 21 Sep 2016, at 07:24, Markus Armbruster <arm...@redhat.com> wrote:
> >
> > "Pavel Dovgalyuk" <dovga...@ispras.ru> writes:
> >
> >>> From: Felipe Franciosi [mailto:fel...@nutanix.com]
> >>> If compiling with -Werror=unused-result, replay-internal.c won't build
> >>> due to a call to fwrite() where the returned value is ignored. A simple
> >>> cast to (void) is not sufficient on recent GCCs, so this fixes it.
> >>>
> >>> Signed-off-by: Felipe Franciosi <fel...@nutanix.com>
> >>> ---
> >>> replay/replay-internal.c | 2 +-
> >>> 1 file changed, 1 insertion(+), 1 deletion(-)
> >>>
> >>> diff --git a/replay/replay-internal.c b/replay/replay-internal.c
> >>> index 5835e8d..6978d76 100644
> >>> --- a/replay/replay-internal.c
> >>> +++ b/replay/replay-internal.c
> >>> @@ -65,7 +65,7 @@ void replay_put_array(const uint8_t *buf, size_t size)
> >>> {
> >>> if (replay_file) {
> >>> replay_put_dword(size);
> >>> - fwrite(buf, 1, size, replay_file);
> >>> + (void)(fwrite(buf, 1, size, replay_file)+1);
> >>> }
> >>> }
> >>
> >> This looks very weird.
>
> Oh I couldn't agree more. I hate this syntax. It is, however, the simplest
> way to get around this issue. See:
> http://stackoverflow.com/questions/11888594/ignoring-return-values-in-c
If we want to ignore return value reliably, lets just pull in the
ignore_value macro from gnulib which is known to work across GCC
versions
/* Normally casting an expression to void discards its value, but GCC
versions 3.4 and newer have __attribute__ ((__warn_unused_result__))
which may cause unwanted diagnostics in that case. Use __typeof__
and __extension__ to work around the problem, if the workaround is
known to be needed. */
#if 3 < __GNUC__ + (4 <= __GNUC_MINOR__)
# define ignore_value(x) \
(__extension__ ({ __typeof__ (x) __x = (x); (void) __x; }))
#else
# define ignore_value(x) ((void) (x))
#endif
GNULIB makes it availavble under LGPLv2.1+
eg used as:
ignore_value(fwrite(buf, 1, size, replay_file));
Regards,
Daniel
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