On Wed, Oct 30, 2013 at 12:21:28AM +1100, Bruce Evans wrote:
> On Tue, 29 Oct 2013, Mark Johnston wrote:
>
> > Log:
> > Revert r257248 and fix the problem in a way that doesn't violate style(9).
>
> Why did gcc complain about the original version?
It looks like this is because of the use of -W, which is apparently an
alias for -Wextra; according to the gcc man page, this will trigger a
warning when "an empty body occurs in an if or else statement."
>
> > Modified: head/lib/libproc/_libproc.h
> > ==============================================================================
> > --- head/lib/libproc/_libproc.h Tue Oct 29 02:25:18 2013
> > (r257297)
> > +++ head/lib/libproc/_libproc.h Tue Oct 29 03:12:31 2013
> > (r257298)
> > @@ -52,6 +52,6 @@ struct proc_handle {
> > #define DPRINTF(...) warn(__VA_ARGS__)
> > #define DPRINTFX(...) warnx(__VA_ARGS__)
> > #else
> > -#define DPRINTF(...)
> > -#define DPRINTFX(...)
> > +#define DPRINTF(...) do { } while (0)
> > +#define DPRINTFX(...) do { } while (0)
> > #endif
> >
> > Modified: head/lib/libproc/proc_util.c
> > ==============================================================================
> > --- head/lib/libproc/proc_util.c Tue Oct 29 02:25:18 2013
> > (r257297)
> > +++ head/lib/libproc/proc_util.c Tue Oct 29 03:12:31 2013
> > (r257298)
> > @@ -145,9 +145,8 @@ proc_wstatus(struct proc_handle *phdl)
> > if (phdl == NULL)
> > return (-1);
> > if (waitpid(phdl->pid, &status, WUNTRACED) < 0) {
> > - if (errno != EINTR) {
> > + if (errno != EINTR)
> > DPRINTF("waitpid");
> > - }
> > return (-1);
> > }
> > if (WIFSTOPPED(status))
>
> Unlike some buggy macros, the null macro expanded to syntactically correct
> code:
>
> if (errno != EINTR)
> ;
>
> so it doesn't need the do-while hack. Empty statements are common in some
> contexts, so compilers shouldn't warn about them. In all versions, the
> macro isn't completely function-like and the if statement is dead code,
> so if compilers warn about too many things then the do-while hack wouldn't
> work here or in most places that it is used.
>
> Nearby style bugs:
> - the error check is for "< 0" instead of for "== -1"
> - the error message is not as loud as old ones. All old ones begin with
> "ERROR: ". The new style is better. "ERROR" is not even redundant.
> It is wrong, since the errors are just warnings.
>
> Bruce
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