lkml.org 
[lkml]   [2018]   [Oct]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [PATCH] KEYS: trusted: fix -Wvarags warning
On Fri, Oct 12, 2018 at 10:05 AM Nick Desaulniers
<ndesaulniers@google.com> wrote:
>
> On Fri, Oct 12, 2018 at 8:14 AM Denis Kenzior <denkenz@gmail.com> wrote:
> >
> > Hi James,
> >
> > >> So can't we simply use 'bool' or uint32 as the type for h3 instead
> > >> of re-ordering everything
> > >
> > > The problem is the standard is ambiguious. The only thing that's
> > > guaranteed to work for all time is a char *. If you want to keep the
> > > order, what I'd suggest is inserting a dummy pointer argument which is
> > > always expected to be NULL between the h3 and the varargs.
> >
> > So maybe I'm misunderstanding something, but the issue seems to be that
> > unsigned char is promoted to 'unsigned char *' by Clang and probably
> > unsigned int or int by gcc.
>
> No. This is extremely well defined behavior in C. In C, integral
> types are NEVER promoted to pointer to integer types, only to larger
> integral types through rules more complicated than the correct flags
> to pass to `tar`.
> https://xkcd.com/1168/

And may have their signedness converted.
https://wiki.sei.cmu.edu/confluence/display/c/INT02-C.+Understand+integer+conversion+rules
is the reference I use, though I always feel like there's quite a bit
of mental gymnastics involved interpreting it.

>
> >
> > So instead of having unsigned char h3, can't we simply have bool h3 or
> > unsigned int h3?
>
> int is the default argument promotion. Proposed:
> https://github.com/ClangBuiltLinux/linux/issues/41#issuecomment-428365339
>
> >
> > Regards,
> > -Denis
> >
>
>
> --
> Thanks,
> ~Nick Desaulniers



--
Thanks,
~Nick Desaulniers

\
 
 \ /
  Last update: 2018-10-12 19:18    [W:0.077 / U:10.852 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site