Re: [PATCH for-4.15 2/2] tools/xenstore: Check the format printf for xprintf() and barf{,_perror}()

[Julien Grall <julien@xxxxxxx>]

Hi Jan,

On 05/03/2021 13:45, Jan Beulich wrote:
> On 05.03.2021 14:01, Jürgen Groß wrote:
> > On 05.03.21 13:40, Julien Grall wrote:
> > > From: Julien Grall <jgrall@xxxxxxxxxx>
> > > --- a/tools/xenstore/utils.h
> > > +++ b/tools/xenstore/utils.h
> > > @@ -29,10 +29,12 @@ const char *dump_state_align(FILE *fp);
> > >    
> > >    #define PRINTF_ATTRIBUTE(a1, a2) __attribute__((format (printf, a1, a2)))
> > >    
> > > -void barf(const char *fmt, ...) __attribute__((noreturn));
> > > -void barf_perror(const char *fmt, ...) __attribute__((noreturn));
> > > +#define __noreturn __attribute__((noreturn))
> > >    
> > > -extern void (*xprintf)(const char *fmt, ...);
> > > +void barf(const char *fmt, ...) __noreturn PRINTF_ATTRIBUTE(1, 2);
> > > +void barf_perror(const char *fmt, ...) __noreturn PRINTF_ATTRIBUTE(1, 2);
> > > +
> > > +extern void (*xprintf)(const char *fmt, ...) PRINTF_ATTRIBUTE(1, 2);
> > ... the extern here would be dropped.
> But this isn't a function declaration, but that of a data object.
> With the extern dropped, a common symbol will appear in every CU.
Urgh, you are right. Actually, the extern was added recently by Anthony:

dacdbf7088d6a3705a9831e73991c2b14c519a65 ("tools/xenstore: mark variable 
in header as extern")
I completely forgot it despite I needed to backport the patch to our 
downstream Xen.
Cheers,

--
Julien Grall