Re: [Qemu-devel] [PATCH 1/4] blockdev.h: Add GCC attribute (check format arguments)

[Stefan Weil]

Am 01.07.2010 22:10, schrieb Blue Swirl:
> On Thu, Jul 1, 2010 at 11:08 AM, Stefan Weil <address@hidden> wrote:
> > Signed-off-by: Stefan Weil <address@hidden>
> > ---
> >  blockdev.h |    3 ++-
> >  1 files changed, 2 insertions(+), 1 deletions(-)
> >
> > diff --git a/blockdev.h b/blockdev.h
> > index 23ea576..3c5c85d 100644
> > --- a/blockdev.h
> > +++ b/blockdev.h
> > @@ -42,7 +42,8 @@ extern int drive_get_max_bus(BlockInterfaceType type);
> >  extern void drive_uninit(DriveInfo *dinfo);
> >  extern const char *drive_get_serial(BlockDriverState *bdrv);
> >
> > -extern QemuOpts *drive_add(const char *file, const char *fmt, ...);
> > +extern QemuOpts *drive_add(const char *file, const char *fmt, ...)
> > +    __attribute__ ((__format__ (__printf__, 2, 3)));
> >  extern DriveInfo *drive_init(QemuOpts *arg, int default_to_scsi,
> >                              int *fatal_error);
>
> I lost the cover letter, so this applies to all patches: Wouldn't it
> make sense to make GCC_FMT_ATTR(n, m) from audio/audio_int.h available
> universally and then use that?


That's a matter of personal taste:

GCC_FMT_ATTR(n, m) is shorter, but a human reader has to
look it up once to see what it does (ok, some readers might
guess it right). The compiler has to look it up, too, so
a common header file is needed.

When I prepared the patches, I did not notice that some
functions used GCC_FMT_ATTR. I added the __attribute__
macro to these functions and got a compiler error...
This shows that at least for me GCC_FMT_ATTR was confusing
(of course it no longer is).

Some people prefer GCC_FMT_ATTR because they want to
be able to redefine it for non-gcc compilers.

__attribute__ can also be redefined for that case, so that
is not a very strong argument.

I prefer using __attribute__ without intermediate macro,
but don't mind if a different style is preferred for qemu.

Regards
Stefan