| Message ID | AANLkTikzSMQAZHUW+JPHQY1z14TCV1Zvs8qu=w-JzWM-@mail.gmail.com |
|---|---|
| State | New |
| Headers | show |
Blue Swirl <blauwirbel@gmail.com> writes: > +For variadic macros, stick with C99 syntax: > + > +#define DPRINTF(fmt, ...) \ > + do { printf("IRQ: " fmt, ## __VA_ARGS__); } while (0) That's not C99 syntax, the combination with ## is a gcc extension. In C99 you cannot have an empty __VA_ARGS__. Andreas.
On Sun, Aug 15, 2010 at 9:27 PM, Andreas Schwab <schwab@linux-m68k.org> wrote: > Blue Swirl <blauwirbel@gmail.com> writes: > >> +For variadic macros, stick with C99 syntax: >> + >> +#define DPRINTF(fmt, ...) \ >> + do { printf("IRQ: " fmt, ## __VA_ARGS__); } while (0) > > That's not C99 syntax, the combination with ## is a gcc extension. In > C99 you cannot have an empty __VA_ARGS__. That's too bad, I picked the example from one of our current macros. Maybe just s/C99/this/ or perhaps we shouldn't specify any non-standard syntax.
On 08/16/2010 01:05 PM, Blue Swirl wrote: > On Sun, Aug 15, 2010 at 9:27 PM, Andreas Schwab<schwab@linux-m68k.org> wrote: > >> Blue Swirl<blauwirbel@gmail.com> writes: >> >> >>> +For variadic macros, stick with C99 syntax: >>> + >>> +#define DPRINTF(fmt, ...) \ >>> + do { printf("IRQ: " fmt, ## __VA_ARGS__); } while (0) >>> >> That's not C99 syntax, the combination with ## is a gcc extension. In >> C99 you cannot have an empty __VA_ARGS__. >> > That's too bad, I picked the example from one of our current macros. > Maybe just s/C99/this/ or perhaps we shouldn't specify any > non-standard syntax. > We definitely should discourage the GCC syntax [#define fn(arg...)] as it's deprecated by the new C99 syntax. Very specifically, only the '##' is an extension and it's a widely adopted one. Regards, Anthony Liguori
On Mon, Aug 16, 2010 at 6:32 PM, Anthony Liguori <anthony@codemonkey.ws> wrote: > On 08/16/2010 01:05 PM, Blue Swirl wrote: >> >> On Sun, Aug 15, 2010 at 9:27 PM, Andreas Schwab<schwab@linux-m68k.org> >> wrote: >> >>> >>> Blue Swirl<blauwirbel@gmail.com> writes: >>> >>> >>>> >>>> +For variadic macros, stick with C99 syntax: >>>> + >>>> +#define DPRINTF(fmt, ...) \ >>>> + do { printf("IRQ: " fmt, ## __VA_ARGS__); } while (0) >>>> >>> >>> That's not C99 syntax, the combination with ## is a gcc extension. In >>> C99 you cannot have an empty __VA_ARGS__. >>> >> >> That's too bad, I picked the example from one of our current macros. >> Maybe just s/C99/this/ or perhaps we shouldn't specify any >> non-standard syntax. >> > > We definitely should discourage the GCC syntax [#define fn(arg...)] as it's > deprecated by the new C99 syntax. Very specifically, only the '##' is an > extension and it's a widely adopted one. I'll do s/C99/this C99-like/.
diff --git a/HACKING b/HACKING new file mode 100644 index 0000000..e60aa48 --- /dev/null +++ b/HACKING @@ -0,0 +1,6 @@ +1. Preprocessor + +For variadic macros, stick with C99 syntax: + +#define DPRINTF(fmt, ...) \ + do { printf("IRQ: " fmt, ## __VA_ARGS__); } while (0)
Add a new file, HACKING, in order to collect recurring issues with submitted patches. Start with preprocessor rules, adapted from libvirt HACKING. Signed-off-by: Blue Swirl <blauwirbel@gmail.com> --- HACKING | 6 ++++++ 1 files changed, 6 insertions(+), 0 deletions(-) create mode 100644 HACKING