On 06/27/2012 04:34 AM, Orit Wasserman wrote:
> Signed-off-by: Orit Wasserman <owass...@redhat.com>
> ---
> arch_init.c | 33 +++++++++++++++++++++++++++------
> 1 files changed, 27 insertions(+), 6 deletions(-)
>
> diff --git a/arch_init.c b/arch_init.c
> index 9dafb6e..ee20c33 100644
> --- a/arch_init.c
> +++ b/arch_init.c
> @@ -44,6 +44,14 @@
> #include "exec-memory.h"
> #include "hw/pcspk.h"
>
> +#ifdef DEBUG_ARCH_INIT
> +#define DPRINTF(fmt, ...) \
> + do { fprintf(stdout, "arch_init: " fmt, ## __VA_ARGS__); } while (0)
Unfortunately, '## __VA_ARGS__' is a gcc extension not portable to C99.
But as HACKING recommends its use, you are not the first offender, nor
should this patch clean it up (rather, it should be a global cleanup).
Here's a portable way to do it (borrowed from libvirt):
>> /* Helper macros to implement VIR_DEBUG using just C99. This
>> * assumes you pass fewer than 15 arguments to VIR_DEBUG, but
>> * can easily be expanded if needed.
>> *
>> * Note that gcc provides extensions of "define a(b...) b" or
>> * "define a(b,...) b,##__VA_ARGS__" as a means of eliding a comma
>> * when no var-args are present, but we don't want to require gcc.
>> */
>> #define VIR_ARG15(_1, _2, _3, _4, _5, _6, _7, _8, _9, _10, _11, _12, _13,
>> _14, _15, ...) _15
>> #define VIR_HAS_COMMA(...) VIR_ARG15(__VA_ARGS__, 1, 1, 1, 1, 1, 1, 1, 1, 1,
>> 1, 1, 1, 1, 0)
>>
>> /* Form the name VIR_DEBUG_[01], then call that macro,
>> * according to how many arguments are present. Two-phase due to
>> * macro expansion rules. */
>> #define VIR_DEBUG_EXPAND(a, b, ...) \
>> VIR_DEBUG_PASTE(a, b, __VA_ARGS__)
>> #define VIR_DEBUG_PASTE(a, b, ...) \
>> a##b(__VA_ARGS__)
>>
>> /* Internal use only, when VIR_DEBUG has one argument. */
>> #define VIR_DEBUG_0(fmt) \
>> VIR_DOMAIN_DEBUG_1(fmt "%s", "")
>>
>> /* Internal use only, when VIR_DEBUG has >=two arguments. */
>> #define VIR_DEBUG_1(fmt, ...) \
>> do { fprintf(stdout, "prefix: " fmt, __VA_ARGS__); } while (0)
>>
>> #define VIR_DEBUG(...) \
>> VIR_DEBUG_EXPAND(VIR_DEBUG_, \
>> VIR_HAS_COMMA(__VA_ARGS__), \
>> __VA_ARGS__)
>>
Ugly, huh? Which is why I won't ask you to fix HACKING.
Note that if you live with the restriction that you always provide an
additional argument beyond the format string, then life is much simpler
for complying with C99:
#define DPRINTF(fmt, ...) \
do { fprintf(stdout, "prefix: " fmt, __VA_ARGS__); } while (0)
but it means you can't use DPRINTF("string") (you would instead have to
use DPRINTF("string", "dummy"), which might trigger a gcc warning about
printf argument mismatch, so to silence that warning, you would have to
use DPRINTF("string%s", "") - which is basically what my goop from
libvirt above was attempting to do automatically).
--
Eric Blake ebl...@redhat.com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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