Re: [Qemu-devel] [PATCH 01/13] hw/ppc.c: LOG_IRQ macro

[Anthony Liguori <anthony@codemonkey.ws>]

Andreas Färber wrote:
>
> Am 11.12.2008 um 22:45 schrieb Anthony Liguori:
>
>> Eduardo Habkost wrote:
>>> This macro will avoid some #ifdefs in the code and create a single 
>>> point
>>> where the logging call can be changed in the future.
>>>
>>> Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
>>> ---
>>> hw/ppc.c |   10 ++++++++++
>>> 1 files changed, 10 insertions(+), 0 deletions(-)
>>>
>>> diff --git a/hw/ppc.c b/hw/ppc.c
>>> index 60d6e86..cbd69e0 100644
>>> --- a/hw/ppc.c
>>> +++ b/hw/ppc.c
>>> @@ -31,6 +31,16 @@
>>> //#define PPC_DEBUG_IRQ
>>> //#define PPC_DEBUG_TB
>>> +#ifdef PPC_DEBUG_IRQ
>>> +#  define LOG_IRQ(...) do {           \
>>> +     if (loglevel & CPU_LOG_INT)      \
>>> +       fprintf(logfile, __VA_ARGS__); \
>>> +   } while (0)
>>> +#else
>>> +#  define LOG_IRQ(...) do { } while (0)
>>> +#endif
>>>
>>
>> This style of macro is less ideal than:
>>
>> #define LOG_IRQ(fmt, ...) fprintf(logfile, fmt, ## __VA_ARGS__).
>
> Now that the TCG conversion is done, does QEMU still require GCC? I 
> remember we had issues with such macros in Mono's eGLib due to some 
> compilers needing "fmt..." instead of "fmt, ..." and some not 
> supporting "__VA_ARGS__" but "...".

fmt... is an old GCC-ism.  __VA_ARGS__ is C99.  Eduardo's syntax (w/o 
##) is actually stricter C99 as ## is a GCC extension.  However, I think 
it's a pretty good one.

In terms of QEMU requiring GCC, I personally would like to maintain the 
status quo.  C99 whenever possible with judicious use of GCC extensions 
when they're necessary.  If someone wants to do the work to port to 
another compiler, posts the patches, and is willing to maintain that 
support (which means constant testing and nagging), we can re-examine 
our GCC dependency.

It's not worth debating about (GCC dependency) unless someone is really 
going to put in the work of maintaining another compiler.

Regards,

Anhtony Liguori

>
> It might make sense then to put such logging macros in a central place 
> (qemu-common.h?) to avoid having to cope with such annoyances in all 
> those source files.
>
> Andreas
>
>