It is an extension of GCC CPP to:
* allow omitting a variable macro argument entirely, and
* use ## __VA_ARGS__ to remove the the comma before ## __VA_ARGS__ when
__VA_ARGS__ is empty.
The only use of ## _VA_ARGS__ is to define the pr_xxx() macros, with the first
argument being the format string and the rest the to-be-formatted arguments. The
format string is explicitly spelled out because another macro pr_fmt() is used
to add to the format string a prefix which is customizable by defining what
pr_fmt() expands to.
For C99 compliance, this patch changes the pr_xxx() macros in the following
pattern.
- #define pr_fatal(fmt, ...) \
- do_logmsg(LOG_FATAL, pr_fmt(fmt), ## __VA_ARGS__); \
+ #define pr_fatal(...) \
+ do_logmsg(LOG_FATAL, pr_prefix __VA_ARGS__); \
Reference:
* https://gcc.gnu.org/onlinedocs/gcc/Variadic-Macros.html#Variadic-Macros
Signed-off-by: Junjie Mao <junjie.mao@intel.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
