Re: [dpdk-dev] [PATCH v3 2/4] ethdev: move error checking macros to header

[Stephen Hemminger <stephen@networkplumber.org>]

On Wed, 4 Nov 2015 11:24:18 +0100
Adrien Mazarguil <adrien.mazarguil@6wind.com> wrote:

> On Wed, Nov 04, 2015 at 02:19:36AM +0100, Thomas Monjalon wrote:
> > 2015-11-03 12:00, Bruce Richardson:
> > > Move the function ptr and port id checking macros to the header file, so
> > > that they can be used in the static inline functions there. In doxygen
> > > comments, mark them as for internal use only.
> > [...]
> > > +/**
> > > + * @internal
> > > + *  Macro to print a message if in debugging mode
> > > + */
> > > +#ifdef RTE_LIBRTE_ETHDEV_DEBUG
> > > +#define RTE_PMD_DEBUG_TRACE(fmt, args...) \
> > > +		RTE_LOG(ERR, PMD, "%s: " fmt, __func__, ## args)
> > > +#else
> > > +#define RTE_PMD_DEBUG_TRACE(fmt, args...)
> > > +#endif
> > 
> > It does not compile because Mellanox drivers are pedantic:
> > 
> > In file included from /home/thomas/projects/dpdk/dpdk/drivers/net/mlx4/mlx4.c:78:0:
> > /home/thomas/projects/dpdk/dpdk/x86_64-native-linuxapp-gcc-shared-next/include/rte_ethdev.h: At top level:
> > /home/thomas/projects/dpdk/dpdk/x86_64-native-linuxapp-gcc-shared-next/include/rte_ethdev.h:933:38: error: ISO C does not permit named variadic macros [-Werror=variadic-macros]
> >  #define RTE_PMD_DEBUG_TRACE(fmt, args...) \
> 
> I suggest something like the following definitions as a pedantic-proof and
> standard compliant method (one drawback being that it cannot be done with a
> single macro), see PMD_DRV_LOG() in drivers/net/mlx5/mlx5_utils.h which also
> automatically appends a line feed:
> 
>  #ifdef RTE_LIBRTE_ETHDEV_DEBUG
> 
>  #define STRIP(a, b) a
>  #define OPAREN (
>  #define CPAREN )
>  #define COMMA ,
> 
>  #define RTE_PMD_DEBUG_TRACE(...) \
>          RTE_PMD_DEBUG_TRACE_(__VA_ARGS__ STRIP OPAREN, CPAREN)
> 
>  #define RTE_PMD_DEBUG_TRACE_(fmt, ...) \
>          RTE_PMD_DEBUG_TRACE__(fmt COMMA __func__, __VA_ARGS__)
> 
>  #define RTE_PMD_DEBUG_TRACE__(...) \
>          RTE_LOG(ERR, PMD, "%s: " __VA_ARGS__)
> 
>  #else /* RTE_LIBRTE_ETHDEV_DEBUG */
> 
>  #define RTE_PMD_DEBUG_TRACE(...)
> 
>  #endif /* RTE_LIBRTE_ETHDEV_DEBUG */
> 
> STRIP() and other helper macros are used to manage the dangling comma issue
> when __VA_ARGS__ is empty as in the first call below:
> 
>  RTE_PMD_DEBUG_TRACE("foo\n");
>  RTE_PMD_DEBUG_TRACE("foo %u\n", 42);

That solution is really ugly.

Why not do something that keeps the expected checks.

diff --git a/lib/librte_eal/common/include/rte_log.h b/lib/librte_eal/common/include/rte_log.h
index ede0dca..f3a3d34 100644
--- a/lib/librte_eal/common/include/rte_log.h
+++ b/lib/librte_eal/common/include/rte_log.h
@@ -99,6 +99,8 @@ extern struct rte_logs rte_logs;
 #define RTE_LOG_INFO     7U  /**< Informational.                    */
 #define RTE_LOG_DEBUG    8U  /**< Debug-level messages.             */
 
+#define RTE_LOG_DISABLED 99U /**< Never printed			    */
+
 /** The default log stream. */
 extern FILE *eal_default_log_stream;
 
diff --git a/lib/librte_ether/rte_ethdev.h b/lib/librte_ether/rte_ethdev.h
index eee1194..e431f2e 100644
--- a/lib/librte_ether/rte_ethdev.h
+++ b/lib/librte_ether/rte_ethdev.h
@@ -931,6 +931,61 @@ struct rte_eth_dev_callback;
 /** @internal Structure to keep track of registered callbacks */
 TAILQ_HEAD(rte_eth_dev_cb_list, rte_eth_dev_callback);
 
+/**
+ * @internal
+ *  Macro to print a message if in debugging mode
+ */
+#ifdef RTE_LIBRTE_ETHDEV_DEBUG
+#define RTE_PMD_DEBUG_TRACE(fmt, args...) \
+	RTE_LOG(ERR, PMD, "%s: " fmt, __func__, ## args)
+#else
+#define RTE_PMD_DEBUG_TRACE(fmt, args...) \
+	RTE_LOG(DISABLED, PMD, "%s: " fmt, __func__, ## args)
+#endif